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In-situ testing techniques applied to embankments over soft organic soils Brown, Stephen Granger 1983

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IN-SITU TESTING TECHNIQUES APPLIED TO EMBANKMENTS OVER SOFT ORGANIC SOILS by STEPHEN GRANGER BROWN B . S c , C a l i f o r n i a State U n i v e r s i t y At Long Beach, 1979 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE in THE FACULTY OF GRADUATE STUDIES Department Of C i v i l E n g i n e e r i n g We accept t h i s t h e s i s as conforming to the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA October 1983 © Stephen Granger Brown, 1983 \ In presenting t h i s thesis i n p a r t i a l f u l f i l m e n t of the requirements fo r an advanced degree at the University of B r i t i s h Columbia, I agree that the Library s h a l l make i t f r e e l y a v a i l a b l e for reference and study. I further agree that permission for extensive copying of t h i s t h e s i s for s c h o l a r l y purposes may be granted by the head of my department or by h i s or her representatives. I t i s understood that copying or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l gain s h a l l not be allowed without my written permission. Department of Cit/il / f y v c j r ^ The University of B r i t i s h Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 Date rt^cber- /h H83 DE-6 (3/81) i \ A b s t r a c t The i n v e s t i g a t i o n of a t e s t f i l l over organic s o i l s has been c a r r i e d out using three i n - s i t u t e s t i n g t e chniques. One-h a l f of the f i l l area i s s e r v i c e d by wick d r a i n s while the other h a l f remains in a n a t u r a l s t a t e . Piezometer cone p e n e t r a t i o n t e s t s , d i l a t o m e t e r t e s t s and f i e l d vane t e s t s were used to monitor the t e s t embankment over a one year p e r i o d d u r i n g both the c o n s t r u c t i o n and c o n s o l i d a t i o n phases. The a b i l i t y of these t e s t s to monitor embankments i s e v a l u a t e d . The r e s u l t s show that the piezometer cone p e n e t r a t i o n t e s t g i v e s the best o v e r a l l performance. The r e s u l t s a l s o show that the wick d r a i n s improved the drainage of the organic s o i l s s i g n i f i c a n t l y . In a separate study, piezometer cone p e n e t r a t i o n t e s t s , d i l a t o m e t e r t e s t s and screw p l a t e t e s t s were performed to determine e n g i n e e r i n g p r o p e r t i e s of the organic s o i l such as undrained shear s t r e n g t h , c o e f f i c i e n t of c o n s o l i d a t i o n and d r a i n e d c o n s t r a i n e d modulus. The s t r e n g t h s and weaknesses of each t e s t are d i s c u s s e d with p a r t i c u l a r r e f e r e n c e to the t e s t i n g of organic s o i l s . F i n a l l y , p r e d i c t i o n s of settlement are made from the i n - s i t u d r a i n e d moduli and are compared with the observed s e t t l e m e n t s . Settlements p r e d i c t e d using S a n g l e r a t ' s (1972) c o r r e l a t i o n f o r d r a i n e d modulus f o r the cone p e n e t r a t i o n t e s t were found to compare w e l l with the observed v a l u e s . i i i Table of Contents A b s t r a c t i i L i s t of Tables v i i L i s t of F i g u r e s v i i i Acknowledgements x Chapter I INTRODUCTION 1 1.1 INTRODUCTION 1 1.2 REPORT ORGANIZATION 2 Chapter II OBSERVED BEHAVIOUR OF THE TEST FILL 4 2.1 GENERAL DESCRIPTION 4 2.2 SITE DESCRIPTION AND GENERALIZED GEOLOGY 5 2.2.1 S i t e D e s c r i p t i o n 5 2.2.2 G e n e r a l i z e d Geology 5 2.3 WICK DRAINS 8 2.4 INSTRUMENTATION 9 2.5 LOADING SEQUENCE 14 2.6 FIELD OBSERVATIONS 16 2.6.1 Observed Settlements 20 2.6.2 C o n s o l i d a t i o n Behaviour 21 1. Rate Of C o n s o l i d a t i o n 21 2. F i e l d V o i d R a t i o Versus Log E f f e c t i v e S t r e s s Curves 23 Chapter III IN-SITU TESTING IN ORGANIC SOILS 26 3.1 FIELD VANE TESTING 26 3.1.1 Equipment 26 3.1.2 I n t e r p r e t a t i o n 26 3.2 CONE PENETRATION TEST (CPT) 29 3.2.1 Equipment 29 3.2.2 Accuracy 30 3.2.3 Data Reduction 33 3.2.4 Piezometer T i p S a t u r a t i o n 35 3.2.5 S t r a t i g r a p h i c Logging 41 3.2.6 I n t e r p r e t a t i o n - 44 3.2.7 Reference Tests 48 3.3 FLAT PLATE DILATOMETER TEST (DMT) 51 3.3.1 Equipment 51 3.3.2 Reference T e s t s 53 3.3.3 I n t e r p r e t a t i o n 58 3.3.4 I n s t a l l a t i o n Of The P e n e t r a t i o n T e s t s 63 3.4 SCREW PLATE TEST: INCREMENTAL LOADING TESTS 63 3.4.1 Equipment 63 1. I n s t a l l a t i o n 64 3.5 GROUNDWATER CONDITIONS 66 Chapter IV TEST FILL MONITORING USING THREE IN-SITU TESTS 71 4.1 INTRODUCTION 71 4.2 MONITORING: AREA WITHOUT WICK DRAINS 74 4.2.1 Cone P e n e t r a t i o n T e s t s 74 1. I n i t i a l C o n d i t i o n s To End Of C o n s t r u c t i o n + 25 Days 74 2. End Of C o n s t r u c t i o n + 25 Days To End Of C o n s t r u c t i o n + 119 Days 79 3. End Of C o n s t r u c t i o n + 119 Days To End Of C o n s t r u c t i o n + 258 Days 81 4. I n i t i a l C o n d i t i o n s To End Of C o n s t r u c t i o n + 258 Days 83 4.2.2 Dilatometer T e s t s 88 1. I n i t i a l C o n d i t i o n s To End Of C o n s t r u c t i o n + 138 Days 88 4.2.3 F i e l d Vane T e s t s 91 1. I n i t i a l C o n d i t i o n s To End Of C o n s t r u c t i o n + 236 Days 91 4.3 MONITORING: WICK DRAIN AREA 93 4.3.1 Cone P e n e t r a t i o n T e s t s 93 1. I n i t i a l C o n d i t i o n s To End Of C o n s t r u c t i o n + 20' Days 93 2. End Of C o n s t r u c t i o n + 20 Days To End Of C o n s t r u c t i o n + 118 Days .....96 3. End Of C o n s t r u c t i o n + 118 Days To End Of C o n s t r u c t i o n + 258 Days 100 4. I n i t i a l C o n d i t i o n s To End Of C o n s t r u c t i o n + 258 Days 103 4.3.2 Dilatometer T e s t s 106 1. I n i t i a l C o n d i t i o n s To End Of C o n s t r u c t i o n + 140 Days 106 4.3.3 F i e l d Vane T e s t s 108 1. I n i t i a l C o n d i t i o n s To End Of C o n s t r u c t i o n + 236 Days 108 Chapter V THE DETERMINATION OF ENGINEERING PROPERTIES OF ORGANIC SOILS BY THREE IN-SITU TESTS 1.10 V 5.1 INTRODUCTION - 110 5.2 UNDRAINED SHEAR STRENGTH 110 5.3 COEFFICIENT OF CONSOLIDATION .116 5.4 DRAINED CONSTRAINED MODULUS 122 5.4.1 Cone P e n e t r a t i o n Test 122 1. C o r r e l a t i o n 122 2. Methodology 123 5.4.2 Dilatometer Test 125 5.4.3 Screw P l a t e T e s t : Incremental Loading T e s t s .130 1 . Theory 130 2. Methodology 132 5.4.4 Screw P l a t e T e s t : U l t i m a t e Load T e s t s 135 5.4.5 Summary Of C o n s t r a i n e d Modulus R e s u l t s 137 Chapter VI SETTLEMENT PREDICTIONS 142 6.1 IN-SITU TESTING METHODS 142 6.1.1 Method Of A n a l y s i s 142 6.1.2 Re s u l t s Of The Settlement A n a l y s i s 145 6.1.3 D i s c u s s i o n 148 1 . Cone P e n e t r a t i o n Test 148 2. Dilatometer Test 153 3. Screw P l a t e : Incremental Loading T e s t s 155 4. Screw P l a t e : U l t i m a t e Load T e s t s 158 6 . 2 CONVENTIONAL METHODS 1 59 6.2.1 Standard Incremental C o n s o l i d a t i o n T e s t s ....159 6.2.2 L o c a l Experience 160 Chapter VII CONCLUSIONS 164 7.1 EVALUATION OF THREE IN-SITU TEST METHODS FOR MONITORING EMBANKMENTS 164 7.1.1 Dilatometer Test 164 7.1.2 F i e l d Vane Test 167 7.1.3 Cone P e n e t r a t i o n Test 167 7.2 EVALUATION OF THREE IN-SITU TEST METHODS FOR DETERMINING ORGANIC SOIL PROPERTIES 170 7.2.1 Undrained Shear Strength 170 7.2.2 C o e f f i c i e n t Of C o n s o l i d a t i o n 171 7.2.3 Constrained Modulus 172 7.3 EVALUATION OF WICK DRAINS 176 7.4 RECOMMENDATIONS FOR FURTHER RESEARCH 178 BIBLIOGRAPHY 180 v i APPENDIX A - COMPLETE CPT LOGS - B.C. HIGHWAYS TEST FILL SITE 185 APPENDIX B - COMPLETE DMT LOGS - B.C. HIGHWAYS TEST FILL SITE 186 APPENDIX C - SCREW PLATE INCREMENTAL LOADING TEST DATA ..187 APPENDIX D - SCREW PLATE ULTIMATE LOAD TEST DATA 188 v i i L i s t of Tables Table Page 2.1 Location of below-ground instrumentation 13 4.1 Summary of i n - s i t u testing: Test f i l l s i t e . . . 72 7.1 Summary of observed and predicted settlements . .17 3 v i i i L i s t of Figures Figure Page 2.1 Site investigation map 6 2.2 The MEBRA-DRAIN type of wick drain: I l l u s t r a t i n g the drain body and porous outer f i l t e r jacket . . 10 2.3 TEST FILL: Instrumentation layout 11 2.4 Below ground instrumentation as of January, 1982 . 13 2.5 TEST FILL: Construction sequence 15 2.6 NON-WICK AREA: Observed settlement and excess pore pressure versus log time 17 2.7 WICK AREA: Observed settlement and excess pore pressure versus log time 18 2.8 F i e l d void r a t i o versus log ef f e c t i v e stress and log t o t a l stress 24 3.1 5-Channel cone penetrometer 31 3.2 Tip design to allow easy saturation with g l y c e r i n 36 3.3 Example of piezometer f r i c t i o n cone logging i n s t r a t i f i e d s o i l s 42 3.4 S o i l c l a s s i f i c a t i o n chart for standard e l e c t r i c cone 45 3.5 I n i t i a l cone bearing resistances for the wick area and the area without wick drains 49 3.6 I n i t i a l undrained shear strength from f i e l d vane tests i n the wick and non-wick areas 50 3.7 Schematic of dilatometer 52 3.8 Reference dilatometer test D.M.T.-3; intermediate parameters, i n i t i a l conditions s i t e 54 3.9 Reference dilatometer test D.M.T.-3; interpreted parameters, i n i t i a l conditions s i t e 55 3.10 Tabular output from dilatometer test D.M.T.-3; i n i t i a l conditions s i t e 56 3.11 Test f i l l s i t e and i n i t i a l conditions s i t e . . . . 57 ix Figure Page 3.12 Dilatometer: S o i l c l a s s i f i c a t i o n chart 61 3.13 Schematic representation of screw plate system . . 65 3.14 Equilibrium pore pressures versus elevation . . . 67 3.15 Excess pore water pressure v a r i a t i o n i n the horizontal d i r e c t i o n i n a homogeneous s o i l layer with v e r t i c a l drains 70 4.1 Test f i l l s i t e : Location of i n - s i t u tests . . . . 73 4.2 NON-WICK AREA CONE PENETRATION TEST COMPARISON: I n i t i a l conditions vs. End of construction + 25 days 75 4.3 NON-WICK AREA CONE PENETRATION TEST COMPARISON: End of construction + 25 days vs. End of construction + 119 days 80 4.4 NON-WICK AREA CONE PENETRATION TEST COMPARISON: End of construction + 119 days vs. End of construction + 258 days 82 4.5 NON-WICK AREA CONE PENETRATION TEST COMPARISON: I n i t i a l conditions vs. End of construction + 258 days 84 4.6 NON-WICK AREA DILATOMETER TEST COMPARISON: I n i t i a l conditions vs. End of construction + 138 days 89 4.7 FIELD VANE TEST COMPARISON: I n i t i a l conditions vs. End of construction + 236 days 92 4.8 WICK AREA CONE PENETRATION TEST COMPARISON: I n i t i a l condition vs. End of construction + 20 days 94 4.9 WICK AREA CONE PENETRATION TEST COMPARISON: End of construction + 20 days vs. End of construction + 118 days 97 4.10 WICK AREA CONE PENETRATION TEST COMPARISON: End of construction + 118 days vs. End of construction + 258 days 101 4.11 WICK AREA CONE PENETRATION TEST COMPARISON: I n i t i a l conditions vs. End of construction + 258 days 104 X Figure Page 4.12 WICK AREA DILATOMETER TEST COMPARISON: I n i t i a l conditions vs. End of construction + 140 days . . 107 4.13 FIELD VANE TEST COMPARISON: I n i t i a l conditions vs. End of construction + 236 days 109 5.1 I n i t i a l conditions s i t e : Location of i n - s i t u tests 111 5.2 Undrained shear strength versus Elevation . . . . . 113 5.3 Summary of existing solutions for pore pressure d i s s i p a t i o n 117 5.4 Selection of s o i l s t i f f n e s s r a t i o for clays . . . 119 5.5 Horizontal and v e r t i c a l c o e f f i c i e n t s of consolidation versus Elevation 120 5.6 Sanglerat's c o r r e l a t i o n : a value versus Water content 124 5.7 Cone penetration t e s t : Log constrained modulus, M, versus Elevation 126 5.8 Correlation between Rm and Kd 128 5.9 Dilatometer t e s t : Log constrained modulus, M, versus Elevation 129 5.10 D e f i n i t i o n of Janbu modulus number k m 131 5.11 Values of Janbu's settlement number "s" 133 5.12 Screw plate test - Incremental loading t e s t : Log constrained modulus, M, versus Elevation . . . 136 5.13 Screw plate: Typical ultimate load test r e s u l t . 138 5.14 Screw plate test - Ultimate load t e s t : Log constrained modulus, M, versus Elevation 139 5.15 Summary of log constrained modulus, M, versus Elevation 140 6.1 Stress d i s t r i b u t i o n below the centerline of the assumed test f i l l configuration 144 6.2 Results of a one-dimensional consolidation settlement analysis 146 x i Figure Page 6.3 Comparisons between Q c obtained with Delft mechanical and Fugro e l e c t r i c s t a t i c cone t i p s . . 150 6.4 Plate movement vs. Log time: Comparison between incremental load tests and extended load tests 157 6.5 Summary of primary settlement data 161 x i i Acknowledgement The w r i t e r wishes t o take t h i s o p p o r t u n i t y t o thank h i s res e a r c h s u p e r v i s o r , Dr. R.G. Campanella, f o r h i s suggestion of the problem and h i s guidance dur i n g t h i s r e s e a r c h . He f u r t h e r wishes to express h i s a p p r e c i a t i o n to Dr. P.K. Robertson f o r h i s guidance and encouragement d u r i n g the development of t h i s t h e s i s . Thanks are a l s o due to Dick Postgate and A r t Brookes f o r t h e i r t e c h n i c a l e x p e r t i s e and f o r t h e i r humor durin g the f i e l d t e s t i n g . The w r i t e r a l s o thanks h i s c o l l e a g u e s , Nancy Laing, Andy N i c h o l , Tony Rice and Ian McPherson f o r a s s i s t i n g i n the f i e l d t e s t i n g program. T h i s study was supported by a grant from E r t e c Western, Inc. The author expresses h i s a p p r e c i a t i o n f o r t h e i r a s s i s t a n c e . The observed f i e l d data f o r the t e s t f i l l p r o j e c t was k i n d l y made.available by the B r i t i s h Columbia Department of Highways. Most of a l l the author would l i k e to thank h i s parents and h i s wi f e , L i s a , f o r t h e i r l o v e which makes a l l t h i n g s p o s s i b l e . 1 I. INTRODUCTION 1.1 INTRODUCTION The performance of a t e s t embankment, or t e s t f i l l , i s commonly monitored v i a i n s t r u m e n t a t i o n that i s permanently i n s t a l l e d at the t e s t s i t e . T h i s method of monitoring works w e l l to p r o v i d e i n f o r m a t i o n r e g a r d i n g the s t a b i l i t y , settlement and pore p r e s s u r e response of the embankment s u b s o i l . However, i n order to monitor changes i n e n g i n e e r i n g behaviour of the s u b s o i l , such as s t r e n g t h , c o m p r e s s i b i l i t y and drainage, a program of t e s t i n g i s r e q u i r e d . Because modern i n - s i t u t e s t i n g techniques, such as the f l a t - p l a t e d i l a t o m e t e r and cone p e n e t r a t i o n t e s t s , can pr o v i d e a l a r g e number of t e s t s in a r a p i d and re p e a t a b l e manner they would appear to be i d e a l l y s u i t e d to such a monitoring program. T h i s t h e s i s d e s c r i b e s a p r e l i m i n a r y i n v e s t i g a t i o n of the c a p a b i l i t y of the f l a t p l a t e d i l a t o m e t e r and the cone p e n e t r a t i o n t e s t to monitor a f u l l y instrumented t e s t embankment c o n s t r u c t e d over a s o f t o r g a n i c s o i l d e p o s i t . The t e s t i n g program was conducted over a one year p e r i o d which covered both the c o n s t r u c t i o n and the c o n s o l i d a t i o n phases of the t e s t embankment study. The t e s t f i l l s t u d i e d i s unique i n that the s u b s o i l area was d i v i d e d i n t o two zones: more than 800 wick d r a i n s were i n s t a l l e d i n one h a l f of the s u b s o i l area and the other h a l f was l e f t i n a n a t u r a l s t a t e . The purpose of d i v i d i n g the t e s t area was to study the e f f e c t of the a r t i f i c i a l drainage system 2 on the c o n s o l i d a t i o n of the f i l l . The performance of the wick d r a i n system i s evaluated i n t h i s paper. Because the i n t e r p r e t a t i o n of an i n - s i t u t e s t i s o f t e n governed by the type of s o i l being t e s t e d , the organic s o i l s at the t e s t s i t e p r ovide an o p p o r t u n i t y to f u r t h e r the understanding of i n - s i t u t e s t i n g techniques. One of the primary uses of i n - s i t u t e s t s i s the de t e r m i n a t i o n of en g i n e e r i n g p r o p e r t i e s of s o i l s . As p a r t of t h i s study, cone p e n e t r a t i o n t e s t s , d i l a t o m e t e r t e s t s and screw p l a t e t e s t s were performed at the t e s t f i l l to estimate the i n - s i t u undrained shear s t r e n g t h , c o e f f i c i e n t of c o n s o l i d a t i o n and dr a i n e d c o n s t r a i n e d modulus. The r e s u l t s of these t e s t s are compared and d i s c u s s e d with respect 'to the r e s u l t s of t r a d i t i o n a l l a b o r a t o r y t e s t s , where a v a i l a b l e . 1.2 REPORT ORGANIZATION T h i s r e p o r t i s or g a n i z e d i n t o two s e c t i o n s . The f i r s t s e c t i o n , (chapters 2, 3 and 4), d e s c r i b e s a monitoring program of the t e s t f i l l . Chapter 2 d e s c r i b e s the observed behaviour of the t e s t f i l l . D e t a i l s are a l s o given concerning the c o n s t r u c t i o n of the t e s t f i l l , the i n s t r u m e n t a t i o n and the wick d r a i n s . Chapter 3 g i v e s background i n f o r m a t i o n about the i n - s i t u t e s t equipment and i n c l u d e s an i n t e r p r e t a t i o n of the t e s t s i n terms of t h e i r expected response to the changing c o n d i t i o n s below the t e s t f i l l . The groundwater c o n d i t i o n s are a l s o d i s c u s s e d i n t h i s chapter. Chapter 4 presents the r e s u l t s of the f i e l d m onitoring 3 program using three i n - s i t u t e s t techniques. These r e s u l t s are d i s c u s s e d with r e f e r e n c e to the observed behaviour of the t e s t f i l l . The second s e c t i o n of the r e p o r t , (chapters 5 and 6), d e s c r i b e s the d e t e r m i n a t i o n of s o i l p r o p e r t i e s by three i n -s i t u t e s t methods. Most of these t e s t s were performed adjacent to the t e s t f i l l to o b t a i n the i n i t i a l c o n d i t i o n s . Chapter 5 presents the undrained shear s t r e n g t h , c o e f f i c i e n t of c o n s o l i d a t i o n and d r a i n e d c o n s t r a i n e d modulus p r o f i l e s that r e s u l t e d from the t e s t i n g program. Chapter 6 e v a l u a t e s the u s e f u l n e s s of the d r a i n e d c o n s t r a i n e d modulus valu e s found i n Chapter 5 by using them i n a simple one-dimensional settlement a n a l y s i s . Conventional methods of p r e d i c t i n g s ettlements are i n c l u d e d f o r comparison. F i n a l l y , Chapter 7 p r e s e n t s the c o n c l u s i o n s of the r e s e a r c h i n three a r e a s : e v a l u a t i o n of i n - s i t u t e s t s f o r both m o n i t o r i n g embankments and f o r determining e n g i n e e r i n g p r o p e r t i e s of o r g a n i c s o i l s , and an e v a l u a t i o n of the performance of wick d r a i n s i n organic s o i l s . 4 I I . OBSERVED BEHAVIOUR OF THE-TEST FILL  2.1 GENERAL DESCRIPTION A f u l l y instrumented t e s t f i l l was c o n s t r u c t e d by the B r i t i s h Columbia Department of Highways at the north l a n d i n g of the proposed Annacis h i g h - l e v e l b r i d g e . In the p r o x i m i t y of the t e s t s i t e , f u t u r e embankments are to be c o n s t r u c t e d f o r highway access ramps to the b r i d g e . The t e s t f i l l was designed and c o n s t r u c t e d to serve a dual purpose: to determine the average c o n s o l i d a t i o n c h a r a c t e r i s t i c s of the organic s o i l s and to determine the c o n s o l i d a t i o n performance of an embankment over organic s o i l s when v e r t i c a l wick d r a i n s are used to improve the s u b s o i l d r a i n a g e . To achieve t h i s a s i n g l e t e s t embankment (80m long and 30m wide) was c o n s t r u c t e d with wick d r a i n s i n s t a l l e d i n one h a l f of the area while the opposite h a l f was l e f t i n a n a t u r a l s t a t e . These two h a l v e s of the embankment are r e f e r r e d to here as the wick d r a i n area and the non-wick area. C o n s t r u c t i o n of the t e s t f i l l was begun on October 21, 1981 and was completed to a f i l l height of 7m on January 28, 1982. D e t a i l e d f i e l d r ecords were kept d u r i n g the c o n s t r u c t i o n p e r i o d and were updated r e g u l a r l y as p a r t of a c o n t i n u i n g t e s t program c a r r i e d out by the B r i t i s h Columbia Department of Highways. The remaining s e c t i o n s of t h i s chapter w i l l give d e t a i l s of the s i t e , wick d r a i n s , i n s t r u m e n t a t i o n , c o n s t r u c t i o n program and f i e l d o b s e r v a t i o n s of the t e s t f i l l . F i n a l l y , the observed behaviour w i l l be 5 presented i n terms of observed s e t t l e m e n t s , r a t e of c o n s o l i d a t i o n and o v e r a l l performance. 2.2 SITE DESCRIPTION AND GENERALIZED GEOLOGY 2.2.1 S i t e D e s c r i p t i o n The s i t e i s l o c a t e d i n the Fra s e r River D e l t a about 30km east of Vancouver at the proposed Annacis Bridge on L u l u I s l a n d , see F i g u r e 2.1. The s i t e i s e s s e n t i a l l y l e v e l and l i e s at an e l e v a t i o n between 0.5m and 1.0m above mean sea l e v e l . Because such l o w - l y i n g ground i s v u l n e r a b l e to r i v e r f l o o d s , a system of dykes has been c o n s t r u c t e d along the r i v e r banks. The land was formerly used f o r g r a z i n g and i s i n i t s n a t u r a l s t a t e s u p p o r t i n g a t h i c k v e g e t a t i o n of g r a s s e s . 2.2.2 G e n e r a l i z e d Geology L u l u I s l a n d i s a major i s l a n d l o c a t e d i n the F r a s e r R i v e r d e l t a complex. The geology of the area has been thoroughly i n v e s t i g a t e d by Blunden, 1975, and the f o l l o w i n g d e s c r i p t i o n i s l a r g e l y based on h i s a n a l y s i s . The s u r f i c i a l d e p o s i t s of the i s l a n d are comprised of c l a y s , s i l t s and peats. These m a t e r i a l s were l a i d down i n a f l u v i a l environment of swamps and marshes to form d i s c o n t i n u o u s l e n s e s . The s u r f i c i a l d e p o s i t s o v e r l i e a sequence of sands and s i l t s having a maximum t h i c k n e s s of about 30m. Below t h i s l i e the p r o - d e l t a d e p o s i t s l a i d down by the advancing d e l t a f r o n t . The pro-d e l t a d e p o s i t s range i n t h i c k n e s s from 10m to 200m. The s i t e i s l o c a t e d on a p o r t i o n of the Lesser L u l u LEGEND :'ilTL F r a s e r River D e l t a Deposits A. Greater L u l u I s l a n d Bog B. Lesser L u l u I s l a n d Bog English Bay S t r a i t of Georgia VANCOUVER BURNABY Sea _L ^Island - s ^ r-'Lulu„IsJLand x B 7 I s l a n d Bog. The s u r f i c i a l d e p o s i t s c o n s i s t of about 6m of peat which has accumulated i n a marsh environment. From the s u r f a c e to a depth of 6m the peat grades from a young, f i b r o u s peat to a more amorphous peat at depth. The peat d e p o s i t s o v e r l i e organic c l a y s which are found to a depth of approximately 16m. The peat d e p o s i t s are d i s t i n g u i s h e d from the organic c l a y s by the l a r g e amount of f i b r o u s o r g a n i c s present i n the peat and the i n c r e a s e d m ineral content of the organic c l a y s . At 16m to 28m depth i s a medium dense sand l a y e r interbedded with compressible s i l t zones 1m to 2m t h i c k . The s o i l s of i n t e r e s t i n t h i s r e p o r t i n c l u d e the organic d e p o s i t s and the interbedded sands and s i l t s down to an e l e v a t i o n of -17 metres. A ge n e r a l s o i l p r o f i l e and range of water contents i s given below. E l e v a t i o n (metres) Wc% D e s c r i p t i o n +1 to -5 200-600 PEAT; f i b r o u s grading to amorphous. -5 to -14 60-100 ORGANIC CLAYS. -14 to -15 40-50 SILT to SILTY SAND; t r a n s i t i o n zone. -15 to -27 20-30 SAND; medium dense t o dense, interbedded with t h i c k SILT l e n s e s . 8 2.3 WICK DRAINS Since 1934 v e r t i c a l d r a i n s have been used as a method f o r deep s o i l s t a b i l i z a t i o n . The i n t r o d u c t i o n of d r a i n s i n t o a s o i l mass reduces the l e n g t h of the drainage path r e s u l t i n g i n an i n c r e a s e i n the r a t e of drainage, hence, a decrease i n the time r e q u i r e d f o r primary c o n s o l i d a t i o n . V e r t i c a l d r a i n s are e s p e c i a l l y e f f e c t i v e i n f i n e g r a i n e d s o i l s such as s i l t s and c l a y s which have a low p e r m e a b i l i t y . The t r a d i t i o n a l type of v e r t i c a l d r a i n i s a simple sand column formed by d r i v i n g , b o r i n g or j e t t i n g a hole and b a c k f i l l i n g with sand. Because of the t y p i c a l l y l a r g e diameter of sand d r a i n s the use of displacement methods can c r e a t e a c o n s i d e r a b l e zone of d i s t u r b e d s o i l around the d r a i n . In 1948 Kjellman developed the f i r s t band, or wick, type of d r a i n . The Kjellman d r a i n c o n s i s t e d of a f l a t cardboard core wrapped i n a t h i n cardboard f i l t e r sheet. Wick d r a i n s are commonly i n s t a l l e d by d r i v i n g which r e s u l t s i n a c o s t advantage over d r a i n s that r e q u i r e d r i l l i n g or j e t t i n g . A small diameter hollow mandrel i s used to i n t r o d u c e the d r a i n i n t o the ground. The wick d r a i n i s threaded down through the c e n t e r of the mandrel and a t t a c h e d to a d i s p o s a b l e end shoe. A f t e r i n s e r t i o n the end shoe serves to anchor the d r a i n at the d e s i r e d depth. At the t e s t f i l l s i t e d r i v i n g was e a s i l y accomplished with a top d r i v e v i b r a t o r . Modern v e r s i o n s of the Kjellman paper d r a i n use a p l a s t i c core and a f i l t e r made out of e i t h e r t r e a t e d paper or 9 en g i n e e r i n g g e o t e x t i l e . The wick d r a i n chosen f o r the t e s t f i l l was the Mebra d r a i n which f e a t u r e s a p l a s t i c inner core and a polypropylene f i l t e r f a b r i c , see Fi g u r e 2.2. The dimensions of the f i l t e r were 95mm width by 3.4mm t h i c k n e s s ; the assumed nominal diameter f o r design i s 63mm (McGown and Hughes, 1981). For the design of d r a i n spacing the d r a i n manufacturer s u p p l i e s graphs which only r e q u i r e knowledge of the h o r i z o n t a l c o e f f i c i e n t of c o n s o l i d a t i o n , C h, f o r the s o i l d e p o s i t . At the s i t e the c o n s o l i d a t i o n of the 8m t h i c k organic c l a y l a y e r u n d e r l y i n g the peat was expected to govern the desig n . The design value of f o r the organic c l a y , based on the r e s u l t s of standard incremental c o n s o l i d a t i o n t e s t s , was 0.13cm 2/min. To achieve 90% of primary c o n s o l i d a t i o n i n 2 months, a d r a i n spacing of 1.25 metres i s r e q u i r e d . I f no d r a i n s are i n s t a l l e d , the time f o r 90% c o n s o l i d a t i o n , c a l c u l a t e d f o r a c o n d i t i o n of uniform pore pressure d i s t r i b u t i o n and double drainage, i s about 25 months. A t o t a l of 832 wick d r a i n s were i n s t a l l e d i n a t r i a n g u l a r p a t t e r n at 1.25m spacing over an area 32m by 26m. The depth of i n s t a l l a t i o n was s p e c i f i e d to pene t r a t e i n t o the sands at a depth of 16 metres. 2.4 INSTRUMENTATION The t e s t f i l l p l a n n i n g i n c l u d e d a s u f f i c i e n t number of instruments so that a l l aspects of the s u b s o i l behaviour c o u l d be monitored. A diagram of the ins t r u m e n t a t i o n l a y o u t i s given i n F i g u r e 2.3. A summary of the below-ground F i g . 2 . 2 The MEBRA-DRAIN type of wick d r a i n : i l l u s t r a t i n g the d r a i n body and porous o u t e r f i l t e r j a c k e t . o M.H. + S.I. M.H. o jfc VS-619X WICK DRAIN AREA 832 wick drains I n s t a l l e d to 16 M. depth on 1.2S M. centers -r S.I. S.S.P., S.P.-614 M.H. | "X"VS-620 " *S . S . P .-606 — o — AREA WITHOUT WICK DRAINS (Non-Wick Area) — S.S.P. — o -*S.S.P.-604 S.S.P.. S.P.-612 P.P.-604a • ® - v s - 6 0 l a " X — f\] _ 7<P . P. -607a S.P.-609 •Vp.P.-609a,b * H- v jiO.S.P.-607 * H VS-603aX * -O VS-617X" fo] S.S.P. . S.P.-613 S.S.P. >*P .P.-605a_) b s.S.P. S.S.P. S.S.P.j S.P.-611 ( Test F111 Slope =• 1.0:1.5 ) VS-618X P.P.-610a P.P.-608a 0 O .H. 0 M.H. +S.I. 0 M.H. M.H.o o M.H. 0 M.H. + S - 1 • o M.H. M.H. O N _J_ LEGEND | |—-—S.S.P. Surface Settlement Plate |\]—D.S.P. Deep Settlement Plate fo] S.P. Standplpe Piezometer O — P.P. Petur Piezometer ii. Primary instruments f o r observations « — A.H. Auger Hole made In t h i s report. -(- — S . I . Slope Indicator o —M.H. Movement Hubs (22) Fig. 2.3 TEST FILL: Instrumentation Layout 1 2 i n s t r u m e n t a t i o n i s given i n Table 2.1 and F i g u r e 2.4. In a l l there are 10 s u r f a c e settlement p l a t e s , 2 deep settlement p l a t e s , 4 standpipe piezometers, 12 Petur pneumatic piezometers, 22 movement hubs and 4 slope i n d i c a t o r c a s i n g s . The movement hubs c o n s i s t e d of wooden stakes d r i v e n i n t o the s u r f a c e peat mat so that s u r f a c e heave adjacent to the t e s t f i l l c o u l d be monitored. Instrument f a i l u r e was common du r i n g the course of c o n s t r u c t i o n . The f a i l u r e s that o c c u r r e d with the piezometers, both pneumatic and standpipe, were the g r e a t e s t detriment to the t e s t r e c o r d s . S e v e r a l piezometers were i n s t a l l e d at -5m e l e v a t i o n j u s t below the f i b r o u s peats. The l a r g e s e t t l e m e n t s tended to d i s r u p t these shallow piezometers. The gas compensated Petur piezometers which are l i n k e d to the s u r f a c e by nylon tubing were the most v u l n e r a b l e to l a r g e s o i l s e t t l e m e n t s . During the winter months some anomolous readings were recorded f o r the standpipe piezometers. These were probably the r e s u l t of f r e e z i n g . A general problem with a l l the piezometer data was that the i n i t i a l 'zero' readings were not p r o p e r l y e s t a b l i s h e d p r i o r to the s t a r t of c o n s t r u c t i o n a c t i v i t y , hence, the accuracy of the data i s somewhat q u e s t i o n a b l e . Some instrument f a i l u r e was expected, however, and replacement piezometers were i n s t a l l e d when f a i l u r e s o c c u r r e d i n key l o c a t i o n s . L i t t l e u s e f u l i n f o r m a t i o n was gained from the movement hubs which t i l t e d as the heave adjacent to the f i l l i n c r e a s e d . The slope i n d i c a t o r c a s i n g s performed w e l l up to the p o i n t when l a r g e l a t e r a l s t r a i n s i n 13 TABLE 2. 1 LOCATION OF BELOW-GROUND INSTRUMENTATION  Piezometers s p -603 • - Petur Piezometers at -4M. , -7M.(cancelled 25-11-81) s p -604 - Petur Piezometers at -5M. . -13M.(cancel led 25-11-81) s p -605 • - Petur Piezometers at -5M. , -13M.(cancelled 25-11-81) s p -606 • - Petur Piezometers at -2M. . -7M.(cancel led 30-11-81) s p -611 • - Standpipe Piezometer at -6 .8M. s p -612 -- Standpipe Piezometer at -6 ,8M. s p -613 • - Standpipe Piezometer at -7 .4M. s p -614 • - Standpipe Piezometer at -8 .OM. p p -604a -- Petur Piezometers at -5M. , -13M. p p -605a • • Petur Piezometers at -5M. , -13M.(cancel led 25-01-82) p p -605b • - Petur Piezometer at --6.5M. ; i n s t a l l e d 11-02-82 p p -607a • - Petur Piezometers at -5M. , -9.6M.(5M. cancelled 25-01-82) p p -608a -• Petur Piezometers at -5M. , -9.3M.;Located on side of F111 p p -609a -• Petur Piezometers: (Not operational since 07-12-81) p p -609b -- Petur Piezometer at --8.2M. ; i n s t a l l e d 11-02-82 p p -610a. - Petur Piezometers at -4M. , -9M.(9M. cancelled 13-01-82); Located on side of F i l l . Deep Sett 1ement P1ates D.S.P.-607 - Located in medium-dense sand at -17.OM. D.S.P.-609 - Located in medium-dense sand at -17.3M. F i g . 2.4 Below ground i n s t r u m e n t a t i o n as of January, 1982. 1 4 the s u b s o i l caused l a r g e bends i n the c a s i n g so that the slope i n d i c a t o r instrument c o u l d not pass. F i g u r e 2.3 a l s o i n d i c a t e s the primary instruments chosen to represent the t e s t f i l l behaviour i n t h i s paper. The c r i t e r i a f o r choosing these instruments was based on, (a) p r o x i m i t y of the instrument to the cente r of the wick or non-wick area, (b) a long and c o n s i s t e n t performance r e c o r d and, ( c ) , a l o c a t i o n c l o s e t o the mid-depth of the compressible s o i l s . 2.5 LOADING SEQUENCE The technique of stage l o a d i n g was used to c o n s t r u c t a l a r g e , s t a b l e p r e l o a d . C o n s t r u c t i o n began i n e a r l y October, 1981, with the placement of a granular working pad. T h i s pad allowed v e h i c l e access onto the s i t e f o r i n s t a l l a t i o n of the wick d r a i n s . The t e s t f i l l piezometers and settlement instruments were monitored r e g u l a r l y d u r i n g c o n s t r u c t i o n f o r warning of any p o t e n t i a l i n s t a b i l i t y . Staged l o a d i n g began i n e a r l y December, 1981, with two s u c c e s s i v e 1.5m l i f t s of f i l l sand. A d d i t i o n a l l i f t s were added at i n t e r v a l s ranging from 1 week to 1 month, see F i g u r e 2.5. Uneven l o a d i n g was minimized by beginning the placement of sand f i r s t from the south end and then from the north end on s u c c e s s i v e l i f t s . In a l l , 4 l i f t s of 1.5m each p l u s the i n i t i a l 1m pad were placed b r i n g i n g the t o t a l f i l l t h i c k n e s s to 7m. C o n s t r u c t i o n was completed on January 28, 1982, n i n e t y - e i g h t days a f t e r the working pad was p l a c e d . C o n s t r u c t i o n day 98 i s r e f e r r e d to i n Fig.2.5 TEST FILL: C o n s t r u c t i o n Sequence 16 t h i s r e p o r t as the 'End of C o n s t r u c t i o n ' . On March 23, 1982 an a d d i t i o n a l 1.5m of f i l l was p l a c e d on the area with wick d r a i n s . The purpose of the a d d i t i o n a l f i l l was t o " t e s t the wick d r a i n area with loads i n excess of d e s i g n . 2.6 FIELD OBSERVATIONS A l l instrument readings were recorded by f i e l d t e c h n i c i a n s of the B r i t i s h Columbia Department of Highways, C o n s t r u c t i o n Branch. The s u r f a c e settlement, deep settlement, excess porewater pressure and embankment pr e s s u r e are p l o t t e d versus l o g time f o r both the non-wick and wick areas i n F i g u r e 2.6 and 2.7. A l s o noted on F i g u r e s 2.6 and 2.7 are the t e s t dates of the i n - s i t u t e s t i n g program. The measured s u r f a c e s e t t l e m e n t s i n F i g u r e s 2.6 and 2.7 have been c o r r e c t e d f o r deep settlement and t h e r e f o r e represent the settlement o c c u r r i n g i n the peat and organic c l a y only.• No settlement p l a t e s were i n s t a l l e d at the bottom of the peat so the c o n t r i b u t i o n of each s o i l group cannot be separated. S u b s t a n t i a l heave i n the n a t u r a l ground surrounding the t e s t f i l l and a sudden i n c r e a s e i n settlement i n the non-wick area was observed i n c o n j u n c t i o n with placement of l i f t No.5 at the end of c o n s t r u c t i o n . The observed heave and settlement i s t y p i c a l of a s u b s o i l f a i l u r e o f t e n c a l l e d a mud-wave type of f a i l u r e . The volume of d i s p l a c e d s o i l was estimated from o b s e r v a t i o n s of s u r f a c e heave and slope i n d i c a t o r l a t e r a l movement adjacent to the non-wick area. The estimated volume it. A \oo W 5 IV t -3 2 s 2tf a £7 4.<? I L IFT #4 ("1^2 M ) L I P T *?> (OM L I F T # 2 f l ' / f M ^ L I F T * I 7 M - FILL EMt>AWK.MENT LCADIM<& ('h-Fh') MEA^>UR£p o OBSERVED o - o - o - 0 v t . V EST IMATED \ S>TANDPIr*E PIEZOMETER, N<?. £C?7A E L E * -9. B M P OF COHSr%UC^\OH *\ SO _L_ LOG T I M E _J r- I c* o I 3 (0 SUK.PACE ©ETTLEfv fEKJT t=lATE N o . <2-e4 SETTLE VfENT C-<9K.KJS£-T£ D £>Y METKEv F^R, SUfceoiL FAILURE. _^ L A- I M M E D I A T E - S E T T L E M E N T - < 7 . £ M 4 E>. U M P / N I £ H E D S E T T L E M E N T + (AT T I M E = AOO P A Y S ) = I •! MI aJ 3 4 0.0 \00 200 AOO OH 2 c.2-1 S E T T L E M E N T P L A T E N o . 6>Cn tlEV. -\C\\A <ft P. 5 J F i g . 2.6 NON-WICK AREA: Observed Settlement and Excess Pore Pressure versus Log Time. a'/2 M. OF F ILL I r-1 r--J & 0 . P 1.67 2.(7-J 4 . 0 - 1 A. I M M E D I A T E - S E T T L E M E N T - <?.5>M-S U R F A C E S E T T L E M E N T P L A T E N o . ft>. P R I M A R Y S t T T L E M E M T = C . UNF IN ISHED StCOH&t&X" S E T T L E M E N T (AT T I M E = 4 0 C D A Y S ) = O - I & M . ESTIMATED END £>F PKJMArVT C-CN&OLIDATIOM 1 3 4 lU i l<7£> ZOO DEEP S E T T L E M E N T P L A T E <?,!», J No. (2*79 ELEV. -!(£.. 2. M. CD F i g . 2.7 WICK AREA: Observed Settlement and Excess Pore Pressure versus Log Time. 19 of d i s p l a c e d s o i l accounted f o r approximately 0.6m of settlement i n the non-wick a r e a . The observed s u r f a c e settlements i n the non-wick area are subsequently decreased by 0.6m to c o r r e c t f o r the s u b s o i l f a i l u r e . Because the two t e s t f i l l areas are p h y s i c a l l y coupled there was a p o s s i b i l i t y of some d i s t u r b a n c e i n the settlement of the wick area due to the non-wick f a i l u r e . The wick area settlement records i n d i c a t e that the d i s t u r b a n c e was s l i g h t and was'therefore n e g l e c t e d . The piezometer responses p l o t t e d i n the F i g u r e s 2.6 and 2.7 amount to an approximation of the a c t u a l pore pressure c o n d i t i o n s . The c o n s t r u c t i o n program was begun before constant i n i t i a l readings had been e s t a b l i s h e d . Consequently, the piezometer records have been c o r r e c t e d to a zero i n i t i a l r e a d i n g . For convenience, piezometer readings were taken only d u r i n g daytime hours thus d e c r e a s i n g the chance of measuring a peak pore pressure that occurs a f t e r l o a d i n g . Anomolous readings o c c u r r e d f o r standpipe piezometer 607A in the non-wick a r e a . A f t e r day 110 the measured pore pre s s u r e s were very high and showed l i t t l e tendency f o r d i s s i p a t i o n . At around day 250 the measured pore pressure dropped suddenly to a lower l e v e l . Examination of standpipe piezometer 611 data i n d i c a t e s that pore pr e s s u r e s decreased s t e a d i l y a f t e r the end of c o n s t r u c t i o n . Based on t h i s evidence the estimated pore pressure response has been added to F i g u r e 2.7. For the wick d r a i n area two piezometer records were r e q u i r e d . Piezometer 605A f a i l e d j u s t p r i o r t o the end of c o n s t r u c t i o n and the i n t e r i m time, u n t i l replacements were 20 i n s t a l l e d , i s estimated from the previous response of 605A. The embankment l o a d i n g represents the pressure at the base of the embankment under the f i l l c e n t e r l i n e . The embankment l o a d i n g i s a d j u s t e d f o r buoyancy e f f e c t s due to settlement below the ground water t a b l e . Because of g r e a t e r submergence i n the wick end, the embankment pressure i s o f t e n l e s s than that estimated f o r the non-wick a r e a . 2.6.1 Observed Settlements For convenience of p r e s e n t a t i o n the settlement versus l o g time curves, ( F i g u r e s 2.6 and 2.7), begin a t day 20 when about 0.5m of settlement had occured. A l a r g e p o r t i o n of the settlement response to the f i r s t l i f t of f i l l was completed by day 6. No anomolous behaviour was observed during the f i r s t 20 days of settlement. Common methods used to c a l c u l a t e immediate set t l e m e n t s d i d not give reasonable estimates f o r the organic s o i l s . The immediate settlement f o r each l i f t i s estimated from the settlement curves t o be about 10cm. T h i s g i v e s a t o t a l immediate settlement of 0.5metres f o r each end of the f i l l . A c c o r d i n g to the piezometer r e c o r d s , the non-wick area at 400 days a f t e r the s t a r t of c o n s t r u c t i o n has not yet completed primary c o n s o l i d a t i o n . The c o n t r i b u t i o n to primary settlement at 400 days i s 1.7 metres. Piezometer records f o r the wick area i n d i c a t e that primary c o n s o l i d a t i o n was e s s e n t i a l l y completed by day 245. Small r e s i d u a l pore pressures are commonly observed d u r i n g the t r a n s i t i o n phase from primary c o n s o l i d a t i o n to secondary c o n s o l i d a t i o n . The primary 21 c o n s o l i d a t i o n settlement f o r the wick area i s about 3.0 metres. The c o n t r i b u t i o n to secondary compression which had o c c u r r e d by day 400 i s about 0.15 metres. The deep settlement f o r the wick and non-wick area at day 400 i s about 30cm and 8cm r e s p e c t i v e l y . 2.6.2 C o n s o l i d a t i o n Behaviour 1. Rate Of C o n s o l i d a t i o n The d e t e r m i n a t i o n of the r a t e of c o n s o l i d a t i o n i s one of the main o b j e c t i v e s of t h i s t e s t f i l l program. The parameter used to d e s c r i b e the rate of c o n s o l i d a t i o n i s the c o e f f i c i e n t of c o n s o l i d a t i o n given by the equation: C v = TH 2/tq 0 ( f o r v e r t i c a l drainage) where, C v = a v e r t i c a l c o e f f i c i e n t of c o n s o l i d a t i o n f o r a degree of c o n s o l i d a t i o n at time t q o (cm 2/min) T = non dimensional time f a c t o r ( t h e o r e t i c a l ) H = l e n g t h of drainage path t«j0 = time (minutes) The time f o r c o n s o l i d a t i o n to occur, u s u a l l y 90% of primary c o n s o l i d a t i o n , i s commonly determined by one of three methods: T a y l o r ' s root^time c u r v e f i t t i n g method, Casagrande's log-time c u r v e f i t t i n g method and Gould's method. A c c o r d i n g to Moran (1958), Gould's method allows computation of the c o e f f i c i e n t of c o n s o l i d a t i o n d u r i n g d i s c r e t e time i n t e r v a l s from estimates of the i n i t i a l and f i n a l degree of c o n s o l i d a t i o n f o r the i n t e r v a l . T h i s method i s p a r t i c u l a r l y u s e f u l when loads are a p p l i e d at an i r r e g u l a r r a t e . 22 Values of the c o e f f i c i e n t of c o n s o l i d a t i o n can be mi s l e a d i n g unless the c o n d i t i o n s f o r which they are v a l i d are s t a t e d . The c o e f f i c i e n t of c o n s o l i d a t i o n depends on the le n g t h . of the drainage path, an accurate d e t e r m i n a t i o n of the time r e q u i r e d f o r completion of primary c o n s o l i d a t i o n and the i n i t i a l pore pressure d i s t r i b u t i o n . The de t e r m i n a t i o n of the c o e f f i c i e n t of c o n s o l i d a t i o n i s only p o s s i b l e when c e r t a i n t y e x i s t s about the magnitude of the u l t i m a t e settlement ( i . e . that the magnitude of the secondary compression i s known). .For organic s o i l s the magnitude of the secondary compression i s g e n e r a l l y very l a r g e . A l s o , a comparison between C v from d i f f e r e n t t e s t s r e q u i r e s that the i n i t i a l d i s t r i b u t i o n s of excess pore pressure be s i m i l a r . In the wick d r a i n area the excess pore p r e s s u r e s vary i n both the v e r t i c a l and h o r i z o n t a l d i r e c t i o n and are t h e r e f o r e not s i m i l a r to the p u r e l y v e r t i c a l d i s t r i b u t i o n assumed f o r the area without wick d r a i n s . F i n a l l y , the c o e f f i c e n t of c o n s o l i d a t i o n f o r peats i s known to change d r a m a t i c a l l y with l o a d i n g . T h e r e f o r e , the value'of C v must be s p e c i f i e d with a p a r t i c u l a r l o a d . When a l a r g e amount of settlement occurs d u r i n g each l o a d increment, as observed f o r the t e s t f i l l , the o v e r a l l f i e l d behaviour would be b e t t e r d e s c r i b e d by a value of Cy f o r each increment. In c o n c l u s i o n , attempts to q u a n t i f y the c o e f f i c i e n t of c o n s o l i d a t i o n f o r the t e s t f i l l were found to be both u n r e p r e s e n t a t i v e of the a c t u a l f i e l d behaviour and t h e o r e t i c a l l y unsound. C a l c u l a t e d v a l u e s of the c o e f f i c i e n t of c o n s o l i d a t i o n from f i e l d o b s e r v a t i o n s are t h e r e f o r e 23 r e p u d i a t e d . 2. F i e l d V o i d R a t i o Versus Log E f f e c t i v e S t r e s s Curves The compression c h a r a c t e r i s t i c s of s o i l s are t y p i c a l l y represented by p l o t t i n g v o i d r a t i o (e) versus l o g e f f e c t i v e s t r e s s ( p ' ) . F i g u r e 2.8 i l l u s t r a t e s the e - l o g p ( t o t a l s t r e s s ) and e - l o g p' curves c a l c u l a t e d from the observed f i e l d r e c o r d s . The i n i t i a l v o i d r a t i o was estimated from an e m p i r i c a l c o r r e l a t i o n to water content (Lea and Brawner, 1963). Changes i n v o i d r a t i o were c a l c u l a t e d u sing the f i n a l settlement readings f o r each stage of c o n s t r u c t i o n . The t o t a l s t r e s s e s are estimates of embankment pre s s u r e under the c e n t r e l i n e of the f i l l . The e f f e c t i v e s t r e s s curves were c o n s t r u c t e d by s u b t r a c t i n g the f i e l d excess pore pressure measured at the end of each stage of c o n s t r u c t i o n from the t o t a l s t r e s s embankment p r e s s u r e . Because the embankment l o a d and settlement represent c o n d i t i o n s at the s u r f a c e and the pore pr e s s u r e s represent c o n d i t i o n s at depth (6 to 11 metres depth), the r e s u l t i n g e - l o g p' curves are only approximate. As can be seen, the wick and non-wick e f f e c t i v e s t r e s s curves do not c o i n c i d e . As d i s s i p a t i o n c o n t i n u e s , the curves approach each other as would be expected. The d i f f e r e n c e s between the e f f e c t i v e s t r e s s curves are exaggerated by the l o g a r i t h m i c s c a l e at low p r e s s u r e s . The t o t a l s t r e s s data p o i n t corresponding to L i f t No.5 (55 days d u r a t i o n ) f o r the wick area represents the c o n d i t i o n s at 55 days a f t e r the end of c o n s t r u c t i o n when the wick area i s approaching the end of primary c o n s o l i d a t i o n . T h i s s i t u a t i o n 8.5 N3 F i g . 2.8 10 20 50 Log P', Log p (KPa) F i e l d v o i d r a t i o v e r s u s l o g e f f e c t i v e s t r e s s and l o g t o t a l s t r e s s . 200 500 25 i s compared to the c o n d i t i o n s f o r the non-wick t o t a l s t r e s s data p o i n t L i f t No.5 (250 days d u r a t i o n ) . At 250 days a f t e r the end of c o n s t r u c t i o n , d i s s i p a t i o n of pore pre s s u r e s i s c o n t i n u i n g i n the non-wick area. If the non-wick area i s to achieve a s i m i l a r magnitude of c o n s o l i d a t i o n ( i . e . s i m i l a r v o i d r a t i o ) to that of the wick area, as i s expected, then F i g u r e 2.8 c l e a r l y demonstrates that a c o n s i d e r a b l e w a i t i n g p e r i o d w i l l be r e q u i r e d . I t can be seen that a d d i t i o n a l time would be r e q u i r e d i f the non-wick area had not f a i l e d . F i g u r e 2.8 a l s o i n d i c a t e s that the wick d r a i n s were p a r t i c u l a r l y e f f e c t i v e a f t e r the placement of l i f t No.3. T h i s i s i n agreement with the r e s u l t s of other t e s t embankments on peats where the use of sand d r a i n s under minor l o a d i n g c o n d i t i o n s gave no a p p r e c i a b l e b e n e f i t (MacFarlane, 1969). The approximate e f f e c t i v e s t r e s s curves do not y i e l d a p r e c i s e value of the p r e c o n s o l i d a t i o n p r e s s u r e . A c a l c u l a t e d value of the maximum past e f f e c t i v e s t r e s s i s i n d i c a t e d on F i g u r e 2.8. The compression index i s approximately 1.8 f o r the e f f e c t i v e s t r e s s c u r v e s . For the depth of i n t e r e s t at the t e s t f i l l , where the average water content i s about 200%, t h i s value of compression index i s reasonable. A change of c u r v a t u r e can be seen i n the wick area e f f e c t i v e s t r e s s curve as the end of primary c o n s o l i d a t i o n i s approached. Such a change i n c u r v a t u r e i s t y p i c a l of a t r a n s i t i o n from primary c o n s o l i d a t i o n to secondary compression. 26 I I I . IN-SITU TESTING IN ORGANIC SOILS  3.1 FIELD VANE TESTING 3.1.1 Equipment The i n - s i t u vane t e s t i n g d i s c u s s e d i n t h i s r e p o r t was made with a N i l c o n Swedish Vane Borer s u p p l i e d by the B r i t i s h Columbia Department of Highways. The f i e l d vane t e s t i s an economical and easy to perform method of d i r e c t l y determining the undrained shear s t r e n g t h of c l a y s . The N i l c o n Swedish Vane Borer c o n s i s t s of a p o r t a b l e frame and a hand operated torque d r i v e which was developed s p e c i f i c a l l y f o r the t e s t i n g of s o f t cohesive s o i l s . A f e a t u r e of the N i l c o n u n i t i s the lack of a p r o t e c t i v e c a s i n g around the rods which allows speedier o p e r a t i o n . A 15 degree s l i p c o u p l i n g at the vane connection allows an independent measurement of rod f r i c t i o n to be made p r i o r to each t e s t . Hardened s t e e l vanes are s u p p l i e d i n three s i z e s : s m a l l , 11.0cm long X 5.0cm diameter; medium, 13.0cm long X 6.5cm diameter and l a r g e , 17.2cm long X 8.0cm diameter. A l l vane p r o f i l e s except one were made using the medium s i z e d vane. 3.1.2 I n t e r p r e t a t i o n The f i e l d vane t e s t r e p r e s e n t s one of the e a r l i e s t t e s t s to measure the shear s t r e n g t h of a s o i l i n - s i t u , and today i t remains a popular method f o r d e t e r m i n a t i o n of the undrained shear s t r e n g t h i n cohesive s o i l s . From an e n g i n e e r i n g standpoint, the i n t e r p r e t a t i o n of vane shear s t r e n g t h i s based 27 l a r g e l y on experience rather than on t h e o r e t i c a l understanding of the t e s t . T h i s s e c t i o n w i l l b r i e f l y d i s c u s s some of the t o p i c s concerning f i e l d vane t e s t i n g i n peats. • E f f e c t of vane s i z e . A t o p i c of r e s e a r c h d u r i n g the 1960's was the e f f e c t of vane s i z e on vane r e s u l t s . C a d l i n g and Odenstad (1950). performed vane t e s t s i n Swedish c l a y s and concluded t h a t , f o r vanes with a height to diameter r a t i o of 2, the vane diameter has no e f f e c t on the t e s t r e s u l t s . Research by T e s s i e r (1967) using f i e l d vanes i n f i b r o u s peat showed a s i g n i f i c a n t i n c r e a s e i n measured shear s t r e n g t h with d e c r e a s i n g vane diameter. Helenelund (1968) showed that peat s t r e n g t h i s mainly d e r i v e d from a combination of f i b r e s t r e n g t h and peat matrix s t r e n g t h with f i b r e s t r e n g t h being the dominant source of s t r e n g t h . Northwood and Sangrey (1971) suggested that the i n c r e a s e i n shear s t r e n g t h measured by T e s s i e r was due to the g r e a t e r i n f l u e n c e of f i b r e s t r e n g t h on a reduced f a i l u r e s u r f a c e area d e s c r i b e d by the small diameter vanes. Using f i v e vane s i z e s , Northwood and Sangrey showed that shear s t r e n g t h i s e s s e n t i a l l y independent of vane diameter but that the s m a l l e r vane s i z e s tend to give a l a r g e r s c a t t e r i n r e s u l t s . To achieve g r e a t e r c o n s i s t e n c y between r e s e a r c h e r s an optimum vane s i z e of 20cm long X 10cm diameter was suggested by Northwood and Sangrey (1971) as a minimum vane s i z e t h at i s fre e of s i z e e f f e c t s . T h i s w r i t e r has conducted f i e l d vane t e s t s at the i n i t i a l c o n d i t i o n s s i t e (VS-1, VS-2) to compare the medium vane and l a r g e vane at s i m i l a r depths 28 between 3.5 and 6.5 metres. The r e s u l t s of the t e s t s VS-1 and VS-2 were s i m i l a r i n d i c a t i n g t h at at the t e s t f i l l s i t e the medium s i z e d vane i s of s u f f i c i e n t s i z e to i n v o l v e a r e p r e s e n t a t i v e number of f i b r e s i n i t s f a i l u r e s u r f a c e . • Rate e f f e c t s . Rate of t e s t i n g e f f e c t s (degrees r o t a t i o n per u n i t time) were i n v e s t i g a t e d at shallow depths i n two mossy peats and one woody f i b r o u s peat by Northwood and Sangrey (1971) and i n one sphagnum moss peat by Landva (1980). For each of the peat types the s t r e n g t h was found to be r a t e independent under the low e f f e c t i v e normal s t r e s s e s . However, f o r l e s s permeable organic s o i l s at depth, r a t e e f f e c t s may become important. • A n i s o t r o p y . Because of the h o r i z o n t a l o r i e n t a t i o n of the f i b r e s i n a f i b r o u s peat i t i s l i k e l y that some a n i s o t r o p y with r e s p e c t to shear s t r e n g t h would e x i s t . However, l i t t l e i n - s i t u r e s e a r c h has been done on peat d e p o s i t s . Northwood and Sangrey (1971) conducted i n - s i t u t e s t s with s p e c i a l vanes that t e s t e d f a i l u r e planes at 45 degrees to the v e r t i c a l and concluded that the peat was stronger when t e s t e d i n the v e r t i c a l d i r e c t i o n than in other d i r e c t i o n s . Landva (1980) made c a r e f u l o b s e r v a t i o n s of the f a i l u r e mechanism of the vane i n sphagnum peats. He concluded t h a t , even f o r a r e l a t i v e l y n o n - f ibrous mossy peat, the vane shear s t r e n g t h r e f l e c t s an a r t i f i c i a l f i b r e matting s t r e n g t h . According to Landva (1980) the mode of deformation of peat i n vane shear has l i t t l e i n common with the behaviour of peat below t y p i c a l b u i l d i n g f oundations. Because of the 29 d i f f i c u l t y i n v o l v e d i n i n t e r p r e t i n g vane shear mechanisms i n peat the value of the t e s t i s reduced somewhat to that of a s t r e n g t h index t e s t . In common p r a c t i c e the f i e l d vane data can be s u c c e s s f u l l y used when c o r r e l a t i o n s are developed from l o c a l e x perience. A l l the vane t e s t s at the t e s t f i l l s i t e were performed by personnel of the B r i t i s h Columbia Department of Highways as p a r t of t h e i r t e s t f i l l m o n i t o r i n g program. 3.2 CONE PENETRATION TEST (CPT) 3.2.1 Equipment The s t a t i c e l e c t r i c piezometer f r i c t i o n cone p e n e t r a t i o n t e s t , r e f e r r e d to here simply as the cone p e n e t r a t i o n t e s t (CPT) i s now widely accepted as the premier i n - s i t u s t r a t i g r a p h i c l o g g i n g t o o l f o r a wide v a r i e t y of s o i l c o n d i t i o n s . The main reasons f o r the i n c r e a s i n g i n t e r e s t i n cone p e n e t r a t i o n t e s t s are the s i m p l i c i t y of t e s t i n g , the r e p r o d u c i b i l i t y of r e s u l t s and the g r e a t e r a m e n a b i l i t y of the t e s t data to r a t i o n a l a n a l y s i s (Robertson, 1982). The cones used i n t h i s study were f a b r i c a t e d at the U n i v e r s i t y of B r i t i s h Columbia (UBC) with dimensions conforming to the European and American Standards (ISSMFE, 1977; ASTM, D3441-79, 1979). The UBC cones have a 10cm2 base area cone t i p with an apex angle of 60 degrees and a f r i c t i o n s l e e v e , l o c a t e d above the c o n i c a l t i p , with a s u r f a c e area of 150cm 2. The UBC cones are a l s o equipped with a pore pressure element which i s l o c a t e d j u s t behind the cone t i p , see F i g u r e 30 3.1. The a d d i t i o n of the pore pressure element a l l o w s for the continuous measurement of dynamic pore p r e s s u r e s (during p e n e t r a t i o n ) and e q u i l i b r i u m pore pressures (at r e s t ) . The a d d i t i o n of pore pressure measurements d u r i n g CPT i s c o n s i d e r e d to be the most s i g n i f i c a n t recent development i n t h i s form of t e s t i n g (Robertson, 1982). The UBC e l e c t r i c cones have two b u i l t - i n l o a d c e l l s that c o n t i n u o u s l y r e c o r d the end r e s i s t a n c e (Qc) and the s i d e f r i c t i o n ( F c ) . A d r o p - i n m i n i a t u r e pressure transducer i s used to r e c o r d the pore pressure (u) c o n t i n u o u s l y . The cones are a l s o f i t t e d with a slope i n d i c a t o r which i s used to monitor the v e r t i c a l i t y d u r i n g p e n e t r a t i o n . An e l e c t r i c cable connects the cone with the r e c o r d i n g equipment at ground s u r f a c e . 3.2.2 Accuracy Research at UBC has shown that the UBC cones operate w e l l i n the sands, s i l t s and c l a y s of the F r a s e r R i v e r d e l t a and that the s e n s i t i v i t y of the cone i s a p p r o p r i a t e f o r these s o i l s . However, the s o i l s at the t e s t f i l l s i t e are extremely s o f t having measured valu e s of Qc between 1 bar and 7.5 bar: between 0.2% and 1.4% of the working end bearing c a p a c i t y (540 b a r ) . At such low end b e a r i n g the l o a d c e l l i s o p e r a t i n g below i t s designed l o a d range and the accuracy becomes important. . de R u i t e r (1981) quotes some values of e r r o r f o r Fugro e l e c t r i c cones which apply t o the l i n e a r i t y and h y s t e r e s i s of the cone l o a d c e l l d u r i n g c a l i b r a t i o n . Under 31 -swoge fitting to lock 10 conductor coble strain gages for-friction load cell thermister-pressure tronsducer-porous plastic--wires spliced to coble inside tube -slope sensor ^equal end area |> friction sleeve (I50cm*area ) -strain gages for cone bearing load cell O - r ings Quad ring smoll cavity--60° cone 35.68mm O.D. F i g . 3.1 5-CHANNEL CONE PENETROMETER. ( a f t e r Campanella and Robertson, 1981) 32 res e a r c h type o p e r a t i n g c o n d i t i o n s the e r r o r i n end bearing i s l e s s than 1% of c a p a c i t y and the zero load e r r o r , when returned to the no loa d c o n d i t i o n f o l l o w i n g a l o a d i n g , i s l e s s than 0.1% of c a p a c i t y . S i n g l e p o i n t c a l i b r a t i o n s of the UBC cones were made to 200 bar. Using de R u i t e r ' s (1981) f i g u r e s would i n d i c a t e that the e r r o r i s l e s s than 2 bar. The r e s u l t s from t h i s study i n d i c a t e t hat UBC cones, under r e s e a r c h c o n d i t i o n s , have an accuracy of about ±0.1% or about ±0.2 bar. The accuracy depends on zero s t a b i l i t y r a t h e r than l i n e a r i t y and h y s t e r e s i s at these low s t r e s s l e v e l s . The UBC cones demonstrated t h e i r r e l i a b i l i t y throughout the i n v e s t i g a t i o n . T h i s i s a t t r i b u t e d p a r t l y t o the q u a l i t y of the UBC cone c o n s t r u c t i o n and p a r t l y to the thorough t e s t procedures f o l l o w e d f o r each sounding. Experience with UBC cones i n d i c a t e s t h a t zero l o a d e r r o r or zero s t a b i l i t y can be a f f e c t e d by changes i n temperature. I f the above ground temperature i s d i f f e r e n t from the below ground temperature then the cone body temperature changes during a sounding c a u s i n g a thermal d r i f t i n the zero l o a d reading. Although t h i s thermal d r i f t i s u s u a l l y small- i t can sometimes be s i g n i f i c a n t i n s o f t s o i l s (Campanella and Robertson, 1981). The m i n i a t u r e t h e r m i s t o r i n s t a l l e d i n the UBC f i v e - c h a n n e l cone was not o p e r a t i o n a l d u r i n g the t e s t f i l l study due to i n c o m p a t i b i l i t i e s i n the cone c a b l i n g system. Th e r e f o r e , a l l cone logs which e x h i b i t e d a thermal zero d r i f t when recovered from a sounding were c o r r e c t e d by assuming the thermal d r i f t o ccurred l i n e a r l y with depth over an average 33 depth of sounding of t h i r t y metres. However, i t i s l i k e l y t h a t most of the thermal d r i f t o c c u r r e d i n the f i r s t f i f t e e n minutes or w i t h i n about ten metres depth. The e r r o r in assuming a l i n e a r v a r i a t i o n over t h i r t y metres versus ten metres i s not c o n s i d e r e d to be l a r g e . The use of a lower c a p a c i t y cone, such as a 1 ton cone, i s u s u a l l y recommended for the very s o f t s o i l s that e x i s t at the t e s t f i l l s i t e . Again, u s i n g de R u i t e r ' s (1981) f i g u r e s , a 1 ton (90 bar c a p a c i t y ) cone c o u l d be a c c u r a t e to l e s s than 0.9 bar. To achieve high q u a l i t y r e s u l t s i n very s o f t s o i l s the accuracy needs to be somewhat b e t t e r than 0.9 bar. T h i s can be achieved through c a r e f u l c a l i b r a t i o n of the cone i n the s t r e s s range of i n t e r e s t and thorough, repeatable t e s t procedures. 3.2.3 Data Reduction The raw data from a l l UBC CPT t e s t s was e l e c t r o n i c a l l y d i g i t i z e d f o r input i n t o a computer data r e d u c t i o n program. S e v e r a l f a c t o r s a f f e c t the measured parameters from an e l e c t r i c piezometer cone and the computer program al l o w s the necessary c o r r e c t i o n s to be made e f f i c i e n t l y . These f a c t o r s are d i s c u s s e d i n d e t a i l by Robertson and Campanella (1982). P a r t i c u l a r f e a t u r e s of the data r e d u c t i o n process i n c l u d e : a c o r r e c t i o n f o r n o n - v e r t i c a l soundings and c o r r e c t i o n s f o r unequal end area e f f e c t s on the f r i c t i o n s l e e v e and t i p . Unequal end area e f f e c t s on the f r i c t i o n s l e e v e occur when the annulus areas at the top and bottom of the sleeve are 34 not e q u a l . T h i s problem has been elimin-ated on recent UBC cones by i n c o r p o r a t i n g equal end areas i n t o the design (Campanella and Robertson, 1981). The c o r r e c t i o n to the cone t i p i s r e q u i r e d because pore water press u r e , l o c a t e d i n the porous element behind the cone t i p , a c t s on the back of the cone t i p . C a l i b r a t i o n t e s t s show that when a piezometer cone t i p i s subject to an a l l around a p p l i e d water pressure the measured bearing i s reduced i n p r o p o r t i o n to the r a t i o of the a c t i n g areas ( G i l l e s p i e , 1981). T h i s e r r o r can be accounted f o r by adding to the bearing reading a p o r t i o n of the water pressure that i s not recorded, i . e . : Qt = Qc + Ut(1-a) where Qt i s the c o r r e c t e d t o t a l s t r e s s b e a r i n g , Qc i s the measured bearing, Ut i s the t o t a l dynamic pore pressure and "a" i s the net area r a t i o (Campanella et a l . , 1983). A l l cone l o g s presented i n t h i s r e p o r t have been c o r r e c t e d f o r pore pressure e f f e c t s on both the cone t i p and f r i c t i o n sleeve and for n o n - v e r t i c a l i t y of the sounding. A c c o r d i n g to the slope i n d i c a t o r records, a l l soundings were v e r t i c a l to at l e a s t 16m depth through the organic s o i l s at which p o i n t some soundings showed s l i g h t d e f l e c t i o n as the sands were pe n e t r a t e d . 35 . 3.2.4 Piezometer T i p S a t u r a t i o n An easy system of piezometer t i p s a t u r a t i o n has been developed at U.B.C. where g l y c e r i n i s used as a s a t u r a t i o n f l u i d , see F i g u r e 3.2 (Campanella et a l . , 1983). G l y c e r i n i s m i s c i b l e with water yet develops a high a i r entry t e n s i o n to prevent l o s s of s a t u r a t i o n d u r i n g g e n e r a l use and a l s o d u r i n g p e n e t r a t i o n of unsaturated s o i l s above the water t a b l e . With the cone t i p and f i l t e r removed, g l y c e r i n i s introduced i n t o the s l i p - o n cup and a hypodermic of g l y c e r i n i s used to f l u s h a i r from the i n t e r i o r c a v i t i e s of the pore pressure measuring chamber. The p r e s a t u r a t e d f i l t e r and t i p are assembled, the excess g l y c e r i n poured o f f and cup removed. T h i s technique has proved to g i v e adequate s a t u r a t i o n d u r i n g more than two years of CPT experience at UBC. Campanella and Robertson (1981), have shown that complete s a t u r a t i o n of the piezometer t i p i s e s s e n t i a l f o r a c c u r a t e measurement of both the maximum dynamic pore pressure and pore pressure d i s s i p a t i o n times. I t was found that the maximum dynamic pore pressure i s reduced s i g n i f i c a n t l y when measured with an unsaturated piezometer. A l s o , when p e n e t r a t i o n of an unsaturated piezometer cone i n a s o f t c l a y was stopped, the measured pore pressure c o n t i n u e d to r i s e f o r a short p e r i o d before d e c r e a s i n g i n the expected manner. Because pore pressure d i s s i p a t i o n t e s t s can be used to determine c o n s o l i d a t i o n parameters care was taken to ensure that the pore pressure measuring system was s a t u r a t e d p r i o r to each sounding. U n f o r t u n a t e l y the design of the cone pore 36 F i g . 3.2 T i p Design To Allow Easy S a t u r a t i o n With G l y c e r i n ( a f t e r Campanella, Robertson and G i l l e s p i e , 1983) 37 pressure measuring u n i t does not allow f o r easy checking of the degree of s a t u r a t i o n a f t e r the piezometer t i p has been assembled. Therefore there was a p o s s i b i l i t y t h a t a small amount of a i r c o u l d remain trapped i n the pore pressure measuring system. Two e f f e c t s a s s o c i a t e d with p o s s i b l e poor s a t u r a t i o n were observed d u r i n g cone p e n e t r a t i o n t e s t i n g i n the organic s o i l s . A pore pressure r i s e was observed f o r a s i g n i f i c a n t p e r i o d a f t e r cone p e n e t r a t i o n was stopped; 30 seconds to 1 minute f o r or g a n i c c l a y s and 2 minutes to 5 minutes f o r the f i b r o u s peat. A l s o , a r e d u c t i o n i n dynamic pore p r e s s u r e s was observed f o l l o w i n g pore pressure d i s s i p a t i o n s . In s e v e r a l i n s t a n c e s a c o n s i d e r a b l e depth of p e n e t r a t i o n (up to 2.5m) was r e q u i r e d to reach pore p r e s s u r e s as l a r g e as those measured p r i o r to the d i s s i p a t i o n . However, the c o n d i t i o n of reduced dynamic pore p r e s s u r e s d i d not appear to p e r s i s t f o r the remainder of the sounding. During the f i e l d t e s t s the dynamic pore pressure response of the sands and s i l t s j u s t below the o r g a n i c s o i l s was observed to be c o n s i s t e n t with the responses f o r s i m i l a r s o i l s not o v e r l a i n by o r g a n i c s . Three causes are proposed f o r the observed response of the cone piezometer. These are; the Mandel Cryer e f f e c t (Tumay et a l . , 1981), which i n v o l v e s the c o m p r e s s i b i l i t y of the s o i l f a b r i c coupled with the equations of motion f o r flow of porewater, the e f f e c t of methane gas (marsh gas) on the measurement of pore water p r e s s u r e s and the p o s s i b i l i t y of an unsaturated cone piezometer system p r i o r to sounding. 38 The Mandel Cryer e f f e c t i s a t h e o r e c t i c a l argument which p r e d i c t s t h a t , at the center of a sphere of s a t u r a t e d s o i l s u b j e c t to a h y d r o s t a t i c pressure and having drainage p r o v i d e d at the s u r f a c e of the sphere, the pore water pressure w i l l i n c r e a s e to a value i n excess of the a p p l i e d pressure before d i s s i p a t i n g (Cryer, 1963). The o p e r a t i n g mechanism of the Mandel Cryer e f f e c t i s thought to i n v o l v e r a p i d changes i n t o t a l s t r e s s e s which a f f e c t the d i s s i p a t i o n of excess pore p r e s s u r e s . T h i s e f f e c t i s expected to be s i g n i f i c a n t i n s o f t , compressible s o i l s such as those present at the t e s t f i l l s i t e . A d e s c r i p t i o n of the processes that are thought to occur d u r i n g piezometer cone t e s t i n g of compressible s o i l s are given below: Drainage of the excess pore p r e s s u r e s generated by cone p e n e t r a t i o n at the f r e e boundary promotes c o n s o l i d a t i o n and a r e d u c t i o n i n the p e r m e a b i l i t y at the boundary. As drainage c o n t i n u e s the zone of reduced p e r m e a b i l i t y advances toward the cone t i p , t r a p p i n g and i n c r e a s i n g the t o t a l s t r e s s e s and thus the excess pore p r e s s u r e s adjacent to the cone t i p . E v e n t u a l l y , e q u i l i b r i u m i s reached and the pore pressure d i s s i p a t i o n process dominates. According to Cryer (1963) the r a t i o of pore water p r e s s u r e to a p p l i e d s t r e s s w i l l i n c r e a s e with i n c r e a s i n g c o m p r e s s i b i l i t y up to a r a t i o of about 1.5. The Mandel Cryer e f f e c t has not been v e r i f i e d e x p e r i m e n t a l l y i n the l a b o r a t o r y because of the d i f f i c u l t y of the t e s t procedure. Because the i n - s i t u average a p p l i e d s t r e s s around the cone a f t e r 39 p e n e t r a t i o n i s not known the Mandel Cryer e f f e c t cannot yet be q u a n t i f i e d f o r the cone p e n e t r a t i o n t e s t . However, i f a r a t i o of the maximum pore p r e s s u r e • d u r i n g a d i s s i p a t i o n t e s t to the generated pore pressure at the s t a r t of the d i s s i p a t i o n i s made then one can get some idea of the magnitude of the pore pressure r i s e . In g e n e r a l the pore pressure r i s e r a t i o estimated from the d i s s i p a t i o n t e s t s i s between 1.1 and 1.3 for' the i n i t i a l c o n d i t i o n s CPT t e s t s . A r a t i o between 1.1 and 1.3 would c e r t a i n l y appear to be p o s s i b l e given Cryer's (1963) a n a l y s i s . T h e r e f o r e , the Mandel Cryer e f f e c t presents a p l a u s i b l e e x p l a n a t i o n of the r i s e i n measured pore pressure a f t e r p e n e t r a t i o n was stopped. However, i t does not appear to e x p l a i n the reduced dynamic pore p r e s s u r e s upon resuming p e n e t r a t i o n . Pore pressure measuring systems are very s e n s i t i v e to changes i n the compliance, or c o m p r e s s i b i l i t y , of the measuring system. Upon r e t r i e v a l of the cone f o l l o w i n g p e n e t r a t i o n i t was commonly observed that some of the g l y c e r i n i n the pore pressure c a v i t y had been r e p l a c e d by the i n - s i t u porewater. I t i s common f o r the porewater of organic s o i l s to c o n t a i n methane gas as a n a t u r a l by-product of decomposition. The c o m p r e s s i b i l i t y of the system i s i n c r e a s e d s i g n i f i c a n t l y with i n c r e a s e s i n the percentage of gas i n the pore water. A gas (or a i r ) content determined from l a b o r a t o r y c o n s o l i d a t i o n t e s t s of 7-10 per cent was r e p o r t e d f o r F r a s e r D e l t a peats by Lea and Brawner (1963). According to Fredlund (1976), a i r volumes of j u s t a few percent of the t o t a l volume can i n c r e a s e 40 the c o m p r e s s i b i l i t y of the pore f l u i d by s e v e r a l orders of magnitude. The replacement of a r e l a t i v e l y i n c o m p r e s s i b l e f l u i d ( g l y c e r i n ) by a r e l a t i v e l y compressible f l u i d (water with methane gas i n s o l u t i o n ) c o n s t i t u t e s a d e s a t u r a t i o n of the pore pressure measuring system. A simple t e s t can be made to determine i f the reduced dynamic pore pressure response i s a problem of s a t u r a t i o n of the t i p . By reducing the r a t e of p e n e t r a t i o n when such a lapse o c c u r s , the pore pressure w i l l show a steeper response when recorded versus depth i f poor t i p s a t u r a t i o n i s the problem. Such a t e s t was not conducted d u r i n g t h i s study because of the time consuming nature of t h i s t e s t procedure. Another method of checking the s a t u r a t i o n i s to compare the u n - s a t u r a t i o n delay at d i f f e r e n t depths. The u n - s a t u r a t i o n delay w i l l be d i m i n i s h e d as the dynamic pore pressure i n c r e a s e s or as depth i n c r e a s e s . The u n - s a t u r a t i o n delay d i d tend, to d i m i n i s h with depth and i n c r e a s e d dynamic pore p r e s s u r e at the t e s t f i l l s i t e . T h i s i n d i c a t e s that the anomolous dynamic pore p r e s s u r e s were at l e a s t p a r t l y due to poor s a t u r a t i o n of the piezometer t i p . Three causes of the anomolous pore p r e s s u r e s measured d u r i n g cone p e n e t r a t i o n t e s t i n g of the organic s o i l s have been proposed. I t appears that the o v e r a l l observed phenomena may be due to a combination of the Mandel Cryer e f f e c t and incomplete s a t u r a t i o n . A thorough i n v e s t i g a t i o n of the s i t u a t i o n i s beyond the scope of t h i s t h e s i s . 41 3.2.5 S t r a t i g r a p h i c Logging • S t r a t i g r a p h i c Logging. F i g u r e 3.3 shows a complete cone l o g , performed and reduced by the author, which was made at the t e s t f i l l s i t e before the f i l l was p l a c e d . F i g u r e 3.3 i l l u s t r a t e s the tremendous amount of d e t a i l t h a t can be obtained by the e l e c t r i c piezometer f r i c t i o n cone duri n g a s i n g l e 10 hour sounding. The cone l o g shows, from l e f t to r i g h t , the pore pr e s s u r e , U, generated dur i n g p e n e t r a t i o n and the measured e q u i l i b r i u m pore p r e s s u r e s ; the f r i c t i o n r e s i s t a n c e , Fc; the t o t a l b e a r i n g r e s i s t a n c e , Qt; the f r i c t i o n r a t i o , Rf=(Fc/Qt)100%, where Fc and Qt are measured at the same depth, and the d i f f e r e n t i a l pore pressure r a t i o AU/Qt. A l l s t r e s s e s are given i n u n i t s of bar (1 bar = lOOkPa). The pore pressure response of s e v e r a l s o i l types are c l e a r l y i l l u s t r a t e d i n F i g u r e 3.3, and are d e s c r i b e d below. Normally c o n s o l i d a t e d sands and c l a y s have been observed to e x h i b i t d e f i n i t e d r a i n e d and undrained pore pressure response to cone p e n e t r a t i o n r e s p e c t i v e l y . S i l t s , on the other hand, have been shown t o e x h i b i t a 'mixed' drainage that i s s e n s i t i v e to the r a t e of p e n e t r a t i o n (Campanella et a l . , 1983). At the standard p e n e t r a t i o n r a t e of 2cm/sec the pore pressure response of the s i l t s at t h i s s i t e appears to be undrained. At 2cm/sec, the r e l a t i v e l y low p e r m e a b i l i t y , low PI and moderate s e n s i t i v i t y of these s i l t s enables generation of dynamic pore pre s s u r e s as h i g h as three times the 42 PORE P R E S S U R E F R J C T I O N R E S I S T A N C E B E A R I N G R E S I S T A N C E F R I E 1 I O N R A 1 1 0 D I F F E R E N T i R l P . P . S O I L «f=FE/Oi m Rfil!OIU/OT PROFILE —i—i—i—i—[- 131 I I l l I ( 3 1 I I I I I I I I I I /3I "i I I I t (31 I l I l (B.C. HIGHWAY TEST FILL) r c . - Q 7 o f f s e t , 6 2 c m o t 2 9 2 m d e p , h Oepih corrected for slope r l v a . J . J J; Equil ibrium woter pressure EXAMPLE OF PIEZOMETER FRICTION CONE LOGGING IN STRATIFIED SOILS 43 e q u i l i b r i u m v a l u e . The p e r m e a b i l i t y of organic s o i l s i n general i s a s u b j e c t of c o n t r o v e r s y . I t i s g e n e r a l l y assumed that peat i s q u i t e permeable, as demonstrated by the r a p i d c o n s o l i d a t i o n that occurs under f i e l d l o a d i n g , but l a b o r a t o r y t e s t s i n d i c a t e that many peats have r e l a t i v e l y low p e r m e a b i l i t i e s (MacFarlane, 1969). At the standard p e n e t r a t i o n r a t e the peat and organic c l a y s generated dynamic pore p r e s s u r e s which are two to three times the e q u i l i b r i u m v a l u e s . A l s o , the pore pressure r a t i o s i n d i c a t e t hat excess dynamic pore p r e s s u r e s r e p r e s e n t 20% to 40% of the measured Qt. The dynamic pore p r e s s u r e s i n d i c a t e a l a r g e l y undrained response and t h e r e f o r e , a r e l a t i v e l y low p e r m e a b i l i t y . Pore pressure d i s s i p a t i o n t e s t s performed with the cone penetrometer a l s o i n d i c a t e that peats can have r e l a t i v e l y low p e r m e a b i l i t i e s . The time f o r f i f t y percent d i s s i p a t i o n , t , i n the peat and organic c l a y was about double the t f o r the s i l t s at twenty metres depth. In order to f u l l y understand the drainage c h a r a c t e r of organic s o i l s a f u t u r e study of r a t e e f f e c t s may be warranted. • S o i l C l a s s i f i c a t i o n The s o i l p r o f i l e given by Campanella et a l . , 1983 and shown i n F i g u r e 3.3 was made without the b e n e f i t of p r i o r knowledge except that i t was known that peat and organic s i l t were near the s u r f a c e . The f r i c t i o n r a t i o was used to d i s t i n g u i s h the peat from the organic s i l t . The most comprehensive recent work on s o i l c l a s s i f i c a t i o n u s ing 44 e l e c t r i c cone p e n e t r a t i o n data i s that by Douglas and Olsen (1981) . T h e i r proposed s o i l - b e h a v i o u r type c l a s s i f i c a t i o n c h a r t i s shown in F i g u r e 3.4. Included in F i g u r e 3.4 are s e v e r a l ' c l a s s i f i c a t i o n s ' from CPT's done at the i n i t i a l c o n d i t i o n s s i t e . The c h a r t has been amended by Robertson (1982) to i n d i c a t e peat s o i l s at f r i c t i o n r a t i o s g r e a t e r than 6. I t i s i n t e r e s t i n g to note that the s o i l behaviour curves appear to be confirmed f o r the organic s o i l s at t h i s s i t e . Expansion of Douglas' c h a r t to i n c l u d e f r i c t i o n r a t i o s up to 10% may be warranted i n the case of f i b r o u s peats. Douglas' c l a s s i f i c a t i o n c h a r t was developed f o r standard e l e c t r i c cone data with no c o r r e c t i o n s f o r unequal end area e f f e c t s . For the pore pressure c o r r e c t e d data from the UBC t e s t s , the u s e f u l n e s s of the c h a r t i s reduced somewhat to t h a t of a guide. 3.2.6 I n t e r p r e t a t i o n A g e n e r a l o u t l i n e of CPT i n t e r p r e t a t i o n w i l l be given with s p e c i a l c o n s i d e r a t i o n to expected changes i n CPT parameters as a r e s u l t of the l o a d i n g and settlement of the t e s t f i l l . • Bearing R e s i s t a n c e , Qt; Cone p e n e t r a t i o n through a s a t u r a t e d s o i l causes complex changes i n s o i l s t r e s s e s and s t r a i n s i n the v i c i n i t y of the cone t i p . Robertson (1982) has made a thorough review of the a v a i l a b l e l i t e r a t u r e and p o i n t s out the i n f l u e n c e of s t r a i n 45 . depth) HH F r o m i n i t i a i c o n d i t i o n s CPT p r o f i l e s . F i g u r e 3.4 S o i l c l a s s i f i c a t i o n c h a r t f o r standard e l e c t r i c cone, (adapted from Douglas and Olsen, 1981) 46 r a t e , a n i s o t r o p y and s t r a i n s o f t e n i n g behaviour on the bearing r e s i s t a n c e of c l a y s . In g e n e r a l , an i n c r e a s e i n be a r i n g r e s i s t a n c e at a given depth i n a normally c o n s o l i d a t e d f i n e g r a i n e d s o i l i s l o o s e l y r e l a t e d to an i n c r e a s e i n undrained shear s t r e n g t h . T y p i c a l l y , organic s o i l s have a very l a r g e i n c r e a s e i n undrained shear s t r e n g t h a f t e r c o n s o l i d a t i o n ; the f i n a l shear s t r e n g t h s are o f t e n s e v e r a l orders of magnitude g r e a t e r than the i n i t i a l v a l u e s (Brawner, 1959). T h e r e f o r e , one would expect the cone b e a r i n g r e s i s t a n c e to show a marked i n c r e a s e a s s o c i a t e d with the process of c o n s o l i d a t i o n . • F r i c t i o n S t r e s s , Fc; The f r i c t i o n s t r e s s has been proposed by many r e s e a r c h e r s as a c o n s e r v a t i v e estimate of undrained shear s t r e n g t h . From elementary p h y s i c s the f r i c t i o n s t r e s s w i l l depend on the i n -s i t u h o r i z o n t a l e f f e c t i v e s t r e s s . In gen e r a l p r a c t i c e the f r i c t i o n s t r e s s i s used i n combination with the cone b e a r i n g f o r s o i l c l a s s i f i c a t i o n . I t i s expected that the measured f r i c t i o n s t r e s s w i l l i n c r e a s e as a r e s u l t of i n c r e a s e s i n s o i l s t r e n g t h and h o r i z o n t a l e f f e c t i v e s t r e s s due to c o n s o l i d a t i o n . • F r i c t i o n R a t i o , Rf=(Fc/Qt)100%; The f r i c t i o n r a t i o w i l l be a f f e c t e d by changes i n both the s l e e v e f r i c t i o n and cone bearing r e s i s t a n c e . Because the change i n be a r i n g a f t e r c o n s o l i d a t i o n may not be i n the same p r o p o r t i o n as the change i n f r i c t i o n r e s i s t a n c e , the f r i c t i o n 47 r a t i o may not maintain i t s i n i t i a l v a l u e . As i n d i c a t e d by the s o i l c l a s s i f i c a t i o n c h a r t i n F i g u r e 3.4, a d e c r e a s i n g f r i c t i o n r a t i o i s g e n e r a l l y r e l a t e d to d e c r e a s i n g v o i d r a t i o f o r cohesive m i n e r a l s o i l s and t h i s t r e n d w i l l l i k e l y a l s o apply to organic s o i l s . • Pore Pressure, U; The t o t a l dynamic pore p r e s s u r e (tit) measured duri n g cone p e n e t r a t i o n i s the sum of the e q u i l i b r i u m pore pressure (Uo) and the excess dynamic pore pressure (Ue) generated by p e n e t r a t i o n . The e q u i l i b r i u m pore pressure w i l l i n c r e a s e . i n accordance with i n c r e a s e s i n t o t a l s t r e s s due to the t e s t f i l l l o a d i n g . An i n c r e a s e i n the generated excess pore p r e s s u r e w i l l l i k e l y r e f l e c t an i n c r e a s e i n undrained shear s t r e n g t h because, f o r a p a r t i c u l a r c l a y type, AUe/ACu i s approximately constant. One can expect an i n c r e a s e i n Ue to occur as a r e s u l t of the t e s t f i l l l o a d i n g . • D i f f e r e n t i a l Pore Pressure R a t i o , (AU/Qt); The d i f f e r e n t i a l pore pressure r a t i o , where AU = Ut-Uo = Ue (Campanella et a l . , 1983), has been shown to be a good i n d i c a t o r of both the volume change c h a r a c t e r i s t i c s and r e l a t i v e p e r m e a b i l i t y of sands, s i l t s and c l a y s (Robertson, 1982). I t has been reasoned above t h a t , f o l l o w i n g c o n s o l i d a t i o n , an i n c r e a s e i n both Ue and Qt can be expected. The r e l a t i v e change i n Qt may not be i n the same p r o p o r t i o n as 48 the change i n Ue and, consequently the d i f f e r e n t i a l pore pressure r a t i o may not maintain i t s i n i t i a l v a l u e . Recent CPT t e s t s performed i n s i l t s before and a f t e r s o i l d e n s i f i c a t i o n showed remarkable changes i n AU/Qt as the s o i l response to p e n e t r a t i o n changed from being c o n t r a c t i v e to d i l a t i v e (Campanella et a l . , 1983). For the very compressible organic s o i l s that make up the t e s t f i l l s u b s o i l , the e f f e c t of c o n s o l i d a t i o n i s expected to reduce the c o m p r e s s i b i l i t y d r a m a t i c a l l y . However, i t should be kept i n mind that the c o n s o l i d a t e d s u b s o i l w i l l s t i l l be a r e l a t i v e l y s o f t , compressible s o i l and i s not expected to be capable of a d i l a t i v e response to CPT. 3.2.7 Reference T e s t s Two cone p e n e t r a t i o n t e s t s were performed at the t e s t f i l l s i t e to e s t a b l i s h the ref e r e n c e CPT p r o f i l e s p r i o r to t e s t f i l l c o n s t r u c t i o n . One sounding (CPT-1) was made i n the area without wick d r a i n s and one sounding (CPT-2) i n the wick area. Sounding CPT-2 was performed at a d i s t a n c e of about 10m from the nearest wick d r a i n . Examination of the r e f e r e n c e cone p r o f i l e s shows t h a t the wick area sounding had a s l i g h t l y lower b e a r i n g r e s i s t a n c e i n the o rganic s o i l s than the non-wick soundings see F i g u r e 3.5. A trend of dec r e a s i n g shear s t r e n g t h a c r o s s the s i t e i s a l s o i n d i c a t e d by the i n i t i a l c o n d i t i o n vane t e s t data provided by the B r i t i s h Columbia Department of Highways, see F i g u r e 3.6. The vane t e s t s had been performed about two weeks p r i o r to the refe r e n c e CPT's and p r i o r t o the s t a r t of c o n s t r u c t i o n . 49 1 . O" to O H C=3 car - 1 1 . OH 1 7 . 0 ' B E R R I N G Q T R E S I S T A N C E ( B R R 3 2 O N O N - W I C K . A R E A W I C K A R E A Wick area, t e s t no. CPT-2 Non-wick area, t e s t no. CPT-1 F i g u r e 3.5 I n i t i a l cone b e a r i n g r e s i s t a n c e s f o r the wick area and the area without wick d r a i n s . 50 Undrained Shear Strength ( S u ) r (KPa) 0 10 ZO 3 0 40 50 60 70 to 4-1 0) z o E-> < > -• Wick area -O Non-wick area Instrument: Nilcon Swedish Vane Borer (6.5 cm x 13.0 cm vane) Wick area, test no. VS-620; station 201+35, center!ine. Non-wick area, test no. VS-617; st a t i o n 200+62, centerline. F i g u r e 3.6 I n i t i a l undrained shear s t r e n g t h from f i e l d vane t e s t s i n the wick and non-wick ar e a s . 51 3.3 FLAT PLATE DILATOMETER TEST (DMT)  3.3.1 Equipment A r e l a t i v e l y new c o n t r i b u t i o n to i n - s i t u t e s t i n g equipment i s the f l a t p l a t e d i l a t o m e t e r . Developed i n I t a l y , the d i l a t o m e t e r was f i r s t d e s c r i b e d i n North American l i t e r a t u r e by the designer Dr. S i l v a n o M a r c h e t t i i n 1975. A schematic r e p r e s e n t a t i o n of the d i l a t o m e t e r i s shown i n F i g u r e 3.7. The d i l a t o m e t e r t e s t (DMT) i n v o l v e s the i n f l a t i o n of a t h i n , c i r c u l a r s t e e l membrane l o c a t e d on the face of a f l a t blade to achieve a one m i l l i m e t r e d e f l e c t i o n . During the t e s t two p r e s s u r e s are read from a c a l i b r a t e d p r e s s u r e gauge. To achieve g r e a t e r c o n s i s t e n c y and accuracy i n the readings, p a r t i c u l a r l y a t low p r e s s u r e s , a pressure transducer was i n s t a l l e d i n p a r a l l e l with the gauge and the pr e s s u r e s were recorded on a s t r i p chart r e c o r d e r . The f i r s t reading (A) corresponds to the membrane l i f t - o f f p r e ssure and the second (B) to the pressure r e q u i r e d to cause one m i l l i m e t r e d e f l e c t i o n a t the center of the membrane. Readings A and B are c o r r e c t e d f o r f r e e - a i r e f f e c t s of membrane s e a t i n g and c u r v a t u r e . The c o r r e c t e d values are termed PO and P1 r e s p e c t i v e l y . The t e s t s are performed at 20cm i n t e r v a l s of depth r e s u l t i n g i n a comprehensive but d i s c o n t i n u o u s p r o f i l e . From the b a s i c d i l a t o m e t e r data (P0,P1) M a r c h e t t i has developed e m p i r i c a l c o r r e l a t i o n s to an e x t e n s i v e set of s o i l parameters. A computer program s u p p l i e d with the d i l a t o m e t e r 52 FIG.3.7 SCHEMATIC OF DILATOMETER. 53 c o n t a i n s the e m p i r i c a l c o r r e l a t i o n s r e q u i r e d to i n t e r p r e t the d i l a t o m e t e r p r o f i l e . An example of the computer analyzed d i l a t o m e t e r r e s u l t s f e a t u r i n g the Intermediate G e o t e c h n i c a l Parameters, the I n t e r p r e t e d G e o t e c h n i c a l Parameters and a t a b u l a r output i s shown in F i g u r e 3.8, 3.9 and 3.10. The d i l a t o m e t e r d e v i c e , having a s i n g l e t e s t membrane on one s i d e of the t o o l , i s p a r t i c u l a r l y s e n s i t i v e to any d e v i a t i o n s from the v e r t i c a l . U n f o r t u n a t e l y , there i s no p r o v i s i o n f o r measurement of slope during p e n e t r a t i o n . Van de Graaf and J e k e l (1982), using CPT, have shown that the e r r o r i n recorded depth due to n o n - v e r t i c a l i t y i n s o f t uniform s o i l s i s g e n e r a l l y n e g l i g i b l e to a depth of 15m, p r o v i d e d no o b s t r u c t i o n s are encountered. The depth of study f o r t h i s paper i s about 18m and the d i l a t o m e t e r t e s t s are c o n s i d e r e d to have been v e r t i c a l . Test procedures were c a r r i e d out i n accordance with the d e t a i l e d o u t l i n e given i n the D i l a t o m e t e r Users Manual (Marchetti and Crapps, 1981). 3.3.2 Reference T e s t s The d i l a t o m e t e r p r o f i l e shown i n F i g u r e s 3.8 and 3.9 i s the r e f e r e n c e d i l a t o m e t e r p r o f i l e f o r the monitoring of the t e s t f i l l s i t e . The r e f e r e n c e t e s t , DMT=3, was performed at the i n i t i a l c o n d i t i o n s s i t e approximately 100m north of the t e s t f i l l s i t e , see F i g u r e 3.11. Recourse to the nearby i n i t i a l c o n d i t i o n s s i t e f o r the r e f e r e n c e t e s t was necessary because -embankment c o n s t r u c t i o n was a l r e a d y underway and the s o i l c o n d i t i o n s below the embankment c o u l d no longer be c o n s i d e r e d i n i t i a l . 54 UJ3.C. INSITU TESTING. 1 Location; INITIAL CONDITIONS SITE INTERMEDIATE GEOTECHNICflL PflRRMETFRS Test No. DMT-3 Test Date* Apr. 5,1982 10 Z) •a a aj Q_ C aj —^ e a ro a to 0*Z - I . 0> I..-(ii) mdaa 0*9 0'9 —I 1 L_ 0*01 J L_ 0*ZI L_ 0>I L X •—I «J ro -o 4-1 CZ C M a M tn n o a t_ X «-• CO tn ui ai CO ro ±» d : L. W QJ > ro in o tn CM 1 1 1 T ~i r "i 1 1 r a. a. t> 0-2 0> "~i 1 r~ 0*9 0*8 1 r-0*01 1 r-0'ZI i—r 0>1 LLI»-to id I 5 VI. o UJ CO VJ a> 0) e 1-1 (0 OH CD 4-> r o TJ 0) E u 0) 4-> c ro I • E-a tn CD • 4-1 a> U -rH ai ui 4-1 CD 01 S C 0 o 4-> -rt rrj 4J l-H -iH •rH TJ T3 C O 0) U O C i-» O) (0 U 01 4J 4-1 O) c CO ro • CP b 55 INSITU TESTING. Location; INITIAL CONDITIONS SITE INTERPRETED GEOTECHNICAL PARAMETERS. c <r S OJ (O T3 C 3 U) a H re c a u ra x i_ - a re in. 0'2 I 0> J L_ 0*9 O'B —I I L_ Test No. DMT-3 Test Dates Ppr. 5,1982 O'OI J L_ O'ZI J L_ J 1 I I I J 1 1 1 1 I I i 0>I J l_ J Ll—i 1 I l I J 1 I L T ~ i nr i — i — i — i — i — i — i — r — r 0 2 0> 0*9 0'8 O'Ol 0'2I 0>1 CO va > n M 3 o 3 u a> 4-> e (0 VJ (0 cu T » OJ 4-> <D lj a u O) 4-> c n i E-i 2 Q 0) • 4-> <D -P 1-1 -rH 0) U) 4-1 S c o o 4J - i-l ro 4-> T3 C o 0) u o C rH 0) (0 U -rH (U 4-> U-l .rH CD c « -rH CO cn •rH C a l i b r a t i o n I n f o r m a t i o n s 0.08 Bars DB= 0.38 Bars ZM= 0.0 Bars ZW= 0.75 metres Gamma=Bulk unit weight Sv =Effect1ve over.stress Uo =Pore pressure Id =Mater1al Index Ed =Dllatometer modulus Kd =Hor1zontal stress Index INTERPRETED GEOTECHNICAL PARAMETERS Ko =Ins1tu earth press.coeff. 0CR=0verconsolldatIon Ratio M =Constralned modulus Cu =Undramed cohes 1 on(cohes 1 ve) PHI=Frlct1on Angle(cohes1onless) Z PO P1 (m) (Bar) (Bar) Ed Uo Id (Bar) (Bar) Gamma Sv (t/CM) (Bar) Kd OCR Pc KO Cu (Bar) PHI (Deg) M (Bar) Soil Type Descr1ptIon 1 .78 0. 12 45. CLAYEY SILT COMPRESSIBLE 1.91 0. 15 23. MUD 1 .35 0.09 23. MUD 1 .22 0.08 26. CLAYEY SILT COMPRESSIBLE 1.12 0.08 27. SILT COMPRESSIBLE 1.17 0.09 22. MUD 1 . 19 0. 10 20. MUD 1 .24 0. 12 23. MUD 1 . 17 0.11 19. MUD 1 .24 0. 13 16. MUD 1 . 16 0.12 18. MUD 1.17 0.13 18. MUD • 1 .03 0. 1 1 18. MUD 1.11 0.13 18 . MUD 0.85 0.09 15. MUD 0.91 0. 10 15. MUD 1 .00 0.13 19. MUD 0.93 0. 12 18. MUD 1 .06 0. 15 14 . MUD 0.97 0. 14 19. SILTY CLAY SOFT 0.99 0. 15 20. CLAY SOFT 0.98 0. 15 23. SILTY CLAY SOFT 0.88 0.13 15. MUD 0.78 0. 1 1 13. MUD 0.86 0. 14 13. MUD 0. 79 0. 12 19. SILTY CLAY SOFT 0.70 0. 1 1 14. SILTY CLAY SOFT 0.69 0. 1 1 22. CLAYEY SILT COMPRESSIBLE 0.68 0. 1 1 18. SILTY CLAY SOFT 0.53 0.08 13 . SILTY CLAY SOFT 0.59 0. 10 16. SILTY CLAY SOFT 0.78 0.15 19. SILTY CLAY KO Cu (Bar) PHI (Deg) M (Bar) S o i l Type Description 00 20 40 1 .60 80 00 2.20 2.40 2.60 2.80 3.00 3.20 3.40 3.60 3.80 00 20 40 60 80 00 5.20 5.40 60 80 00 20 40 6.60 6.80 7.00 7.20 0.73 0.95 0.65 0.66 0.67 0. 77 0.86 0.98 0.99 1 . 14 1.12 1 .20 1 . 10 1 .27 1 .03 1 . 15 1.31 1 .29 1 .53 1 .46 1 .56 1 .62 1.51 1 .42 1 .60 1 .54 1 .46 1 .50 1 .53 1 . 36 1 .49 1 .86 .27 19. 0 .02 0 .75 1 .60 0 .075 9 .5 11 . 29 0 .85 1 .21 9. 0 .04 0 . 29 1 .50 0 .085 10 .6 13 .52 1 . 15 0 .98 11 . 0 .06 0 .55 1 .50 0 .095 6 .2 5 .85 0 . 56 1 .06 14. 0 .09 0 .69 1 .60 0 . 107 5 .4 4 .69 0 .50 1 . 12 16. 0 . 11 0 .80 1 .60 0 . 1 19 4 .7 3 .84 0 .46 1 . 12 12. 0 . 13 0 .53 1 .50 0 . 129 5 .0 4 .21 0 . 54 1 . 18 11 . 0 . 14 0 .44 1 .50 0 . 139 5 .2 4 .41 0 .61 1 . 33 12. 0 . 16 0 .42 1 .50 0 . 149 5 .5 4 .84 0 .72 1 .29 1 1 . 0 . 19 0 . 38 1 .50 0 . 159 5 .0 4 .22 0 .67 1 .39 9. 0 .20 0 .27 1 .50 0 . 169 5 .5 4 .87 0 .82 1 .40 10. 0 .22 0 . 32 1 .50 0 . 179 5 .0 4 . 15 0 . 74 1 .48 10. 0 .24 0 .30 1 .50 0 . 189 5 .0 4 .22 0 .80 1 .42 11 . 0 . 26 0 .38 1 .50 0 . 199 4 .2 3 .21 0 .64 1 .57 11 . 0. .29 0. .31 1 .50 0. . 209 4 . 7 3 .78 0 . 79 1 .36 11 . 0. .31 0. .45 1 .50 0. .219 3 .3 2 .22 0. .49 1 .44 10. 0. .32 0. 36 1 .50 0. 229 3. .6 2, .49 0. .57 1 .66 12. 0. 34 0. 36 1 .50 0. 239 4 , . 1 3. .01 0. .72 1 .64 12. 0. 36 0. 37 1 .50 0. 249 3. ,7 2 . 64 0. 66 1 . 78 9. 0. 38 0. 22 1 .50 0. 259 4 . 4 3. 44 0. 89 1. .82 12. 0. 40 0. 34 1 . 60 0. 271 3. 9 2 . 84 0. 77 1. .93 13. 0. 42 0. 32 1 , .60 0. 283 4. 0 2. 97 0. 84 2. 05 15. 0. 44 0. 37 1 . ,60 0. 295 4. 0 2. 93 0. 86 1 . 83 1 1 . 0. 46 0. 30 1 . 50 0. 305 3. 4 2 . 33 0. 71 1 . 72 1 1 . 0. 49 0. 33 1 . 50 0. 315 3. 0 1 . 84 0. 58 1 . 87 9. 0. 50 0. 25 1 . 50 0. 325 3. 4 2. 25 0. 73 1 . 97 15. 0. 52 0. 42 1 . 60 0. 337 3. 0 1 . 89 0. 64 1 . 82 12. 0. 54 0. 39 1 . 60 0. 349 2. 6 1 . 53 0. 54 2. 07 20. 0. 56 0. 60 1 . 60 0. 361 2. 6 1 . 50 0. 54 2. 00 16. 0. 59 0. 50 1 . 60 0. 373 2 . 5 1 . 44 0. 54 1 . 81 16. 0. 61 0. 60 1 . 60 0. 385 2. 0 0. 97 0. 37 1 . 97 17 . 0. 63 0. 56 1 . 60 0. 397 2. 2 1 . 14 0. 45 2. 30 15. 0. 64 0. 36 1 . 60 0. 409 3. 0 1 . 85 0. 76 z (m) PO P1 (Bar) (Bar) Ed Uo Id (Bar) (Bar) Gamma Sv (t/CM) (Bar) Kd OCR Pc (Bar) Fig. 3.10 Tabular output from d i l a t o m e t e r t e s t DMT-3, i n i t i a l c o n d i t i o n s s i t e . 57 / ^_ THOMPSON ROAD (PAVED) * F r a s e r R i v e r Fig.3.11 T e s t F i l l S i t e and I n i t i a l C o n d i t i o n s S i t e 58 I t i s important that the s o i l c o n d i t i o n s at the i n i t i a l c o n d i t i o n s s i t e be comparable to those at the t e s t f i l l s i t e . Cone p e n e t r a t i o n t e s t s performed at both s i t e s p rovided a comparison between the two s i t e s . Between the e l e v a t i o n s -7m and -11m the i n i t i a l c o n d i t i o n s s i t e was found to have a cone bearing r e s i s t a n c e about 30% gr e a t e r than the t e s t s performed at the t e s t f i l l s i t e . T h e r e f o r e , the re f e r e n c e d i l a t o m e t e r t e s t , DMT-3, i s a l s o l i k e l y to measure a somewhat stronger s o i l at these e l e v a t i o n s . T h i s d i s c r e p a n c y i s found to be minor when compared to the changes i n s o i l c o n d i t i o n s which oc c u r r e d below the t e s t f i l l . O v e r a l l , the t e s t DMT-3 i s co n s i d e r e d to be s u f f i c i e n t l y r e p r e s e n t a t i v e of the i n i t i a l c o n d i t i o n s at the t e s t f i l l s i t e . 3.3.3 I n t e r p r e t a t i o n From the c o r r e c t e d d i l a t o m e t e r data (pressures P0 and P1), M a r c h e t t i (1980) developed three s o i l index parameters Id, Kd and Ed termed the Intermediate G e o t e c h n i c a l Parameters. The e x p r e s s i o n s f o r these parameters a r e : Id = (P1-P0)/(P0-Uo) = M a t e r i a l Index Kd = (P0-U0)/o; = H o r i z o n t a l S t r e s s Index Ed = 34.6(P1-P0) = Dilatometer Modulus where Uo i s the h y d r o s t a t i c water pressure and i s the i n -s i t u v e r t i c a l e f f e c t i v e s t r e s s . Uo i s c a l c u l a t e d by the computer assuming a h y d r o s t a t i c groundwater c o n d i t i o n . The c a l c u l a t i o n of i n - s i t u v e r t i c a l e f f e c t i v e s t r e s s i s based on c o r r e l a t e d u n i t weight data accessed by s o i l type from Id. 59 M a r c h e t t i developed c o r r e l a t i o n s between d i l a t o m e t e r data and l a b o r a t o r y r e s u l t s f o r s e v e r a l s i t e s i n I t a l y . Id, Kd and Ed from d i l a t o m e t e r t e s t s at 10 s i t e s i n I t a l y were c o r r e l a t e d with s o i l type, s o i l u n i t weight, undrained shear s t r e n g t h , Ko, OCR, c o n s t r a i n e d modulus and f r i c t i o n angle. Clay d e p o s i t s were t e s t e d at e i g h t of the ten s i t e s and sands at the remaining two s i t e s . F i v e of the c l a y s i t e s were thoroughly researched f o r the development of c o r r e l a t i o n s . These s i t e s i n c l u d e two s i t e s having normally c o n s o l i d a t e d d e p o s i t s and three having o v e r c o n s o l i d a t e d d e p o s i t s . None of the s i t e s c i t e d by M a r c h e t t i (1980) had h i g h organic content s o i l s such as peats or organic c l a y s . More i n f o r m a t i o n on the s i t e s and e m p i r i c a l c o r r e l a t i o n s i s given by M a r c h e t t i (1980). General I n t e r p r e t a t i o n The p r i n c i p a l parameters used for i n t e r p r e t a t i o n of the d i l a t o m e t e r t e s t are the Intermediate G e o t e c h n i c a l parameters. A g e n e r a l o u t l i n e of Id, Kd and Ed i s given below. • Id - M a t e r i a l Index Id was i n i t i a l l y proposed as an i n d i c a t o r of m a t e r i a l g r a i n s i z e and has a l s o been proposed as an i n d i c a t o r of undrained shear s t r e n g t h ( M a r c h e t t i , 1980). Id can be s e n s i t i v e to the assumption of a h y d r o s t a t i c ground water c o n d i t i o n (Uo) i n c e r t a i n s i t u a t i o n s . 60 • Kd - H o r i z o n t a l S t r e s s Index According to Robertson (1982) and M a r c h e t t i and Crapps (1981) Kd appears to represent the i n f l u e n c e of the f o l l o w i n g s o i l v a r i a b l e s ; i . i n - s i t u s t r e s s e s , Ko; i i . s t r e s s h i s t o r y and pre s t r e s s i n g ; i i i . r e l a t i v e d e n s i t y , Dr; i v . aging and cementation; U n f o r t u n a t e l y , the i n d i v i d u a l c o n t r i b u t i o n of each v a r i a b l e i s not i d e n t i f i a b l e . M a r c h e t t i (1980) concludes that f o r normally c o n s o l i d a t e d c l a y s Kd i s about 2.0. Cases where Kd i s g r e a t e r than 2.5 i n d i c a t e an o v e r c o n s o l i d a t e d c o n d i t i o n . A Kd value of l e s s than 2.0 f o r an uncemented cohesive s o i l i s not d i s c u s s e d by M a r c h e t t i . The value of Kd depends on an estimate of u n i t weight. M a r c h e t t i and Crapps (1981) produced an e m p i r i c a l c o r r e l a t i o n c h a r t f o r e s t i m a t i n g s o i l type and u n i t weight from the m a t e r i a l index, Id, and the d i l a t o m e t e r modulus, Ed, see Fi g u r e 3.12. Using t h i s c o r r e l a t i o n , the c l a s s i f i c a t i o n termed 'mud and/or peat' has a minimum u n i t weight of 1.5t/m 3. In t h i s study the u n i t weight t y p i c a l l y a s s i g n e d to the peat by the data r e d u c t i o n program ranges from 1.5t/m3 to 1.7t/m 3. However, the u n i t weight of the peat at the s i t e i s somewhat l e s s ranging from about 1.1t/m3 to 1.3t/m 3. Consequently, the e r r o r i n estimated u n i t weight may be as much as 40%. For the i n i t i a l c o n d i t i o n s d i l a t o m e t e r t e s t s Kd w i l l be under estimated by about 40% or approximately h a l f . On the ref e r e n c e d i l a t o m e t e r p r o f i l e ( F i g u r e 3.8) the p r o f i l e of Kd 61 2000 0.5 1 MATERIAL INDEX I, F i g . 3.12 D i l a t o m e t e r : S o i l C l a s s i f i c a t i o n Chart (adapted from M a r c h e t t i and C r a p p s , l 9 8 l ) 62 c o r r e c t e d f o r u n i t weight has been added. • Ed - Dilatometer Modulus Ed i s d e r i v e d from the d i l a t o m e t e r t e s t u sing the theory of e l a s t i c i t y and has been proposed to represent a deformation modulus ( M a r c h e t t i , 1980). With t h i s a n a l y s i s the s o i l i s assumed to be p e r f e c t l y e l a s t i c . Ed i s p r i m a r i l y used as a c o r r e l a t i o n parameter to other g e o t e c h n i c a l p r o p e r t i e s and as an i n d i c a t o r of s o i l s t i f f n e s s . T h i s parameter does not r e q u i r e estimates of e i t h e r Uo or u n i t weight. For the program of d i l a t o m e t e r t e s t s which monitor the t e s t f i l l behaviour, the d i s c u s s i o n i s l i m i t e d to the parameters Kd and Ed with P0 and P1 i n c l u d e d i n p l a c e of the M a t e r i a l Index, Id. The i n t e r p r e t e d parameters of undrained shear s t r e n g t h and c o n s t r a i n e d modulus are d i s c u s s e d i n l a t e r c hapters of the r e p o r t . Pore Pressure E f f e c t s T h i s s e c t i o n w i l l present h i g h l i g h t s of the thorough d i s c u s s i o n of pore p r e s s u r e e f f e c t s given by Robertson (1982). The assumption of a h y d r o s t a t i c groundwater c o n d i t i o n can s i g n i f i c a n t l y a f f e c t the parameters Id and Kd when a non-h y d r o s t a t i c ground water c o n d i t i o n e x i s t s i n the f i e l d . T h i s i s p a r t i c u l a r l y t rue i n the case of s o f t c l a y e y s o i l s at depth where the magnitude of Uo can be as high as that of P0 and the d i f f e r e n c e P1-P0 i s s m a l l . The d i l a t o m e t e r t e s t i s a l s o a f f e c t e d by pore pressure d i s s i p a t i o n that occurs between the time p e n e t r a t i o n i s 63 stopped and the time membrane i n f l a t i o n begins. To reduce the d i s s i p a t i o n e f f e c t s , the e x i s t i n g procedure recommends that the t e s t be performed "without delay"; an adequate s t i p u l a t i o n f o r the t e s t i n g of normally c o n s o l i d a t e d c l a y s . 3.3.4 I n s t a l l a t i o n Of The P e n e t r a t i o n T e s t s Both the cone p e n e t r a t i o n t e s t and the d i l a t o m e t e r t e s t were i n s t a l l e d u s ing the UBC G e o t e c h n i c a l Research t r u c k . The truck i s equipped with two v e r t i c a l h y d r a u l i c p i s t o n s which are l i m i t e d to p r o v i d i n g 75kN of t h r u s t ; the r e a c t i o n f o r c e of the t r u c k . The p e n e t r a t i o n t e s t s were performed at the standard r a t e of 2cm/sec. A complete d e s c r i p t i o n of the r e s e a r c h v e h i c l e , i t s h y d r a u l i c c o n t r o l s , and i n s t r u m e n t a t i o n i s given by Campanella and Robertson (1981). 3.4 SCREW PLATE TEST; INCREMENTAL LOADING TESTS  3.4.1 Equipment The development of a screw p l a t e system at the U n i v e r s i t y of B r i t i s h Columbia that i s compatible with the G e o t e c h n i c a l Research truck was achieved i n 1981 ( B e r z i n s and Campanella, 1981). The UBC system c u r r e n t l y f e a t u r e s a 500cm 2 s i n g l e f l i g h t screw p l a t e which can be recovered at the end of a sounding and a s e r v o - c o n t r o l l e d h y d r a u l i c l o a d i n g system which can p r o v i d e a wide range of l o a d i n g modes. 64 1 . I n s t a l l a t i o n I n s t a l l a t i o n of the screw p l a t e and rods i s accomplished through a combination of t h r u s t , from the h y d r a u l i c p i s t o n s , and r o t a t i o n , from a h y d r a u l i c torque motor. A schematic of the screw p l a t e system i s shown in F i g u r e 3.13. The one-metre l e n g t h screw p l a t e rods are s p e c i a l l y s p l i n e d at the c o u p l i n g to allow both c l o c k w i s e and c o u n t e r - c l o c k w i s e r o t a t i o n d u r i n g i n s t a l l a t i o n and removal of the p l a t e . D e t a i l s of the screw p l a t e design and the s u p p o r t i n g h y d r a u l i c system are given by B e r z i n s and Campanella (1981). The l o a d i n g of the screw p l a t e i s done v i a the screw p l a t e rods; the l o a d i s a p p l i e d from above ground su r f a c e through the h y d r a u l i c p i s t o n s l o c a t e d i n the t r u c k . The load a p p l i e d to the screw p l a t e was recorded by a l o a d c e l l p l a c e d i n - l i n e at the head of the screw p l a t e rod s t r i n g . The a c t u a l l o a d at the screw p l a t e i s found by c o r r e c t i n g the l o a d c e l l r e a d i n g by i n c l u d i n g a d d i t i o n a l l o a d due to rod weight and s u b t r a c t i n g the estimate l o s s due to rod f r i c t i o n . A x i a l displacements were recorded at the ground s u r f a c e by a d i r e c t c u r r e n t displacement transducer (DCDT) mounted independently from the l o a d i n g frame on a r e f e r e n c e beam. The e l a s t i c compression of the screw p l a t e rods i s c a l c u l a t e d to be about 0.25 c e n t i m e t r e s a t 90kN l o a d f o r 20 metres of rod. For a l l the screw p l a t e t e s t s performed i n t h i s study the l o a d was l e s s than 15kN and the rod l e n g t h l e s s than 15 metres g i v i n g , by p r o p o r t i o n , a compression of l e s s than 0.03 c e n t i m e t r e s . E l a s t i c compression of the rods was t h e r e f o r e n e g l e c t e d i n TORQUE MOTOR 2000 Nm (17,000 In.lbs.) TORQUE OUTPUT at 140 bar (2000 pil) INPUT PRESSURE 0-100 RPM HYDRAULIC PISTOMS TOTAL THRUST AREA 122 tq.cm. (18 88 to In) MAXIMUM SAFE THRUST 75 KN (17,000 Ibt.) WITHOUT ANCHORS SCREW PLATE FLOW FORWARD-SYSTEM RATE REVERSE CUTOFF CONTROL CONTROL MAIN TRUCK HYDRAULICS MANUAL PISTON CONTROL! SERVO-LOOP CONTROLLER 0 4 SCREW PLATE R0D8 4 45 cm. (179 In.) O.D. - 1015 6RADE MECHANICAL STEEL TUBIN8 1-27 cm (-5 In) ft 21 SPLINE COUPLINGS MAXIMUM TENSILE LOAD ACROSS PINNED COUPLIN0S 22 UN (9000 Ibl.)  TORQUE PLATE LOAD CELL OUTER RING CONNECTED TO PISTONS INNER RMG ATTACHED TO BASE OF TORQUE MOTOR GAUGES ATTACHED TO SPOKES CELL OUTPUT 10 mV at 2000 Nm im> CELL AXIAL [J 1 LOAD _ GAUGES [§] 1 TORQUE 11 GAUGES THRUST BEARING HOUSINQ FEMALE SPLINE TO RECEIVE MOTOR HUB 'ROLLER BEARINGS MALE SPLINE t 2cm TRAVEL DISPLACEMENT TRANSDUCER - TRANSTEK LVDT ± 3* (76 cm) - MAGNET ATTACHED TO RODS FIG. 3 / 3 S CHEMATIC REPRESENTATION 0 F SCREW PLATE SYSTEM 66 t h i s study. Two types of screw p l a t e t e s t were performed. The f i r s t type of t e s t i s a d r a i n e d t e s t to determine the c o n s t r a i n e d modulus M, which i s u s e f u l i n settlement a n a l y s e s . In t h i s t e s t the p l a t e movement versus time was recorded f o r a constant l o a d and was repeated fo r s e v e r a l i n c r e a s i n g l o a d l e v e l s . T h i s t e s t i s r e f e r r e d to as the incremental l o a d t e s t and i s the t e s t proposed by Janbu and Senneset (1973) f o r d e t e r m i n a t i o n of the c o n s t r a i n e d modulus, M. The second type of t e s t i s an undrained l o a d d e f l e c t i o n t e s t . T h i s t e s t i n v o l v e s a r e l a t i v e l y r a p i d r a t e of l o a d i n g u n t i l the u l t i m a t e screw p l a t e bearing i s achieved. T h i s t e s t i s termed the u l t i m a t e l o a d t e s t i n t h i s study and w i l l be d i s c u s s e d i n g r e a t e r d e t a i l i n a l a t e r c h a p ter. 3.5 GROUNDWATER CONDITIONS Measurements of e q u i l i b r i u m pore p r e s s u r e s made with the piezometer cone at the t e s t f i l l s i t e i n d i c a t e a non-h y d r o s t a t i c groundwater c o n d i t i o n . F i g u r e 3.14 shows e q u i l i b r i u m pore pr e s s u r e s from measurements made d u r i n g a s i n g l e cone sounding p l o t t e d versus e l e v a t i o n . The CPT was performed i n the wick d r a i n area of the s i t e p r i o r to embankment c o n s t r u c t i o n . S i m i l a r r e s u l t s were found in the area without wick d r a i n s . The e q u i l i b r i u m pore p r e s s u r e s i n F i g u r e 3.14 i n d i c a t e the presence of a perched water t a b l e i n the organic s o i l s 67 PORE PRESSURE (METERS OF WATER PRESSURE) G R O U N D Q_ S U R F A C E 0 5 v I I i I i i i i CO Ui t-l i l 2 10H 15H 20-Q. UJ Q 25 3 OH 35-" 10 15 I I I I I I I 20 25 30 i i i i i i i i i SAND B .C . HIGHWAYS T E S T FILL * PIEZOMETER CONE SOUNDING: 8CP 2014-15 <4_ of WICK DRAIN AREA) CONE C6FPST - 3UBC K E Y : + EQUIL IBRIUM P O R E P R E 8 8 U R E - M E A 8 U R E D O EQUIL IBRIUM P O R E P R E S 8 U R E - E S T I M A T E D F O R C A L C U L A T I O N O F t , 0 F i g . 3.14 E q u i l i b r i u m pore pressures versus e l e v a t i o n . 68 above 15m depth. The cause of the excess water pressure (about 20kPa) between depths 3.5m and 11.0m i s not f u l l y understood. A p o r t i o n of the excess pressure can be a t t r i b u t e d to the l o a d of the sand working pad that was i n p l a c e at the time of the t e s t s . An i n t e r e s t i n g c o n d i t i o n i s seen below 15m depth. Here the e q u i l i b r i u m values are much lower than the expected h y d r o s t a t i c v a l u e . The geology t r a n s i t i o n s at 15m depth from organic s o i l s t o sands. The sand l a y e r i s about 12m t h i c k and c o n t a i n s two s i l t l a y e r s that are 1 to 2 metres t h i c k . E q u i l i b r i u m pore p r e s s u r e s i n the sand l a y e r measured with the piezometer cone on d i f f e r e n t days were observed to vary by about 0.5 bar (approx. 5m of water p r e s s u r e ) . Approximately 120m south of the s i t e i s a channel of the F r a s e r R i v e r . The normal t i d a l v a r i a t i o n of the F r a s e r R i v e r near the t e s t f i l l s i t e i s about 4 metres (Hoos and Packman, 1974). I n q u i r y at a l o c a l boat marina r e v e a l e d that t i d a l changes up to 6 metres have o c c u r r e d i n extreme cases. I t i s concluded t h a t the pore water of the sands below 15m depth i s i n h y d r a u l i c communication with the F r a s e r R i v e r . The f l u c t u a t i o n s of pore water p r e s s u r e s i n the sand are a l s o l i k e l y t o i n f l u e n c e the v e r t i c a l drainage from the perched water t a b l e i n the organic s o i l s above. In a d d i t i o n to the n o n - h y d r o s t a t i c groundwater c o n d i t i o n at the s i t e , there are pore pressure v a r i a t i o n s due to both embankment l o a d i n g and the presence of wick d r a i n s . Embankment l o a d i n g w i l l cause the pore p r e s s u r e s to r i s e i n 69 keeping with the v e r t i c a l d i s t r i b u t i o n of t o t a l s t r e s s e s . During c o n s o l i d a t i o n the excess pore pr e s s u r e s w i l l d i s s i p a t e u n t i l an e q u i l i b r i u m s t a t e i s reached. The presence of wick d r a i n s i n a s o i l l a y e r s u b j e c t to l o a d i n g r e s u l t s i n a h o r i z o n t a l v a r i a t i o n of excess pore p r e s s u r e s , see F i g u r e 3.15. A h o r i z o n t a l v a r i a t i o n of pore p r e s s u r e s means that the t o t a l s t r e s s measurements from i n - s i t u t e s t s w i l l depend on the h o r i z o n t a l d i s t a n c e of the sounding from the wick d r a i n s . The groundwater c o n d i t i o n s d e s c r i b e d above have important consequences f o r i n - s i t u t e s t measurements. The e f f e c t s of a changing e q u i l i b r i u m pore pressure have been d i s c u s s e d p r e v i o u s l y with respect to i n t e r p r e t a t i o n of the CPT and DMT du r i n g embankment l o a d i n g . 70 _4 4 t_ Z (M) t 1 ' — ^ t - o V t . t , U = U, AU _ U = 0 Arrows i n d i c a t e d i r e c t i o n of pore water flow F i g u r e 3.15 Excess pore water p r e s s u r e v a r i a t i o n i n the h o r i z o n t a l d i r e c t i o n i n a homogenous s o i l l a y e r with v e r t i c a l d r a i n s , (adapted from Hansbo, 1975) 71 IV. TEST FILL MONITORING USING THREE IN-SITU TESTS  4.1 INTRODUCTION T h i s s e c t i o n w i l l present and d i s c u s s the r e s u l t s of an i n - s i t u t e s t i n g program that was c a r r i e d out over a p e r i o d of approximately one year with the purpose of m o n i t o r i n g the s o i l c o n d i t i o n s below the t e s t f i l l . The i n - s i t u t e s t i n g program c o n s i s t e d of t h i r t e e n cone p e n e t r a t i o n soundings, three d i l a t o m e t e r soundings and s i x f i e l d vane p r o f i l e s . A summary of the i n - s i t u t e s t s i s given i n Table 4.1. The l o c a t i o n s of the i n - s i t u t e s t s are shown i n F i g u r e 4.1. The c o n s t r u c t i o n sequence of the t e s t f i l l and the settlement versus l o g time records have been presented p r e v i o u s l y ( r e f e r to F i g u r e s 2.4, 2.5 and 2.6). To f a c i l i t a t e comparisons, the t e s t p r o f i l e s are presented i n o v e r l a y form and are sequenced with time to i l l u s t r a t e the p r o g r e s s i o n of events. Complete cone logs are given so that the f u l l i n t e r a c t i o n of the measured parameters can be observed. To f a c i l i t a t e comparisons between cone soundings made at d i f f e r e n t e l e v a t i o n , a l l cone logs are p l o t t e d versus e l e v a t i o n r a t h e r than versus depth. T e s t s made i n the non-wick area are pre s e n t e d f i r s t , w i t h the wick area t e s t s f o l l o w i n g as a s p e c i a l case of the non-wick area c o n d i t i o n s . The r e f e r e n c e t e s t s used to e s t a b l i s h the ' i n i t i a l c o n d i t i o n s ' have been d i s c u s s e d p r e v i o u s l y . On each f i g u r e i s shown the cumulative settlement' f o r the date of t e s t i n g . T h i s settlement i n c l u d e s deep set t l e m e n t . 72 TABLE 4.1 SUMMARY OF IN-SITU TESTING: TEST FILL SITE Sounding Location Date Final Depth Elevation Remarks (m) (m) CONE PENETRATION TESTS 1. CPT- 1 Non-W i ck 10-1 1 -81 75 .0 1 .90 2. CPT- 2 Wick 11-11 -81 33 .0 1 .50 3. CPT- 3 Non-Wick 11-11 -81 34 .6 1 .90 4. CPT- 4 Wick 27-1 1 -81 34 .6 0 .85* 5. CPT- 5 Non-W1ck 27-1 1 -81 35 .4 0, .90* 6. CPT-6 Wick 17-02 -82 35 .0 4, .77 7 . CPT- 7 Non-Wick 22-02 -82 36, .0 5. ,22 10. CPT- 10 Wick 26-05 -82 35, .0 5. ,82 12 . CPT- 12 Non-Wick 27-05 -82 37, ,0 5. 30 16 . CPT- 16 Non-W i ck 16-08 -82 1 1 . 5 5. 17 17. CPT- 17 Wick 13-10 -82 24 . 3 5. 55 18 . CPT- 18 Non-W i ck 13-10 -82 21 . 2 5. 14 19. CPT- 19 Non-Wick 26-01 -83 19. 6 5. 05 I n i t i a l Conditions I n i t i a l Conditions P. P. Dissipations Adjacent to F111 Adjacent #E.O.C. + E.O.C. + E.O.C. + E.O.C. + to F i l l 20 Days 25 Days 118 Days 119 Days P. P. Dissipations E.O.C. + 258 Days E.O.C. + 258 Days P. P. Dissipations DILATOMETER TESTS DMT- 1 DMT-4 DMT-5 Wick Non-Wick Wick 16- 02-82 15-06-82 17- 06-82 21 .0 27.0 27.4 4.82 E.O.C. + 19 Days 5.27 E.O.C. + 138 Days 5.77 E.O.C. + 140 Days Pore Pressure Diss i p a t i o n * Original Ground Elevation # End of Construction ZL 74 The c o n t r i b u t i o n of deep settlements by the end of the t e s t s e r i e s i s about 8cm i n the non-wick area and 25cm i n the wick area. The settlements are p o r t r a y e d i n the f i g u r e s as the change i n e l e v a t i o n of the con t a c t between the sand f i l l and the n a t u r a l s o i l s . The e q u i l i b r i u m pore pressure l i n e , Uo, i s only an approximation due to the v a r i a t i o n of Uo with time at the s i t e . On March 23, 1982 (End of C o n s t r u c t i o n + 56 Days) an a d d i t i o n a l 1.5m l i f t of f i l l was p l a c e d on the wick end only, r a i s i n g the t o t a l f i l l on the wick end to 8.5m. T h i s event i s noted on the a p p r o p r i a t e figure.' As p r e v i o u s l y noted, the term 'End of C o n s t r u c t i o n ' r e f e r s to day 98 when the f i f t h l i f t of f i l l was added, b r i n g i n g the t o t a l f i l l p l a c e d to 7.0m f o r both the wick and non-wick ends. Then, f o r example, End of C o n s t r u c t i o n + 25 Days w i l l r e f e r to day 123 on the settlement versus l o g time r e c o r d s . 4.2 MONITORING: AREA WITHOUT WICK DRAINS  4.2.1 Cone P e n e t r a t i o n T e s t s 1. I n i t i a l C o n d i t i o n s To End Of C o n s t r u c t i o n + 25 Days • Cone Bearing R e s i s t a n c e , Qt; (see F i g u r e 4.2) At 25 days a f t e r the end of c o n s t r u c t i o n the non-wick su r f a c e settlement i s 2.3 metres. Almost a l l of t h i s settlement o c c u r r e d d u r i n g c o n s t r u c t i o n . At the end of PORE PRESSURE FRICTION RESISTANCE BERRING RESISTANCE FRICTION RATIO DIFFERENTIAL P . P . SOIL U (BAR) FC (BAR) OT (BAR) RF-FC/OT (Z) RATIO &U/OT PROFILE 0 5 . 0 0 0 . 5 0 2 0 . 0 0 1 0 . 0 0 . 8 0 1 . 0 UI •11.OH 1 7 . 0 1 .0' -5.04 h - 1 1 . 0 - 1 7 . 0 • • i r - 5 . 0 1.0' - 1 1 . 0 4 _ i I i u Settlement « 2.30 M 1 . 0 ' I n i t i a l Conditions - 5 . 0 End of Construction + 25 Days i i i i—r-1 1 . 0 • 1 7 . 0 - 1 K-17. 0-1 3t Equilibrium Pore Pressure F1g.4.2 NON-WICK AREA CONE PENETRATION TEST COMPARISON: I n i t i a l Conditions vs. End of Construction + 25 Days - 5 . 0 11.0' 1 7 . 0 FILL SAND FIBROUS PEAT (Pt) AMORPHOUS PEAT (Pt) to ORGANIC CLAY (OH) SILT (ML) SAND (SP) -J tn 76 c o n s t r u c t i o n a 'mud wave' type of s u b s o i l f a i l u r e r e s u l t e d i n a sudden 0.6m settlement. The f i e l d piezometer records show that only a small amount of pore pressure d i s s i p a t i o n o c c u r r e d d u r i n g c o n s t r u c t i o n . A l r e a d y , a c o n s i d e r a b l e i n c r e a s e i n Qt has o c c u r r e d above -6.5m e l e v a t i o n ; almost d o u b l i n g above -5m e l e v a t i o n . The improved Qt r e f l e c t s a zone where s i g n i f i c a n t i n c r e a s e s i n h o r i z o n t a l s t r e s s have o c c u r r e d . No i n c r e a s e i n Qt i s observed below -6.5m e l e v a t i o n . The absence of improvement in Qt below -6.5m i n d i c a t e s t h a t the s o i l s d i s p l a c e d d u r i n g f a i l u r e came from below the peat mat. I t i s i n t e r e s t i n g that no major l o s s of b e a r i n g r e s i s t a n c e appears to be a s s o c i a t e d with the f a i l u r e . I t i s i n t e r e s t i n g to note t h a t , by s u b t r a c t i n g the dynamic pore pressure generated dur i n g p e n e t r a t i o n from the t o t a l s t r e s s b e a r i ng r e s i s t a n c e the e f f e c t i v e s t r e s s r e q u i r e d f o r p e n e t r a t i o n can be found. For example, at -11m e l e v a t i o n , f o r the i n i t i a l c o n d i t i o n s sounding, the e f f e c t i v e bearing r e q u i r e d f o r p e n e t r a t i o n i s about one-half of the t o t a l s t r e s s measurement. • F r i c t i o n R e s i s t a n c e , Fc; The most s t r i k i n g f e a t u r e of the f r i c t i o n r e s i s t a n c e p r o f i l e i s the decrease i n f r i c t i o n r e s i s t a n c e measured below -6.5m e l e v a t i o n . From -6.5m to -12.5m e l e v a t i o n the f r i c t i o n s t r e s s p r o f i l e i s n e a r l y constant with depth. The r e d u c t i o n i n f r i c t i o n r e s i s t a n c e i s at most 0.1 bar. T h i s i s a very 77 small v a l u e . N e v e r t h e l e s s , the decrease i n measured f r i c t i o n r e s i s t a n c e r e p r e s e n t s a s u b s t a n t i a l percentage of the o r i g i n a l v a l u e . I t i s proposed that the decrease i n measured f r i c t i o n s t r e s s i s r e l a t e d to the mud wave f a i l u r e and p o s s i b l y r e p r e s e n t s a decrease i n h o r i z o n t a l s o i l c o n s t r a i n t due to l a t e r a l s t r a i n and shear. However, i t i s anomolous that the g r e a t e s t decreases i n f r i c t i o n r e s i s t a n c e occurred at the g r e a t e s t depth. From o r d i n a r y s t r e s s d i s t r i b u t i o n a n a l y s i s we would expect that the m a j o r i t y of the d i s p l a c e d s o i l s would come from high i n the s t r a t a where the a p p l i e d s t r e s s would be g r e a t e s t . • F r i c t i o n R a t i o , Rf; The i n i t i a l c o n d i t i o n s Rf i s between 6 and 8 .percent f o r the f i b r o u s peats and i s n e a r l y constant at 3 percent f o r the organic c l a y s . The end of c o n s t r u c t i o n + 25 days (EOC + 25 Days) p r o f i l e shows a decrease i n Rf to 3 to 5 percent f o r the f i b r o u s peat and a s l i g h t decrease to 2 percent f o r the organic c l a y s . In the organic c l a y s t r a t a the r a t i o has a s l i g h t tendency to decrease with depth. Although the change i n Rf i s f a i r l y s i m i l a r f o r both peat and organic c l a y , d i f f e r e n t mechanisms are r e s p o n s i b l e i n each s o i l . The decrease i n Rf f o r the f i b r o u s peat i s due to a g r e a t e r r e l a t i v e i n c r e a s e i n Qt, whereas the decrease i n Rf f o r the organic c l a y s i s p r i m a r i l y due to the decrease i n Fc. 78 • Pore Pressure, U; G e n e r a l l y , a small i n c r e a s e i n t o t a l dynamic pore pressu r e , U, of about 0.5 bar (5 metres of water pressure) i s observed f o r the organic s o i l s . One e q u i l i b r i u m pore pressure measurement was made i n the organic s o i l s d u r i n g each of the soundings. A gr e a t e r number of measurements i s r e q u i r e d to a c c u r a t e l y e s t a b l i s h Uo with depth. With Uo e s t a b l i s h e d the c o n t r i b u t i o n of Ue can be found a c c o r d i n g to U = Ue + Uo. The lack of an adequate p r o f i l e of Uo presents a major d e f i c i e n c y i n t h i s study. Supplementary e q u i l i b r i u m pore pressure data c o u l d be obtained from the f i e l d piezometer r e c o r d s . However, d i s c r e p a n c i e s were found when the f i e l d r ecords of d i f f e r e n t piezometers were compared and the c r e d i b i l i t y of the f i e l d r ecords f o r t h i s purpose was reduced. • D i f f e r e n t i a l Pore Pressure R a t i o , AU/Qt; As d i s c u s s e d above, the d i f f e r e n t i a l pore p r e s s u r e r a t i o does not r e f l e c t the c o r r e c t Uo p r o f i l e f o r the t e s t EOC+25 days. The r e c o r d of f i e l d piezometer 607A (-9.6m e l e v . ) at the time would i n d i c a t e a Uo that i s about 0.6 bar g r e a t e r than h y d r o s t a t i c p r e s s u r e . A c a l c u l a t i o n of AU/Qt based on t h i s data i n d i c a t e s that the d i f f e r e n t i a l pore pressure r a t i o at -9.6m e l e v a t i o n i s s i m i l a r i n magnitude to the i n i t i a l c o n d i t i o n s p r o f i l e . At -9.6m e l e v a t i o n , and f o r the organic c l a y s i n g e n e r a l , no i n c r e a s e i n measured Qt oc c u r r e d . I t i s i n f e r r e d t h a t , f o r the organic c l a y s , the i n c r e a s e i n dynamic 79 pore pressure generated by p e n e t r a t i o n i s p r i m a r i l y due to an in c r e a s e i n Uo r a t h e r than an i n c r e a s e i n Ue. 2. End Of C o n s t r u c t i o n + 25 Days To End Of C o n s t r u c t i o n  + 119 Days • Cone Bearing R e s i s t a n c e , Qt; (see F i g u r e 4.3) The t o t a l settlement at EOC+119 days i s 2.62m. Th i s r e p r e s e n t s an a d d i t i o n a l 0.32m settlement i n 94 days s i n c e EOC+25 days. I t i s expected t h a t the cone b e a r i n g r e s i s t a n c e w i l l i n c r e a s e with time. Although F i g u r e 4.3 shows some in s t a n c e s where Qt has i n c r e a s e d above -5m e l e v a t i o n there i s no o v e r a l l t rend f o r the p r o f i l e . The m a j o r i t y of f i e l d piezometers showed that the excess pore p r e s s u r e s d i s s i p a t e d r e l a t i v e l y r a p i d l y ( d e c r e a s i n g approximately 0.2 bar between -10 to -12m elev. ) d u r i n g the 94 day p e r i o d . A small i n c r e a s e i n b e a r i n g would be i n f e r r e d from the d i s s i p a t i o n but no in c r e a s e i s evident from the .CPT p r o f i l e . A probable cause of the u n c l e a r Qt tr e n d i s s p a t i a l v a r i a t i o n of the s o i l and the somewhat l i m i t e d s e n s i t i v i t y , of the equipment. Evidence of s p a t i a l v a r i a t i o n can be seen i n the presence of l a r g e generated pore p r e s s u r e s above -5m e l e v a t i o n which l i k e l y i n d i c a t e s i l t i n c l u s i o n s i n the peat. O v e r a l l the d i f f e r e n c e between Qt p r o f i l e s i s smal l and , when measurement e r r o r a s s o c i a t e d with the bearing l o a d c e l l s e n s i t i v i t y i s con s i d e r e d , the p r o f i l e s are e s s e n t i a l l y the same. ELEVATION CNETERS) cn 08 81 • F r i c t i o n R e s i s t a n c e , Fc; The f r i c t i o n r e s i s t a n c e shows a s t r i k i n g recovery i n the 94 day p e r i o d between t e s t s . The change i n r e s i s t a n c e ranges from about a 50% to a 100% i n c r e a s e . The recovery of f r i c t i o n r e s i s t a n c e i s a t t r i b u t e d to c o n s o l i d a t i o n drainage. The c h a r a c t e r of the p r o f i l e r e f l e c t s that of the previous sounding, remaining n e a r l y constant with depth. I n c i d e n t a l l y , c o n s i d e r a b l e s p a t i a l v a r i a t i o n i n the s i l t at -13.5m e l e v a t i o n i s shown i n the f r i c t i o n p r o f i l e . 3. End Of C o n s t r u c t i o n + 119 Days To End Of C o n s t r u c t i o n  + 258 Days • Cone Bearing R e s i s t a n c e , Qt; (see F i g u r e 4.4) The t o t a l settlement at EOC+258 i s 2.81m which rep r e s e n t s an a d d i t i o n a l 0.19m of settlement i n 139 days. The rate of pore pressure d i s s i p a t i o n measured by the f i e l d piezometers d u r i n g t h i s 139 day p e r i o d decreased i n comparison to the pr e v i o u s 94 day t e s t i n t e r v a l . The expected b e a r i n g i n c r e a s e f o r t h i s 139 day p e r i o d i s consequently reduced i n magnitude. However, comparison of the Qt p r o f i l e s shows that an apparent decrease i n Qt has occurred above -5m e l e v a t i o n . T h i s i s c o n t r a r y to the expected t r e n d and i s l i k e l y due to s i l t i n c l u s i o n s above -5m e l e v a t i o n i n the 119 day p r o f i l e . PORE PRESSURE FRICTION RES[STANCE BEARING RESISTANCE FRICTION RATIO DIFFERENTIAL P . P . SOIL U (BAR) FC (BAR) OT (BAR) RF-FC/QT (Z) RATIO AU/OT PROFILE 00 M jjj- Equilibrium Pore Pressure Fig. 4.4 NON-WICK AREA CONE PENETRATION TEST COMPARISON: End of Construction + 119 Days vs. End of Construction + 258 Days 83 • F r i c t i o n R e s i s t a n c e , Fc; As can be seen i n the f i g u r e , the f r i c t i o n r e s i s t a n c e i s e s s e n t i a l l y unchanged f o r the m a j o r i t y of the p r o f i l e . T h i s i s a s i m i l a r s i t u a t i o n to that of the b e a r i n g r e s i s t a n c e . The r e l a t i v e l y unchanged bearing and f r i c t i o n may i n d i c a t e that a sm a l l e r i n c r e a s e i n s t r e n g t h o c c u r r e d d u r i n g t h i s time p e r i o d than was o r i g i n a l l y expected. 4. I n i t i a l C o n d i t i o n s To End Of C o n s t r u c t i o n + 258 Days T h i s s e c t i o n summarizes the CPT trends f o r the non-wick a r e a . • Cone Bearing R e s i s t a n c e , Qt; (see F i g u r e 4.5) a. A f t e r 258 days of c o n s o l i d a t i o n , i n c r e a s e s i n b e a r i n g r e s i s t a n c e were c o n f i n e d to the upper 6m of s o f t d e p o s i t s i n d i c a t i n g a l i m i t e d extent of c o n s o l i d a t i o n with depth. T h i s agrees with the vane t e s t r e s u l t s (see F i g u r e 4.7) which a l s o show that the improvement o c c u r r e d above -6m e l e v a t i o n . Assuming that Nk i s constant with l o a d i n g and given that Nk i s approximately 5 f o r the f i b r o u s o r g a n i c s the undrained shear s t r e n g t h p r e d i c t e d by the Qt p r o f i l e can be compared with the f i e l d vane r e s u l t s . At -3m e l e v a t i o n the f i e l d vane i n d i c a t e s a s t r e n g t h of about 60kPa. At the same depth the cone p r e d i c t s a s t r e n g t h of about 80kPa. T h i s shows that most of the i n c r e a s e i n cone bearing was due to an increase i n the undrained shear s t r e n g t h . The a d d i t i o n a l s t r e n g t h i n d i c a t e d by the cone b e a r i n g probably r e f l e c t s an increase i n the v e r t i c a l e f f e c t i v e s t r e s s . T h i s agrees with r e s e a r c h by Law PORE PRESSURE FRICTION RESISTANCE BEARING RESISTANCE FRICTION RATIO DIFFERENTIAL P . P . SOTL •+ Equilibrium Pore Pressure Fig. 4.5 NON-WICK AREA CONE PENETRATION TEST COMPARISON: I n i t i a l Conditions vs. End of Construction + 258 Days 85 (1979) which showed that the measured vane s t r e n g t h i s r e l a t i v e l y i n s e n s i t i v e to i n c r e a s e s i n the v e r t i c a l e f f e c t i v e s t r e s s . Because c o n s o l i d a t i o n o c c u r r e d p r i n c i p a l l y i n the upper p o r t i o n of the s t r a t a i t can be concluded that the drainage was p r i m a r i l y s i n g l e drainage v e r t i c a l l y to the ground s u r f a c e . A l i m i t e d amount of downward drainage can be i n f e r r e d from the s l i g h t improvement i n Qt between -10m and 14m e l e v a t i o n , F i g u r e 4.5. b. The non-wick cone p e n e t r a t i o n t e s t s e r i e s i n d i c a t e d that l i t t l e or no l o s s of be a r i n g r e s i s t a n c e r e s u l t e d from the mud-wave type s u b s o i l f a i l u r e . Some decrease was expected t o have o c c u r r e d . • F r i c t i o n R e s i s t a n c e , Fc; a. An i n c r e a s e i n f r i c t i o n r e s i s t a n c e o c c u r r e d f o r the c o n s o l i d a t i n g s o i l s , as expected. T h i s i n d i c a t e s that an in c r e a s e i n h o r i z o n t a l s t r e s s o c c u r r e d as a r e s u l t of the in c r e a s e d v e r t i c a l s t e s s i . e . , embankment l o a d i n g . b. At the end of c o n s t r u c t i o n (EOC+25 days t e s t ) a decrease i n f r i c t i o n r e s i s t a n c e was observed below -6m e l e v a t i o n . T h i s decrease i s a t t r i b u t e d t o d i s t u r b a n c e , p o s s i b l y a l o s s of h o r i z o n t a l c o n s t r a i n t , a s s o c i a t e d with the mud-wave type s u b s o i l f a i l u r e . c. At 258 days f o l l o w i n g the end of c o n s t r u c t i o n the f r i c t i o n r e s i s t a n c e shows c o n s i d e r a b l e improvement to -6m e l e v a t i o n . Between -6m and -9m e l e v a t i o n improvement i n Fc has a l s o o c c u r r e d . Here the Fc has recovered to approximately 86 equal the i n i t i a l c o n d i t i o n s . T h i s recovery r e q u i r e d about 9 months time. Below -9m e l e v a t i o n the f r i c t i o n r e s i s t a n c e has improved, but has not yet recovered to the i n i t i a l c o n d i t i o n v a l u e s . • F r i c t i o n R a t i o , Rf; a. The f r i c t i o n r a t i o was observed to decrease markedly f o r both peats and organic c l a y s due to the decrease i n f r i c t i o n r e s i s t a n c e d e s c r i b e d above. With the recovery of the f r i c t i o n r e s i s t a n c e , the f r i c t i o n r a t i o at 258 days a f t e r the end of c o n s t r u c t i o n i s approximately equal t o the i n i t i a l c o n d i t i o n r a t i o s . b. I t i s i n t e r e s t i n g t o note that the f r i c t i o n r a t i o maintained the same c h a r a c t e r i s t i c shape throughout the l o a d i n g and c o n s o l i d a t i o n p r o c e s s e s . • Pore P r e s s u r e , U; a. The t o t a l dynamic pore pressure tended to i n c r e a s e with l o a d i n g , as expected. T h i s i n c r e a s e appeared to r e f l e c t i n c r e a s e s i n the e q u i l i b r i u m pore p r e s s u r e , Uo, ra t h e r than the excess pore p r e s s u r e , Ue. A change i n Ue would r e f l e c t a change i n shear-volume c o u p l i n g behaviour of the organic s o i l s . b. T h i s study has served to p o i n t out the importance of e s t a b l i s h i n g an adequate and acc u r a t e p r o f i l e of e q u i l i b r i u m pore p r e s s u r e s , Uo, when the values of Uo are expected to change duri n g the course of study. I t i s a l s o suggested that 87 the measurements be taken at c o n s i s t e n t e l e v a t i o n s to ease comparisons between p r o f i l e s . F i e l d measurements of e q u i l i b r i u m pore p r e s s u r e s c o u l d be used to supplement a CPT study. However, i n the case of t h i s t e s t f i l l , a l a c k of confidence i n the piezometer readings combined with the lack of a one-dimensional l o a d i n g c o n d i t i o n rendered the f i e l d i n f o r m a t i o n e s s e n t i a l l y u s e l e s s f o r t h i s purpose. • D i f f e r e n t i a l Pore Pressure R a t i o , AU/Qt; a. In the case of t h i s t e s t f i l l a u s e f u l i n t e r p r e t a t i o n of the d i f f e r e n t i a l pore pressure r a t i o s s t r o n g l y depends on an adequate p r o f i l e of e q u i l i b r i u m pore p r e s s u r e s . U n f o r t u n a t e l y , the number of measurements of e q u i l i b r i u m pore pressure d u r i n g the CPT study proved to be inadequate f o r a proper assessment of the pore pressure response of the s o i l s . b. For the depth of o r g a n i c c l a y only a l i m i t e d amount of c o n s o l i d a t i o n o c c u r r e d and hence, a l i m i t e d i n c r e a s e was observed i n Qt. For t h i s r e g ion i t was found that the v a r i a t i o n i n dynamic pore pressure was p r i m a r i l y due to v a r i a t i o n i n e q u i l i b r i u m pore p r e s s u r e s . By accounting f o r the v a r i a t i o n i n e q u i l i b r i u m pore p r e s s u r e s u s i n g f i e l d piezometer data, the d i f f e r e n t i a l pore p r e s s u r e r a t i o f o r these s o i l s proved to be approximately constant throughout the monitored p e r i o d . 88 4.2.2 Dilatometer T e s t s 1. I n i t i a l C o n d i t i o n s To End Of C o n s t r u c t i o n + 138 Days (see F i g u r e 4.6) At the time of the t e s t EOC+138 days, approximately 2.66m of settlement had occurred and between 10% and 30% of the excess pore pressure at the end of c o n s t r u c t i o n i s estimated to have d i s s i p a t e d . • B a s i c Measurements, PO, P1, and D i l a t o m e t e r Modulus, Ed; Because of the i n c r e a s e d t o t a l s t r e s s due to l o a d i n g , the value of PO has i n c r e a s e d . The s h i f t i n PO can be seen c l e a r l y to a depth of -10m e l e v a t i o n . The d i f f e r e n c e between the PO and P1 p l o t s , which can be thought of as an i n d i c a t o r of the s o i l s t i f f n e s s , has i n c r e a s e d g r e a t l y above -5m e l e v a t i o n , - decreased between -5m and -10m e l e v a t i o n and i n c r e a s e d s l i g h t l y again between -10m and -13m e l e v a t i o n . The changes i n the q u a n t i t y (P1-P0) are c l e a r l y i l l u s t r a t e d i n the Ed p r o f i l e where (P1-P0) i s m u l t i p l i e d by 34.6 to represent a deformation modulus. The zone of g r e a t e s t i n c r e a s e i n s t i f f n e s s corresponds to the f i b r o u s peats with only a s l i g h t i n c r e a s e i n s t i f f n e s s o c c u r r i n g at g r e a t e r depth. The zone of d i m i n i s h e d s t i f f n e s s corresponds to the amorphous peats and the upper p o r t i o n of the organic c l a y s . At the time of t e s t i n g (EOC+138 days) the s o i l at mid-depth has about one-half of i t s o r i g i n a l s t i f f n e s s . F i e l d P0,P1,Vertical Stress Horizontal Dilatometer Modulus (MPa) Stress Index (MPa) Fig.4.6 NON-WICK AREA DILATOMETER TEST COMPARISON: I n i t i a l Conditions vs. End of Construction + 138 Days 90 pore p r e s s u r e measurements i n d i c a t e that h i g h excess pore p r e s s u r e s are present i n the organic c l a y zone with the highest excess pore pre s s u r e s measured i n the mid-depth r e g i o n . • H o r i z o n t a l S t r e s s Index, Kd; Acc o r d i n g to work by M a r c h e t t i (1980) a value of Kd gr e a t e r than 2.5 can i n d i c a t e an o v e r c o n s o l i d a t e d s o i l . Such a c o n d i t i o n can be seen f o r the i n i t i a l c o n d i t i o n s t e s t at e l e v a t i o n s above -6m. Some evidence of o v e r c o n s o l i d a t i o n c o u l d be present i n the i n i t i a l c o n d i t i o n s p r o f i l e because of d e s s i c a t i o n and ground water f l u c t u a t i o n s t h a t are a p a r t of the area's n a t u r a l h i s t o r y . O v e r c o n s o l i d a t i o n due to groundwater f l u c t u a t i o n s does not appear to be s i g n i f i c a n t at t h i s s i t e because the n a t u r a l peat e x i s t s under very low e f f e c t i v e s t r e s s e s . Most l i k e l y , the high Kd i n peats does not r e p r e s e n t an o v e r c o n s o l i d a t e d c o n d i t i o n but ra t h e r that the i n t e r a c t i o n between the f i b r o u s o r g a n i c m a t e r i a l s , h o r i z o n t a l l y a l i g n e d , gave an i n c r e a s e i n Kd. Upon l o a d i n g , the value of Kd decreases as shown by t e s t EOC+138 days. The ambient pore pressure i s assumed to be h y d r o s t a t i c and t h e r e f o r e f a i l s to i n c l u d e the excess pore p r e s s u r e s that are i n f a c t p r e s e n t . Because of t h i s , the value of Kd i s over estimated. Using data from the f i e l d piezometer records to account f o r the excess pore p r e s s u r e , the Kd value at -10m e l e v a t i o n would decrease from 1.6 to about 1.2. 91 At EOC+138 days the e r r o r due to the e s t i m a t i o n of u n i t weight i s dimi n i s h e d because the v e r t i c a l e f f e c t i v e s t r e s s has in c r e a s e d due to l o a d i n g . The under e s t i m a t i o n of Kd due to u n i t weight e r r o r i n t h i s case i s about 20% or 0.4. The r e f o r e , f o r t h i s p a r t i c u l a r s i t u a t i o n , the e r r o r s due to the assumed h y d r o s t a t i c c o n d i t i o n and the assumed u n i t weight tended to c a n c e l each other out. Consequently, the EOC+138 day p r o f i l e of Kd i s approximately c o r r e c t as presented i n Figu r e 4.6. 4.2.3 F i e l d Vane Te s t s 1. I n i t i a l C o n d i t i o n s To End Of C o n s t r u c t i o n + 236 Days (see F i g u r e 4.7) As can be seen i n F i g u r e 4.7, the vane t e s t s show that s i g n i f i c a n t improvement' i n undrained shear s t r e n g t h i s r e a l i z e d to a depth of -6m e l e v a t i o n . Below t h i s e l e v a t i o n the vane i n d i c a t e s a decrease i n undrained shear s t r e n g t h that appears to worsen with depth. T h i s trend i s s i m i l a r to that of the Fc and Qt p r o f i l e s of the non-wick CPT's i n F i g u r e 4.5. According to piezometer 607A at -9.6m e l e v a t i o n the excess pore water pressure at EOC+236 days was about 45kPa. The excess pore water pressures are expected to i n c r e a s e the f i e l d vane Su v a l u e s . The comparison between i n i t i a l and f i n a l t e s t s shown i n Fi g u r e 4.7 c o n t r a d i c t s the expected r e s u l t s p a r t i c u l a r l y below -6m e l e v a t i o n where the EOC+236 day r e s u l t s are l e s s than the i n i t i a l c o n d i t i o n s . The low values of Su from the EOC+236 day t e s t l i k e l y r e f l e c t the d i s t u r b a n c e 92 Undrained Shear S t r e n g t h ( S u ) , (KPa) 0 10 ZO 30 4 0 SO 60 70 -I 104 ~i 1 1 1 1 r NON-WICK AREA FIELD VANE TEST Nilcon Swedish Vane Borer: 6.5cm x 13.0cm Vane O——O I n i t i a l Conditions •i + End of Construction + 236 Days Fig.4.7 FIELD VANE TEST COMPARISON: I n i t i a l C o n d i t i o n s v s . End of C o n s t r u c t i o n + 236 Days 93 caused by the s u b s o i l f a i l u r e . The magnitude of improvement i n undrained shear s t r e n g t h measured by the f i e l d vane, assuming Nk i s constant at 5 f o r the f i b r o u s peat, i s about two- t h i r d s of the undrained s t r e n g t h p r e d i c t e d by the cone be a r i n g p r o f i l e i n F i g u r e 4.5. The a d d i t i o n a l cone b e a r i n g i s probably due to the i n c r e a s e d v e r t i c a l e f f e c t i v e s t r e s s . 4.3 MONITORING: WICK DRAIN AREA 4.3.1 Cone P e n e t r a t i o n T e s t s 1 . I n i t i a l C o n d i t i o n s To End Of C o n s t r u c t i o n + 20 Days • Cone Bearing R e s i s t a n c e , Qt; (see Fig u r e 4.8) At 20 days a f t e r the end of c o n s t r u c t i o n , the sur f a c e settlement i s 3.15m i n the wick d r a i n area. Almost a l l of t h i s settlement o c c u r r e d d u r i n g c o n s t r u c t i o n , with about 20 cm o c c u r r i n g as deep set t l e m e n t . During c o n s t r u c t i o n , pore pressure d i s s i p a t i o n o c c u r r e d r a p i d l y , commonly d i s s i p a t i n g 20% to 30% of the i n i t i a l excess p r e s s u r e between s u c c e s s i v e l i f t s of f i l l . By EOC+20 days, a c o n s i d e r a b l e improvement i n Qt had oc c u r r e d f o r the e n t i r e depth of organic s o i l . The in c r e a s e i n Qt i n the f i b r o u s peat i s between 100% and 200%. Below -5m e l e v a t i o n , the i n c r e a s e i s n e a r l y uniform with depth but r e p r e s e n t s a d e c r e a s i n g degree of improvement; from about 100% at -5m e l e v a t i o n to about 50% at -12m e l e v a t i o n . ELEVATION (METERS) *6 95 • F r i c t i o n R e s i s t a n c e , Fc; The f r i c t i o n r e s i s t a n c e i n c r e a s e d markedly down to -6m e l e v a t i o n . Below -6m e l e v a t i o n there i s no apparent improvement. I t i s unusual that improvement occurred i n the Qt p r o f i l e and not i n the Fc p r o f i l e . P o s s i b l y the non-wick f a i l u r e caused some d i s t u r b a n c e to the wick d r a i n area; the di s t u r b a n c e being r e f l e c t e d i n the s e n s i t i v e f r i c t i o n measurements. • F r i c t i o n R a t i o , Rf; In g e n e r a l a decrease i n f r i c t i o n r a t i o , p a r t i c u l a r l y i n the f i b r o u s peats, can be seen. E v i d e n t l y a g r e a t e r improvement occurred i n bearing r e l a t i v e to f r i c t i o n r e s i s t a n c e . • Pore Pressure, U; A l a r g e , uniform i n c r e a s e i n U has oc c u r r e d i n both the organic c l a y s and i n the sands below. The magnitude of the in c r e a s e (about 0.7 bar or 7m of water pressure) i s gr e a t e r than the i n c r e a s e i n Uo i n d i c a t e d by f i e l d piezometers (about 0.5 b a r ) . For a p a r t i c u l a r c l a y type the r a t i o of the in c r e a s e i n pore pressure to the i n c r e a s e i n undrained shear s t r e n g t h i s approximately c o n s t a n t . T h e r e f o r e , f o r a given cohesive s o i l the i n c r e a s e i n pore p r e s s u r e can be taken as approximately equal to the in c r e a s e i n undrained shear s t r e n g t h . The in c r e a s e i n pore pressure (U - Uo) i s about 0.2 96 bar - i n d i c a t i n g an i n c r e a s e i n undrained shear s t r e n g t h of about 20 kPa. C o n s i d e r i n g the d i s s i p a t i o n of pore pressure d u r i n g t h i s p e r i o d a 20 kPa i n c r e a s e i s q u i t e reasonable. According to f i e l d settlement records about 20cm of deep settlement had o c c u r r e d to t h i s date. Any p o r t i o n of that deep settlement or d e n s i f i c a t i o n o c c u r r i n g i n the sands would not tend to i n c r e a s e the generated dynamic pore pressure response of the sand to cone p e n e t r a t i o n . T h e r e f o r e , i t i s proposed that a l a r g e p o r t i o n of the i n c r e a s e d water pressure i n the sands and some p o r t i o n of the i n c r e a s e d water pressure i n the organic c l a y s i s due to t i d a l f l u c t u a t i o n s i n the nearby r i v e r . The t o p i c of t i d a l v a r i a t i o n has been d i s c u s s e d i n the s e c t i o n 'Groundwater C o n d i t i o n s ' . • D i f f e r e n t i a l Pore Pressure R a t i o , AU/Qt; The pore pressure r a t i o f o r EOC+25 days i s f a l s e because the pore pressure p r o f i l e l a c k s an adequate p r o f i l e of Uo. I t can be reasoned t h a t , because the percent i n c r e a s e i n Qt exceeds the percent i n c r e a s e i n U and because an i n c r e a s e i n Uo was measured by the f i e l d piezometer, the d i f f e r e n t i a l pore pressure r a t i o would a c t u a l l y have decreased. 2. End Of C o n s t r u c t i o n + 20 Days To End Of C o n s t r u c t i o n  + 118 Days • Cone Bearing R e s i s t a n c e , Qt; (see F i g u r e 4.9) An a d d i t i o n a l .65m of settlement has o c c u r r e d i n the 98 ELEVATION (METERS) (Q 10 + m TJ 2 2 m <B -I 01 O S 2 0) < -t 01 m o D < (/l o o z > </» a z — 11-0-—17.0-1 in • o • o ••uu- •! , 71 : l _ l 1 1 '"" </l 3 g SILT (ML) AMORPHOUS PEAT (Pt) to ORGANIC CLAY (OH) FIBROUS PEAT (Pt) FILL SAND L6 98 day p e r i o d between t e s t s . Above -5m e l e v a t i o n the improvement in Qt can be seen c l e a r l y . Below -5m e l e v a t i o n there i s evidence of some improvement but the tr e n d i s not c l e a r . At f i f t y - s i x days a f t e r the end of c o n s t r u c t i o n (EOC+56 days) an a d d i t i o n a l 1.5m of f i l l was p l a c e d on the wick end alone. When the added f i l l was p l a c e d the pore pre s s u r e s had d i s s i p a t e d to approximately 15% of the end of c o n s t r u c t i o n v a l u e . The r i s e i n pore pressure due to the a d d i t i o n a l l o a d was small (approx. 0.15 b a r ) . By EOC+118 days the excess pore p r e s s u r e s had n e a r l y completed d i s s i p a t i o n . T h e r e f o r e , the t e s t EOC+118 days was made j u s t p r i o r to the estimated end of primary c o n s o l i d a t i o n f o r the wick end. • F r i c t i o n R e s i s t a n c e , Fc; A l a r g e i n c r e a s e i n f r i c t i o n r e s i s t a n c e occurred at a l l depths. The g r e a t e s t improvement occu r r e d i n the f i b r o u s peats. A l a r g e p o r t i o n of the d i s t u r b e d f r i c t i o n i n the orga n i c c l a y s i s recovered d u r i n g t h i s p e r i o d . • F r i c t i o n R a t i o , Rf; The net inc r e a s e i n f r i c t i o n r a t i o i n d i c a t e d that the in c r e a s e i n f r i c t i o n r e s i s t a n c e was s l i g h t l y g r e a t e r than the in c r e a s e i n bearing r e s i s t a n c e . • Pore Pressure, U; An i n c r e a s e i n dynamic pore pressure occurred at a l l 99 depths i n c l u d i n g the sands. According t o f i e l d piezometers the t e s t EOC+118 days was performed when the f i e l d excess pore p r e s s u r e s had n e a r l y completed d i s s i p a t i o n . T h e r e f o r e , the in c r e a s e i n generated pore pressure was not due to an in c r e a s e d Uo from l o a d i n g . As noted f o r the EOC+20 days p r o f i l e most of the inc r e a s e i n the generated pore pressure probably r e s u l t e d from i n c r e a s e s i n the undrained shear s t r e n g t h d u r i n g c o n s o l i d a t i o n . I t i s i n t e r e s t i n g to note that small p o s i t i v e pore p r e s s u r e s are generated i n the f r e e d r a i n i n g f i l l sands. Because the e n t i r e p r o f i l e shows an inc r e a s e i n dynamic pore p r e s s u r e , i t i s i n f e r r e d t h at the groundwater t a b l e has r i s e n . In f a c t , the i n f e r e n c e can be extended to i n c l u d e a p o s s i b l e a r t e s i a n c o n d i t i o n . Evidence f o r an a r t e s i a n c o n d i t i o n i s given as f o l l o w s : the sands at -15m e l e v a t i o n are f r e e -d r a i n i n g and are s u f f i c i e n t l y dense that they do not tend to generate p o s i t i v e excess pore p r e s s u r e s . T h e r e f o r e , the dynamic pore pressure i n the sand i s l i k e l y to be l e s s than or equal t o the e q u i l i b r i u m pore p r e s s u r e . At -16m e l e v a t i o n (17m depth) the dynamic pore pressure i s g r e a t e r than 2 bar (20m of water p r e s s u r e ) . T h i s tends to c o n f i r m the presence of an a r t e s i o n c o n d i t i o n . The a r t e s i a n p r e s s u r e s are probably caused by high t i d e r i v e r l e v e l s i n the nearby F r a s e r R i v e r . • D i f f e r e n t i a l Pore Pressure R a t i o , AU/Qt; Due to a l a c k of i n f o r m a t i o n concerning the e q u i l i b r i u m pore p r e s s u r e s at the s i t e the d i s c u s s i o n of the d i f f e r e n t i a l 100 pore pressure r a t i o i s d i s c o n t i n u e d . 3. End Of C o n s t r u c t i o n + 118 Days To End Of C o n s t r u c t i o n  + 258 Days • Cone Bearing R e s i s t a n c e , Qt; (see F i g u r e 4.10) The rate of settlement slowed c o n s i d e r a b l y d u r i n g t h i s p e r i o d ; a c h i e v i n g only 20 cm of a d d i t i o n a l settlement i n 140 days. According to the f i e l d r e c o r d s , most of t h i s settlement took plac e a f t e r the end of primary c o n s o l i d a t i o n . The end of primary c o n s o l i d a t i o n f o r organic s o i l s i s o f t e n not a d i s t i n c t event but occurs as a t r a n s i t i o n phase from primary to secondary c o n s o l i d a t i o n that i s c h a r a c t e r i z e d by small excess pore p r e s s u r e s (Brawner, 1959; Scotton, 1981). The b e a r i n g p r o f i l e shows a d e f i n i t e i n c r e a s e to -8m e l e v a t i o n ; d i m i n i s h i n g with g r e a t e r depth. • F r i c t i o n R e s i s t a n c e , Fc; The f r i c t i o n r e s i s t a n c e i s unusual i n t h i s sounding. The p r o f i l e shows a decrease i n r e s i s t a n c e at a l l depths in the o r g a n i c c l a y s . A decrease i n f r i c t i o n r e s i s t a n c e i s not expected. T h i s c o n d i t i o n i n d i s c u s s e d i n g r e a t e r d e t a i l i n the upcoming d i s c u s s i o n of the pore pressure p r o f i l e . • F r i c t i o n R a t i o , Rf; Due to the g e n e r a l decrease i n f r i c t i o n r e s i s t a n c e there PURE PRESSURE FRICTION RESISTANCE BEARING RESISTANCE FRICTION RATIO DIFFERENTIAL P . P . SOIL o Equilibrium Pore Pressure F1g.4.10 WICK AREA CONE PENETRATION TEST COMPARISON: End of Construction + 118 Days vs. End of Construction * 258 Days 102 i s a corresponding decrease i n f r i c t i o n r a t i o . • Pore Pressure, U; A l a r g e decrease i n generated pore pressure at a l l depths can be seen i n F i g u r e 4.10. The generated pore pressure at -16m e l e v a t i o n i s about 1.1 bar (11m of water pressure) which would i n d i c a t e a groundwater t a b l e at -5m e l e v a t i o n . Generated pore p r e s s u r e s can be seen to s t a r t at about -2m e l e v a t i o n g i v i n g a 3m drop i n the groundwater t a b l e from ground s u r f a c e . In the i n t r o d u c t i o n i t was mentioned that the pore pressure response of the CPT w i l l vary with h o r i z o n t a l d i s t a n c e from a wick d r a i n . T h i s w i l l only be s i g n i f i c a n t i f l a r g e g r a d i e n t s e x i s t between the d r a i n s . For the EOC +258 days p r o f i l e the excess pore p r e s s u r e s have e s s e n t i a l l y completed d i s s i p a t i o n . The low generated pore pressure i s t h e r e f o r e not due to p r o x i m i t y of the sounding to a wick d r a i n . Furthermore, the pore pressure decrease a l s o o c c u r r e d i n the sands at -17m e l e v a t i o n where the wick d r a i n s have l i t t l e i n f l u e n c e . P o s s i b l y the a d d i t i o n of wick d r a i n s served to i n c r e a s e the pore p r e s s u r e response time of the organic s o i l s so that f l u c t u a t i o n s i n r i v e r l e v e l c o u l d i n f l u e n c e the groundwater l e v e l i n the organic s o i l s . A more probable cause of the reduced pore pressure response i s poor s a t u r a t i o n f o r t h i s p a r t i c u l a r CPT sounding. The poor response i s most acute between e l e v a t i o n s +1.0 and -8.0 metres. 103 • D i f f e r e n t i a l Pore Pressure R a t i o , AU/Qt; Not i n t e r p r e t e d . 4. I n i t i a l C o n d i t i o n s To End Of C o n s t r u c t i o n + 258 Days T h i s s e c t i o n i n c l u d e s a summary of CPT trends f o r the wick d r a i n a r e a . • Cone Bearing R e s i s t a n c e , Qt; (see F i g u r e 4.11) a. As expected an i n c r e a s e i n b e a r i n g r e s i s t a n c e o c c u r r e d f o r the s o i l s c o n s o l i d a t i n g under the embankment lo a d . I t i s important to note that with the a d d i t i o n of wick d r a i n s the improvement i n Qt occurs at a l l depths of the organic s o i l s (see F i g u r e 4.10) and that a l a r g e percentage of the improvement has occurred by the end of c o n s t r u c t i o n (see F i g u r e 4.8). The improvement at the end of the study ranges from about a 25% i n c r e a s e at -12.5m e l e v a t i o n to about a 500% i n c r e a s e i n the f i b r o u s peats d i r e c t l y below the f i l l . • F r i c t i o n R e s i s t a n c e , Fc; a. The f r i c t i o n r e s i s t a n c e improved by s e v e r a l orders of magnitude i n the f i b r o u s peats above -6m e l e v a t i o n . b. Below -6m e l e v a t i o n there i s no apparent improvement i n f r i c t i o n r e s i s t a n c e . T h i s i s anomolous c o n s i d e r i n g the tremendous improvement that o c c u r r e d i n Qt f o r the same p e r i o d . T h i s decrease might be r e l a t e d to the drop i n ambient water pressure i n d i c a t e d i n t e s t EOC + 258 days. PORE PRESSURE FRICTION RESISTANCE BEARING RESISTANCE FRICTTON RATIO DIFFERENTIAL P . P . SOIL U (BAR) FC (BAR) UT (BAR) RF-FC/QT (Z) RATIO MI/OT PROFTLE + Equilibrium Pore Pressure Fig; 4.11 WICK AREA CONE PENETRATION TEST COMPARISON: I n i t i a l Conditions vs. End of Construction + 258 Days 105 • F r i c t i o n R a t i o , Rf; a. Due to a g r e a t e r p r o p o r t i o n of improvement o c c u r r i n g i n the b e a r i n g r e s i s t a n c e , a decrease i n f r i c t i o n r a t i o has occ u r r e d . However, the Rf p r o f i l e has maintained a c h a r a c t e r i s t i c shape throughout the study. • Pore Pressure, U; a. As expected, the t o t a l dynamic pore pressure tended to i n c r e a s e with l o a d i n g . However, t h i s i n c r e a s e appeared to r e f l e c t i n c r e a s e s i n the e q u i l i b r i u m pore p r e s s u r e , Uo, ra t h e r than the excess pore p r e s s u r e , Ue. b. I t i s evident from the t e s t s presented that the groundwater l e v e l i n the organic s o i l s i s i n f l u e n c e d by t i d a l f l u c t u a t i o n s i n the l o c a l r i v e r l e v e l . T h i s c o n d i t i o n appears to be t r u e f o r the wick area and, to a l e s s e r degree, the non-wick a r e a . The a d d i t i o n of wick d r a i n s appears to make the perched groundwater l e v e l i n the org a n i c s o i l s more s e n s i t i v e to change i n the nearby r i v e r l e v e l . • D i f f e r e n t i a l Pore Pressure R a t i o , AU/Qt;. a. No u s e f u l i n t e r p r e t a t i o n of the d i f f e r e n t i a l pore pressure r a t i o c o u l d be made d u r i n g t h i s s e r i e s of t e s t s i n the wick d r a i n area. A u s e f u l i n t e r p r e t a t i o n depends upon an adequate p r o f i l e of e q u i l i b r i u m pore p r e s s u r e s . 106 4.3.2 D i l a t o m e t e r T e s t s 1. I n i t i a l C o n d i t i o n s To End Of C o n s t r u c t i o n + 140 Days (see F i g u r e 4.12) One hundred and f o r t y days a f t e r the end of c o n s t r u c t i o n the wick area settlement i s 3.84m and the primary phase of c o n s o l i d a t i o n i s e s s e n t i a l l y completed. • Basic Measurements, P0, P1, and D i l a t o m e t e r Modulus, Ed; An i n c r e a s e i n P0 can be seen c l e a r l y to a depth of -10m e l e v a t i o n . The i n c r e a s e i n P0 i s n e a r l y 30% g r e a t e r than that measured f o r the non-wick end and, because the excess pore pr e s s u r e s have d i s s i p a t e d , the i n c r e a s e may represent a permanent change i n the i n - s i t u s t r e s s e s . In the f i b r o u s peats the values of P1-P0, as i n d i c a t e d by Ed, are more than double those of the non-wick t e s t . In g e n e r a l , the s o i l s t i f f n e s s has i n c r e a s e d at a l l depths. • H o r i z o n t a l S t r e s s index, Kd; The magnitude of Kd decreased with l o a d i n g as shown by the c o r r e c t e d i n i t i a l c o n d i t i o n s p r o f i l e and the EOC + 140 days p r o f i l e i n F i g u r e 4.12. The EOC + 140 days Kd p r o f i l e i s under estimated by about 20% due to an e r r o r i n the e s t i m a t i o n of u n i t weight. Because pore p r e s s u r e s have d i s s i p a t e d i n the wick area the c o r r e c t i o n f o r excess pore pre s s u r e s does not a p p l y . A f t e r l o a d i n g and c o n s o l i d a t i o n the EOC + 140 day S O I L PROFILE Fig.4.12 WICK AREA DILATOMETER TEST COMPARISON:Initial Conditions vs. End of Construction + 140 Days 108 p r o f i l e has a c o r r e c t e d value of about 2.4 f o r the organic c l a y s i n d i c a t i n g a normally c o n s o l i d a t e d c o n d i t i o n . In the f i b r o u s peat the trend i s to values of Kd between 3 and 4. Comparing EOC + 140 days (wick area) with EOC + 138 days (non-wick area, see F i g u r e 4.6) i t appears that Kd decreases with c o n s o l i d a t i o n . T h i s i s reasonable c o n s i d e r i n g the i n c r e a s e i n v e r t i c a l e f f e c t i v e s t r e s s that occurs with c o n s o l i d a t i o n . An a s s o c i a t e d i n c r e a s e i n h o r i z o n t a l s t i f f n e s s i n a l s o i n d i c a t e d by the wick area Ed p r o f i l e . 4.3.3 F i e l d Vane Tes t s 1 . I n i t i a l C o n d i t i o n s To End Of C o n s t r u c t i o n + 236 Days (see F i g u r e 4.13) The i n i t i a l and f i n a l wick area f i e l d vane t e s t s show that the undrained shear s t r e n g t h more than doubled down to 6m e l e v a t i o n , and i n c r e a s e d s i g n i f i c a n t l y down to -9m e l e v a t i o n . At -5m e l e v a t i o n the i n c r e a s e i n undrained shear s t r e n g t h i s about 400%. T h i s agrees w e l l with the i n c r e a s e i n Qt at s i m i l a r e l e v a t i o n s . U n f o r t u n a t e l y , the t e s t s were l i m i t e d i n depth to -10m e l e v a t i o n by the a v a i l a b l e rod s t r i n g . The r e s u l t s of the vane t e s t s do not show a s i m i l a r i n c r e a s e i n shear s t r e n g t h below -11m e l e v a t i o n as shown by the CPT t e s t s . In g e n e r a l , the i n i t i a l and f i n a l f i e l d vane t e s t s c o n f i r m the r e s u l t s of the CPT and DMT monitoring to -9m e l e v a t i o n . F i g u r e 4.13 a l s o i n c l u d e s the f i e l d vane t e s t s from the non-wick area f o r comparison. 0.0-Undrained Shear Strength ( S u ) , (KPa) Undrained Shear S t r e n g t h ( S u ) , (KPa) 0 10 10 30 40 50 60 70 80 90 J 00 0 10 20 30 40 SO 60 70 -I.0H -2.0 -3.0--4.0--5.0 »-» E-g - 7 . 0 - 1 M U -8.0-1 -9.0-1 —I 0.0 -I 1.0-I 1 1 WICK AREA ^ I I T FIELD VANE TEST O.O -2.0 -3.0--40--5.0-I - 7 . 0 4 > w ^ - & 0 - J -90--10.0-- i 10-_L 1 1 1 1 1 NON-WICK AREA FIELD VANE TEST Nilcon Swedish Vane Borer: 6.5cm x 13.0cm Vane 0 O I n i t i a l Conditions 1 + End of Construction + 236 Days Fig.4.13 FIELD VANE TEST COMPARISON:Initial C o n d i t i o n s vs. End of C o n s t r u c t i o n + 236 Days 1 10 V. THE DETERMINATION OF ENGINEERING PROPERTIES OF ORGANIC SOILS BY THREE IN-SITU TESTS 5.1 INTRODUCTION T h i s chapter d i s c u s s e s the dete r m i n a t i o n of three s o i l p r o p e r t i e s using i n - s i t u t e s t methods; shear s t r e n g t h , c o e f f i c i e n t of c o n s o l i d a t i o n and the d r a i n e d c o n s t r a i n e d modulus. The m a j o r i t y of t h i s program of i n - s i t u t e s t i n g was performed at the i n i t i a l c o n d i t i o n s s i t e . F i g u r e 5.1 g i v e s the l o c a t i o n s and a short d e s c r i p t i o n of the t e s t s . 5.2 UNDRAINED SHEAR STRENGTH The undrained shear s t r e n g t h of a s o i l i s not a s o i l p r o perty but r a t h e r a s o i l behaviour. The measured undrained shear s t r e n g t h depends on the type of t e s t , the rate of s t r a i n , the o r i e n t a t i o n of the f a i l u r e planes, e t c . In g e n e r a l , a c l a y shows an inc r e a s e i n undrained shear s t r e n g t h when sheared at i n c r e a s e d r a t e s of s t r a i n . The st r e n g t h measured by a f i e l d vane t e s t of s e v e r a l minutes d u r a t i o n w i l l l i k e l y be higher than the f i e l d s t r e n g t h m o b i l i z e d d u r i n g a c o n s t r u c t i o n p r o j e c t . P r o g r e s s i v e f a i l u r e and r o t a t i o n of the p r i n c i p a l s t r e s s e s along a f i e l d f a i l u r e s u r f a c e a l s o m o d i f i e s the o v e r a l l f i e l d u l t i m a t e s t r e n g t h at f a i l u r e . The r e s u l t s of the f i e l d vane t e s t are commonly ad j u s t e d to f i e l d s t r e n g t h s by c o r r e l a t i o n with l o c a l e x perience. 1 1 1 SUMMARY OF IN-SITU TESTING: INITIAL CONDITIONS SITE 1. DMT-2 2. DMT-3 3. CPT-8 4. CPT-9 5. CPT-11 6. CPT-13 7. CPT-14 8. CPT-15 9. ScPT-1 O. ScPT-2 1 . ScPT-3 2. VS-1 3. VS-2 r Poor test : Leak at the pressure gauge Reference Probe Hole (to 23.6M depth) Reference Probe Hole C6FPST-3UBC (to 31.OM depth) Probe Saturation Study - Saturated Probe C9FPS-4UBC (to 18.OM depth) Equilibrium Pore Pressure Study C6FPS-2UBC (® 10M depth, 4hr. diss i p a t i o n ) Probe Saturation Study - Unsaturated Probe C9FPS-4UBC (to 16M depth) Probe Saturation Study - Saturated Probe C9FPS-4UBC (to 17M depth) Pore Pressure Dissi p a t i o n Tests C9FPS-4UBC (to 6M depth) Load vs. Plate Movement (to 15.0M depth) / ' Load vs. Time: Incremental Loading (to 14.OM depth) Load vs. Time: Extended Duration (© 3.0M depth, 4 hr. test) Reference Test - Medium Vane (6.5cm X 13.0cm) Supplementary Test - Large Vane (8.0cm X 17.0cm) THOMPSON ROADL ( P A V E D ) (Metres) Greater Vancouver Sewer D i s t r i c t (manhole cover) Fig.5.1 I n i t i a l C o n d i t i o n s S i t e : L o c a t i o n of I n - s i t u T e s t s 1 1 2 Often, ' the qu e s t i o n an engineer must answer i s ; 'which f i e l d s t r e n g t h do we need to c o r r e l a t e to?' Unexpected f a i l u r e s can occur i f the c o r r e l a t e d undrained shear s t r e n g t h i s i n c o r r e c t f o r the a c t u a l f i e l d s t r e s s path. Apparently t h i s was the case at the t e s t f i l l . A s u b s o i l f a i l u r e o ccurred that was not expected based on the f i e l d vane data. To estimate the f i e l d undrained shear s t r e n g t h a back-c a l c u l a t i o n was made based on the f i e l d c o n d i t i o n s at the time of f a i l u r e . Assuming that the f a i l u r e o c c u r r e d i n the s o i l s u n d e r l y i n g the peat at 6m depth the undrained shear s t r e n g t h i s c a l c u l a t e d to be about 15kPa. For the area without wick d r a i n s the f i e l d vane ( r e f e r to F i g u r e 4.8) at 6m depth over estimated the c a l c u l a t e d f i e l d s t r e n g t h by n e a r l y a f a c t o r of two. P r o f i l e s of undrained shear s t r e n g t h , Su, versus e l e v a t i o n f o r the cone p e n e t r a t i o n t e s t , d i l a t o m e t e r t e s t , screw p l a t e t e s t and the f i e l d vane t e s t are presented i n Fi g u r e 5.2. F i g u r e 5.2 a l s o g i v e s the e m p i r i c a l c o r r e l a t i o n used i n each case. These e m p i r i c a l c o r r e l a t i o n s are based upon l a b o r a t o r y t e s t s and f i e l d vane t e s t s of c l a y s . Researchers i n Scandinavia have been accumulating data from e l e c t r i c f r i c t i o n cone p e n e t r a t i o n t e s t s and f i e l d vane t e s t s f o r many years i n order to b e t t e r d e f i n e the cone f a c t o r , Nk. Lunne and Kleven (1981) determined that the value of Nk f a l l s between 11 and 19 with an average of 15 f o r normally c o n s o l i d a t e d marine c l a y s u sing c o r r e c t e d f i e l d vane s t r e n g t h s ( i . e . Bjerrum's, 1972, c o r r e c t i o n f o r P . I . ) . For 113 Undrained Shear St r e n g t h ( S ^ t K P a ) 0 10 20 30 40 50 60 70 INITIAL CONDITIONS SITE • • N i l c o n Swedish Vane Borer: 6.5cm x 13.0cm Vane • — — • Cone P e n e t r a t i o n Test using the c o r r e l a t i o n : Su = (QT ~ JfZ)/Nk ; where Nk = Cone F a c t o r • • D i l a t o m e t e r Test u s i n g the c o r r e l a t i o n : S u • 0.22 srXO.SKj, ) u " ( M a r c h e t t i , 1 981 ) + + Screw P l a t e Test from the r e l a t i o n s h i p : Su - P u l t / ( 9 . 0 t o 11.35) ; p l o t t e d with d i v i s o r - 9.0 Fig. 5.2 Undrained Shear St r e n g t h versus E l e v a t i o n 1 1 4 the i n i t i a l c o n d i t i o n s s i t e Nk i s between 10 and 5 f o r the organic c l a y s below -5m e l e v a t i o n and l e s s than 5 i n the f i b r o u s peats. Because of i t s more fundamental nature, Qt, the cone bearing c o r r e c t e d f o r dynamic water p r e s s u r e s , was used i n t h i s study r e s u l t i n g i n a s l i g h t l y l e s s c o n s e r v a t i v e estimate of Su. Bjerrums' c o r r e c t i o n f o r P.I. was not s i g n i f i c a n t at the t e s t f i l l s i t e and was n e g l e c t e d . The c h a r a c t e r of the CPT data d i f f e r s from the other t e s t s , i n c r e a s i n g l i n e a r l y with depth. T h i s d i f f e r e n c e i s p a r t i c u l a r l y e v i d e n t i n the f i b r o u s peats i n d i c a t i n g that the cone, a p e n e t r a t i o n t e s t , i s perhaps l e s s i n f l u e n c e d by the presence of f i b r e s than are the other t e s t s . F i g u r e 5.2 i n d i c a t e s that u s i n g a cone f a c t o r , Nk, of about 10 w i l l g ive a more c o n s e r v a t i v e estimate of Su than t h a t determined by f i e l d vane. T h i s estimate w i l l a l s o g i v e a b e t t e r Su value f o r the s u b s o i l f a i l u r e a n a l y s i s . Values of Su have been taken d i r e c t l y from the d i l a t o m e t e r data r e d u c t i o n output sheet and p l o t t e d i n F i g u r e 5.2. According to M a r c h e t t i (1980), the c o r r e l a t i o n of Su/a' to Kd i s based on lower bound l a b o r a t o r y and f i e l d vane s t r e n g t h s . As d i s c u s s e d p r e v i o u s l y the value of Kd f o r the peat has been under estimated by about 50% due to an i n c o r r e c t value a s s i g n e d to u n i t weight. The c o r r e l a t i o n to Su i s normalized with r e s p e c t to the v e r t i c a l e f f e c t i v e s t r e s s ( i . e . estimated u n i t weight) so t h a t the e r r o r i n Su due to u n i t weight i s , f o r the most p a r t , c a n c e l l e d . The values of Su f o r the d i l a t o m e t e r t e s t are given i n F i g u r e 5.2. The d i l a t o m e t e r 1 1 5 r e s u l t s are approximately constant with depth and about one-h a l f of the f i e l d vane t e s t v a l u e s . The f i b r o u s peat l a y e r does not appear to have had a l a r g e e f f e c t on the estimated Su. S e l v a d u r a i et a l . , 1980, reviewed the e x i s t i n g t h e o r e t i c a l s o l u t i o n s r e l a t i n g the u l t i m a t e screw p l a t e s t r e s s , P u l t , with undrained shear s t r e n g t h , Su, and found that ( P u l t / ( 9 . 0 to 11.35) gave the upper and lower bounds of Su r e s p e c t i v e l y . F i g u r e 5.2 shows good agreement between the screw p l a t e data and the f i e l d vane data when a value of 9.0 i s used. Using a l a r g e r value of d i v i s o r would give a more c o n s e r v a t i v e estimate of Su. The screw p l a t e t e s t s were slower and more complex to perform than the CPT and DMT t e s t s . In summary, the cone p e n e t r a t i o n t e s t and the screw p l a t e t e s t each gave a reasonable estimate of the undrained shear s t r e n g t h . In p a r t i c u l a r , the CPT with Nk equal to 8 g i v e s a s i m i l a r estimate of Su to that provided by the d i r e c t f i e l d vane measurement i n the organic c l a y s but f o r peat an u n r e a l i s t i c value of Nk l e s s than 3 i s needed because of the f a b r i c r e i n f o r c i n g which occurs i n peat. The r e s u l t s of t h i s study i n d i c a t e that the value of Su given by the f i e l d vane t e s t i n f i b r o u s peat may not be reproducable with the cone p e n e t r a t i o n t e s t . The d i l a t o m e t e r r e s u l t s g i v e a c o n s e r v a t i v e estimate of Su compared to the f i e l d vane. Given the back-c a l c u l a t e d value of .Su from the s u b - s o i l f a i l u r e (l5kPa) the d i l a t o m e t e r values appear to be of the c o r r e c t magnitude. 1 16 5.3 COEFFICIENT OF CONSOLIDATION Th i s s e c t i o n compares c o e f f i c i e n t s of c o n s o l i d a t i o n determined i n - s i t u from e l e c t r i c piezometer cone d i s s i p a t i o n t e s t s to those determined by standard incremental c o n s o l i d a t i o n t e s t s . The standard incremental c o n s o l i d a t i o n t e s t s were performed by the B r i t i s h Columbia Department of Highways, G e o t e c h n i c a l T e s t i n g D i v i s i o n . G i l l e s p i e (1981) reviewed the e x i s t i n g s o l u t i o n s f o r determining the c o e f f i c e n t of c o n s o l i d a t i o n from the e l e c t r i c piezometer cone, see F i g u r e 5.3a,b. F i g u r e 5.3a h i g h l i g h t s the d i f f e r e n c e s i n the s o l u t i o n s and F i g u r e 5.3b shows the r e s u l t s p l o t t e d i n non-dimensionalized form w i t h time f a c t o r T =Ct/r 2. G i l l e s p i e (1981) found that the h o r i z o n t a l c o e f f i c i e n t of c o n s o l i d a t i o n , C>,, determined from the CPT u s i n g Torstenssons' (1977) c y l i n d r i c a l method, compared w e l l with C from constant r a t e of s t r a i n c o n s o l i d a t i o n t e s t s . A l s o , through f i e l d t e s t s , G i l l e s p i e and Campanella (1981) showed that the d i s s i p a t i o n of pore p r e s s u r e f o r the piezometer element l o c a t e d j u s t behind the t i p i s p r i m a r i l y governed by h o r i z o n t a l drainage r a t h e r than v e r t i c a l d rainage. These f i n d i n g s lend support to use of a c y l i n d r i c a l s o l u t i o n . From the time f a c t o r T, knowing the r a d i u s of the c a v i t y , r, and the time f o r d i s s i p a t i o n , t , the c o e f f i c i e n t of c o n s o l i d a t i o n , Cj,, can be q u i c k l y c a l c u l a t e d . The s o l u t i o n by Torstensson (1977) a l s o r e q u i r e d knowledge of the s o i l s t i f f n e s s r a t i o . S e l e c t i o n of an exact s o i l s t i f f n e s s r a t i o i s complicated by the v a r i a t i o n i n moduli with s t r e s s l e v e l , 1 17 Author Ceslty type Material Medal Ult lal Port Preeaure ettatrlautloo Proposed Applications •aaarka •ellah t Levedoux 1980 caaalaad radial aed spherical •BD - l l B M r •oetoo Blue clay froa P.I. atudlee •alas, atrala path •etbod consolidation charactarlatlca shows very email leflueac* el spherical " ceapooaot of dissipation •aadelpb 4 Wrath 1979 cylindrical •laetlc-plaatlc a» 4 • 2 cu 1 » £ ] f - <C/cu)"* coaaoUdatloa around pllaa pressureaeter analysis analytical aolutloo •oderseri 1*62 cylindrical •laatlc-plaatlc » i r consolidation around piles Torsteas SOD 1977 cylindrical •laatlc-alaatlc a^ - 2 cu l a £ ) f - • (C/cu)»'* o coaaolldatlon charactarlatlca propoaes averat* af taxi results Ibrsteessoo 1977 epherlcal •laatlc-alaatlc * J 1 - * CU ln(|) f - - (C/cu)1" o coaaolldatlon charactarlatlca vertical dralas (o) T • Urn* factor c • coofflclont *f eamolMotlen t • flmt r • radius ar cavity A Boligh and Lovodoux 1980 B Sod*rb«rg 1962 C Tontetmon 1977 tphtrical solution 0 Torattmton 1977 cylindrical solution E/CM *500 1  I I I I I 1111 • .01 g. 5 .1 1 10 100 T - « l / r « ( b ) .3 SUMMARY OF EXISTING SOLUTIONS FOR PORE PRESSURE DISSIPATION. (Adapted from Gillespie,1982). 118 see F i g u r e 5.4. G i l l e s p i e suggests using a s t i f f n e s s r a t i o at an i n t e r m e d i a t e s t r e s s l e v e l (say Th/Cu=0.5). The procedure used d u r i n g d i s s i p a t i o n t e s t s was i n accordance with that recommended by G i l l e s p i e (1981) with the f o l l o w i n g e x c e p t i o n . Because c o n s i d e r a b l e d e l a y s were o f t e n observed i n pore pressure response d u r i n g the i n i t i a l p o r t i o n of the d i s s i p a t i o n t e s t s , the zero time f o r d i s s i p a t i o n was c o n s i s t e n t l y measured from the p o i n t of maximum pore p r e s s u r e . The f u l l consequences of such an e s t i m a t i o n are not known. However, i n terms of the c a l c u l a t i o n of the c o e f f i c i e n t of c o n s o l i d a t i o n from d i s s i p a t i o n t e s t s the e r r o r i n v o l v e d i s not expected to be l a r g e . S e l e c t i o n of the s o i l s t i f f n e s s r a t i o was a i d e d by l i q u i d l i m i t and p l a s t i c i t y index data s u p p l i e d by the B r i t i s h Columbia Department of Highways. D i s s i p a t i o n t e s t s were c a r r i e d to the 50% l e v e l of d i s s i p a t i o n . . The c o e f f i c e n t s of c o n s o l i d a t i o n from the CPT d i s s i p a t i o n t e s t s and the standard incremental c o n s o l i d a t i o n t e s t s (SICT) are presented i n F i g u r e 5.5. Given i n the border of the Fi g u r e are the chosen s o i l s t i f f n e s s r a t i o s and an approximate s o i l p r o f i l e . The SICT c o e f f i c i e n t s were c a l c u l a t e d at a. loa d l e v e l of about lOOkPa t o model the f i e l d l o a d i n g at the end of c o n s t r u c t i o n . The CPT t e s t s were performed at both the t e s t f i l l s i t e p r i o r to l o a d i n g and at the i n i t i a l c o n d i t i o n s s i t e . The d i s s i p a t i o n t e s t s i n the wick area were made at l e a s t 10m from the nearest wick d r a i n . The f a c t that i t i s not p o s s i b l e to b a c k - c a l c u l a t e a meaningful f i e l d c o e f f i c i e n t of c o n s o l i d a t i o n u sing 119 2000 No. DESCRIPTION cu/p' ~! Portsmouth 1 CL Cloy PI = 15 •t-IO LL= 35 Boston CL Cloy LL = 41 PI = 22 Bangkok CH Clay LL=65 Pl = 4r Maine CH OH Clay LL=65 PI = 38 AGS CH Clay LL=7| P| = 40 Atchafolaya CH Clay LL =95 Pl = 75 Tailor River Peat w = 5 0 0 % 1 2 - 4 - 5 - 6 20 .20 .27 .29 26 24 — CK U simple shear tests — All soils normally consolidated 0.8 APPLIED SHEAR STRESS RATIO T ./c , n u ( a ) I 2 4 6 8 1 0 I 2 4 6 8 10 OCR-<W< c OCR-o-v„/<rvc ( b ) F i g . 5 . 4 SELECTION OF SOIL STIFFNESS RATIO FOR CLAYS. (Adapted from Ladd et al.1977). 120 o.i \o.o u h 2 r-< > -J IU + I - 5 - 5> - & 10 • • ww • lc A • P O o w lc 10(2) • MW W ® • NW I C w N W • W M W ( 2 ) • M W •IC 2 r 2 a: O *q -J V) o 2 < o 0 \ u vH f IU o CM 0 . 0 5 - O.I (7.2 £>-5- 1.0 2 . 0 C y A N D C(-, £ C M V M I N U T E ) 10.0 COUZ PETSIETEAT/ON T£5T - Toe.6T£Ne«?isi C Y L I N D R I C A L DISTRI&UTICTN £ . • MCAe>U(^E.P PRIOR. TO LOAQIWCi : WICJC (+t). MOM- WICK* ( N W ) , A N D n INITIAL C0NDn70M£> ( IC ) C n ® MCA6UR£P 200 D A Y S AFTER. F INAL FILL LOAD &.lf*T # 5 ) J N 0 K | - W l C ^ C n H " 3&C7 PAY i> " " u 11 " " E>. C. HIG HWAY3 - S T A N DAKT> INCZ^M E N T A L cout>ou P A T U ? N TE/£>T C v A VERTICAL 0 W E N T A T I 0 M • HtfEJZONTAL OE.I ENTA71 <? N C v O ( S A M P L E * FKjPM A MEARJ5Y SITE) F i g . 5.5 H o r i z o n t a l and V e r t i c a l C o e f f i c i e n t s of C o n s o l i d a t i o n versus E l e v a t i o n . 121 c u r v e f i t t i n g methods has been d i s c u s s e d p r e v i o u s l y . Because of t h i s , the d i s c u s s i o n w i l l not compare the SICT and CPT data to a r e f e r e n c e f i e l d v a l u e . From F i g u r e 5.5 one can see that the SICT data gives a c o e f f i c i e n t of c o n s o l i d a t i o n between 0.1 and 0.2cm 2/minute and shows l i t t l e s e n s i t i v i t y to the o r i e n t a t i o n of the t e s t ; h o r i z o n t a l or v e r t i c a l . The CPT data show a d e f i n i t e t rend with depth and i n d i c a t e s a zone of somewhat f r e e r drainage between -6m and -8m e l e v a t i o n . I t i s i n t e r e s t i n g to note that the d i s s i p a t i o n t e s t s i n the wick end form the lower bound values i n the organic c l a y s . The wick area was a l s o found to have a lower i n i t i a l undrained shear s t r e n g t h . When compared at s i m i l a r depths, the CPT values are between f i v e and f i f t y times g r e a t e r than the SICT v a l u e s . One reason f o r the tremendous d i f f e r e n c e between CPT and SICT values l i k e l y r e s u l t s from the d i f f e r e n c e i n a p p l i e d load d u r i n g the t e s t s . The c o e f f i c i e n t of c o n s o l i d a t i o n i n organic s o i l s i s known to decrease tremendously with l o a d i n g . The oedometer sample i s small and i s subject to very l a r g e loads whereas the i n - s i t u d i s t r i b u t i o n i n v o l v e s a l a r g e r area and i s only s u b j e c t to loads r e s u l t i n g from probe i n s e r t i o n . N a t u r a l s o i l v a r i a b i l i t y i s probably the cause of the s c a t t e r i n the CPT data which represent p o i n t or l o c a l v a l u e s f o r the s o i l near the cone t i p . However, the area i n v o l v e d i n the d i s s i p a t i o n process i s s t i l l l a r g e r than the SICT samples. For o r g a n i c s o i l s , where both the r a t e and magnitude of compression i s high, the c o e f f i c i e n t of c o n s o l i d a t i o n needs to 1 22 be found f o r the range of expected loads to adequately model the c o n s t r u c t i o n sequence. An important f i n d i n g of t h i s study i s , as expected, the decrease i n the c o e f f i c i e n t of c o n s o l i d a t i o n with l o a d i n g . Tests made i n the area without wick d r a i n s at 200 days and at 360 days a f t e r the end of c o n s t r u c t i o n show a f i v e to t e n - f o l d decrease with the s m a l l e s t v a l u e s measured i n the near s u r f a c e s o i l s . A higher degree of agreement can be seen between the CPT and SICT r e s u l t s a f t e r l o a d i n g . The settlement at the time of the 200 and 360 day t e s t s i s about 2.5m and 3.0m, r e s p e c t i v e l y . 5.4 DRAINED CONSTRAINED MODULUS  5.4.1 Cone P e n e t r a t i o n Test 1. C o r r e l a t i o n The e s t i m a t i o n of d r a i n e d parameters from t o t a l s t r e s s undrained measurements i s c o n c e p t u a l l y i n a c c u r a t e and can l e a d to s e r i o u s e r r o r (Robertson, 1982). There are many c o r r e l a t i o n s i n e x i s t e n c e , however, that r e l a t e the cone bearing r e s i s t a n c e to c o m p r e s s i b i l i t y . The gen e r a l form of the r e l a t i o n s h i p i s : M=tfQc where, ' -— M = an e q u i v a l e n t d r a i n e d c o n s t r a i n e d modulus. (kPa) a = a dimensionless parameter that r e l a t e s the cone bearing with the c o n s t r a i n e d modulus. 123 Qc = cone bearing r e s i s t a n c e . (kPa) Commonly, the c h o i c e of a f o r a p a r t i c u l a r m ineral s o i l i s determined by the value of cone b e a r i n g , Qc. T r a d i t i o n a l l y , when organic s o i l s are encountered the g e o t e c h n i c a l parameters are e m p i r i c a l l y c o r r e l a t e d from water content data. S a n g l e r a t et a l . , (1972), presented a r e l a t i o n s h i p f o r peat and organic c l a y where values of a are r e l a t e d to the d r a i n e d c o n s t r a i n e d modulus through water content. S a n g l e r a t ' s r e l a t i o n s h i p i s given g r a p h i c a l l y i n F i g u r e 5.6. In e s t a b l i s h i n g h i s r e l a t i o n s h i p , Sanglerat used D e l f t mechanical cone p r o f i l e s of Qc and valu e s of the d r a i n e d c o n s t r a i n e d modulus, M, from standard incremental c o n s o l i d a t i o n t e s t s . 2. Methodology To use S a n g l e r a t ' s r e l a t i o n s h i p a r e p r e s e n t a t i v e water content versus depth p r o f i l e i s r e q u i r e d . Laboratory water content d e t e r m i n a t i o n s were made by the B r i t i s h Columbia Department of Highways from eleven boreholes that span the s i t e . The r e s u l t s show that the water content i n the peat v a r i e s with depth from between 300% to 600% near the su r f a c e to approximately 200% at 6m depth. Due to the s c a t t e r i n the s u r f i c i a l water contents a d d i t i o n a l water content t e s t s were performed on samples hand-cut from a t e s t p i t . A r e p r e s e n t a t i v e water content at the s u r f a c e was chosen to be 400%. As can be seen i n Figure 5.6 the tr e n d i n S a n g l e r a t ' s c o r r e l a t i o n i s vague when e x t r a p o l a t i n g to water contents above 300%. A value of 0.3 f o r a was assumed to be the lower 124 O lOO ZOO 3QO 400 Water Content, W% Cjc<2 bars 50 <W%< 100 1 .5< *<4.0 100<W%< 200 1 .0<et<1.5 W%>300 oc<4.0 Fig . 5.6 S a n g l e r a t ' s C o r r e l a t i o n : oC Value versus Water Content 125 l i m i t f o r water contents up to 400%. The r e p r e s e n t a t i v e cone bearing p r o f i l e i s the re f e r e n c e t e s t CPT-8 from the i n i t i a l c o n d i t i o n s s i t e . Values of Qt were s u b s t i t u t e d i n the c o r r e l a t i o n f o r Qc. Because the d i f f e r e n c e between Qt and Qc i s small f o r the CPT t e s t s at the t e s t f i l l s i t e the s u b s t i t u t i o n w i l l not s i g n i f i c a n t l y a f f e c t the r e s u l t s . The c a l c u l a t i o n of M was made at 20cm i n t e r v a l s of depth down to -13m e l e v a t i o n . The p r o f i l e of l o g M versus e l e v a t i o n f o r the cone p e n e t r a t i o n t e s t i s given i n F i g u r e 5.7. 5.4.2 Dila t o m e t e r Test M a r c h e t t i (1980) developed a c o r r e l a t i o n f o r o b t a i n i n g the d r a i n e d c o n s t r a i n e d modulus from an e l a s t i c undrained modulus, Ed, which i s found from the d i l a t o m e t e r t e s t r e s u l t s . The d i l a t o m e t e r modulus, Ed, has the form: Ed = E / ( 1 - P 2 ) = 2DAP/SOTT = 38.2AP where, E =' Young's Modulus v = Poisson's r a t i o f o r the s o i l D = membrane diameter; 60mm. AP = (P1-P0) So = membrane d e f l e c t i o n ; 1mm. A number of parameters i n f l u e n c e the r e l a t i o n s h i p between Ed and the l o c a l tangent c o n s t r a i n e d modulus, M. Among these parameters a r e : m a t e r i a l type, a n i s o t r o p y , pore pressure parameters and drainage c h a r a c t e r i s t i c s . To h e l p d e f i n e the c o r r e l a t i o n , M a r c h e t t i (1980) i n c l u d e d the d i l a t o m e t e r 126 LOG CONSTRAINED MODULUS, M, (KPa) 10 20 40 8 0 1 ? 0 2i» "00 80of° 2T°° 8°°° 10000 -4.0 -5.0 -7.0 -8.0 -9.0 •10.0 11.0-•* * Cone Penetration Test (Sanglerat C o r r e l a t i o n : M - ^ 0 T> 127 m a t e r i a l index, Id, and the d i l a t o m e t e r h o r i z o n t a l s t r e s s index, Kd, as measures of m a t e r i a l type and s t r e s s h i s t o r y r e s p e c t i v e l y . The r e l a t i o n s h i p between M and Ed with Kd as a parameter i s shown in F i g u r e 5.8. F i g u r e 5.8 was d e r i v e d using v a l u e s of l o c a l tangent c o n s t r a i n e d modulus M from oedometer t e s t s on c l a y samples. In g e n e r a l , the a p p l i c a t i o n of the d i l a t o m e t e r i s l i m i t e d to s a t u r a t e d i n s e n s i t i v e normally c o n s o l i d a t e d cohesive s o i l s . For the d e t e r m i n a t i o n of the c o n s t r a i n e d modulus, M a r c h e t t i (1980) assumes that the v a r i a t i o n of the c o n s t r a i n e d modulus over the s t r e s s increment i s s m a l l . T h e r e f o r e , the c o r r e l a t i o n i s only v a l i d up to the p r e c o n s o l i d a t i o n p r e s s u r e , beyond which the value of M can decrease markedly. The c o n s t r a i n e d modulus v e r s u s depth p r o f i l e was o b t a i n e d from the r e f e r e n c e d i l a t o m e t e r t e s t DMT-3 performed at the i n i t i a l c o n d i t i o n s s i t e . Values of M were obtained d i r e c t l y from the d i l a t o m e t e r data r e d u c t i o n program f o r each t e s t depth ( i . e . at 20cm i n t e r v a l s ) . I t i s important to note that these v a l u e s of M were c a l c u l a t e d from u n c o r r e c t e d values of Kd. Using the c o r r e c t e d values of Kd would r e s u l t i n a 25% to 50% i n c r e a s e i n M. The r e l a t i o n s h i p between Kd and M w i l l be d i s c u s s e d i n g r e a t e r d e t a i l i n Chapter 6 w i t h r e f e r e n c e to settlement p r e d i c t i o n s . The p r o f i l e of l o g M versus e l e v a t i o n f o r the d i l a t o m e t e r t e s t i s given i n F i g u r e 5.9. 128 M=TANGENT MODULUS=1/mv v SAND (Chamber T e s t s ) • SAND ( I n - s i t u ) • CLAY I i i i i i i i i - » • • • * • i'y. .••••:•••.••*•.•.•••• •.••/.•/.•:••.•;*:••/ • * • • • •* • • • • m • • * i • S i • •*•* * . • *, •••.•*• •V • • • -A/ i i i i i i i i 3 4 5 10 Kd (dimensionless) 20 Fi g . 5.8 C o r r e l a t i o n between Rm and Kd ( a f t e r M a r c h e t t i , 1980) 129 LOG CONSTRAINED MODULUS, M, (KPa) 1 30 5.4.3 Screw P l a t e T e s t : Incremental Loading T e s t s 1. Theory Janbu and Senneset (1973) developed a t h e o r e t i c a l s o l u t i o n f o r o b t a i n i n g the settlement of a c i r c u l a r p l a t e at an a r b i t r a r y depth below ground s u r f a c e . T h i s s o l u t i o n allows f o r the i n - s i t u d e t e r m i n a t i o n of the d r a i n e d c o n s t r a i n e d modulus using the screw p l a t e t e s t . The one-dimensional tangent d r a i n e d c o n s t r a i n e d modulus, M, i s d e f i n e d by the i d e a l i z e d s t r e s s s o l u t i o n : M = mPa(P'/Pa) 1~* (a) where, m = modulus number Pa = r e f e r e n c e s t r e s s = lOlkPa P' = v e r t i c a l e f f e c t i v e s t r e s s and, K = s t r e s s exponent, such t h a t , K = 1 f o r o v e r c o n s o l i d a t e d c l a y s K = 1/2 f o r many sands and s i l t s K = 0 f o r normally c o n s o l i d a t e d c l a y s The case that best r e p r e s e n t s the normally c o n s o l i d a t e d s o i l s at the t e s t s i t e i s K = 0. According to M i t c h e l l and Gardner (1975), the case K = 0 corresponds to a l i n e a r s t r e s s -dependent modulus t h a t i s a p p r o p r i a t e f o r normally c o n s o l i d a t e d f i n e - g r a i n e d s o i l s . The c l o s e d form s o l u t i o n f o r o b t a i n i n g the modulus number, d e p i c t e d i n F i g u r e 5.10, i s as f o l l o w s : 131 J \ i D 1 t i r i s •* •> B F i g . 5.10 DEFINITION OF JANBU MODULUS NUMBER k m (adapted from Janbu and Senneset, 1973) 1 32 m = SPnB/Pa6 (b) where, m = modulus number S = dimensionless settlement number Pn = P'-Po' = net pressure on p l a t e B = p l a t e diameter = 25.2cm Pa = r e f e r e n c e s t r e s s = lOlkPa 5 = v e r t i c a l p l a t e movement The settlement number, S, i s a c o r r e c t i o n f a c t o r that v a r i e s with the e f f e c t i v e overburden s t r e s s , Po', and net p l a t e p r e s s u r e . The v a r i a t i o n of S f o r three s o i l types i s shown i n F i g u r e 5.11. Due to the low e f f e c t i v e overburden pressures estimated f o r the t e s t f i l l s i t e , the v a l u e s of S f o r normally c o n s o l i d a t e d s o i l s was e x t r a p o l a t e d to i n c l u d e v a l u e s of Po' down to lOkPa. A key assumption i n t h i s method of a n a l y s i s i s that s t r a i n s are v e r t i c a l , hence, i f l a t e r a l s t r a i n s occur d u r i n g the t e s t , the c o n s t r a i n e d modulus i s under estimated. 2. Methodology Screw p l a t e incremental l o a d i n g t e s t s were performed at the i n i t i a l c o n d i t i o n s s i t e at e i g h t depths ranging from 2m to 13m. In order to determine M, s e v e r a l increments of constant l o a d must be a p p l i e d and the r e s u l t i n g screw p l a t e movement recorded with time f o r each increment. T e s t s were performed at every metre f o r the f i r s t seven metres and every second metre t h e r e a f t e r . F i g . 5 .11 VALUES OF JANBU'S SETTLEMENT NUMBER " S " (adapted from Janbu and Senneset, 1973) 134 The l o a d i n g program f o r each t e s t was planned to model the t e s t f i l l c o n s t r u c t i o n sequence: the f i n a l pressure at the base of the t e s t f i l l , due to f i v e equal l i f t s , was estimated to be 100 kPa. However, the i n f l u e n c e of rod f r i c t i o n was under estimated and the p l a t e movements were very s m a l l . An a d d i t i o n a l t e s t was made with the screw p l a t e removed to determine the f r i c t i o n on the rods a l o n e . The s u r f a c e f r i c t i o n on the screw p l a t e rods accounted f o r about 24kg per metre of rod l e n g t h i n the f i b r o u s peat and about one-half that value i n the organic c l a y s . C o r r e c t i o n s were made f o r the rod f r i c t i o n r e s u l t i n g i n a reduced estimate of p l a t e l o a d . The measured loads were a l s o c o r r e c t e d f o r the weight of the screw p l a t e and the rods. Because the loa d measuring device i s l o c a t e d at the ground s u r f a c e the exact l o a d at the p l a t e i s not known. However, based on the above c o r r e c t i o n s , s e v e r a l of the t e s t s were estimated to generate a net p l a t e s t r e s s of about 40kPa. The method of data r e d u c t i o n f o l l o w s the procedure d e s c r i b e d by Janbu and Senneset (1973). F i r s t , the p l a t e movement versus time measurements were r e p l o t t e d versus square-root time. Next, the p l a t e displacement corresponding to 90% of primary c o n s o l i d a t i o n was found f o r each increment of load u s i n g a v e r s i o n of T a y l o r ' s root-time c u r v e f i t t i n g method m o d i f i e d to account f o r r a d i a l drainage as suggested by Janbu and Senneset (1973). A f t e r p l o t t i n g the p l a t e displacement versus t o t a l p l a t e l o a d and marking o f f the e f f e c t i v e overburden pressure the r e s u l t i s s i m i l a r to the 135 curve d e p i c t e d i n F i g u r e 5.10. - A net p l a t e s t r e s s of 40kPa was chosen from the curve and, with S, was entered i n t o equations (a) and (b) to c a l c u l a t e M. Although a net p l a t e s t r e s s of 40kPa i s about h a l f as l a r g e as the estimated end of c o n s t r u c t i o n embankment pressu r e , i t repr e s e n t s a s i g n i f i c a n t p ressure comparable to a 4 metre t h i c k embankment. The p r e d i c t e d settlements from the screw p l a t e incremental l o a d i n g t e s t s should t h e r e f o r e be compared with s e t t l e m e n t s due to an embankment of 4 metres t h i c k n e s s . Settlement p r e d i c t i o n s from the incremental l o a d i n g s e r i e s of t e s t s w i l l be d i s c u s s e d f u r t h e r i n a subsequent s e c t i o n . The r e s u l t i n g p r o f i l e of l o g M versus e l e v a t i o n f o r the screw p l a t e incremental l o a d i n g t e s t s i s given i n F i g u r e 5.12. 5.4.4 Screw P l a t e T e s t : U l t i m a t e Load T e s t s A s e r i e s of u l t i m a t e load t e s t s were made with the screw p l a t e a t the i n i t i a l c o n d i t i o n s s i t e . The t e s t procedure f o r determining the u l t i m a t e load i n v o l v e s c o n t i n u o u s l y i n c r e a s i n g the l o a d u n t i l the s o i l f a i l s as evidenced by very l a r g e s t r a i n s i n the organic s o i l s . Some p l a t e r o t a t i o n was observed upon f a i l u r e i n d i c a t i n g t h a t s l i p s u r f a c e s developed p a r a l l e l to the screw p l a t e blades. I f the r o t a t i o n had not been allowed, then a more general f a i l u r e would l i k e l y occur r e s u l t i n g i n an i n c r e a s e d u l t i m a t e l o a d . The d u r a t i o n of the l o a d i n g was betwean-one and two minutes f o r most t e s t s . A s t r i p - c h a r t r e corder was employed to d i r e c t l y r e c o r d the loa d versus d e f l e c t i o n c urves. A 136 LOG CONSTRAINED MODULUS, M, (kPa) 1 0 2 0 4 0 8 0 ' ? ° 2 0 0 4P° a 0 0 1 0 0 0 0 1 0 0 0 2 0 O 0 4 0 0 0 8 0 0 0 1 From -7m to -13m elev., M > 10,000 kPa. Screw P l a t e : Incremental Loading Test (Janbu and Senneset, (1973) method) F i g . 5.12 Screw Plate Test - Incremental Loading Test: log constrained modulus, M, versus e l e v a t i o n . 1 37 t y p i c a l u l t i m a t e load t e s t curve i s shown in Fi g u r e 5.13. The recorded loads were c o r r e c t e d f o r the e f f e c t s of rod and screw p l a t e weight and rod f r i c t i o n . U l t i m a t e load t e s t s were performed every metre to a depth of 14 metres. The r e s u l t s of these t e s t s i n d i c a t e d t h a t the measured u l t i m a t e s t r e n g t h v a l u e s , Q u i t , are s i m i l a r i n magnitude to the nearby r e f e r e n c e cone bearing v a l u e s , Qt. Because of the s i m i l a r i t y between Quit and Qt values, S a n g l e r a t ' s c o r r e l a t i o n , o r i g i n a l l y developed f o r the cone p e n e t r a t i o n t e s t , was a p p l i e d to the u l t i m a t e load t e s t r e s u l t s . The de t e r m i n a t i o n of M from u l t i m a t e l o a d t e s t s i s made by simply s u b s t i t u t i n g Quit f o r Qt i n Sa n g l e r a t ' s c o r r e l a t i o n ; the values of a remain unchanged. The p r o f i l e of l o g M versus e l e v a t i o n f o r the u l t i m a t e l o a d t e s t s i s given i n F i g u r e 5.14. 5.4.5 Summary Of C o n s t r a i n e d Modulus R e s u l t s The p r o f i l e s of l o g c o n s t r a i n e d modulus M versus e l e v a t i o n are summarized f o r the i n - s i t u t e s t s i n F i g u r e 5.15. The d i f f e r e n c e s between the t e s t r e s u l t s i s apparent from the F i g u r e . The value of M, a t shallow depths, v a r i e s by as much as a f a c t o r of 10 3 between the CPT and the screw p l a t e incremental l o a d t e s t s . The r e s u l t s of the d i l a t o m e t e r and screw p l a t e incremental l o a d t e s t s are much higher than the r e s u l t s of the cone p e n e t r a t i o n t e s t and the screw p l a t e u l t i m a t e l o a d t e s t s i n the f i b r o u s peats above -5m e l e v a t i o n . The c h a r a c t e r of the p r o f i l e s a l s o d i f f e r s . The d i l a t o m e t e r 138 -\ 1 : 1 1 1 1 1 1 1 1 1 1 I O Z 4 6 8 10 \% PLATE MOVEMENT (cm) Fig.5.13 Screw P l a t e : T y p i c a l U l t i m a t e Load Test R e s u l t 139 Ul u 4J <D X z o -7.0 < > W -8.0' -12.0 LOG CONSTRAINED MODULUS, M, (KPa) 0 < — I 0 0 \ ) ) ) • • Screw Plate Test - Ultimate Load Test (an adaption of Sanglerat's C o r r e l a t i o n : M >°<Qult) Fig.5;14 Screw P l a t e Test - Ultimate Load Test: l og constrained modulus, M, versus e l e v a t i o n . 140 LOG CONSTRAINED MODULUS, M, (KPa) Dilatometer Test (Marchetti C o r r e l a t i o n ) Fig.5.15 Summary of Log Constrained Modulus, M, versus E l e v a t i o n 141 p r o f i l e and the screw p l a t e incremental l o a d t e s t p r o f i l e g ive high values f o r the e n t i r e depth whereas the CPT and screw p l a t e u l t i m a t e l o a d t e s t p r o f i l e s s t a r t with very low v a l u e s and i n c r e a s e s t e a d i l y with depth. I t i s not s u r p r i s i n g that the CPT and screw p l a t e u l t i m a t e load t e s t r e s u l t s agree because they stem from the same assumption. In the next chapter, the above c o n s t r a i n e d modulus data w i l l be used i n a settlement a n a l y s i s to p r e d i c t the c o n s o l i d a t i o n settlement f o r the t e s t f i l l . In t h i s way, the i n - s i t u c o n s t r a i n e d moduli and the i n - s i t u t e s t methods can be compared i n terms of t h e i r u s e f u l n e s s i n a p r a c t i c a l a p p l i c a t i o n . The settlement p r e d i c t i o n s from the i n - s i t u t e s t s w i l l then be compared to p r e d i c t i o n s from both standard incremental c o n s o l i d a t i o n t e s t s and l o c a l e x perience. 1 42 VI. SETTLEMENT PREDICTIONS  6.1 IN-SITU TESTING METHODS 6.1.1 Method Of A n a l y s i s The method used to p r e d i c t settlement i s the same f o r each of the i n - s i t u t e s t i n g techniques and i n v o l v e s the co n v e n t i o n a l one-dimensional c o n s o l i d a t i o n settlement method. T h i s method assumes a c o n d i t i o n of zero l a t e r a l s t r a i n w i t h i n the l a y e r i n q u e s t i o n . U s u a l l y l a t e r a l s t r a i n s can be negl e c t e d i f the l e a s t dimension of the loaded area i s l a r g e in comparison to the t h i c k n e s s of the compressible l a y e r : a r a t i o of area dimension to l a y e r t h i c k n e s s of b e t t e r than 5:1 i s commonly accepted as a minimum requirement. The l e a s t dimension of the loaded area i s 30 metres. The t h i c k n e s s of the compressible l a y e r i s 15 metres and the assumption of zero l a t e r a l s t r a i n does not apply at the t e s t f i l l s i t e . The one-dimensional c o n s o l i d a t i o n settlement equation (shown below) w i l l not account f o r the a d d i t i o n a l s ettlements that r e s u l t from l a t e r a l s t r a i n . Sc = mvAa'H where, Sc = the one-dimensional c o n s o l i d a t i o n settlement, (metres) ACT' = change i n e f f e c t i v e s t r e s s i n a l a y e r at some depth due to the a p p l i e d surcharge l o a d . (kPa) H = the t h i c k n e s s of the c o n s o l i d a t i o n l a y e r . (metres) mv = 1/M = the c o e f f i c i e n t of volume change f o r the l a y e r . (1/kPa) Values of M and hence, mK are obtained d i r e c t l y from the i n - s i t u t e s t i n g r e s u l t s of Chapter 5. To c a l c u l a t e the s t r e s s d i s t r i b u t i o n with depth (ACT' versus depth) a s o l u t i o n based on 143 e l a s t i c theory has been chosen. Winterkorn and Fang (1975), present a s o l u t i o n , based on the o r i g i n a l Boussinesq s o l u t i o n , for the v e r t i c a l s t r e s s at a p o i n t w i t h i n an e l a s t i c h a l f -space beneath the corner of a un i f o r m l y loaded r e c t a n g l e . I n f l u e n c e f a c t o r s used i n the c a l c u l a t i o n s depend on the shape of the d i s t r i b u t e d l o a d . The t e s t f i l l i s a c t u a l l y two square surcharge areas j o i n e d t o form a r e c t a n g l e ; one square with wick d r a i n s , the other without. For t h i s a n a l y s i s , both ends of the t e s t f i l l are assumed to act i n unison and the d i s t r i b u t e d l o a d i s consequently r e c t a n g u l a r . To s i m p l i f y the pres s u r e d i s t r i b u t i o n below the s i d e s l o p e s the v e r t i c a l volume of the e n t i r e t e s t f i l l i s represented as a r e c t a n g u l a r d i s t r i b u t i o n . The assumed t e s t f i l l c o n f i g u r a t i o n and the consequent d i s t r i b u t i o n of s t r e s s with depth i s shown i n F i g u r e 6.1. The s t r e s s e s at any depth depend on the magnitude of the embankment s t r e s s . An over e s t i m a t i o n of the embankment s t r e s s w i l l r e s u l t i n an over e s t i m a t i o n of the s e t t l e m e n t s . Using the assumed t e s t f i l l c o n f i g u r a t i o n an embankment s t r e s s of 68kPa was estimated for the c r o s s s e c t i o n . As a check, the s t r e s s at the base of the embankment, i n c l u d i n g bouyancy e f f e c t s of the settlement, was c a l c u l a t e d f o r the end of c o n s t r u c t i o n c o n f i g u r a t i o n . Under the c e n t r e l i n e of the f i l l the embankment s t r e s s reached approximately 90kPa. C o n s i d e r i n g the reduced s t r e s s under the s i d e s l o p e s , the assumed uniform s t r e s s of 68kPa i s c o n s i d e r e d to be a reasonable estimate of the average s t r e s s f o r a c r o s s - s e c t i o n . 1 4 4 F R O N T S I 1 > E -AO" (KPa) F i g . 6 . 1 S t r e s s d i s t r i b u t i o n below the c e n t e r l i n e of the assumed t e s t f i l l c o n f i g u r a t i o n . 1 45 6.1.2 R e s u l t s Of The Settlement A n a l y s i s The r e s u l t s of the c o n s o l i d a t i o n settlement a n a l y s i s w i l l be presented i n g r a p h i c a l form by p l o t t i n g the dimensionless product m v Ao' versus the sublayer t h i c k n e s s , H, represented as e l e v a t i o n . Using t h i s form the area under the curve r e p r e s e n t s the sett l e m e n t . The r e s u l t s of the c o n s o l i d a t i o n settlement a n a l y s i s f o r the cone p e n e t r a t i o n t e s t , d i l a t o m e t e r t e s t and screw p l a t e t e s t are given i n F i g u r e 6.2. For the cone p e n e t r a t i o n t e s t and the u l t i m a t e l o a d t e s t the product m v Aa ' between Om and 2.4m e l e v a t i o n was c a l c u l a t e d t o be g r e a t e r than or equal t o one. Each of these s u b l a y e r s would be r e q u i r e d to compress completely to zero t h i c k n e s s . Such a c o n d i t i o n i s due to an over e s t i m a t i o n of m . The v o i d r a t i o at the t e s t s i t e i s estimated to range between 4 and 8. Assuming a v o i d r a t i o of 8 i n the f i b r o u s peat the settlement due to primary c o n s o l i d a t i o n i s l i m i t e d to about 90% of the o r i g i n a l t h i c k n e s s . For t h i s reason, the va l u e s of m v Aa ' f o r the i n v o l v e d s u b l a y e r s are l i m i t e d to 0.9 or 90% settlement as a reasonable upper bound. For i l l u s t r a t i v e purposes the settlement p r o f i l e i s s u b d i v i d e d i n t o three s o i l groups. The settlement c o n t r i b u t i o n i s summed f o r each s o i l .group and t a b u l a t e d . A l s o l i s t e d i s the settlement as a percent of the t o t a l settlement f o r each i n - s i t u t o o l . For the cone p e n e t r a t i o n t e s t the c o n t r i b u t i o n to c o n s o l i d a t i o n settlement, Sc, f o r each s o i l group i s as f o l l o w s : f i b r o u s peat (0m to -2.4m), Sc=2.0 metres; f i b r o u s to 7HV A^T ( d i m e n s i o n l e s s ) 0 . 0 + 1 .OH 0.0 -1 .0 - 2 . OH - 3 .0-- 4 . 0 - 5 .0H - 6 .0 -7.0-- 8 .0 -- 9 . 0 -10.OH -11.0 -12.0 -13 .0 0.1 0 . 2 0 . 3 i 0 . 4 0 . 5 0 . 6 0.7 0 . 6 0 . 9 1.0 C o n s o l i d a t i o n Settlement Sc-mvA0H (area under the curve summed f o r each 20cm. increment) Cone P e n e t r a t i o n Test - CPT D i l a t o m e t e r Test - DMT Screw P l a t e ( u l t i m a t e l o a d t e s t ) - S c P T Fig.6.2 R e s u l t s of a one-dimensional c o n s o l i d a t i o n settlement a n a l y s i s . • COM F i b r o u s Peat 2.4M - 5 . ON Organic S i l t s - 1 2 . 8M Sc %Total CPT 2.0M 55% DMT 0.07M 20% ScPT I.9M 45% CPT 1.2M 33% DMT 0.11M 30% ScPT 1.4M 33% CPT 0.4M 12% DMT 0.I8M 50% ScPT Q.9M 21% T o t a l -CPT 3.6M IOOX DMT 0.36N " ScPT 4.2M " it" 147 amorphous peat (-2.4m to -5.0m), Sc=1.2 metres; organic c l a y s (-5.0m to -12.8m), Sc=0.4 metres. The p r e d i c t i o n of primary settlement f o r the CPT i s the sum of the s o i l group settl e m e n t s , Sc=3.6 metres. For the d i l a t o m e t e r t e s t the c o n t r i b u t i o n to settlement fo r each s o i l group i s as f o l l o w s : f i b r o u s peat, Sc=0.07 metres; f i b r o u s to amorphous peat, Sc=0.11 metres; organic c l a y s , Sc=0.4 metres. The t o t a l settlement f o r the di l a t o m e t e r i s Sc=0.36 metres. For the screw p l a t e incremental l o a d i n g t e s t s no settlement p r e d i c t i o n i s made. The values of c o n s t r a i n e d modulus M were s e v e r a l times g r e a t e r than those found from the di l a t o m e t e r t e s t . The settlement p r e d i c t i o n from the screw p l a t e r e s u l t s would be unreasonably sma l l ( s e v e r a l c e n t i m e t r e s ) and consequently the p r e d i c t i o n has been dropped from t h i s study. The settlement p r e d i c t i o n based on the c o n s t r a i n e d modulus v a l u e s from the screw p l a t e u l t i m a t e l o a d t e s t s i s d i v i d e d among the three s o i l groups as f o l l o w s : f i b r o u s peat, Sc=1.9 metres; f i b r o u s to amorphous peat, Sc=1.4 metres; organic c l a y s , Sc=0.9 metres. The t o t a l settlement f o r the screw p l a t e u l t i m a t e l o a d t e s t s i s Sc=4.2 metres. 148 6.1.3 D i s c u s s i o n 1. Cone P e n e t r a t i o n Test The c o r r e l a t i o n developed by Sanglerat et a l . (1972) was developed from the r e s u l t s of standard incremental c o n s o l i d a t i o n t e s t s with 24 hour l o a d increments. The use of the d r a i n e d c o n s t r a i n e d modulus, M, i n the c o r r e l a t i o n i m p l i e s that the r e s u l t s w i l l r e f l e c t only primary s e t t l e m e n t s . The observed primary settlement f o r the wick d r a i n area i s 3.0 metres. The CPT p r e d i c t i o n of 3.6 metres over estimates the observed v a l u e . The c a l c u l a t i o n of M from standard incremental c o n s o l i d a t i o n t e s t s i s commonly made us i n g the r e s u l t s of the e n t i r e 24 hour p e r i o d . According to MacFarlane (1969), a 24 hour l o a d i n g p e r i o d on organic s o i l s can i n c l u d e immediate, primary and an a p p r e c i a b l e amount of secondary s e t t l e m e n t . T h e r e f o r e , a p r e d i c t i o n made from S a n g l e r a t ' s c o r r e l a t i o n does not represent primary settlements e x c l u s i v e l y but w i l l r a t h e r be an i n d i c a t o r of some p o r t i o n of the t o t a l s e ttlement. At the time of w r i t i n g , approximately one year a f t e r the end of c o n s t r u c t i o n , the wick d r a i n area has completed primary c o n s o l i d a t i o n and i t i s expected t h a t , given time, the area without wick d r a i n s w i l l have a s i m i l a r magnitude of c o n s o l i d a t i o n s e t t l e m e n t . The sum of the immediate and primary settlement f o r the wick area i s 3.50 metres and — t h e c o n t r i b u t i o n of secondary settlement i s 0.15 metres. T h i s g i v e s a t o t a l observed settlement of 3.65 metres. The CPT 149 p r e d i c t i o n of 3.6 metres i s a good estimate of the t o t a l observed settlement at one year a f t e r the end of c o n s t r u c t i o n . • Cone Bearing R e s i s t a n c e Values The settlement a n a l y s i s was found to be i n s e n s i t i v e to using the c o r r e c t e d bearing, Qt, i n p l a c e of Qc. However, the type of cone employed appears to be q u i t e important. S a n g l e r a t ' s c o r r e l a t i o n was o r i g i n a l l y developed using the D e l f t mantle mechanical cone. Schmertmann (1978) has shown that f o r cohesive s o i l s where the D e l f t cone bearing value i s l e s s than 20 bar the r a t i o of Qc ( D e l f t cone) to Qc (Fugro e l e c t r i c cone) can be as h i g h as 1.5, see F i g u r e 6.3. Updating S a n g l e r a t ' s c o r r e l a t i o n using e l e c t r i c cone data i s d e s i r a b l e . • C o m p r e s s i b i l i t y The r e l a t i o n s h i p given by Sanglerat et a l . (1972) between cr, r e p r e s e n t i n g the compression index C c, and water content i s fundamental to the c o r r e l a t i o n . The c o m p r e s s i b i l i t y c h a r a c t e r i s t i c s are g r e a t l y i n f l u e n c e d by both the f a b r i c and the water content of the peat. In t h i s case f a b r i c r e f e r s to the degree of f i b r o s i t y and interweaving. S a n g l e r a t et a l . (1972) f a i l to give an adequate c l a s s i f i c a t i o n of the peats t e s t e d f o r the c o r r e l a t i o n and, t h e r e f o r e , i t i s remarkable that the c o r r e l a t i o n which was developed f o r peat d e p o s i t s i n France worked w e l l f o r the L u l u I s l a n d d e p o s i t s . The c o r r e l a t i o n (see F i g u r e 5.6) i s a l s o 150 LO, 1 bar = 100 kPa = 1.02 kg/cm 2 i 1 1 r \jC ^ estimated as due to continuous versus incremental t i p advance T rgA ' — • trend line ® I % A © J L 20 BO 100 150 200 250 mechanical Qc (kg/cm !) Legend: O Fugro tests, below WT (Joustra, 1974) B Delft tests, below WT (Heijnen, 1973) A Kok (1974), below WT • U.F., field below WT + U.F., field, below WT, sandy clay • U.F., field, above WT • U.F., chamber, dry uniform med. sand 9 Ft. Pierce, Fla., silty sand below WT X Raleigh, NC, above WT, residual silt M Raleigh, NC. below WT, residual silt All points represent averages of a layer at least 1.0 m thickness F i g u r e 6.3 Comparisons between Qc obtained with D e l f t mechanical and Fugro e l e c t r i c s t a t i c cone t i p s , (adapted from Schmertmann, 1978) 151 s e n s i t i v e to the water content. For example, a r e d u c t i o n i n the water content i n a s o i l l a y e r from 300% to 200% would reduce the p r e d i c t e d settlement f o r that l a y e r by one-half. Accurate determinations of water content are b a s i c to producing meaningful r e s u l t s with t h i s method i n peats. • L a t e r a l S t r a i n Because of c o n s i d e r a b l e l a t e r a l s t r a i n as evidenced by heave adjacent to the t e s t f i l l , the observed settlement are l a r g e r than would be expected under the assumed one-dimensional settlement c o n d i t i o n s . The c o n t r i b u t i o n of the l a t e r a l s t r a i n to the observed settlement i s not known e x a c t l y but appears to be s i g n i f i c a n t . Due to t h i s u n c e r t a i n t y i n the observed settlement the settlement p r e d i c t e d by the i n - s i t u methods can only be judged a rough estimate of the i d e a l one-dimensional settlement. 152 • Summary The p r e d i c t i o n of immediate p l u s primary settlement using the cone p e n e t r a t i o n t e s t has s e v e r a l b e n e f i c i a l a s p e c t s . The d i s t r i b u t i o n of settlement, with the g r e a t e s t amount of settlement o c c u r i n g i n the near s u r f a c e s o i l s , i s r e a l i s t i c . The settlement p r e d i c t i o n i s of the c o r r e c t magnitude and the t e s t i t s e l f i s a r a p i d and economical method of determining an approximate d r a i n e d modulus i n organic s o i l s when combined with water content measurements. Conversely, the drawbacks to the method i n c l u d e : the ambiguity concerning the r e l a t i v e c o n t r i b u t i o n of the v a r i o u s phases of c o n s o l i d a t i o n (immediate, primary and secondary) i n -b u i l t i n the c o r r e l a t i o n , the u n c e r t a i n t y inherent i n using c o r r e l a t i o n s where the s o i l type i s not adequately d e f i n e d and the development of the c o r r e l a t i o n using mechanical cone data. The p o t e n t i a l f o r e r r o r was present i n the t e s t i n g aspects of the study because the s e n s i t i v i t y of the b e a r i n g l o a d c e l l was not i d e a l f o r very s o f t s o i l s and because the measurement of water contents i n s u p e r - s a t u r a t e d peats i s s u b j e c t to c o n s i d e r a b l e e r r o r . O v e r a l l , as a f i r s t estimate of the t o t a l settlement at one year a f t e r the end of c o n s t r u c t i o n , the CPT p r e d i c t i o n i s c o n s i d e r e d to be q u i t e good. However, the agreement between the p r e d i c t e d and observed settlement i s somewhat s u r p r i s i n g i n view of the p o t e n t i a l e r r o r s i n v o l v e d i n the study. 1 53 2. Dilatometer Test S i m i l a r to the c o r r e l a t i o n f o r the cone p e n e t r a t i o n t e s t , the d i l a t o m e t e r t e s t c o r r e l a t i o n to M i s based on oedometer t e s t s . Because these t e s t s were performed on c l a y s r a t h e r than o r g a n i c s o i l s one would expect the c o r r e l a t i o n to represent immediate and primary settlements but not a p p r e c i a b l e amounts of secondary settlement. The sum of immediate and primary settlement observed f o r the wick end i s 3.50 metres. The d i l a t o m e t e r p r e d i c t i o n of 0.36 metres under estimates the observed value by a f a c t o r of almost 10. The under e s t i m a t i o n of settlement i s d i r e c t l y due to the over e s t i m a t i o n of the d i l a t o m e t e r c o n s t r a i n e d modulus, M. An important parameter i n the c a l c u l a t i o n of M i s the h o r i z o n t a l s t r e s s index, Kd. M a r c h e t t i (1980) developed the c o r r e l a t i o n to M v i a the parameters Ed and Kd, r e f e r to F i g u r e 5.8. I t can be seen from F i g u r e 5.8 that the minimum r a t i o , Rm, of M to Ed i s about 0.85. The magnitude of Ed f o r the re f e r e n c e d i l a t o m e t e r t e s t (Figure 3.8) i s about 1.0 to'1.5 MPa i n the f i b r o u s p e a t s . T h e r e f o r e , the minimum value of M that can be p r e d i c t e d from the r e f e r e n c e d i l a t o m e t e r p r o f i l e using t h i s c o r r e l a t i o n i s about 0.85MPa or 850kPa. A value of M of 850kPa, c o n s i d e r i n g the CPT values of M, i s a p p r o p r i a t e f o r the organic c l a y but i s too l a r g e to adequately p r e d i c t settlement f o r the f i b r o u s peats. Because F i g u r e 5.8 r e l a t e s an i n c r e a s i n g Kd with an i n c r e a s i n g M the use of the c o r r e c t e d values of Kd ( i n c r e a s e d by about 40%) would r e s u l t i n l a r g e r values of M and, consequently, to an even s m a l l e r estimated 1 54 s e t t l e m e n t . M a r c h e t t i ' s c o r r e l a t i o n shows that i n c r e a s i n g Kd i s a s s o c i a t e d with i n c r e a s i n g M. For f i b r o u s peats i t appears t h a t an i n v e r s e a s s o c i a t i o n may be t r u e . The reason f o r t h i s probably l i e s i n the o r i e n t a t i o n of the d i l a t o m e t e r t e s t which, being p e r p e n d i c u l a r to the h o r i z o n t a l l y a l i g n e d f i b r e s , r e q u i r e s the membrane expansion to work a g a i n s t the h i g h h o r i z o n t a l s t i f f n e s s of the f i b r e s . O v e r a l l the t e s t does not appear to give a good i n d i c a t i o n of the v e r t i c a l c o m p r e s s i b i l i t y of the peat. The d i l a t o m e t e r i n t e r p r e t a t i o n would be improved by extending the c o r r e l a t e d data base. A f t e r s e v e r a l years of development the data base remains sparse and i s not c l e a r l y d e f i n e d with respect to the s p e c i f i c s o i l types recommended by M a r c h e t t i (1980) for d i l a t o m e t e r a p p l i c a t i o n . The i n a b i l i t y of the data r e d u c t i o n system to d i f f e r e n t i a t e measurements f o r s o i l s recommended f o r d i l a t o m e t e r a p p l i c a t i o n from those not recommended i s a major drawback. U l t i m a t e l y , i t i s q u e s t i o n a b l e whether the data r e d u c t i o n system w i l l be able to d i f f e r e n t i a t e s o i l c o n d i t i o n s i n a dependable manner even i f the data base i s extended. T h i s i s because the b a s i c d i l a t o m e t e r measurements give only a minimum of i n f o r m a t i o n about the a c t u a l s o i l c o n d i t i o n s . 1 55 3. Screw P l a t e : Incremental Loading Te s t s Because the values of the d r a i n e d c o n s t r a i n e d modulus c a l c u l a t e d from the screw p l a t e were very l a r g e the r e s u l t i n g settlement p r e d i c t i o n was very s m a l l . The method of t e s t i n t e r p r e t a t i o n i s reviewed with res p e c t to the small p l a t e movements measured d u r i n g the t e s t s . The method of a n a l y s i s given by Janbu and Senneset (1973) r e q u i r e s knowledge of the t o t a l p l a t e movement corresponding to the end of primary c o n s o l i d a t i o n . Because there i s no p r o v i s i o n f o r measurement of pore pr e s s u r e s with the screw p l a t e d e v i c e the end of primary c o n s o l i d a t i o n i s i n t e r p r e t e d from the p l a t e movement versus root-time curve using curve f i t t i n g methods. T a y l o r ' s root-time method gave the time f o r 90% c o n s o l i d a t i o n , t ^ , to be between one to f i v e minutes per load increment depending on the s o i l type. T h e r e f o r e , the t y p i c a l t e s t r e s u l t c o u l d be i n t e r p r e t a t e d as having a f a s t primary phase (a few minutes) f o l l o w e d by a slower secondary c o n s o l i d a t i o n phase. T h i s i n t e r p r e t a t i o n gave t q o p l a t e movements which were unexpectedly small and r e s u l t e d i n l a r g e c a l c u l a t e d v a l u e s of M. C r i t i c a l to the method i s an a ccurate d e t e r m i n a t i o n of t a 0 . The p o s s i b i l i t y that the t e s t s were i n c o r r e c t l y i n t e r p r e t e d by a p p l y i n g curve f i t t i n g methods was i n v e s t i g a t e d . An a l t e r n a t i v e i n t e r p r e t a t i o n was proposed; i t i s p o s s i b l e that the t e s t s may have been terminated before reaching 90% of primary c o n s o l i d a t i o n . To i n v e s t i g a t e t h i s p r o p o s a l , an extended screw p l a t e t e s t was performed and the 156 p l a t e movement, f o r a s i n g l e increment of 50kPa, was recorded f o r 240 minutes. The t e s t curves f o r the extended t e s t and f o r a s i n g l e increment of a t y p i c a l incremental l o a d i n g t e s t are p l o t t e d versus l o g time i n F i g u r e 6.4. A f t e r ten minutes both t e s t s are seen to approach a new s l o p e . The i n c r e a s e i n slope shown by the t e s t s i s s i m i l a r to t h a t expected f o r the beginning of v i r g i n compression. A f t e r 240 minutes a s l i g h t decrease i n the slope of the t e s t can be seen. T h i s i s p o s s i b l y the s t a r t of a t r a n s i t i o n phase to secondary compression. The extended t e s t appears to support the p r o p o s a l that the incremental t e s t s were terminated before t was e s t a b l i s h e d . From F i g u r e 6.4 i t appears l i k e l y t h a t up to 24 hours would be r e q u i r e d to p r o p e r l y d e f i n e the end of primary c o n s o l i d a t i o n . The extended t e s t i n d i c a t e s that the values of M c a l c u l a t e d from the incremental l o a d i n g t e s t s are not v a l i d due to an i n c o r r e c t i n t e r p r e t a t i o n of t q o . I f long d u r a t i o n screw p l a t e t e s t s were performed so that t was d e f i n e d , the r e s u l t i n g c o n s t r a i n e d modulus c o u l d be of a u s e f u l magnitude f o r settlement p r e d i c t i o n . However, i t i s l i k e l y that a very long d u r a t i o n t e s t would be r e q u i r e d . Because the UBC screw p l a t e uses a l o a d i n g system which r e q u i r e s constant o p e r a t i o n of the engine d r i v e n h y d r a u l i c pump, a t e s t of more than 8 hours was c o n s i d e r e d i m p r a c t i c a l . A c o n v e n t i o n a l system of l o a d i n g using deadweights or a p o r t a b l e h y d r a u l i c jack would be b e t t e r s u i t e d to long d u r a t i o n l o a d i n g . In summary, the screw p l a t e theory d e s c r i b e d by Janbu and o.o 2.0 4-.0 6jO 6 6 EH 8 0 82 o X w < O4 i4.o - A Extended Screw P l a t e Test Depth = 3.0 M.; Pn = 48.5 KPa; Po = 10.0 KPa, o—-o Incremental Load Screw P l a t e Test Depth - 2.0 M.; Pn = 49.0 KPa; Po 9.0 KPa. 0 . 1 0.2. 0.+ 1.0 Z.O 4-.0 10.0 2D.O lOO.O 2.00.0 4 0 O . 0 IOOO.O LOG TIME (minutes) Fi g . 6.4 P l a t e Movement vs. Log Time: Comparison Between Incremental Load T e s t s and Extended Load T e s t s 01 1 58 Senneset (1973) was not developed f o r the t e s t i n g of s o i l s with a h i g h organic content. A s e r i e s of long d u r a t i o n t e s t s are needed before t h e i r theory can be thoroughly assessed f o r the t e s t i n g of peat. At present the g r e a t e s t drawback i n measuring volume change i n low p e r m e a b i l i t y s o i l s with the screw p l a t e i s the l a r g e amount of time r e q u i r e d to d e f i n e the end of primary c o n s o l i d a t i o n . Other u n c e r t a i n t i e s i n c l u d e knowledge of the load t r a n s m i t t e d to the p l a t e and the p o s s i b i l i t y of l a t e r a l s t r a i n o c c u r r i n g d u r i n g the t e s t . 4. Screw P l a t e : U l t i m a t e Load T e s t s The t o t a l observed settlement at one year a f t e r the end of c o n s t r u c t i o n f o r the wick d r a i n area i s 3.65 metres. The settlement p r e d i c t e d from the screw p l a t e u l t i m a t e l o a d t e s t s i s 4.2 metres. The screw p l a t e p r e d i c t i o n over estimates the p r e d i c t i o n from the CPT by about 0.6m. Settlements p r e d i c t e d by the screw p l a t e exceeded those of the CPT at depths below -3.8m e l e v a t i o n ( r e f e r to F i g u r e 6.2) i n d i c a t i n g that the Quit value i s l e s s than Qt i n t h i s r e g i o n . Fundamentally, the CPT and the screw p l a t e u l t i m a t e l o a d t e s t s are d i f f e r e n t i n s e v e r a l ways. The CPT develops a maximum s t r a i n f i e l d d u r i n g continuous p e n e t r a t i o n whereas the screw p l a t e t e s t i n v o l v e s a l e s s e r amount of s t r a i n . A l s o the r e l a t i v e s i z e of the b e a ri n g area and r a t e of l o a d i n g are d i f f e r e n t i n the two t e s t s . The e f f e c t s of b e a r i n g area s i z e , r a t e of l o a d i n g and degree of s t r a i n f i e l d development c o u l d 159 be s i g n i f i c a n t i n peat and are not w e l l understood at t h i s time. To summarize, the p r e d i c t e d values of settlement from the screw p l a t e u l t i m a t e l o a d t e s t are s i m i l a r to the CPT when the r e s u l t s are c o n s i d e r e d i n terms of t e s t i n g e r r o r s . Each of the t e s t s can be improved: the CPT by using a bearing l o a d c e l l of the a p p r o p r i a t e s e n s i t i v i t y and the screw p l a t e t e s t by measuring l o a d at the screw p l a t e and thereby e l i m i n a t i n g the need to estimate rod f r i c t i o n . The screw p l a t e should a l s o be r e s t r i c t e d d u r i n g t e s t i n g so that r o t a t i o n cannot occur. 6.2 CONVENTIONAL METHODS 6.2.1 Standard Incremental C o n s o l i d a t i o n T e s t s Three standard incremental c o n s o l i d a t i o n t e s t s were performed by the G e o t e c h n i c a l T e s t i n g D i v i s i o n of the B r i t i s h Columbia Department of Highways on samples taken at s e v e r a l depths i n the organic c l a y s . Averaged values of the i n i t i a l v o i d r a t i o , e0 , and compression index, C c, from the t e s t s are s u b s t i t u t e d i n t o the one-dimensional equation f o r e s t i m a t i o n of the wick d r a i n area c o n s o l i d a t i o n settlement. The c o n s o l i d a t i o n s e t t l e m e n t , f o r the organic c l a y l a y e r only, due to 8.5m of f i l l i s estimated to be 0.87 metres. 160 6.2.2 L o c a l Experience Since 1958, when the p r a c t i c e of p r e l o a d i n g peat d e p o s i t s was begun i n B r i t i s h Columbia, instrumented t e s t s e c t i o n s have been documented and compiled with the i n t e n t of developing e m p i r i c a l c o r r e l a t i o n s . A recent v e r s i o n of settlement data fo r peat s i t e s i n the Greater Vancouver area has been presented by Scotton (1981), see F i g u r e 6.5. H i g h l i g h t e d i n Fi g u r e 6.5 are the data p o i n t s corresponding to average i n i t i a l water contents l e s s than 600%. The water contents f o r the peats at the t e s t f i l l s i t e range between 300% and 600%. Co n s i d e r a b l e s c a t t e r can be seen i n the data of F i g u r e 6.5. Settlement p r e d i c t i o n s w i l l be made with r e s p e c t t o the upper bound data p o i n t s f o r water contents between 400% and 600% thus g i v i n g the most c o n s e r v a t i v e e s t i m a t e . F i g u r e 6.5 i n c l u d e s s i t e s where peat o v e r l i e s organic c l a y by r e p r e s e n t i n g the data f o r these s i t e s as an e q u i v a l e n t peat depth (Scotton, 1981). A p o r t i o n of the org a n i c c l a y depth (roughly i n the r a t i o of the water c o n t e n t s of the or g a n i c s i l t t o the peat) i s added t o the peat depth g i v i n g an e q u i v a l e n t peat depth. The r a t i o of the water c o n t e n t s at the t e s t f i l l s i t e i s about 1:4 g i v i n g an a d d i t i o n a l 'peat depth' of 2.5 metres. The e q u i v a l e n t peat depth i s then 8.5 metres. E n t e r i n g F i g u r e 6.5 with a r a t i o of f i l l h e i g h t (8.5m) to e q u i v a l e n t peat depth (8.5m) of 1.0 the upper bound settlement i s about 3.4m. S t u d i e s by Cook (1956) showed t h a t r e l a t i o n s h i p s e x i s t between f i e l d water content and v o i d r a t i o and a l s o v o i d r a t i o RATIO F i g u r e 6.5 Summary of OF PRIMARY SETTLEMENT p r i m a r y s e t t l e m e n t TO ORIGINAL PEAT d a t a ( a d a p t e d DEPTH (Sc/P)(dfmenslonless) f r o m S c o t t o n , 1981). 162 and c o m p r e s s i b i l i t y . These r e l a t i o n s h i p s agreed w e l l with t e s t s conducted by Brawner (1959) on Lower Fr a s e r V a l l e y f i b r o u s peats. T h e r e f o r e , i t appears to be p o s s i b l e to adequately estimate settlement simply from a knowledge of the f i e l d water content. For the t e s t f i l l s i t e , where the r e p r e s e n t a t i v e water content i n the peat i s about 400%, Cook's c o r r e l a t i o n g i v e s a v o i d r a t i o of 8 and a compression index of 4. S u b s t i t u t i n g these v a l u e s i n t o the one-dimensional equation y i e l d s an estimated settlement f o r the 6m peat l a y e r of 2.3 metres. By combining the r e s u l t s of the standard incremental c o n s o l i d a t i o n t e s t s f o r the organic c l a y s and Cook's (1956) method f o r peats, the c o n s o l i d a t i o n settlement was estimated to be about 3.2 metres. Scotton's (1981) method p r e d i c t s a primary settlement of 3.4 metres. T h i s i s c l o s e to the observed primary settlement of 3.5 metres. However, because of the s c a t t e r i n the data of F i g u r e 6.5 the p r e d i c t e d settlement c o u l d be as low as 2.2 metres. Therefore the u s e f u l n e s s of F i g u r e 6.5 i s reduced somewhat to that of a p r e l i m i n a r y guide to expected s e t t l e m e n t s . Cook's (1956) c o r r e l a t i o n appears to be based on averaged peat settlement data and t h e r e f o r e the c o r r e l a t i o n tends to under estimate the s e t t l e m e n t s at the t e s t f i l l s i t e . Although the sum of the r e s u l t s from Cook's (1956) c o r r e l a t i o n and standard incremental c o n s o l i d a t i o n t e s t s gave a reasonable estimate, the standard incremental c o n s o l i d a t i o n t e s t r e s u l t s can i n c l u d e s i g n i f i c a n t e r r o r s such as sampling d i s t u r b a n c e 1 63 and sample p r e p a r a t i o n d i s t u r b a n c e , e t c . A drawback with Cook's (1956) c o r r e l a t i o n i s that i t only a p p l i e s to peats. Where peat i s u n d e r l a i n by organic c l a y s a program of standard incremental c o n s o l i d a t i o n t e s t s i s r e q u i r e d to complete the p r e d i c t i o n . 1 64 V I I . CONCLUSIONS 7.1 EVALUATION OF THREE IN-SITU TEST METHODS FOR MONITORING  EMBANKMENTS A l a r g e amount of d e t a i l e d i n f o r m a t i o n has been presented and d i s c u s s e d with regard to the monitoring of the t e s t f i l l u sing i n - s i t u t e s t techniques. The understanding of the s u b s o i l behaviour i n terms of a simple c o n s o l i d a t i o n model was made d i f f i c u l t by the complex embankment c o n f i g u r a t i o n , s o i l and groundwater c o n d i t i o n s p r e s e n t . Each of the i n - s i t u t e s t s (CPT, DMT and f i e l d vane) gave s i m i l a r i n d i c a t i o n s of s o i l improvement with depth f o r both the wick and the non-wick areas. For the CPT and f i e l d vane t e s t the improvement was p r i m a r i l y r e f l e c t e d as an i n c r e a s e i n s o i l s t r e n g t h (Qt and Su, r e s p e c t i v e l y ) , whereas the DMT showed an i n c r e a s e i n s o i l s t i f f n e s s (Ed). 7.1.1 D i l a t o m e t e r Test The d i l a t o m e t e r parameter Kd was s u b j e c t to two s i g n i f i c a n t e r r o r s d u r i n g t h i s study because of i n - b u i l t assumptions r e g a r d i n g the ambient pore pressure and the s o i l u n i t weight. The under e s t i m a t i o n of Kd due to an i n c o r r e c t s o i l u n i t weight was l a r g e (approximately 40%) f o r the i n i t i a l c o n d i t i o n s t e s t s where the v e r t i c a l e f f e c t i v e s t r e s s was s m a l l . T h i s e r r o r i n Kd was reduced to about 20% f o r the a f t e r l o a d i n g t e s t s because the v e r t i c a l e f f e c t i v e s t r e s s had doubled. Ambient pore water pre s s u r e s i n excess of 165 h y d r o s t a t i c were s i g n i f i c a n t • only d u r i n g the a f t e r c o n s t r u c t i o n t e s t i n the non-wick a r e a . The r e s u l t of c o r r e c t i n g t h i s t e s t f o r pore water p r e s s u r e s i n excess of h y d r o s t a t i c was to decrease Kd by about 20%. O v e r a l l Kd appears to give an i n d i c a t i o n of changes i n h o r i z o n t a l s t r e s s which can be u s e f u l to i d e n t i f y zones of s u b s o i l improvement. The c o r r e l a t i o n of Kd with s t r e s s h i s t o r y was not u s e f u l f o r the peat i n i t s n a t u r a l s t a t e due to f i b r e i n t e r a c t i o n which caused u n u s u a l l y l a r g e values of Kd. During and a f t e r primary c o n s o l i d a t i o n Kd c o r r e c t l y i n d i c a t e d that the s o i l was normally c o n s o l i d a t e d . Kd must be used with c a u t i o n because the assumptions which are used i n the data r e d u c t i o n of the parameter can produce m i s l e a d i n g r e s u l t s i f the s o i l d e n s i t y and the ambient pore water pr e s s u r e s are not c o r r e c t e d to the i n - s i t u c o n d i t i o n s . The d e t e r m i n a t i o n of the f i e l d undrained shear s t r e n g t h (Su) from d i l a t o m e t e r t e s t r e s u l t s has been d i s c u s s e d f o r the t e s t f i l l s i t e under i n i t i a l c o n d i t i o n s i n s e c t i o n 5.2. For the d i l a t o m e t e r t e s t the values of Su were found to be independent of the a s s i g n e d u n i t weight because the c o r r e l a t i o n to Su i s normalized with r e s p e c t to the v e r t i c a l e f f e c t i v e s t r e s s . Under i n i t i a l c o n d i t i o n s the d i l a t o m e t e r t e s t r e s u l t s gave a reasonable estimate of Su, i . e . the r e s u l t s were on the c o n s e r v a t i v e s i d e of the d i r e c t f i e l d vane measurements and a l s o c l o s e i n magnitude to Su b a c k - c a l c u l a t e d from the s u b - s o i l f a i l u r e . The v a l u e s of Su from the d i l a t o m e t e r t e s t s which were used to monitor the embankment 166 l o a d i n g program were s u b j e c t to e r r o r due to the f i e l d excess pore water pre s s u r e s generated during the embankment c o n s t r u c t i o n . A d e t a i l e d a n a l y s i s of the e r r o r i n Su d u r i n g the monitoring program i s beyond the scope of t h i s paper. In t h i s w r i t e r s o p i n i o n the e r r o r i n Su i s probably s i m i l a r i n magnitude to the e r r o r i n Kd due to f i e l d excess pore water p r e s s u r e s , say between 10% and 20%. In a s i m i l a r manner to the vane t e s t r e s u l t s , the d i l a t o m e t e r modulus, Ed, gave some u s e f u l i n f o r m a t i o n r e g a r d i n g b a s i c s u b s o i l improvement. The parameter Ed does appear to represent some form of s o i l s t i f f n e s s . A broader i n t e r p r e t a t i o n of Ed i n terms of an e q u i v a l e n t e l a s t i c modulus fo r organic s o i l s i s beyond the scope of t h i s paper. The b a s i c d i l a t o m e t e r measurements (PO and P1) from which Ed i s d e r i v e d are s u b j e c t to 'hidden' pore pressure e f f e c t s such as pore pressure d i s s i p a t i o n before membrane i n f l a t i o n and the p o s s i b i l i t y of a mixed drainage response of the i n -s i t u s o i l ( i . e . n e i t h e r a f u l l y d r a i n e d response or a f u l l y undrained response). These e f f e c t s may have important i m p l i c a t i o n s f o r the d i l a t o m e t e r t e s t i n s i l t y s o i l s . A study of the pore pressure e f f e c t s which occur d u r i n g d i l a t o m e t e r t e s t i n g i s c u r r e n t l y i n progress at UBC. Because the e f f e c t of excess pore p r e s s u r e s on the d i l a t o m e t e r t e s t i s not f u l l y understood at t h i s time the a p p l i c a t i o n of the d i l a t o m e t e r t e s t i n s i t u a t i o n s where ambient excess pore p r e s s u r e s are present, such as embankment mo n i t o r i n g , i s not recommended. 167 7.1.2 F i e l d Vane Test The f i e l d vane t e s t gave a u s e f u l i n d i c a t i o n of the degree of s o i l improvement from the i n i t i a l c o n d i t i o n to the f i n a l c o n d i t i o n , see s e c t i o n s 4.2.3 and 4.3.3. In the non-wick area the f i n a l Su v a l u e s were lower than expected due to d i s t u r b a n c e s a r i s i n g from the s u b s o i l f a i l u r e . I n t e r p r e t a t i o n of the f i n a l non-wick area d i l a t o m e t e r t e s t r e s u l t s was f u r t h e r c o m plicated by ambient excess pore water p r e s s u r e s . T e s t s conducted i n the wick d r a i n area where l i t t l e or no excess pore water pre s s u r e s were present showed good agreement with the r e s u l t s of the wick area cone p e n e t r a t i o n t e s t m o n i t o r i n g . A l s o , the i n i t i a l c o n d i t i o n s undrained shear s t r e n g t h from the f i e l d vane appeared to be somewhat too l a r g e when compared with a value of Su b a c k - c a l c u l a t e d from the s u b s o i l f a i l u r e . Other drawbacks of the f i e l d vane t e s t are t h a t i t i s r e l a t i v e l y slow to perform and that the t e s t spacing with depth r e s u l t s i n a l o s s of s t r a t i g r a p h i c d e t a i l when compared to the CPT and DMT p r o f i l e s . 7.1.3 Cone P e n e t r a t i o n Test • There are s e v e r a l i n s t a n c e s i n p a r t i c u l a r where the piezometer cone p e n e t r a t i o n t e s t gave i n f o r m a t i o n which f u r t h e r e d the understanding of the embankment t e s t . In g e n e r a l , the measurement of pore p r e s s u r e s during p e n e t r a t i o n allowed f o r a g r e a t e r understanding and a • f u l l e r i n t e r p r e t a t i o n of the t o t a l s t r e s s CPT measurements. 168 • - The piezometer cone measurements provided u s e f u l i n f o r m a t i o n about e q u i l i b r i u m pore pressure c o n d i t i o n s . E q u i l i b r i u m pore pr e s s u r e s measured d u r i n g i n i t i a l c o n d i t i o n s t e s t s i n d i c a t e d a no n - h y d r o s t a t i c groundwater c o n d i t i o n . E q u i l i b r i u m pore pressure measurements made du r i n g the monitoring of the t e s t f i l l gave i n s i g h t i n t o a f l u c t u a t i n g groundwater c o n d i t i o n which would otherwise have gone unnoticed. • An i n t e r e s t i n g phenomena was observed f o r f r i c t i o n r e s i s t a n c e measurements i n the non-wick a r e a . The f r i c t i o n r e s i s t a n c e decreased markedly f o l l o w i n g the s u b s o i l f a i l u r e . The observed f i e l d pore water pressure d i d not i n c r e a s e a f t e r the f a i l u r e , see F i g u r e 2.6. However, the generated pore water p r e s s u r e from cone p e n e t r a t i o n d i d i n c r e a s e s i g n i f i c a n t l y a f t e r the f a i l u r e had oc c u r r e d , see F i g u r e 4.2. As the f i e l d c o n s o l i d a t i o n progressed the f r i c t i o n r e s i s t a n c e was observed to recover towards i t s i n i t i a l v a l u e . I t i s i n f e r r e d from these trends that the decrease i n f r i c t i o n r e s i s t a n c e was d i r e c t l y r e l a t e d to d i s t u r b a n c e s a s s o c i a t e d with the s u b s o i l f a i l u r e . • The s t r a t i g r a p h i c d e t a i l given by the CPT was u s e f u l f o r demonstrating s o i l v a r i a b i l i t y across the s i t e . The cone be a r i n g r e s i s t a n c e i n d i c a t e d a v a r i a t i o n i n s o i l s t r e n g t h a c r o s s the s i t e which was confirmed by f i e l d vane r e s u l t s . • The excess pore p r e s s u r e s present d u r i n g the monitoring of the t e s t f i l l made i n t e r p r e t a t i o n of the i n - s i t u t e s t s d i f f i c u l t . I t was o r i g i n a l l y expected that the piezometer 169 cone would e x c e l under such c o n d i t i o n s . However, due to inadequate p r o f i l i n g of e q u i l i b r i u m pore p r e s s u r e s , Uo, the e f f e c t of the excess pore p r e s s u r e s (both due to l o a d i n g and due to p e n e t r a t i o n ) c o u l d not be p r o p e r l y accounted f o r when i n t e r p r e t i n g the CPT parameters. O b t a i n i n g an adequate p r o f i l e of Uo i s p o s s i b l e with the piezometer cone. However, t h i s may r e q u i r e a c o n s i d e r a b l e amount of time depending on the number of e q u i l i b r i u m s needed and the s o i l p e r m e a b i l i t y . If r e l i a b l e e q u i l i b r i u m pore p r e s s u r e data i s a v a i l a b l e from nearby f i e l d piezometers then t h i s data can be e a s i l y i n c o r p o r a t e d i n t o the CPT p r o f i l e as supplementary i n f o r m a t i o n . The a c c e s s i b i l i t y of the CPT data r e d u c t i o n process to e n g i n e e r i n g judgement i s a major b e n e f i t over the closed-system process developed f o r the DMT. From t h i s p r e l i m i n a r y study the piezometer cone p e n e t r a t i o n t e s t proved to be the best instrument f o r i n - s i t u m onitoring of an embankment over organic s o i l s . Key f a c t o r s i n t h i s c h o i c e a r e : the vast amount of d e t a i l e d i n f o r m a t i o n given, the r e p r o d u c i b i l i t y and speed of the t e s t , the a b i l i t y to measure pore pressures and the a c c e s s i b i l i t y of the data to e n g i n e e r i n g judgement. 170 7.2 EVALUATION OF THREE IN-SITU TEST METHODS FOR DETERMINING  ORGANIC SOIL PROPERTIES 7.2.1 Undrained Shear S t r e n g t h Based on the r e s u l t s of a l i m i t e d number of t e s t s , reasonable estimates of the undrained shear s t r e n g t h were gained from the CPT and screw p l a t e t e s t . For these t e s t s the c h o i c e of c o r r e l a t i o n f a c t o r s i s based on the a v a i l a b l e e n g i n e e r i n g experience. The screw p l a t e t e s t , with d i v i s o r equal to 9.0, g i v e s a very s i m i l a r r e s u l t to the f i e l d vane t e s t . I f the upper bound d i v i s o r of 11.35 i s used then the estimate of Su w i l l be more c o n s e r v a t i v e . The CPT r e s u l t s i n the o r g a n i c c l a y s , with Nk equal to 8, gave a s i m i l a r estimate of Su to that p r o v i d e d by the f i e l d vane i n the organic c l a y s . Because of f i b r e reinforcement i n the f i b r o u s peat the cone t e s t does not reproduce the f i e l d vane Su w i t h i n the boundaries of a r e a l i s t i c value of Nk. The d i l a t o m e t e r t e s t gave a u s e f u l estimate of Su f o r the organic s o i l s . The d i l a t o m e t e r values of Su were s i m i l a r i n magnitude to the b a c k - c a l c u l a t e d value of Su from the s u b s o i l f a i l u r e and were the most c o n s e r v a t i v e e s t i m a t e s when compared to the other t e s t i n g techniques. The e r r o r i n Su due to the estimate of u n i t weight was found to be n e g l i g i b l e . Based on t h i s l i m i t e d study the v a l u e s of Su from the d i l a t o m e t e r appear to give c o n s e r v a t i v e estimates of the i n - s i t u s t r e n g t h i n the o r g a n i c s o i l s a t the t e s t f i l l s i t e . The undrained shear s t r e n g t h r e s u l t s presented i n t h i s 171 paper are p r e l i m i n a r y i n nature, more experience i s r e q u i r e d i n a v a r i e t y of peat d e p o s i t s before the r e s u l t s can be a p p l i e d with c o n f i d e n c e . 7.2.2 C o e f f i c i e n t Of C o n s o l i d a t i o n A s e r i e s of piezometer cone d i s s i p a t i o n t e s t s were performed at the t e s t f i l l s i t e p r i o r to l o a d i n g and the c o e f f i c i e n t of c o n s o l i d a t i o n c a l c u l a t e d , see F i g u r e 5.5. The c a l c u l a t e d values were then compared with the c o e f f i c i e n t of c o n s o l i d a t i o n from standard incremental c o n s o l i d a t i o n t e s t s (SICT). The CPT data was found to be between f i v e and f i f t y times l a r g e r than the SICT data f o r t e s t s a t s i m i l a r depths. A major cause of the l a r g e d i f f e r e n c e between CPT and SICT r e s u l t s i s the d i f f e r e n c e i n the l o a d i n g c o n d i t i o n s of the t e s t s . The SICT values were c a l c u l a t e d f o r a sample which was h i g h l y s t r a i n e d under a l a r g e a p p l i e d l o a d whereas the i n - s i t u s o i l s are only s u b j e c t to l o c a l l y h i g h s t r a i n s and loads r e s u l t i n g from probe i n s e r t i o n . The pore p r e s s u r e d i s s i p a t i o n around the cone p e n e t r a t i o n probe i s a l s o i n f l u e n c e d by the r e l a t i v e l y u ndisturbed f r e e f i e l d c o n d i t i o n s at g r e a t e r d i s t a n c e s from the probe. T h i s f r e e f i e l d e f f e c t tends to reduce the average s t r e s s and s t r a i n at a given r a d i a l d i s t a n c e from the probe so that the average a p p l i e d s t r e s s d u r i n g a pore pressure d i s s i p a t i o n t e s t i s l i k e l y to be somewhat l e s s than the a p p l i e d s t r e s s i n an SICT t e s t . The decrease i n c o e f f i c i e n t of c o n s o l i d a t i o n with l o a d was confirmed i n - s i t u by piezometer cone d i s s i p a t i o n t e s t s 1 72 performed a f t e r the end of c o n s t r u c t i o n . A f i v e , to t e n - f o l d decrease i n the i n - s i t u c o e f f i c i e n t of c o n s o l i d a t i o n was measured a f t e r l o a d i n g , b r i n g i n g the CPT r e s u l t s i n t o c l o s e r agreement with the SICT t e s t s , r e f e r to F i g u r e 5.5. S e v e r a l anomolous e f f e c t s were observed in the pore pressure measurements made with the piezometer cone, see s e c t i o n 3.2.4. These anomolies, such as pore pressure r i s e d u r i n g the i n i t i a l p o r t i o n of a d i s s i p a t i o n and a r e d u c t i o n i n the generated pore pressure response when p e n e t r a t i o n i s resumed f o l l o w i n g a d i s s i p a t i o n , i n d i c a t e that the pore pressure response of organic s o i l s i s s u b j e c t to c o m p l e x i t i e s not commonly found in mineral s o i l s . 7.2.3 C o n s t r a i n e d Modulus The d r a i n e d c o n s t r a i n e d modulus has been determined from four i n - s i t u t e s t s , see F i g u r e 5.15. A p r o f i l e of c o n s t r a i n e d modulus from each t e s t was then used in a settlement a n a l y s i s to p r e d i c t the observed t e s t f i l l s e t t l e m e n t s , see F i g u r e 6.2. In t h i s way, t h e • u s e f u l n e s s of the c o n s t r a i n e d modulus r e s u l t s c o u l d be assessed f o r a p r a c t i c a l a p p l i c a t i o n . Settlements were a l s o p r e d i c t e d from c o n v e n t i o n a l oedometer s t u d i e s and e m p i r i c a l l o c a l experience methods. A summary of the observed and p r e d i c t e d settlements i s given i n Table 7.1. S e v e r a l i n t e r e s t i n g c o n c l u s i o n s can be drawn from the r e s u l t s of t h i s study. • The d r a i n e d c o n s t r a i n e d modulus c a l c u l a t e d f o r the cone 173 TABLE 7.1 SUMMARY OF OBSERVED AND PREDICTED SETTLEMENTS * OBSERVED SETTLEMENTS (metres) Immediate 0.5 Primary 3.0 Secondary (t = 400 days) 0.15 T o t a l 3.65 PREDICTED SETTLEMENTS (metres) Cone p e n e t r a t i o n t e s t 3.60 Dil a t o m e t e r t e s t 0.36 Screw p l a t e : i n c r e m e n t a l l o a d i n g t e s t N.A. Screw p l a t e : u l t i m a t e l o a d t e s t 4.2 LABORATORY METHODS & LOCAL EXPERIENCE (metres) Cook (1956) method and SICT r e s u l t s 3.2 Scotton (1981) - e q u i v a l e n t peat depth 3.4 * observed se t t l e m e n t s from w i c k . d r a i n area at about 1 year a f t e r the end of c o n s t r u c t i o n . 174 p e n e t r a t i o n t e s t using S a n g l e r a t ' s c o r r e l a t i o n gave a-very good estimate of the t o t a l observed settlement at one year a f t e r the end of c o n s t r u c t i o n . The d i s t r i b u t i o n of settlement with depth shows that the g r e a t e s t amount of settlement o c c u r r e d i n the f i b r o u s peat and a l e s s e r p o r t i o n i n the o r g a n i c c l a y s , as would be expected. Although an accurate p r o f i l e of water content versus depth i s r e q u i r e d , i t i s not c o n s i d e r e d to be a major drawback. Water content d e t e r m i n a t i o n s a l r e a d y c o n s t i t u t e a major part of the t r a d i t i o n a l i n v e s t i g a t i o n of o r g a n i c s o i l s . The accuracy of the settlement p r e d i c t i o n i s s u r p r i s i n g when i t i s c o n s i d e r e d that the CPT c o r r e l a t i o n was developed f o r peats i n France and was based upon mechanical cone data. O v e r a l l , the d r a i n e d c o n s t r a i n e d modulus c a l c u l a t e d by t h i s method appears to be of the c o r r e c t order of magnitude and g i v e s a reasonable d i s t r i b u t i o n of settlement with depth. • The same c o n c l u s i o n s given f o r the CPT concerning S a n g l e r a t ' s c o r r e l a t i o n a l s o apply to the screw p l a t e u l t i m a t e l o a d t e s t s . The u l t i m a t e l o a d t e s t s over estimated the t o t a l observed settlement at one year a f t e r the end of c o n s t r u c t i o n by 0.55 metres. In terms of the accuracy commonly found i n settlement p r e d i c t i o n s f o r o r g a n i c s o i l s , the p r e d i c t i o n i s q u i t e a reasonable estimate. The d i s t r i b u t i o n of settlement with depth i s s i m i l a r to t h a t found f o r the CPT study and i s considered, to be r e a l i s t i c . Compared to the CPT the u l t i m a t e l o a d screw p l a t e t e s t i s a slower and more complex t e s t and r e s u l t s i n a d i s c o n t i n u o u s p r o f i l e . The UBC screw p l a t e 175 system a l s o r e q u i r e s an e s t i m a t i o n of rod f r i c t i o n . • The d i l a t o m e t e r t e s t gave a poor estimate of settlements; under e s t i m a t i n g the observed primary settlement by a f a c t o r of 10. The d i l a t o m e t e r was not developed f o r use i n peat and s e v e r a l e r r o r s r e s u l t e d from the a p p l i c a t i o n . S e r i o u s e r r o r s were found i n the c a l c u l a t i o n of Kd which i n v o l v e s estimates of s o i l u n i t weight and the ambient pore p r e s s u r e . The c o r r e c t i o n of Kd f o r u n i t weight would have l e d to an even sm a l l e r estimated s e t t l e m e n t . O v e r a l l , the d i l a t o m e t e r t e s t does not give a good estimate of the d r a i n e d c o n s t r a i n e d modulus f o r use i n h i g h l y organic s o i l s . • Due to an i n a c c u r a t e determination of t<j0, the values of d r a i n e d c o n s t r a i n e d modulus determined from the screw p l a t e incremental l o a d i n g t e s t s are erroneous, see s e c t i o n 6.1.3.3. Th e r e f o r e , no settlement p r e d i c t i o n i s given f o r t h i s s e r i e s of t e s t s . An extended d u r a t i o n t e s t showed that the time r e q u i r e d to reach t q o may be on the order of 24 hours per l o a d increment. T e s t s of such l e n g t h were c o n s i d e r e d to be i m p r a c t i c a l with the UBC screw p l a t e system. O v e r a l l , the t e s t method proposed by Janbu and Senneset (1973) was time consuming both i n the f i e l d work and data r e d u c t i o n a n a l y s i s . The present l e v e l of understanding of the screw p l a t e incremental l o a d t e s t , which has developed from experience on m i n e r a l s o i l s , does not appear to be d i r e c t l y a p p l i c a b l e to h i g h l y organic s o i l s . • As can be seen i n Table 7.1 both of the l o c a l experience methods give a good estimate of the c o n s o l i d a t i o n settlement. 176 The p r e d i c t i o n made from Scotton's (1981) graph (Figure 6.5) g i v e s the c l o s e s t e s t i m a t e . However, t h i s estimate represents an upper bound v a l u e . C o n s i d e r a b l e s c a t t e r i s present i n the p l o t t e d data which reduces the confidence t h a t can be p l a c e d in a p r e d i c t i o n from t h i s graph. A drawback with Cook's (1956) c o r r e l a t i o n i s that i t only a p p l i e s to peats. Where the peat i s u n d e r l a i n by organic c l a y s a program of oedometer t e s t s are r e q u i r e d to complete the p r e d i c t i o n . O v e r a l l , e m p i r i c a l methods based on l o c a l experience can produce good r e s u l t s f o r many organic d e p o s i t s w i t h i n the region of c o r r e l a t i o n . However, even on a l o c a l b a s i s , the s c a t t e r i n v o l v e d i s o f t e n very l a r g e so that the l i k e l i h o o d of e r r o r with t h i s method i s high. 7.3 EVALUATION OF WICK DRAINS 1. The s u r f a c e settlement f i e l d records (see F i g u r e s 2.6 and 2.7) show t h a t the a d d i t i o n of wick d r a i n s allowed about 60% more settlement to occur by the 400th day a f t e r the s t a r t of c o n s t r u c t i o n . A l s o , the c o n s o l i d a t i o n of the s o i l and the a s s o c i a t e d i n c r e a s e i n shear s t r e n g t h took p l a c e at a g r e a t l y a c c e l e r a t e d r a t e and to a g r e a t e r depth with wick d r a i n s . In the case of the t e s t f i l l c o n s o l i d a t i o n o c c u r r e d over the e n t i r e 16m depth s e r v i c e d by the wick d r a i n s . T h i s i s compared to the area without wick d r a i n s where the 177 c o n s o l i d a t i o n was predominantly i n the upper 6m of the s o f t d e p o s i t s . 2. Due to the improved s o i l drainage with wick d r a i n s , the excess pore pre s s u r e s generated d u r i n g c o n s t r u c t i o n and the time r e q u i r e d f o r t h e i r d i s s i p a t i o n were g r e a t l y reduced. These q u a l i t i e s allow embankments to be c o n s t r u c t e d at f a s t e r r a t e s and with decreased r i s k of s u b s o i l f a i l u r e . 3. Whether or not wick d r a i n s w i l l have the important long term b e n e f i t of reducing the r a t e and magnitude of the secondary compression cannot be determined at t h i s time. A p e r i o d of s e v e r a l years i s r e q u i r e d before the r a t e and magnitude of secondary compression i s a c c u r a t e l y known. 4. Two deep settlement p l a t e s were i n s t a l l e d below the organic s o i l s at an e l e v a t i o n of about -17 metres. The f i e l d records (see F i g u r e s 2.6 and 2.7) show that i n . one year the deep settlement that occurred i n the wick d r a i n area i s more than double that of the area without wick d r a i n s . In g e n e r a l , the wick d r a i n s were i n s t a l l e d i n t o the sand l a y e r at -15m e l e v a t i o n . One e x p l a n a t i o n f o r the l a r g e r deep settlement i s that the wick d r a i n s sometimes pe n e t r a t e d through the sand i n t o the s i l t l a y e r at -17m e l e v a t i o n and expedited the c o n s o l i d a t i o n o c c u r r i n g t h e r e . Another e x p l a n a t i o n i s that the i n c r e a s e d deep settlement might have been caused by a d i f f e r e n t s t r e s s d i s t r i b u t i o n due to the r a p i d c o n s o l i d a t i o n 1 78 in the wick area. 5. The f i n d i n g s of t h i s study i n d i c a t e that wick d r a i n s are very b e n e f i c i a l when used i n organic d e p o s i t s that have a t h i c k l a y e r of s o f t s o i l s u n d e r l y i n g the peat mat. In cases where the peat mat i s not u n d e r l a i n by s o f t s o i l s the b e n e f i t r e a l i z e d by using wick d r a i n s may l i k e l y be s m a l l . The study a l s o supports e a r l i e r f i n d i n g s (MacFarlane, 1969) that the use of wick d r a i n s under minor l o a d i n g c o n d i t i o n s i s not very benef i c i a l . 7.4 RECOMMENDATIONS FOR FURTHER RESEARCH 1. The cone p e n e t r a t i o n t e s t s documented i n t h i s study were performed with a cone bearing l o a d c e l l of a high c a p a c i t y (5 tons) f o r the s o f t s o i l s at the t e s t f i l l s i t e . For f u t u r e t e s t i n g of these very s o f t organic s o i l s a lower c a p a c i t y cone, such as a one ton cone c a l i b r a t e d f o r the s t r e s s range of i n t e r e s t , i s recommended. 2. Anomolous pore pressure responses such as a r i s e i n the pore p r e s s u r e a f t e r p e n e t r a t i o n was stopped and a reduced dynamic pore pressure response when p e n e t r a t i o n was resumed were o f t e n observed f o r the piezometer cone p e n e t r a t i o n t e s t s , see s e c t i o n 3.2.4. Research i n t o the nature of these anomolies may have important i m p l i c a t i o n s f o r both piezometer i n s t a l l a t i o n s and piezometer cone t e s t i n g i n organic s o i l s . 179 3. . Disturbances to the s u b s o i l s t r e n g t h a p p a r e n t l y had a s i g n i f i c a n t e f f e c t on the measured CPT f r i c t i o n s t r e s s f o l l o w i n g a s u b s o i l f a i l u r e but had l i t t l e or no e f f e c t on the measured cone b e a r i n g . Because the cone b e a r i n g measurement i s s e n s i t i v e to changes in the v e r t i c a l e f f e c t i v e s t r e s s and the f r i c t i o n s leeve measurement i s s e n s i t i v e to changes in the h o r i z o n t a l e f f e c t i v e s t r e s s , the i n t e r r e l a t i o n s h i p between v e r t i c a l and h o r i z o n t a l e f f e c t i v e s t r e s s e s i n peat under v a r i e d l o a d i n g c o n d i t i o n s c o u l d be s t u d i e d with the CPT. 4. The cone p e n e t r a t i o n t e s t has demonstrated c o n s i d e r a b l e f a c i l i t y i n the monitoring of the t e s t embankment. S i m i l a r programs using i n - s i t u t e s t i n g methods to monitor embankments on e i t h e r organic or i n o r g a n i c s o i l are encouraged. In the case of embankments c o n s t r u c t e d over i n o r g a n i c s o i l s where c o m p l e x i t i e s such as l a r g e secondary compression and methane gas are not g e n e r a l l y present, the i n - s i t u t e s t s are expected to be more u s e f u l f o r e v a l u a t i n g the e n g i n e e r i n g behaviour of the s u b s o i l . 5. The d i l a t o m e t e r can be improved as a t e s t by the a d d i t i o n of a pore pressure measurement c a p a b i l i t y . A r e s e a r c h d i l a t o m e t e r has r e c e n t l y been completed at the U n i v e r s i t y of B r i t i s h Columbia which measures pore pressures i n the center of the f l e x i b l e membrane. T h i s r e s e a r c h i s expected to provide a great d e a l of i n f o r m a t i o n about the pore pr e s s u r e response of the s o i l d u r i n g the d i l a t o m e t e r t e s t . 180 BIBLIOGRAPHY Adams, J . I . , The e n g i n e e r i n g behaviour of Canadian muskeg. Proceedings of the S i x t h I n t e r n a t i o n a l Conference on S o i l Mechanics and Foundation E n g i n e e r i n g , V o l . 1 , U n i v e r s i t y of Toronto Press, Montreal, Canada, 1965, pp.3-7. Adams, J . I . , Laboratory compression t e s t s on peat. Proceedings of the Seventh Muskeg Research Conference, T e c h n i c a l Memorandum No.71, N a t i o n a l Research C o u n c i l of Canada, U n i v e r s i t y of Toronto Press, Montreal, Canada, 1961, pp.36-54. B a l d i , G., B e l l o t t i , R., Ghionna, V., Jamiolkowski, M. and P a s q u a l i n i , E., Design parameters f o r sands from CPT. Proceedings of the Second European Symposium on P e n e t r a t i o n T e s t i n g , ESOPT I I , Amsterdam, 1982, A.A. Balkema. B a l i g h , M.M., V i v a t r a t , V. and Ladd, C.C., Cone p e n e t r a t i o n i n s o i l p r o f i l i n g . American S o c i e t y of C i v i l E n gineers, J o u r n a l of the G e o t e c h n i c a l E n g i n e e r i n g D i v i s i o n , Vol.106, GT4, A p r i l 1980, p.447. B e r z i n s , W.E. and Campanella, R.G., Development of the screw p l a t e t e s t f o r i n - s i t u d e t e r m i n a t i o n of s o i l parameters. Department of C i v i l E n g i n e e r i n g , S o i l Mechanics S e r i e s No.48, U n i v e r s i t y of B r i t i s h Columbia, May 1981. Bjerrum, L., Embankments on s o f t grounds. American S o c i e t y of C i v i l E ngineers, Proceedings of the S p e c i a l t y Conference on Performance of E a r t h and Earth-Supported S t r u c t u r e s , Vol.2, L a f a y e t t e , 1972, pp.1-54. Blunden, R.H., Urban geology of Richmond, B r i t i s h Columbia. Adventures i n E a r t h S c i e n c e s , No.15, Department of G e o l o g i c a l S c i e n c e s , U n i v e r s i t y of B r i t i s h Columbia, Vancouver, B r i t i s h Columbia, 1975. Brawner, CO., The p r i n c i p l e of p r e c o n s o l i d a t i o n i n highway c o n s t r u c t i o n over muskeg. Roads and E n g i n e e r i n g C o n s t r u c t i o n , September 1959. C a d l i n g , L. and Odenstad, S., The vane borer. Proceedings, Swedish G e o t e c h n i c a l I n s t i t u t e , No.2, Stockholm, 1950. Campanella, R.G., G i l l e s p i e , D. and Robertson, P.K., Pore p r e s s u r e s d u r i n g cone p e n e t r a t i o n t e s t i n g . Proceedings of the Second European Symposium on P e n e t r a t i o n T e s t i n g , ESOPT I I , Amsterdam, 1982, pp.507-181 512, A.A. Balkema. 11. Campanella, R.G. and Robertson, P.K., A p p l i e d cone r e s e a r c h . Symposium on Cone P e n e t r a t i o n T e s t i n g and Experience, G e o t e c h n i c a l E n g i n e e r i n g D i v i s i o n , ASCE, October 1981, pp.343-362. 12. Campanella, R.G., Robertson, P.K. and G i l l e s p i e , D., Cone p e n e t r a t i o n t e s t i n g i n d e l t a i c s o i l s , Canadian G e o t e c h n i c a l J o u r n a l , Vol.20, February 1983. 13. Campanella, R.G. and Robertson, P.K., State of the a r t i n i n - s i t u t e s t i n g of s o i l s : developments s i n c e 1978. E n g i n e e r i n g Foundation Conference on Updating Subsurface Sampling of S o i l s and Rocks and t h e i r I n - s i t u T e s t i n g , Santa Barbara, C a l i f o r n i a , January 1982. 14. Campanella, R.G., Robertson, P.K. and G i l l e s p i e , D.G., I n - s i t u t e s t i n g i n s a t u r a t e d s i l t , ( d r a i n e d or undrained?). Proceedings, 34th. Canadian G e o t e c h n i c a l Conference, F r e d e r i c t o n , Canada, 1981. 15. Cryer, C.W., A comparison of the t h r e e - d i m e n s i o n a l c o n s o l i d a t i o n t h e o r i e s of B i o t and T e r z a g h i . Q u a r t e r l y J o u r n a l of Mechanics and A p p l i e d Mathematics, Vol.16, Pt.4, 1963, pp.401-412. 16. de R u i t e r , J . , The s t a t i c cone p e n e t r a t i o n t e s t s t a t e -o f - t h e - a r t r e p o r t . Proceedings of the Second European Symposium on P e n e t r a t i o n T e s t i n g , ESOPT I I , Amsterdam, 1982, A.A. Balkema. 17. Douglas, B.J., and Olsen, R.S., S o i l c l a s s i f i c a t i o n u s i n g e l e c t r i c cone penetrometer. Symposium on Cone P e n e t r a t i o n T e s t i n g and Experience, G e o t e c h n i c a l E n g i n e e r i n g D i v i s i o n , ASCE, October 1981, S t . L o u i s . 18. F r e d l u n d , D.G., D e n s i t y and c o m p r e s s i b i l i t y c h a r a c t e r i s t i c s of a i r - w a t e r mixtures. Canadian G e o t e c h n i c a l J o u r n a l , Vol.13, 1976, p.386. 19. G i l l e s p i e , D.G. and Campanella, R.G., C o n s o l i d a t i o n c h a r a c t e r i s t i c s from pore pressure d i s s i p a t i o n a f t e r piezometer cone p e n e t r a t i o n . S o i l Mechanics S e r i e s No.47, Department of C i v i l E n g i n e e r i n g , U n i v e r s i t y of B r i t i s h Columbia, 1981. 20. G i l l e s p i e , D.G., The piezometer cone p e n e t r a t i o n t e s t . M.A.Sc. T h e s i s , Department- of C i v i l E n g i n e e r i n g , U n i v e r s i t y of B r i t i s h Columbia, December 1981. 21. Hansbo, S., C o n s o l i d a t i o n of c l a y with s p e c i a l r e f e r e n c e to the use of g e o d r a i n s . F i r s t B a l t i c Conference on S o i l Mechanics and Foundation E n g i n e e r i n g , Gdansk, 1975. 182 22. Helenelund, K.V., Compression t e n s i o n and beam t e s t s on f i b r o u s peat. Canada N a t i o n a l Research C o u n c i l , 3rd. I n t e r n a t i o n a l Peat Congress, 1968. 23. H o l l i n g s h e a d , G.W. and Raymond, G.P., P r e d i c t i o n of undrained movements caused by embankments on muskeg. Canadian G e o t e c h n i c a l J o u r n a l , Vol.18, No.1, 1971, pp.23-35. 24. Hoos, L.M. and Pachman, G.A., The F r a s e r River e s t u a r y : s t a t u s of environmental knowledge to 1974. Report of the Estuary Working Group, Department of the Environment, Regional Board P a c i f i c Region, 1974, p.518. 25. Janbu, N. and Senneset, K., F i e l d compressometer -p r i n c i p l e s and a p p l i c a t i o n s . 7th I n t e r n a t i o n a l Conference of S o i l Mechanics and Foundation E n g i n e e r i n g , 1973, pp.191-198. 26. Ladd, C.C., Foot, R., I s h i h a r a K., S c h l o s s e r , F. and Poulos, H.G., S t r e s s - d e f o r m a t i o n and s t r e n g t h c h a r a c t e r i s t i c s . Proceedings, Ninth I n t e r n a t i o n a l Conference on S o i l Mechanics and Foundation E n g i n e e r i n g , Tokyo, Japan, 1977, Vol.11, pp.421-494. 27. Lambe, T.W. and Whitman, R.V., S o i l mechanics. John Wiley, New York, 1969, 553 pp. 28. Law, K.T., T r i a x i a l - v a n e t e s t s on a s o f t marine c l a y . Canadian G e o t e c h n i c a l J o u r n a l , Vol.16, No.1, February 1979, pp.11-18. 29. Lea, N.D. and Brawner, CO., Highway design and c o n s t r u c t i o n over peat d e p o s i t s i n lower B r i t i s h Columbia. Highway Research Record, No.7, 1963, pp.1-32. 30. Lunne, T. and Kleven, A., Role of CPT i n North Sea foundation e n g i n e e r i n g . Symposium on Cone P e n e t r a t i o n T e s t i n g and Experience, G e o t e c h n i c a l E n g i n e e r i n g D i v i s i o n , ASCE, October 1981. 31. Lunne, T., E i d e , 0. and de R u i t e r , J . , C o r r e l a t i o n s between cone r e s i s t a n c e and vane shear s t r e n g t h i n some Skandinavian s o f t to medium s t i f f c l a y s . Canadian G e o t e c h n i c a l J o u r n a l , 13(4), November 1976, pp.430-441. 32. MacFarlane, I . C , ed., Muskeg e n g i n e e r i n g handbook. N a t i o n a l Research C o u n c i l of Canada, U n i v e r s i t y of Toronto Press, Toronto, Canada, 1969, pp.78-176. 33. M a r c h e t t i , S., I n - s i t u t e s t s by f l a t d i l a t o m e t e r . J o u r n a l G e o t e c h n i c a l E n g i n e e r i n g D i v i s i o n , ASCE, Vol.106, GT3, 1980, pp.299-321. 183 34. M a r c h e t t i , S., A new i n - s i t u t e s t f o r the measurement of h o r i z o n t a l s o i l d e f o r m a b i l i t y . Proceedings of the ASCE S p e c i a l t y Conference on I n - S i t u Measurement of S o i l P r o p e r t i e s , R a l e i g h , Vol.2, 1975, pp.255-259. 35. M a r c h e t t i , S. and Crapps, D.K., P r o v i s o r y d r a f t - f l a t d i l a t o m e t e r manual. Unpublished, May 11, 1981. 36. McGown, A. and Hughes, F.H., P r a c t i c a l a spects of the design and i n s t a l l a t i o n of deep v e r t i c a l d r a i n s . Geotechnique, Vol.31, No.1, March, 1981. 37. M i t c h e l l , J.K. and Gardner, W.S., I n - s i t u measurement of volume change c h a r a c t e r i s t i c s . S t a t e - o f - t h e - A r t Report, Proceedings of the Conference on I n - S i t u Measurement of S o i l P r o p e r t i e s , R a l e i g h , Vol.2, 1975. 38. M i t c h e l l , J.K., Guzikowski, F. and V i l l e t , W.C.B., The measurement of s o i l p r o p e r t i e s i n - s i t u . Report prepared fo r U.S. Department of Energy Contract W-7405-ENG-48, Lawrence Berkeley Laboratory, U n i v e r s i t y of C a l i f o r n i a , B e r k e l e y , C a l i f . , March 1978. 39. Moran, P r o c t o r , Mueser and Rutledge, Study of deep s o i l s t a b i l i z a t i o n by v e r t i c a l sand d r a i n s . Report to the U.S. Navy Bureau of Yards and Docks, Washington D.C., 1958, pp.156-177. 40. Northwood, R.P. and Sangrey, D.A., The vane t e s t i n o r g a n i c s o i l s . Canadian G e o t e c h n i c a l J o u r n a l , Vol.8, 1971 . 41. Raymond, G.P., C o n s t r u c t i o n method and s t a b i l i t y of embankments on muskeg. Canadian G e o t e c h n i c a l J o u r n a l , 4(1), 1969, pp.81-96. 42. Robertson, P.K., I n - s i t u t e s t i n g of s o i l with emphasis on- i t s a p p l i c a t i o n to l i q u e f a c t i o n assessment. Ph.D. T h e s i s , Department of C i v i l E n g i n e e r i n g , U n i v e r s i t y of B r i t i s h Columbia, December 1982, pp.394. 43. Robertson, P.K. and Campanella, R.G., Recent developments i n i n t e r p r e t a t i o n of cone p e n e t r a t i o n t e s t s , U n i v e r s i t y of B r i t i s h Columbia, C i v i l E n g i n e e r i n g Department S o i l Mechanics S e r i e s No.60, 1982. 44. Samson, L. and L a R o c h e l l e , P., Design and performance of an expressway c o n s t r u c t e d over peat by p r e l o a d i n g . Canadian G e o t e c h n i c a l J o u r n a l , Vol.9, No.4, November 1972, pp.447-466. 45. S a n g l e r a t , G., The penetrometer and s o i l e x p l o r a t i o n . Developments in G e o t e c h n i c a l E n g i n e e r i n g , V o l . 1 , 184 E l s e v i e r , Amsterdam, 1972. 46. Schmertmann, J.H., G u i d e l i n e s f o r cone p e n e t r a t i o n t e s t , performance and des i g n . F e d e r a l Highway A d m i n i s t r a t i o n , Report FHWA-TS-78-209, Washington, 1978. 47. Torstensson, B.A., The pore pressure probe. Nordiske Geotekniske Mote, Oslo, Paper No.34, 1977, pp.15. 48. Tumay, M.T., Boggess, R.L. and Acar, Y., Subsurface i n v e s t i g a t i o n s with piezo-cone penetrometer. ASCE, S t . Lo u i s Convention, Session 35, Cone P e n e t r a t i o n T e s t i n g and Experience, pp.325-342. 49. Weber, W.G., Performance of embankments c o n s t r u c t e d over peat. J o u r n a l of the S o i l Mechanics and Foundations D i v i s i o n , Proceedings of the ASCE, Vol.95, No.SMI, January 1969, pp.53-76. 185 APPENDIX A - COMPLETE CPT LOGS - B.C. HIGHWAYS TEST FILL SITE 9 8 I P O R E P R E S S U R E F R I C T I O N R E S I S T A N C E B E A R I N G R E S I S T A N C E F R I C T I O N R A T I O D I F F E R E N T I A L P . . FC-Q1 OFFSET 8.HCK- ' ' F ig .A4 B . C . H I G H W A T 3 T E S T F I L L - N O V E M B E R 21. 1 9 8 1 S C P 2 0 1 M 5 C f l D J f i C E N T TO T E S T F I L L ) PORE P R E S S U R E F R I C T I O N R E S J S T R N C E . B E R R J N G R E S I S T A N C E F R i C T I ON R R T I 0 .0 J F F E R E N T ] R L . P 0 IBflR) FC (BRRT OT (BPR) R F - F C / Q T m - P.PTJO uU/QT rr.-in J f r s u lo.ocn Fig.AB e . r . . H J G H W A T S T C J I M I L - M A R C H 2 S . ' I 9 B Z I N J I I f i l C O N D I T I O N S 56T P QBE P R E S S U R E F R I C T I O N R E S I S T A N C E B E A R I N G R E S I S T A N C E F B I C T J O N HAT 10 D I F F E R E N T I A L P . P . S O I L U (BAR) F C (BAR) OT (BAR) R F = F C / O T I*) R A T I O A U / Q T P R O F I L E 0 5 . 0 0 D . 5 D 2 D . 0 D 1 0 . D D . 8 0 Fig.A15 B . C . HIC-nWflT3 TEST F I L L - OCTOBER 1 3 . 1 f l S 2 S C P 2 0 D + f l H CAREA H / 0 WICK DRAIN J-. EL C¥ . F I L L i- 5 . 1 M •. T 0 T A L F I L L ^ 7 . OMl 201 APPENDIX B - COMPLETE DMT LOGS - B.C. HIGHWAYS TEST FILL SITE 2 0 2 Z 7 J ? X \ INSITU TESTING. Location: WICK DRAIN AREA INTERMEDIATE GEOTECHNICRL PARAMETERS Test No. DH-1 Test Date; Feb.16,1982 u> Z3 —H •8 D rz ^  t "3 u 0_ *-> JZ eu E O «-> ro X — I u ro-g 4-1 C M a N tn r c a c_ rr. ^  CO tn •J t_ CO ™ CD aj > CD a co' 0 ' 9 I (0) mdaa o'oi o'zi o>t o*9i o e i J — i — i — i — i — i i i i i J — i — i — i i i i i i i i i " i — i — i — i — i — i — i — i — i — i — r 0'9 O'B O'OI O'ZI 0>I 0*91 (B) Lp.d3Q i — r 0'8l T3&. LLJ J* CO b o m •l-t 2 0 3 UJ3.C. INSITU TESTING. Location: WICK DRAIN AREA INTERPRETED GEOTECHNICAL PARAMETERS, Test No. DH-1 Test Date? Feb.16,1982 c Y, pi ra in_J I s in QJ ^ CD T3 in 3 3 T3 O _ to Ik CD tn C o CD X u c 2 A I I 1 ~™ ro (0| mdaa O'OT O'ZI j i i L i 1 — i — r O'Ol O'ZI 0>I {•] mfca c_ CO •—I C CD fc, CO o u O > 3-i I CM n cn •rH fa 204 UJ9.C. INSITU TESTING. Location: INITIAL CONDITIONS SITE INTERMEDIATE GEOTECHNICAL PARAMETERS Test No. OH-3 Teat Dote} Opr. 5,1982 IA •8 a XZ ^ t_ " Oj u_ E XZ oj E O re re ^  C M Q N in n c a (_ co u w OJ CO 3 E L. OJ > If) (•J mdaa O'S 08 J 1 L T r —T-0> I 1 1 -0*9 0*8 "I r -O'OI 1 r -O'Zl i — r 0>I UJ V PI b r CO m fc, 205 UM.C. INSITU TESTING. Location: INITIAL CONDITIONS SITE INTERPRETED GEOTECHNICRL PARAMETERS. Test No, DH-3 Test Date; Opr. 5,1982 *H ™ « cr 2 o 10 8*-n X •a c ZD U) —« •s O CO a. OJ , £Z i -re L. *-• OJ g 18 x re O'Z 0 > 0*8 0*8 O'OI O'ZT D P ! — I I I I I I I I I I ' ' • J I I L J L J I • I J I I L T — i — i — r J L «_ n CD h 1 10 8 o T — i — i — i — i — i — i — i — i i i r 0 * 2 0 > 0 * 9 0 ' B 0*01 0 21 0 > 1 (•I i n . d a a 3 00 t S B t—1 a_ <q i g m • iH 206 UJ3.C. INSITU TESTING. Location: AREA W/0 UICK DRAINS INTERflEDIflTE GEOTECHNICAL PARAMETERS Test No. DH-4 Test Date} June15,1982 3 •g , CD cu w E O ro x ro -° c M o isi cn TJ 0 o I— x CD in OJ CO f j CD OJ > O 0_ (•) m«*a J I I L 1 1 1 1 1 1 1 1 1 1 1 1 1 t i l l 1 1 1 1 1 1 1 1 1 i 1 1 r O'ZT O'W pi) mdaa B T LUX-CO T3^ o & in m Cn -rH fa 2 0 7 U£.C. INSITU TESTING. Location: AREA W/0 WICK DRAINS INTERPRETED GEOTECHNICRL PARAMETERS. Test No. DH-4 Test Date; June15,1982 3-c • H £ T 3 C Q —i us OJ ^ JC to u T3 C U) 3 a to OJ ro a o ro x - H OJ OJ e re in. CM 0'8 O'OI O'ZI O'M 0'9I 0 -8I O'OZ _ l I I I I I I I I I I I I— J I I L l l I I I I LL 1 1 1 1 1 T O'ZI O'W 0'9l (•] mdaa c_ CO to h 2 0 8 U&.C. IN SITU TESTING. Location: UICK DRAIN AREA INTERMEDIATE GEOTECHNICAL PARAMETERS Test No. DH-5 Test Date; June17,1982 to 3 -3 Q TZ oj Q_ OJ E O W re 13 T re "2 C M o ISI tn t B O 1_ x *-• CO u U) OJ t_ to ™ '53 " Q-L. OJ > ex o CL (•) m^ a 0*6 O'l l 0"ei 0"SI O'Ll 0'6T 0' 12 J I I I I I I I I I I ) . ,1 i 1 — r — r O'El Q*Sl 2 0 9 UMJC. INSITU TESTING. Location: UICK DRRIN RREfl INTERPRETED GEOTECHNICRL PflRRflETERS, Test No. DH-5 Test Date: June 17.1982 c 5 cu c o u CD Q_ c ZZt U) Z3 •8 o I I —« — ro t _ *-> cn cz o ro x • H OJ t _ -a OJ c (•] M**>a 0 ' 6 0"I1 0 ' £ 1 0"SI O ' L l 0 '6 I 0"IZ ' ' I I I I I I I I 1 1 L_ o-=r I T — i — i — i — i — i 1 — i — r 0 ' 6 O ' t l O ' E l 1 J I I l I I I I I I I I 1 L CD h i — i — r l l l l I I I I I I _ l 1 L 1 1 1 1 1 1 1 _. : o 1 1 1 zE t-\ i i i i i i i J : - M l A - m tA A / - >-CE " _J O 1 r r i i i i i i * 1 > CO M 8 o > 91 O'Ll 0 '6 I Q'\Z (Hi mdaa 3-s i -DO <o T & CO m cn 210 APPENDIX C - SCREW PLATE INCREMENTAL LOADING TEST DATA F i g . C1 Screw P l a t e Test - Incremental Loading Test B.C. Highways Test F i l l , June 8-9, 1982. V t (min.y o \ 2 *, 4-Vfc (min.) F i g . C2 Screw P l a t e Test - Incremental Loading Test B.C. Highways Test F i l l , June 8-9, 1982. -V t (min V F i g . C3 Screw P l a t e Test - Incremental Loading Test B.C. Highways Test F i l l , June 8-9, 1982. -yjt (mm? F i g . C4 Screw P l a t e Test - Incremental Loading Test B.C. Highways Test F i l l , June 8-9, 1982. 215 APPENDIX D - SCREW PLATE ULTIMATE LOAD TEST DATA 216 ELEV. -0.2M-O 23 5.0 7.5 \0.O PLATE M£V£MHNT (cv.) F i g . D1 Screw P l a t e Test - U l t i m a t e Load Test B.C. Highways Test F i l l , June 10, 1982. 217 F i g . D2 Screw P l a t e Test - U l t i m a t e Load Test B.C. Highways Test F i l l , June 10, 1982. 218 •boo 1<?0 A O 2b 7.5 \0.0 PLATE- MOVt-Mtm (CM) F i g . D3 Screw P l a t e Test - U l t i m a t e Load Test B.C. Highways Test F i l l , June 10, 1982. 219 F i g . D4 Screw P l a t e Test - U l t i m a t e Load Test B.C. Highways Test F i l l , June 10, 1982. 220 O 2 5> SO 75. \0.0 12.5 PLATE. k/|c7VEM£.NT CCM.) F i g . D5 Screw P l a t e Test - U l t i m a t e Load Test B.C. Highways Test F i l l , June 10, 1982. 221 •boo 750 \ O -i 1 1 1 1 ' 1 r O 2.£ 5.<? 7.5- IO.O I2S PLATE Mc9VE.ME.KIT (CM.) F i g . D6 Screw P l a t e Test - Ult i m a t e Load Test B.C. Highways Test F i l l , June 10, 1982. 222 WO F i g . D7 Screw P l a t e Test - U l t i m a t e Load Test B.C. Highways Test F i l l , June 10, 1982. 223 F i g . D8 Screw P l a t e Test - Ul t i m a t e Load Test B.C. Highways Test F i l l , June 10, 1982. 224 O 2 .£ 5.0 7 , 5 lO.O 12. S PLATE MCVtlvl&NT ( C M . ^ F i g . D9 Screw P l a t e Test - U l t i m a t e Load Test B.C. Highways Test F i l l , June 10, 1982. 225 COO F i g . D10 Screw P l a t e Test - U l t i m a t e Load Test B.C. Highways Test F i l l , June 10, 1982. 226 bOO 300 A O A 1 1 1 1 1 1 1 1 1 • 1 O Z5 5.0 7.5 \O.Q \2.5> PLATE. M<?V£MESJT (CM.) F i g . D11 Screw P l a t e Test - U l t i m a t e Load Test B.C. Highways Test F i l l , June 10, 1982. 2 2 7 F i g . D12 Screw P l a t e Test - Ul t i m a t e Load Test B.C. Highways Test F i l l , June 10, 1982. 228 GOO bOO A EL&Y. -/I.&M. 2.5 7.5 lO.O l?.5> PLATE Mc9V£MENT ( C M . ) F i g . D13 Screw P l a t e Test - Ult i m a t e Load Test B.C. Highways Test F i l l , June 10, 1982. 2 2 9 F i g . D14 Screw P l a t e Test - U l t i m a t e Load Test B.C. Highways Test F i l l , June 10, 1982. 

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