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The analysis and interpretation of the cone pressuremeter in cohesive soils 1989

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THE ANALYSIS AND INTERPRETATION OF THE CONE PRESSTJREMETER IN COHESIVE SOILS by IAN HERS B.A.Sc, The U n i v e r s i t y of B r i t i s h Columbia, 1986 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE in THE FACULTY OF GRADUATE STUDIES Department of C i v i l Engineering We accept t h i s t hesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA ^September, 1989 © I A N HERS, 1989 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of The University of British Columbia Vancouver, Canada Date DE-6 (2/88) ABSTRACT The cone pressuremeter i s a promising new i n s i t u t e s t i n g device which combines the we l l known c a p a b i l i t i e s of a piezocone with a f u l l displacement pressuremeter (FDPM). The focus of t h i s thesis i s to present r e s u l t s from FDPM tes t s performed as part of a cone pressuremeter sounding at three cohesive s o i l s i t e s i n the Vancouver area. The i n s e r t i o n of a cone pressuremeter r e s u l t s i n a s u b s t a n t i a l amount of disturbance and the generation of excess pore pressures. As a r e s u l t of the changing stress conditions, the length of the r e l a x a t i o n time or time delay between i n s e r t i o n and t e s t i n g has a s i g n i f i c a n t e f f e c t on the l i f t - o f f pressure and shape of the FDPM curve. Results in d i c a t e that increased r e l a x a t i o n periods lead to lower l i f t - o f f pressures. The s t r a i n rate used during a t e s t i s also s i g n i f i c a n t with lower rates r e s u l t i n g i n higher l i m i t pressures and undrained shear strengths. Comparisons were made between the FDPM, s e l f - b o r i n g pressuremeter (SBPM) and dilatometer l i f t - o f f and expansion pressures. FDPM t e s t r e s u l t s are also influenced by the design and performance of the pressuremeter. Important equipment r e l a t e d considerations discussed are compliance,strain arm design and pressuremeter L/D r a t i o . The r e s u l t s of FDPM tests were used to estimate the undrained shear strength, shear modulus, stress h i s t o r y and i n s i t u h o r i z o n t a l stress of cohesive s o i l s and when possible compared to SBPM, f i e l d vane and dilatometer r e s u l t s . The use of c a v i t y expansion theory f o r the analysis of the FDPM te s t i s made d i f f i c u l t by the unknown str e s s conditions created by i i i disturbance. Nevertheless, reasonable estimates of the undrained shear strength were made using c a v i t y expansion methods with the FDPM undrained shear strength generally greater than the f i e l d vane and s i m i l a r to those obtained from the SBPM t e s t . Cavity c o n t r a c t i o n theory was also used to estimate the undrained shear strength with the r e s u l t s generally being le s s than the f i e l d vane undrained shear strength. Good comparisons were obtained between the FDPM and SBPM unload- reload shear moduli. Both the unload-reload shear moduli and the r i g i d i t y index were shown to attenuate with increasing shear s t r a i n . Two new methods using the r i g i d i t y index and normalized pressuremeter l i m i t pressure were proposed to estimate s t r e s s h i s t o r y . Both techniques appear to be promising. Attempts to use the FDPM to estimate the i n s i t u h o r i z o n t a l stress were unsuccessful when compared to the r e s u l t s of other a v a i l a b l e t e s t s . i v TABLE OF CONTENTS Page ABSTRACT i i LIST OF TABLES v i LIST OF FIGURES v i i ACKNOWLEDGEMENTS x i 1.0 INTRODUCTION 1 2.0 EQUIPMENT AND TEST PROCEDURES 5 2.1 The UBC Seismic Cone Pressuremeter (SCP) 5 2.1.1 Des c r i p t i o n of the UBC SCP 5 2.1.2 The UBC SCP Data A c q u i s i t i o n System 11 2.1.3 Test Procedures f o r the UBC SCP 14 2.1.4 UBC SCP Compliance 18 2.2 The Fugro Cone Pressuremeter 21 2.3 The Hughes Self-Boring Pressuremeter (SBPM) 26 3.0 TEST SITES AND FIELD PROGRAMME 33 3.1 Scope 33 3.2 S i t e Descriptions and F i e l d Programme 33 3.2.1 McDonald Farm 33 3.2.2 Lulu Island UBC P i l e Research 38 3.2.3 Langley Lower 232 .41 4.0 THE INTERPRETATION OF THE PRESSUREMETER TEST 45 4.1 A n a l y t i c a l Approaches to the Pressuremeter Test 45 4.2 Factors A f f e c t i n g Pressuremeter Test I n t e r p r e t a t i o n ....50 4.2.1 E f f e c t s of Pressuremeter I n s e r t i o n and Relaxa- t i o n Period 53 4.2.2 E f f e c t s of S t r a i n Rate 57 4.2.3 E f f e c t s of Disturbance 59 4.2.4 E f f e c t s of Pressuremeter L/D Ratio 61 4.3 Comparison of SBPM and FDPM Tests 63 4.4 Parameters Obtained from the Pressuremeter Test ...72 4..4.1 Undrained Shear Strength 72 4.4.2 Shear Modulus 81 4.4.3 Stress History and In S i t u Horizontal Stress ...86 5.0 UNDRAINED SHEAR STRENGTH 93 5.1 Reference Undrained Shear Strength 93 5.2 T h e o r e t i c a l Techniques 98 5.2.1 Windle and Wroth Average Strength Method 98 5.2.2 Arnold Curve F i t t i n g Method 101 5.2.3 Houlsby Unloading Method 101 5.3 Empirical Techniques 104 5.4 Conclusions 113 V TABLE OF CONTENTS ( CONT. ) Page 6.0 SHEAR MODULUS AND RIGIDITY INDEX 115 6.1 Shear Modulus 115 6.2 R i g i d i t y Index 121 6.3 Conclusions 125 7.0 STRESS HISTORY AND IN SITU HORIZONTAL STRESS 129 7.1 Reference Overconsolidation Ratio 129 7.2 Stress History 129 7.3 Reference In S i t u Horizontal Stress ; 131 7.4 In S i t u Horizontal Stress 133 7.5 Conclusions 136 8.0 CONCLUSIONS AND RECOMMENDATIONS 139 8.1 Factors A f f e c t i n g the I n t e r p r e t a t i o n of the FDPM Test .139 8.2 Parameters Obtained from FDPM Tests 141 8.2.1 Undrained Shear Strength 141 8.2.2 Shear Modulus and R i g i d i t y Index 143 8.2.3 Stress History and In S i t u Horizontal Stress ..143 8.3 Recommendations 144 REFERENCES 146 APPENDICES I Pressuremeter Test Data at McDonald Farm 152 II Pressuremeter Test Data at Lulu Is-UBCPRS 247 III Pressuremeter Test Data at Langley Lower 232 363 IV D e r i v a t i o n of Unload Reload Shear Modulus 419 V Shear Modulus Values 425 VI In S i t u Test Locations 430 v i LIST OF TABLES Table Page 1.1 C l a s s i f i c a t i o n of Pressuremeters According to Method of I n s e r t i o n (adapted from Huang and Haefele, 1988) 2 2.1 Test Depth and D r i l l i n g Parameters f o r the Hughes SBPM at McDonald Farm ( adapted from Hughes, 1984 ) 30 3.1 S o i l Properties at McDonald Farm 37 3.2 In S i t u Tests Performed at McDonald Farm 38 3.3 S o i l Properties at Lulu Is. - UBCPRS 41 3.4 In S i t u Tests Performed at Lulu Is. - UBCPRS 41 3.5 S o i l Properties at Langley Lower 232 44 3.6 In S i t u Tests Performed at Langley Lower 232 44 4.1 E f f e c t of Relaxation Time on FDPM L i f t Off Pressures at Lulu Is. - UBCPRS 55 4.2 Numerical Simulation of SBPM Tests with Varying L/D Ratios f o r E l a s t i c P e r f e c t l y P l a s t i c S o i l •( a f t e r Baguelin et a l , 1986) .62 4.3 E f f e c t of Ins e r t i o n Method on the Radius of the P l a s t i c Zone f o r an E l a s t i c P e r f e c t l y P l a s t i c S o i l 63 4.4 Comparison of Undrained Shear Strength from Pressuremeter, F i e l d Vane and T r i a x i a l Tests 80 v i i LIST OF FIGURES Figure Page 2.1 Schematic of the UBC SCP 6 2.2 UBC SCP S t r a i n Arm Design 8 2.3 E f f e c t of D i f f e r e n t S t r a i n Arm Designs on the L i f t - o f f Stage of a Pressure-Displacement Curve 10 2.4 Schematic Layout of the UBC SCP Data A c q u i s i t i o n System ....13 2.5 T y p i c a l S t r a i n Arm C a l i b r a t i o n f o r the UBC SCP 15 2.6 Membrane Correction Curve f o r the UBC SCP 17 2.7 T y p i c a l S t r a i n Rate Used f o r a UBC SCP Test 19 2.8a,b Results of a UBC SCP Test Inside a 44 mm Diameter St e e l Cylinder 20 2:9 Schematic of the Fugro CP ( a f t e r Withers et a l , 1986 ) ....22 2.10 The Pressuremeter Component of the Fugro CP ( a f t e r Withers et a l , 1986 ) 23 2.11 S t r a i n Arm C a l i b r a t i o n f o r the Fugro CP 25 2.12 Membrane Correction Curve for the Fugro CP ( a f t e r Withers et a l , 1986 ) 27 2.13 Hughes SBPM J e t t i n g System ( a f t e r Hughes, 1984 ) 28 2.14 Membrane Correction Curve f o r the Hughes SBPM 32 3.1 General Location of Research Sit e s 34 3.2 T y p i c a l CPTU P r o f i l e at McDonald Farm 36 3.3 T y p i c a l CPTU P r o f i l e at Lulu Is. - UBCPRS 40 3.4 T y p i c a l CPTU P r o f i l e at Langley Lower 232 43 4.1 E f f e c t of Pressuremeter In s e r t i o n Method and Relaxation Time on Pressure Expansion Curves ( a f t e r Baguelin et a l , 1978 ) 52 4.2 Comparison Between Dilatometer P Q and Penetration Pore Pressures from Piezoblade i n Normally Consolidated and L i g h t l y Overconsolidated Clays ( a f t e r Lutenegger, 1988) ....54 v i i i LIST OF FIGURES ( CONT. ) Figure Page 4.3 Comparison Between Dilatometer P Q and Penetration Pore Pressures from Piezoblade i n Overconsolidated Clays ( a f t e r Lutenegger, 1988) 54 4.4 E f f e c t of Relaxation Time on FDPM Tests at Lulu Is. - UBCPRS 56 4.5a,b Comparison of FDPM and SBPM Tests at McDonald Farm 64 4.6a,b Comparison of FDPM and SBPM Tests at Lulu Is.-UBCPRS 66 4.7 Comparison of FDPM, SBPM and Dilatometer L i f t - o f f Pressures 69 4.8 Comparison of FDPM and SBPM P r a c t i c a l L i m i t Pressures and Dilatometer P^ Values 71 4.9 Determination of Undrained Shear Strength using the Windle and Wroth Average Strength Method 74 4.10 Determination of the S t r e s s - s t r a i n Curve using the Modified Arnold Type 1 Analysis 76 4.11 Determination of Undrained Shear Strength using the Houlsby Unloading Analysis 77 4.12 Comparison of Cone Bearing and FDPM P r a c t i c a l L i m i t Pressure 79 4.13 Hierarchy and V a r i a t i o n i n Undrained Strength Ratio f o r Various Test Methods ( adapted from Wroth, 1984) 82 4.14 Shear Modulus Attenuation Curves i n Cohesive S o i l s 84 4.15 V a r i a t i o n i n (q^ - « " v o ) A v o ' with OCR at Onsoy ( a f t e r Wroth, 1988 ) 88 4.16 Values of G/S u P l o t t e d Against OCR from CK QU DSS Tests on Three Clays ( a f t e r Ladd and Edgers, 1972 ) 90 5.1 F i e l d Vane Undrained Shear Strength 95 5.2 Normalized Undrained Shear Strength from F i e l d Vane 96 5.3 Proposed Reference S u For Lulu Is. - UBCPRS 97 5.4 FDPM and SBPM Undrained Shear Strength from Windle and Wroth Average Strength Method 99 i x LIST OF FIGURES ( CONT. ) Figure Page 5.5 SBPM Undrained Shear Strength from Arnold Curve F i t t i n g Method 102 5.6 FDPM Undrained Shear Strength from Houlsby Unloading Method 103 5.7 FDPM and SBPM Pressuremeter Factor N - ( P L - P Q ) / S U R E F vs Depth 105 5.8 FDPM and SBPM Pressuremeter Factor N - ( P L - ^ v o ) / S u R E F vs Depth 107 5.9 Cone Factor N k t - ( q t - < 7 v o)/S u j^p vs Depth 110 5.10 Cone Factor N A u - Au/S u R £ F V S D E P T N 1 1 1 5.11 Comparison of S u using FDPM Factor N and Cone Factor N k t 112 6.1 Unload-Reload, G u r, and Houlsby Unloading, G^, Shear Moduli vs Depth 116 6.2 Dynamic Small S t r a i n Shear Modulus, G m a x , vs Depth 118 6.3 Gur/ Gmax v s s h e a r S t r a i n at McDonald Farm 119 6.4 Gur/ Gmax v s s h e a r S t r a i n at Lulu Is.-UBCPRS 120 6.5 G u r / S u REF a n d H o u l s b v Unloading I r vs Depth 122 6 - 6 Gmax/ Su REF v s D E P T H 1 2 4 6.7 G u r / S u REF v s S n e a r S t r a i n at McDonald Farm 126 6.8 G U R / S U R E F v s S n e a r S t r a i n at Lulu Is.-UBCPRS . ... 127 7.1 Stress H i s t o r y from F i e l d Vane at Langley Lower 232 130 7.2 V a r i a t i o n i n G m a x / S u with OCR at Langley Lower 232 132 7.3 V a r i a t i o n i n ̂ O ' ^ v o ^ v o ' a n d ^ t ^ v o ^ v o ' w i t h OCR at Langley Lower 232 132 7.4 FDPM K Q Values Obtained Using Empirical Method 134 X LIST OF FIGURES ( CONT. ~) Figure Page 7.5 SBPM K Q Values Obtained Using Empirical Method at McDonald Farm 135 7.6 Comparison of Dilatometer K D and FDPM K p M Values 137 x i ACKNOWLEDGEMENT I would l i k e to thank my research supervisor, Dr. R.G. Campanella f o r h i s guidance during the course of t h i s study. The h e l p f u l suggestions and assistance with data c o l l e c t i o n from my colleagues, E r i c k Basiw, Jim Greig, John Howie, John S u l l y , and Damika Wickremesinghe are much appreciated. The ex c e l l e n t t e c h n i c a l support received from A r t Brookes, Scott Jackson, Glen J o l l y and Harald Schrempp i s also acknowledged. A s p e c i a l thanks i s extended to my wife, Leanne, whose support and encouragement throughout the duration of t h i s research p r o j e c t has been much appreciated. The t e c h n i c a l and f i n a n c i a l assistance of Foundex Explorations Ltd. and the f i n a n c i a l support provided by N.S.E.R.C. i s g r a t e f u l l y acknowledged. 1 CHAPTER 1 INTRODUCTION In recent years, the i n s i t u t e s t i n g of s o i l s has i n c r e a s i n g l y become emphasized as an important a l t e r n a t i v e and/or a d d i t i o n to laboratory or f u l l scale t e s t s . The purpose of t h i s thesis i s to analyze and i n t e r p r e t the performance of a r e l a t i v e l y new i n s i t u t e s t i n g device, the cone pressuremeter. The cone pressuremeter c o n s i s t s of a 60 degree , 15 square cm. piezocone, and a pressuremeter of equal diameter to the cone s i t u a t e d a short distance behind the cone t i p . The focus of t h i s study i s to i n t e r p r e t the r e s u l t s of f u l l displacement pressuremeter (FDPM) tests performed as part of a cone pressuremeter (CP) sounding. The r a t i o n a l f o r the development of the cone pressuremeter i s described below. The c a p a b i l i t i e s of the piezocone penetration t e s t (CPTU) have been we l l documented (Campanella and Robertson,1988; Jamiolkowski et al,1985). The CPTU t e s t i s of p a r t i c u l a r value i n providing a d e t a i l e d s o i l p r o f i l e . Furthermore, the evaluation of the flow and co 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 and a tentative evaluation of the str e s s h i s t o r y i n cohesive s o i l s can be made. The cone resistance can also be used to estimate to varying degrees of r e l i a b i l i t y the drained and undrained shear strength of both granular and cohesive s o i l s . However, the CPTU t e s t generally gives a poor estimate of s o i l s t i f f n e s s . The pressuremeter t e s t , i n p r i n c i p l e , w i l l provide a better estimate of s o i l s t i f f n e s s and strength than the CPTU t e s t . Several d i f f e r e n t types of pressuremeters have been developed since Menard f i r s t 2 introduced the pressuremeter i n 1954 and can be c l a s s i f i e d according to the i n s e r t i o n method used as shown i n Table 1.1. Table 1.1 : C l a s s i f i c a t i o n of Pressuremeters According to Method of I n s e r t i o n (adapted from Huang and Haefele , 1988) 1 1 | I n s e r t i o n Method Pressuremeter Type 1 1 | Reference | | Pre-bored Menard OYO LLT j Baguelin et a l (1978) | j Suyama et a l (1982) j | Self-bored Camkometer PAF | Wroth & Hughes (1973) | j Baguelin et a l (1978) j | Push-in Stress Probe j Henderson et a l (1979) j | Fyffe et a l (1982) j | Full-Displacement FDPM j Hughes & Robertson(1985) j Cone Pressuremeter I Howie (1989) The Menard s t y l e probe i s placed i n a pre-bored hole and i s expanded to provide a pressure-volume curve. Due to disturbance and str e s s r e l i e f i n the s o i l surrounding the borehole, most Menard pressuremeter data i s used i n an empirical manner and i s d i r e c t l y c o r r e l a t e d to the performance of foundations. In an attempt to overcome the l i m i t a t i o n s created by s o i l disturbance, the s e l f - b o r i n g pressuremeter (SBPM) was developed independently i n France and England (Baguelin et al,1972; Wroth and Hughes, 1973) . The SBPM i s slowly pushed into the ground as s o i l at the bottom 'of the c y l i n d e r i s chopped up by a r o t a t i n g c u t t e r and flushed to the surface. When the SBPM i s i n s e r t e d with a minimal amount of s o i l disturbance, the c a p a b i l i t y e x i s t s to derive the s o i l s t r e s s - s t r a i n 3 behavior, the i n s i t u h o r i z o n t a l stress and i n some cases the con 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 s o i l . However, the SBPM t e s t i s c o s t l y to perform and takes h i g h l y s k i l l e d personnel to i n s e r t the probe with the minimum possible amount of s o i l disturbance. The push-in pressuremeter (PIP) or stress probe (Henderson et al,1979; Fyffe et al,1982) , developed p r i m a r i l y f o r offshore use, i s a hollow open-ended pressuremeter with an end area r a t i o of 40 %. The probe i s pushed a short depth below the bottom of a borehole c r e a t i n g a small but s i g n i f i c a n t amount of disturbance. The FDPM t e s t i s performed i n s o i l which has been s u b s t a n t i a l l y disturbed. However, the disturbance created i s repeatable and i s operator independent. Furthermore, r e s u l t s from the FDPM t e s t can be d i r e c t l y c o r r e l a t e d to a d d i t i o n a l data c o l l e c t e d during the seismic cone pressuremeter sounding . In an offshore environment, the cone pressuremeter has p r a c t i c a l advantages over the s e l f - b o r i n g or push-in pressuremeter t e s t . The SBPM t e s t i s d i f f i c u l t to perform offshore (Fyffe et al,1982) and the PIP t e s t involves repeated cycles of d r i l l i n g , removing d r i l l rods and performing a pressuremeter t e s t . The i n s e r t i o n of a cone pressuremeter into s o i l creates a large amount of disturbance and complex and dynamic str e s s and s t r a i n f i e l d s around the pressuremeter. The primary objective of t h i s research i s to in t e r p r e t the r e s u l t s of the FDPM t e s t i n l i g h t of t h i s problem and to assess the s u i t a b i l i t y of using the FDPM t e s t to determine the undrained shear strength, shear modulus and to a l e s s e r extent stress h i s t o r y and i n s i t u h o r i z o n t a l stress of cohesive s o i l s . Piezocone and seismic data obtained as part of the cone pressuremeter sounding are not comprehensively analyzed but where appropriate are used to supplement 4 the FDPM t e s t r e s u l t s . Furthermore, whenever po s s i b l e , the r e s u l t s of the FDPM t e s t have been compared to SBPM, piezocone, dilatometer and f i e l d vane t e s t r e s u l t s . 5 CHAPTER 2 EQUIPMENT AND TEST PROCEDURES Three pressuremeter probes were u t i l i z e d f o r t h i s study : the UBC Seismic Cone Pressuremeter (UBC SCP), the Fugro Cone Pressuremeter (Fugro CP) and the Hughes Self-Boring Pressuremeter (Hughes SBPM). This chapter describes the t e s t equipment, data a c q u i s i t i o n systems and the t e s t procedures used for the three pressuremeters. These considerations are considered i n d e t a i l f o r the UBC SCP but not f o r the two other probes. A more d e t a i l e d d e s c r i p t i o n of the Fugro CP and the Hughes SBPM i s given by Howie (1990). 2.1 The UBC SCP 2.1.1 D e s c r i p t i o n of the UBC SCP The major components of the UBC SCP are shown i n F i g . 2.1 and are described below. The probe begins with a piezocone having a 60 degree, .15 cm^ c o n i c a l t i p followed by a f r i c t i o n sleeve having a surface area of 225 2 cm . B u i l t i n load c e l l s allow the near continuous measurement of end resi s t a n c e ( q c ) and sleeve f r i c t i o n ( f ) . Two e l e c t r i c pressure transducers located j u s t above the cone t i p and f r i c t i o n sleeve allow pore pressures to be measured during cone penetration. The d i s s i p a t i o n with time of the pore pressures generated can be monitored during h a l t s i n the penetration. Mounted j u s t below the f r i c t i o n sleeve are two p i e z o - e l e c t r i c bender elements or accelerometers which are aligned v e r t i c a l l y at 90 degree angles to each other. Two more accelerometers are mounted j u s t below the pressuremeter body i n the same manner. The 6 PO Electronics Pressuremeter ( P M ) PM Electronics Cone Electronics n Pressure Developer ( P D ) Piezocone Module — Adapter to 10 cm2 Cone Rod Controlled Change Volume / Change Time Pressure Transducer Pressure Transducer Three Strain Arms Two Accelerometers Direct Current Regulation, Amplification Two Accelerometers Two Pore Pressure Sensors Friction Sleeve ( 225 cm2 ) Bearing ( 1 5 cm2 ) 60 Degree Tip Temperature Slope F i g . 2.1 : Schematic of the UBC SCP 7 accelerometers are used to obtain a seismic p r o f i l e of the s o i l using the downhole seismic technique ( Rice , 1984 ). To obtain r e l i a b l e and consistent CPTU data, the piezocone should be properly be c a l i b r a t e d and saturated and standardized t e s t procedures should be used. Robertson and Campanella (1986) provide a comprehensive guideline to piezocone equipment, t e s t procedures and data reduction. The center of the pressuremeter i s located 1.34 m behind the cone t i p . The core of the pressuremeter i s a 39 mm diameter hollow c y l i n d e r with threads on e i t h e r end. A pressure transducer i s mounted i n the pressuremeter core and pressure developer . Three v e r t i c a l l y aligned s t r a i n arms are mounted i n shallow channels cut i n the pressuremeter core at 120 degree spacings. The s t r a i n arms are s t r a i g h t metal s t r i p s attached to the cone at one end to form a c a n t i l e v e r beam. Arm contact pl a t e s , which follow the membrane expansion, are connected to the free end of the metal s t r i p . Two d i f f e r e n t designs of arm contact plates and methods of attaching the plate to the metal s t r i p were used ( F i g . 2.2). The f i r s t or "old" design attached the 5 mm wide arm contact plate on top of the end of the metal s t r i p . This proved to be a problem when the pressuremeter was f u l l y deflated. V e r t i c a l and h o r i z o n t a l forces imposed on the contact plates due to s o i l and water stresses caused the ends of the metal s t r i p to "bottom" out i n the channel cut i n the pressuremeter core. This i s thought to have generated a moment at point 0 ( F i g . 2.2 ) with the end r e s u l t being a voltage output from the s t r a i n gauge on the metal s t r i p i n d i c a t i n g an apparent outward d e f l e c t i o n of the s t r a i n arm. The new design allowed the arm contact plates to " f l o a t " on the end of the metal s t r i p , the point of contact being the rounded edge of the 8 A r m Cover Plate SIDE VIEW SIDE VIEW Screw NEW DESIGN Not to Sca le Metal Strip ( Canti lever B e a m ) FRONT VIEW F OLD DESIGN Not to Sca le FRONT VIEW Metal Strip ( Canti lever B e a m ) Fig. 2.2 : UBC SCP Strain Arm Design 9 screw shown i n F i g . 2.2. V e r t i c a l and h o r i z o n t a l forces cause the arm contact p l a t e housing to "bottom" out instead of the metal s t r i p . This change solved the problem of apparent outward d e f l e c t i o n s of the s t r a i n arms when the pressuremeter was f u l l y d eflated. The e f f e c t of the d i f f e r e n t arm designs on the l i f t - o f f stage of the pressuremeter pressure-displacement curve i s shown i n F i g 2.3. The change i n s t r a i n arm design also seems to a f f e c t the i n i t i a l stages of the corrected pressuremeter expansion curve . For tes t s performed with the o l d s t r a i n arm design, a small but prevalent bump i n the corrected pressuremeter expansion curve i s found between 0 and 4 % c a v i t y s t r a i n or r a d i a l displacement ( e - AR/RQ ). The new s t r a i n arm design appears to reduce or eliminate the small bump ( f o r comparison purposes, a complete set of pressuremeter expansion curves are found i n appendices I to III ). Other causes f o r the small bump i n the pressuremeter expansion curve are discussed i n s e c t i o n 2.1.3 Two n a t u r a l rubber membranes, each with an average thickness of 1.2 mm are attached to the pressuremeter body using tapered metal rings and r e t a i n i n g nuts. Protecting the membrane i s a Chinese l a n t e r n made of s t a i n l e s s s t e e l metal s t r i p s . The ends of the s l o t t e d s t r i p s f i t over a nut with r a i s e d nipples and are held i n place by a tapered metal r i n g . The" s l o t s i n the metal s t r i p s allow the lanter n to move f r e e l y during membrane i n f l a t i o n and d e f l a t i o n . The exact diameter of the pressuremeter with two membranes and lanter n s t r i p s was d i f f i c u l t to determine. An average diameter of 43.6 mm was obtained when clamps were used to compress the lanter n around the pressuremeter body. This would suggest that the probe i s s l i g h t l y undersized since the r e s t of the UBC SCP probe has a diameter of 44 mm. Although the length of the 10 UBC SCP 300 OLD ARM DESIGN r T 0.1 0.2 DEFLECTION F i g . 2.3 : E f f e c t of D i f f e r e n t S t r a i n Arm Designs on the L i f t - o f f Stage of a Pressure-Displacement Curve 11 pressuremeter core i s 385 mm, the length of the membrane which i s free to i n f l a t e i s 220 mm. This leads to a L/D r a t i o of 5. The pressuremeter i s i n f l a t e d with s i l i p o n o i l using a downhole pressure developer. The 83 cm long pressure developer can generate pressures as high as 6900 kPa ( 1000 p s i ) using a p i s t o n b a l l screw driven by an e l e c t r i c motor. Since a closed system i s used, a i r i n the o i l going i n t o s o l u t i o n , a small leak i n the pressuremeter or backlash of the b a l l screw i n the f u l l y r e t r a c t e d p o s i t i o n w i l l a l l create negative pressures. The t e s t s shown i n F i g . 2.3 i n d i c a t e at the beginning of the t e s t s , negative pressures of 20 to 40 kPa existed. This range i s t y p i c a l of the negative pressures obtained at the beginning and end of t e s t s performed using the UBC SCP. I f the pressure developer b a l l screw i s h e l d i n the f u l l y r e t r a c t e d p o s i t i o n f o r an extended period of time, the negative pressures tend to d i s s i p a t e . To reduce the amount of a i r going into s o l u t i o n , the o i l f o r the pressuremeter was f i r s t placed under vacuum to remove as much a i r as poss i b l e . o The pressure developer i s attached to 10 cm area cone rods using an adapter enabling the probe to be pushed using the UBC In S i t u Testing truck which i s described i n d e t a i l by Campanella and Robertson (1981). The UBC SCP probe has been s u c c e s s f u l l y pushed to depths greater than 30 m and through s o i l layers with end bearing resistances greater than 200 bar. 2.1.2 The UBC SCP Data A c q u i s i t i o n System The UBC SCP has the c a p a b i l i t y to c o l l e c t three d i f f e r e n t types of data; piezocone, pressuremeter and seismic. Three separate data 1 2 a c q u i s i t i o n systems were used with the UBC SCP as shown by the schematic layout of the e n t i r e system shown i n F i g . 2.4 Piezocone data i s c o l l e c t e d using the Hogentogler f i e l d computer (FCS), a surface 12 b i t d i g i t a l data a c q u i s i t i o n system. The piezocone i s designed so that the analog signals which are ampl i f i e d downhole are compatible with the Hogentogler FCS. Data i s stored i n a magnetic bubble fo r l a t e r downloading to a microcomputer and i s also immediately p r i n t e d . A microcomputer based system developed at UBC i s used to c o l l e c t and process pressuremeter t e s t data. The UBC data a c q u i s i t i o n (DAS) consists of an IBM PC compatible microcomputer and analog to d i g i t a l (A/D) converter. The microcomputer uses an I n t e l 8088 microprocessor card and a 8087 math coprocessor. Two m u l t i f u n c t i o n I/O ( input/output) cards provide 512 KB of memory, two RS232 s e r i a l ports and two p a r a l l e l ports. Two h a l f height 360 KB floppy drives are used f o r data storage. A Data T r a n s l a t i o n DT2801-A 12 b i t A/D converter board i s used f o r analog to d i g i t a l conversion. The analog si g n a l s are converted to a 12 b i t representation of t h e i r voltage which means the voltages are represented by 4096 states ( 2 r a i s e d to the 12 t h power ) . This represents an analog output with r e s o l u t i o n equal to 0.024 % of the sel e c t e d analog input range. The DAS can provide data conversions f o r up to 8 channels. The data sampling rate i s user sel e c t a b l e with the maximum rate being equal to .4 seconds. Data sampling does not take place when the contents of a b u f f e r are being w r i t t e n to a disk. For the f i r s t few tests performed with the UBC SCP t h i s created a problem since the contents of a b u f f e r were oc c a s i o n a l l y w r i t t e n to the disk at c r i t i c a l 1 3 Wcolet 40S4 16 tilt Digital Oscilloscope Hogentogler Field Computer IBM PC Compatible Microcomputer fi DT2801 12 bit A/D Converter J— Display Monitor Keyboard Printer Analog Signals Interface Unit Pressuremeter, Seismic or Cone Mode If- I. Strip Chart Recorder 12 V DC Power Supply for PD Motor Trigger Box Seismic Source fl K3 j Depth E tooder +/- 15V DC Power Supply for PM & Cone Electronics Hydraulic Lood Volve Switch Switch Reaction Cylinders Loading Head I UBC SCP Probe F i g . 2.4 : Schematic Layout of the UBC SCP Data A c q u i s i t i o n System 0 14 times during a t e s t , Eg. at l i f t - o f f and during an unload-reload loop. This problem was solved by c r e a t i n g a l a r g e r b u f f e r and w r i t i n g to the disk at n o n - c r i t i c a l times. Seismic shear waves are generated by s t r i k i n g a metal pad, weighted to the ground, with a sledge hammer. Seismic wave traces are recorded by a N i c o l e t 4094 d i g i t a l o s c i l l o s c o p e with 16 b i t analog to d i g i t a l s i g n a l r e s o l u t i o n . This u n i t has very accurate timing c a p a b i l i t y and a t r i g g e r delay capacity. Data i s stored on floppy disks. Two power supplies are needed f o r the probe : a 12 v o l t d i r e c t current supply f o r the pressure developer motor and a +/- 15 v o l t d i r e c t current power supply f o r the pressuremeter and cone e l e c t r o n i c s . 2.1.3 Test Procedures f o r the UBC SCP The c a l i b r a t i o n of s t r a i n arms using a micrometer and pressure transducers using a dead-weight pressure t e s t e r was done r e g u l a r l y . A t y p i c a l s t r a i n arm c a l i b r a t i o n i s shown i n F i g . 2.5. Both the s t r a i n arm and pressure transducer c a l i b r a t i o n s showed v i r t u a l l y no h y s t e r e s i s or n o n - l i n e a r i t y . The slope from a l i n e a r regression best f i t l i n e i s used to convert s t r a i n arm data to engineering u n i t s . Before the beginning of each cone pressuremeter sounding, the probe was placed i n a 44 mm diameter s t e e l s p l i t c y l i n d e r and zeros or reference voltage outputs f o r the pressure transducers and s t r a i n arms were obtained. Zeros were found to be r e l a t i v e l y stable when subject to small temperature f l u c t u a t i o n s . As an extra precaution, the probe temperature was allowed to come into equilibrium with the outside a i r temperature. Since a l l tests included i n t h i s study took place between 15 F i g . 2.5 : T y p i c a l S t r a i n Arm C a l i b r a t i o n f o r the UBC SCP 16 December and A p r i l , i t i s l i k e l y that the di f f e r e n c e between the ground and a i r temperature was less than 5 degrees C e l s i u s . The membrane c o r r e c t i o n curve was determined by i n f l a t i n g and d e f l a t i n g the pressuremeter with the Chinese lant e r n attached i n a i r ( F i g . 2.6 ). The probe was i n f l a t e d at approximately the same rate as subsequent te s t s i n the ground. The shape of the membrane c o r r e c t i o n curve was consistent with no apparent softening under prolonged use. Furthermore, the c o r r e c t i o n curve was not a l t e r e d when the maximum s t r a i n achieved during expansion was changed. The membrane c o r r e c t i o n expansion curve f o r c a v i t y s t r a i n s between 0 and 4 % i s quite steep. The steepness of the a i r i n f l a t i o n curve i s a drawback when i t i s used to c o r r e c t pressuremeter tests since a small s h i f t i n zeros f o r the s t r a i n arms w i l l a f f e c t the shape of the corrected pressuremeter expansion curve. This e f f e c t could be a co n t r i b u t i n g f a c t o r to the small but prevalent bump found i n pressure expansion curves at c a v i t y s t r a i n s between 0 and 4 %. For c a v i t y s t r a i n s greater than 4 %, the pressure increases only s l i g h t l y . Unfortunately, a pressure c o r r e c t i o n of approximately 50 kPa can be a s i g n i f i c a n t proportion of the t o t a l expansion pressures obtained during a t e s t i n s o f t cohesive s o i l s at shallow depths. In order to corre c t a pressuremeter t e s t , the a i r i n f l a t i o n and d e f l a t i o n curves were f i t t e d using a hyperbolic equation of the form : € P - Q + 2.1 a + be The parameters a and b and the pressure axis i n t e r c e p t Q are found by choosing 3 points from the pressure versus c a v i t y s t r a i n curve. In 17 UBC SCP 10/12/87 Langley Lower 232 Air Inflation Cavity Strain [%] + Avg. of Arms 1 -2-3 F i g . 2.6 : Membrane Correction Curve f o r the UBC SCP 18 general Q was close to zero f o r a l l membrane c o r r e c t i o n expansion curves. A l l pressuremeter tests performed with the UBC SCP probe were run using a quasi-constant s t r a i n r a te. An example of the c a v i t y s t r a i n rate during a representative t e s t i s shown i n F i g . 2.7. A summary of the s t r a i n rates used f o r a l l pressuremeter te s t s can be found i n appendices I through I I I . A maximum c a v i t y s t r a i n of 27 % can be achieved. 2.1.4 UBC SCP Compliance The UBC SCP system compliance a f f e c t s both pressure and s t r a i n measurements and i s caused p r i m a r i l y by compression of the lant e r n s t r i p s , creep and compression of the membrane and a i r i n the o i l going into s o l u t i o n . Figures 2.8a,b show the r e s u l t s of a pressuremeter t e s t run i n s i d e a 44 mm diameter s t e e l s p l i t c y l i n d e r . A membrane c o r r e c t i o n curve i s also included i n F i g . 2.8b f o r comparison purposes. Below approximately .7 % c a v i t y s t r a i n ( AR - .15 mm ), very l i t t l e compression of the lant e r n s t r i p s i s taking place, a r e s u l t of the probe being s l i g h t l y undersized. For s t r a i n s greater than .7 %, a considerable amount of l a n t e r n compression occurs. From pressuremeter expansions i n the s t e e l c y l i n d e r without the lant e r n s t r i p s attached, i t appears that very l i t t l e membrane compression occurs f o r pressures l e s s than 500 kPa. For a pressuremeter t e s t performed i n a saturated cohesive s o i l , i t i s extremely d i f f i c u l t to assess the e f f e c t of l a n t e r n compression on a pressuremeter t e s t . I t i s l i k e l y that water w i l l r a p i d l y flow i n behind the l a n t e r n s t r i p s as expansion proceeds therefore making the compliance of the l a n t e r n s t r i p s dependent on the e f f e c t i v e stress state around the pressuremeter. This i s an important assumption since i t i s apparent from 1 9 c E 3 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 - 1 - 0 UBC SCP 3/4/87 Lulu Is.-UBCPRS Depth=6.35 m EXPANSION UNLOAD-RELOAD LOOP CONTRACTION STRAIN RATE - AVERAGE VALUES FOR 7 DATA POINTS - T — 40 —r - 80 —I— 120 160 —I— 200 240 TIME ( sec ) F i g . 2.7 : T y p i c a l S t r a i n Rate Used f o r a UBC SCP Test 20 2000 UBC SCP 4/12/87 Inflation in 44 mm Dio. Split Cylinder 1500 o a. 3 i. 1000 500 - EXPANSION • CONTRACTION Cavity Strain [X] Avg,. of arms 1—2—3 a 500 UBC SCP 4/12/87 Inflation in 44 mm Dio. Split Cylinder 400 - 300 & 3 c a. •o e TJ E o o c => 200 - 100 - EXPANSION IN SPLIT CYLINDER • EXPANSION IN AIR -100 Cavity Strain [X] Avg. of arms 1-2-3 F i g . 2.8a,b Results of a UBC SCP Test Inside a 44 mm Diameter St e e l Cylinder 21 F i g . 2.8b that a pressure drop due to a change from t o t a l to e f f e c t i v e stresses could cause a s i g n i f i c a n t reduction i n compliance f o r pressures l e s s than approximately 200 kPa. I f the compression of the la n t e r n s t r i p s are governed by e f f e c t i v e stresses, the compliance w i l l approximately be constant f o r an undrained t e s t i n a cohesive s o i l . The e f f e c t of a i r going into s o l u t i o n and membrane creep can be observed by r a p i d l y i n f l a t i n g the pressuremeter i n the s t e e l c y l i n d e r to a set s t r a i n and then holding the s t r a i n constant. A r a p i d pressure decrease i s i n i t i a l l y observed, the rate becoming slower with time. The magnitude of the pressure decrease f o r a constant time peri o d i s propo r t i o n a l to the i n i t i a l pressure reached. The e f f e c t s of a i r going into s o l u t i o n and membrane creep are f e l t to be of minor importance f o r the pressures reached during tests performed f o r t h i s study. Due to the complex and indeterminate nature of compliance, no attempt was made to co r r e c t pressuremeter tests f o r compliance. A pressuremeter design incorporating a pore pressure transducer on the membrane would allow f o r a more accurate assessment of the e f f e c t s of compliance. 2.2 The Fugro CP The prototype Fugro CP used f o r t h i s study was b u i l t by Cambridge In s i t u i n conjunction with Fugro Geotechnical Engineers B.V. Figure 2.9 shows the components of the Fugro CP. Future versions of the cone pressuremeter w i l l use a 15 cm piezocone instead of a dummy cone. The d e t a i l s of the pressuremeter component of the Fugro CP are shown i n F i g . 2.10. The distance between the center of the membrane and the c o n i c a l 22 PUSH HEAD • n / - " ^ w ELECTRO/HYDRAUL IC HOSE CONE ROOS CONDUCTING HOSE ' STANDARD CONE ROD CONE ROD ADAPTOR AMPLIFIER HOUSING CONTRACTION RING ' PRESSUREMETER MODULE CONTRACTION RING CONE SPACER DUMMY CONE CONTROLE UNIT ' • R E A D OUT F i g . 2.9 : Schematic of the Fugro CP ( a f t e r Withers et a l , 1986 ) 23 CONTRACTION RING CHINESE LANTERN MEMBRANE CLAMP RING MEMBRANE ARM COVER SLEEVE STRAIN GAUGED SPRING 3 STRAIN SENSING ARMS AT 120° SPACING INSTRUMENT BODY MEMBRANE MEMBRANE CLAMP RING CHINESE LANTERN CONTRACTION RING CONNECTION TO CONE SPACER AND CONE CONNECTION TO AMPLIFIER SUB c 8 O «-< E £ s 43.7 mm F i g . 2.10 : The Pressuremeter Component of the Fugro CP ( a f t e r Withers et a l , 1986 ) 24 t i p has a minimum value of 930 mm. This distance can be increased through the use of spacers. The outside diameter of the Fugro CP i s 43.7 mm which corresponds o to the dimensions of an almost 15 cm cone. The L/D r a t i o i s 10.3. The pressuremeter measures the i n f l a t i o n pressures and the c a v i t y s t r a i n or r a d i a l displacement at 120 degree spacings using 3 s t r a i n arms. The s t r a i n arms, which c o n s i s t of a pivoted arm and s t r a i n gauged spring, are s i m i l a r i n design to the ones used i n the Cambridge SBPM . The pressure c a p a b i l i t y of the pressuremeter i s 10 MPa while the c a v i t y s t r a i n capacity i s 50 %. Nitrogen gas was used to i n f l a t e the probe with te s t s being performed i n a q u a s i - s t r a i n c o n t r o l l e d manner by s t e a d i l y turning the pressure regulator to maintain an approximately constant i n f l a t i o n r a t e. Two regulators were used : a 14 - 826 kPa (2 - 120 p s i ) regulator f o r s o f t e r s o i l s and a 34 to 3100 kPa (5 - 450) p s i regulator f o r t e s t s r e q u i r i n g a l a r g e r range. The analog s i g n a l s were amplified downhole and transmitted to the surface through an e l e c t r i c a l cable. Both the e l e c t r i c a l cable and the i n f l a t i o n hose were placed inside standard 20 tonne cone rods of 16 mm i n s i d e diameter. The use of a XYY s t r i p chart recorder allowed the analog monitoring of s t r a i n and pressure. A 12 b i t analog to d i g i t a l data t r a n s l a t i o n board was added to a standard portable COMPAQ microcomputer. D i g i t a l output was stored on floppy disks. A scanning range of 0 to 1.25 V was used r e s u l t i n g i n a r e s o l u t i o n of close to 0.3 mV. The minimum time between data points was one second. The pressure transducer and s t r a i n arms were c a l i b r a t e d using a dead weight pressure t e s t e r and micrometer r e s p e c t i v e l y . A t y p i c a l s t r a i n arm c a l i b r a t i o n i s shown i n F i g . 2.11. Since the s t r a i n arm data 25 3.00 E E U J O 2.00 CO Q o: U J t3 1.00 o ct: o 0.00 FUGRO CP STRAIN ARM CALIBRATION T — I — I — i — I — I — r ^ ~ i — i — i — i $fx>s*i—r ***** ARM 0 0 0 0 0 ARM 111 111 ARM A A A A A ARM 00000 ARM I I I I I ARM EXPANSION 1 CONTRACTION EXPANSION CONTRACTION EXPANSION CONTRACTION —0.1 0 LINEAR REGRESSION BEST FIT LINE ARM 1 DISTANCE - 9.700»OUTPUT - 0 .3213 ARM 2 DISTANCE - 9.7B9»0UTPUT - 0 .1387 ARM 3 DISTANCE - 9.679»0UTPUT + 0 .9333 1 [ — T 0.00 0.10 TRANSDUCER 0.20 OUTPUT - i — r - 0.30 V o l t s ) i — r 0.40 F i g . 2.11 : S t r a i n Arm C a l i b r a t i o n f o r the Fugro CP 26 was converted using a l i n e a r regression best f i t l i n e , some e r r o r may have been introduced due to the h y s t e r e s i s and i n i t i a l n o n - l i n e a r i t y . I n i t i a l zeros were taken before each pressuremeter t e s t . Pressuremeter te s t s were corrected using a membrane c o r r e c t i o n curve s i m i l a r to the one shown i n F i g . 2.12. For t h i s p a r t i c u l a r c o r r e c t i o n curve the l i f t - o f f pressure i s 27 kPa and the maximum hy s t e r e s i s i s approximately 10 kPa. The membrane c o r r e c t i o n at 20 % r a d i a l displacement i s approximately 100 kPa which i s twice as much as the c o r r e c t i o n obtained with the UBC SCP. 2.3 The Hughes SBPM The Hughes SBPM was b u i l t by Dr. J.M.O. Hughes and except f o r a few mechanical di f f e r e n c e s i s s i m i l a r to the SBPM b u i l t by Cambridge In S i t u . The major d i f f e r e n c e i s that the Hughes SBPM employs a j e t t i n g device to remove s o i l and advance the probe as opposed to the t r a d i t i o n a l method of f i r s t c u t t i n g up the s o i l using a r o t a t i n g cutter and then f l u s h i n g the s o i l to the surface. Figure 2.13 shows how the Hughes SBPM j e t t i n g system works. Water or mud i s pumped down the d r i l l rods and out the j e t t i n g ports j u s t i n s i d e the c u t t i n g shoe. An advantage of t h i s system i s that the probe can be in s e r t e d i n to the s o i l using one rod as opposed to the double rod system used with the Cambridge SBPM. A disadvantage with the j e t t i n g system i s that c e r t a i n s o i l s such as s t i f f or s t i c k y s o i l s w i l l not break up e a s i l y under water and therefore the f l u s h i n g system w i l l tend to c l o g . The Hughes SBPM has an outside diameter of 74 mm and a L/D r a t i o of 6. The t o t a l gas pressure inside the probe and pore pressures at two 27 F i g . 2.12 Membrane Correction Curve f o r the Fugro CP ( a f t e r Withers et al, 1986 ) 28 Drilling Mud F i g . 2.13 : Hughes SBPM J e t t i n g System ( a f t e r Hughes, 1984 29 l o c a t i o n s are measured using pressure transducers while the displacement i s measured by 3 s t r a i n arms at 120 degree spacings. The analog si g n a l s are transmitted to the surface through an e l e c t r i c a l cable. Several d i f f e r e n t data a c q u i s i t i o n systems and t e s t procedures were u t i l i z e d with the Hughes SBPM. For tests performed at McDonald Farm, the pressure and s t r a i n values were monitored using a d i g i t a l v o l t meter plugged into the co n t r o l box. Using a XYY s t r i p chart recorder simultaneous analog p l o t s of two of the three displacement sensors and t o t a l pressure were also made. During a standard t e s t the reading from the pressure and s t r a i n sensors were recorded manually a f t e r each increase i n pressure. Using t h i s procedure, the i n t e r v a l between successive pressure increments was greater than 30 seconds which r e s u l t e d i n an average t e s t taking about h a l f an hour to complete. This corresponds to an average expansion c a v i t y s t r a i n rate of roughly 10 %/min. Several quick tests were performed i n which no manual reading were taken. Instead the analog recordings from the s t r i p chart were l a t e r d i g i t i z e d . The quick t e s t took about 2 minutes to perform r e s u l t i n g an average expansion s t r a i n rate of roughly 1 %/min. For te s t s performed at the Lulu Is.-UBC P i l e Research S i t e (PRS) , the analog s i g n a l s were amplified downhole and transmitted to the surface using a time d i v i s i o n multiplexed s i g n a l . Using t h i s system 8 channels could be output every 1 second. The analog si g n a l s were converted to d i g i t a l output using a 8 b i t A/D converter i n the co n t r o l box. The d i g i t a l output was simultaneously p l o t t e d on a microcomputer computer screen and output to a floppy disk. Tests were performed i n a q u a s i - s t r a i n c o n t r o l l e d manner by s t e a d i l y turning the pressure regulator to maintain an approximately steady i n f l a t i o n r a t e. 30 A l l Hughes SBPM tests were performed using a lightweight d r i l l r i g anchored into the ground. Such v a r i a b l e s as j e t t i n g pressure, v e l o c i t y of the j e t t i n g f l u i d , l o c a t i o n of the j e t t i n g ports and the rate of advance should be c a r e f u l l y monitored and c o n t r o l l e d i f p o s s i b l e . The d r i l l i n g parameters were monitored at McDonald Farm and are shown i n Table 2.1. Table 2.1 : Test Depth and D r i l l i n g Parameters f o r the Hughes SBPM at McDonald Farm ( adapted from Hughes, 1984 ). j Depth | ( m ) | Rate of | Penetration 1 ( m/min ) j Flow Rate 1 ( L/sec ) Mud Pump Pressure ( kPa ) | Ram Force | | ( kN ) | | 16.75 | 1.0 160 | 6.4 | | 17.75 | 0.3 | 0.47 830 1 8.5 | | 18.76 1 0.5 | 0.2 1030 | 6.5 | | 19.76* | 0.14 | 0.15 690 8.4 j | -20.76 | 0.33 | 0.64 620 | 8.4 | | 21.76* | 0.32 | 0.20 480 I 8.4 | | 22.76 I 0.27 | 0.18 550 1 8.4 | | 23.76* | 0.34 | 0.12 480 | 8.1 | | 24.76* | 0.21 0.16 620 1 8.4 | 25.76 j 0.17 | 0.17 480-690 8.4 - Quick te s t s performed i n approximately 2 minutes. The j e t t i n g ports were set 10 mm behind the bottom of c u t t i n g shoe f o r a l l t e s t s . No comparable records were kept f o r the tes t s at Lulu Is.-UBCPRS. However, the mud pump pressure and ram force were p e r i o d i c a l l y checked to t r y to ensure that the i n s e r t i o n process was cr e a t i n g as l i t t l e s o i l disturbance as po s s i b l e . Nevertheless, excessive mud pump pressures and/or ram forces i n d i c a t i v e of clogging of the SBPM c u t t i n g shoe occurred several times each time f o r c i n g the probe to be r e t r i e v e d f o r 31 cleaning. The fibrous organic nature of the s o i l at Lulu Is.-UBCPRS appeared to make the s e l f - b o r i n g process more susceptible to clogging. A membrane c o r r e c t i o n curve s i m i l a r to the one shown i n F i g . 2.14 was used to c o r r e c t a l l Hughes SBPM data. The applied pressure increases monotonically as the s t r a i n increases and i s subject to only a small amount of h y s t e r e s i s when unloaded.. 32 H U G H E S S B P M 1 6 / 2 / 8 7 Lulu Is. - UBCPRS Air Inflation 100 - i 90 - 80 - 70 - 60 - 0 2 4 6 8 10 12 14- 16 18 20 CAVITY STRAIN (%) Avg. of Arms 1 - 2 - 3 F i g . 2.14 : Membrane Correction Curve f o r the Hughes SBPM 33 CHAPTER 3 TEST SITES AND FIELD PROGRAMME 3.1 Scope The f i e l d programme was conducted at three s o i l s i t e s i n the Lower Fraser V a l l e y where cohesive s o i l s predominate as located i n F i g . 3.1. The focus of t h i s report i s to present and i n t e r p r e t the r e s u l t s of FDPM te s t s performed as part of a cone pressuremeter sounding. Whenever possibl e , the FDPM t e s t r e s u l t s have been compared to the following i n s i t u t e s t s : 1. Self-Boring Pressuremeter Test ( SBPMT ) 2. Piezocone Penetration Test ( CPTU ) 3. Down-hole Seismic Cone Penetration Test ( SCPT ) 4. F l a t Dilatometer Test ( DMT ) 5. F i e l d Vane Test ( FVT ) A l l t e s t s included i n t h i s study except SBPM tes t s conducted at McDonald Farm were performed by the UBC In S i t u Testing Group. The SBPM tests at McDonald Farm were conducted by Dr. J.M.O. Hughes. 3. 2 S i t e Descriptions 3.2.1 McDonald Farm McDonald Farm i s located at the northern edge of Sea Island i n the mun i c i p a l i t y of Richmond. The i s l a n d i s contained by a system of dikes to protect against f l o o d i n g from the r i v e r . The s i t e has a ground e l e v a t i o n of 1.6 m ( Geodetic Datum ) and i s reasonably l e v e l . The water table i s approximately 1 m below the ground surface and i s subject to t i d a l f l u c t u a t i o n s . F i g . 3.1 : General Location of Research Sit e s 35 McDonald Farm i s wit h i n the p o s t - g l a c i a l Fraser River d e l t a ( F i g . 3.1 ). The marine d e l t a i c sediments of Sea Is. have been forming since the r e t r e a t of the Fraser G l a c i a t i o n i c e sheets some 8000 - 10000 years ago ( Blunden, 1975). The present thickness of the d e l t a i c deposits are roughly 200 m and have formed on basal layers undergoing i s o s t a t i c rebound at a rate which i s greater than the p o s t - g l a c i a l marine transgression. The s u r f i c i a l deposits of Sea Island c o n s i s t of d e l t a i c d i s t r i b u t a r y channel f i l l and overbank deposits which o v e r l i e post g l a c i a l estuarine and marine sediments ( Armstrong, 1978). A representative CPTU p r o f i l e from McDonald Farm i s presented i n F i g 3.2. The time f o r 50 % d i s s i p a t i o n of pore pressure measured d i r e c t l y behind 2 a 10 cm area cone t i p from several CPTU soundings i s also included. The findings i n t h i s report are l i m i t e d to the clayey s i l t between 15 and 30 m. The cone bearing, q t, i n F i g 3.2 has been corrected f o r unequal end area r a t i o s ( Campanella and Robertson, 1981). Both the cone bearing and pore pressure p r o f i l e s increase l i n e a r l y with depth suggesting a normally consolidated s o i l . The s o i l properties and i n s i t u tests performed at McDonald Farm are given i n Tables 3.1 and 3.2. The l o c a t i o n of the i n d i v i d u a l i n s i t u t e s t s performed are included i n appendix VI. The permeability value i n Table 3.1 was measured by a v a r i a b l e head inflow t e s t using the BAT Groundwater Monitoring System b u i l t by BAT Envitech Inc ( Petsonk, 1985 ). U B C I M SI to Location! McDONALD FARM On Si to Loo MFB5-4 S I T U X E CPT Doto i 28/09/85 Cono Usedi UBC #6 STD PP T I M G Pago Noi 1 / 1 Commantsi PORE PRESSURE U («. of »oter> 0 100 10 20 30 V - I 1——1 L . SLEEVE FRICTION <bcr) 0 . 5 CONE BEARING Ot (bar) FRICTION RATIO Rf tt) 0 5 - 10 DIFFERENTIAL P.P, RATIO AU/Ot - .2 0 .8 0 INTERPRETED PROFILE •sow 20 30 r LOOM to Dsnss Coons Sand Soms 10-j Fins Sand 2D 30 Soft Organic Slty Clay Fins Sand Soms SfK Soft N.C. Claysy Slit Depth Increment F i g . 3.2 . 025 m Max Dopth i 2B. 95 m T y p i c a l CPTU P r o f i l e at McDonald Farm 134 158 384 179 2BS 383 133 136 163 IBS 120 360 270 330 101 37 Table 3.1 : S o i l Properties at McDonald Farm S p e c i f i c Gravity : 2.8 Natural Water Content (%) : Range 23-40 Average 34 L i q u i d L i m i t (%) : Range 25-42 Average 35 P l a s t i c L i m i t (%) : Range 22-25 Average 24 P l a s t i c i t y Index (%) : Range 3-20 Average 15 S e n s i t i v i t y ( f i e l d vane ) : Range 2-7 Average 5 Coef. of Consolidation (cm2/s) : Range 0 012-0.018 ( 2 oedometer tes t s ) Average 0.015 Permeability (cm/s) 4*10-7 ( 1 BAT inflow t e s t @ 21.5 m ) 0 38 Table 3.2 In S i t u Tests Performed at McDonald Farm | No. j In S i t u Test | Name In S i t u j Date j Device 1 | 1 j Seismic Cone Pressuremeter UBC SCP-1 1 UBC SCP | 27 JAN 87 | 1 2 | Cone Pressuremeter FUGRO CP-1 2 FUGRO CP | 7 NOV 85 j 1 3 j Self-Boring Pressuremeter SBPM-1 SBPM j 18 OCT 83 j 1 4 | Piezocone Penetration CPTU-1 UBC * 1 15 APR 81 j j 5 | Piezocone Penetration CPTU-2 UBC 4 I 23 JULY 82 | 1 6 | Piezocone Penetration CPTU-3 UBC 4 1 4 AUG 82 j | 7 | Piezocone Penetration CPTU-4 UBC 6 I 26 JAN 84 | 1 8 | Piezocone Penetration CPTU-5 UBC 8 I 26 SEPT 85 j 1 9 | Piezocone Penetration CPTU-6 ; UBC 26 SEPT 85 j 1 1 0 | Piezocone Penetration CPTU-7 HOG SUPER| 25 SEPT 86 | 1 11 | Piezocone Penetration CPTU-8 UBC 8 I 25 SEPT 88 | 1 12 | Seismic Cone Penetration SCPT-l(Acc) | UBC 8 ] 14 MAY 85 | 1 13 | Seismic Cone Penetration SCPT-2(Geo) UBC 6 ! 17 OCT 85 j 1 14 | Seismic Cone Penetration SCPT-3(Acc) UBC 8 8 JAN 86 | 1 15 | Seismic Cone Penetration SCPT-4(Acc) | UBC 8 16 OCT 86 | 1 16 | Seismic Cone Penetration SCPT-5(Geo) | UBC 6 14 MAY 86 j 1 17 | Seismic Cone Penetration SCPT-6(Geo) I HOG SUPER 2 JULY 87 | 1 18 j F l a t Dilatometer DMT-1 | MARCHETTI 14 MAY 80 j 1 I 9 | F l a t Dilatometer DMT-2 | MARCHETTI 2 OCT 86 | | 20 j F i e l d Vane FVT-1 | GEONOR 27 SEPT 83 | 1 2 1 j F i e l d Vane FVT-2 GEONOR 29 SEPT 83 1 - No seismic or piezocone data obtained 2 - No piezocone data obtained Acc - Accelerometer Geo = Geophone HOG SUPER => Hogentogler Super Cone SBPM = Hughes SBPM 3.2.2 Lulu Island UBC P i l e Research S i t e The Lulu Is.-UBC P i l e Research S i t e (PRS) i s located at the eastern end of Lulu Is. at the j u n c t i o n of Boundary and Dike Roads. A group of s i x p i l e s i n s t a l l e d by the B r i t i s h Columbia M i n i s t r y of Transportation and Highways have been used to study the a x i a l and l a t e r a l load behavior of p i l e s at the UBCPRS. Davies ( 1987 ) presents the r e s u l t s of t h i s study. The gently sloping s i t e i s covered by 2 to 4 m of heterogeneous f i l l . This f i l l was removed and replaced with clean r i v e r sand i n the 39 general area of the p i l e group to f a c i l i t a t e p i l e d r i v i n g and i n s i t u t e s t i n g . The water table i s approximately 1.5 m below the ground surface. The Lulu Is.-TJBCPRS i s located w i t h i n the p o s t - g l a c i a l Fraser River d e l t a . The s u r f i c i a l deposits to a depth of 15 m c o n s i s t of peat and organic clayey s i l t deposited i n swamp or marsh environment. The organic sequence i s underlain by a sand layer, representing a higher energy d e p o s i t i o n a l environment p o s s i b l y being a former channel bank of the Fraser River. A representative CPTU p r o f i l e of the top 15 m of s o i l i s shown i n F i g . 3.3. The time f o r 50 % d i s s i p a t i o n of pore pressure measured behind o a 10 cm area cone t i p from several CPTU soundings i s also included. The low cone bearing values and high f r i c t i o n r a t i o s between approximately 2.5 and 5.0 m depth suggest and organic clayey s i l t with some peat l a y e r s . A water content of 269 % and an organic content of 27 % by weight was obtained f o r a s o i l sample from 3.0 m depth. Below a depth of 5.0m the cone bearing increases i n an approximately l i n e a r fashion with depth suggesting a normally consolidated s o i l deposit. Between 11.5 and 13.5 m , several small spikes i n the cone bearing p r o f i l e suggest the presence of perhaps s l i g h t l y more dense s i l t or discontinous s i l t y f i n e sand l a y e r s . The material properties of the organic clayey s i l t l a y e r i s given i n Table 3.3 and the i n s i t u tests performed at Lulu Is.-UBCPRS are given i n Table 3.4. The locations of the i n d i v i d u a l i n s i t u t e s t performed are included i n appendix VI. U B C I M S I T U T " E S T I M G Site Location! Lulu Is. UBCPRS . CPT Data i 09/10/86 Pago Noi 1 / 2 On Si to Loci PLTSCPT2 Cona Usadt Hog Supar StdPP CoRimantsi CPT3 PORE PRESSURE SLEEVE FRICTION CONE BEARING FRICTION RATIO DIFFERENTIAL P.P. INTERPRETED Dopth Increment • .025 m Max Dopth i 16 m F i g . 3.3 : T y p i c a l CPTU P r o f i l e at Lulu Is. - UBCPRS 4 1 Table 3.3 : S o i l Properties at Lulu Is.-UBCPRS S p e c i f i c Gravity : 2.7 Natural Water Content (%) : Range 64-86 Average 69 L i q u i d L i m i t (%) : Range 49-90 Average 64 P l a s t i c L i m i t (%) : Range 38-50 Average 42 P l a s t i c i t y Index (%) : Range 10-47 Average 21 S e n s i t i v i t y ( f i e l d vane ) : Range 3-19 Average 11 Coef. of Consolidation (cm2/s) : Range 0 032-0.070 ( 2 oedometer tests ) Average 0.05 Table 3.4 : In S i t u Tests Performed at Lulu Is.-UBCPRS No. In S i t u Test Name In S i t u Device Date 1 Seismic Cone Pressuremeter UBC SCP-1 1 UBC SCP 3 APR 87 2 Seismic Cone Pressuremeter UBC SCP-2 UBC SCP 8 JAN 88 2 Self-Boring Pressuremeter SBPM-1 SBPM 11 FEB 87 4 Self-Boring Pressuremeter SBPM-2 SBPM 19 FEB 87 5 Piezocone Penetration CPTU-1 UBC 6 13 JUNE 84 6 Piezocone Penetration CPTU-2 UBC 6 13 AUG 85 7 Piezocone Penetration CPTU-3 HOG SUPER 9 OCT 86 8 Piezocone Penetration CPTU-4 HOG SUPER 31 OCT 86 9 Seismic Cone Penetration SCPT-l(Acc) UBC 8 8 OCT 86 10 F l a t Dilatometer DMT-1 MARCHETTI 23 AUG 85 11 F l a t Dilatometer DMT-2 MARCHETTI 29 AUG 85 12 F i e l d Vane FVT-1 NILCON 31 OCT 86 1 - No seismic or piezocone data obtained 3.2.3 Langley Lower 232 The Langley Lower 232 s i t e i s located at the 232 s t r e e t e x i t of the Trans Canada Highway i n Langley. The s i t e i s north of the highway and 42 west of the overpass. The water table i s approximately 1 m below the gently sloping ground. The s i t e i s located at the western extent of the Fort Langley Formation. The Quaternary formation consists of marine s i l t s and clays deposited during the g l a c i a l regressions and are o c c a s i o n a l l y interbedded with sand lay e r s . Underneath the s i l t s and clays are dense glaciomarine sands and gravels. The f i n e grained s o i l s at the surface are overconsolidated due to d e s i c c a t i o n . A representative CPTU p r o f i l e of the Lower Langley s i t e i s shown i n F i g . 3.4. An over consolidated surface crust roughly 3 m t h i c k i s underlain by a r e l a t i v e l y homogeneous s i l t y c l a y deposit. The sharp increases i n cone bearing and negative pore pressures measured between 13 an 16 m i n d i c a t e the presence of several t h i n sand l a y e r s . An i n t e r l a y e r e d s i l t y c l a y and sand u n i t i s found below 23 m. The material properties of the s i l t y c l a y layer are given i n Table 3.5 and the i n s i t u t e s t s performed at Langley Lower 232 are given i n Table 3.6. The l o c a t i o n s of the i n d i v i d u a l i n s i t u t e s t s performed are included i n appendix VI. U B C I M S I T U T E S T I N G S i t e L o c a t i o n ! LANGLEY On SI t o Loci LOWER 232 CPT Date • J1-J9 -B7 18i 15 Cona Usedi HOG SUPER STO u Pago Noi 1 / 1 Comment*! C77-8713 5MMFILT PORE PRESSURE SLEEVE FRICTION U (a. of »at«r) (bar) 0 100 0 . 3 CONE BEARING Ot (bar) 10 20 30 FRICTION RATIO Rf (X) 40 0 5 DIFFERENTIAL P.P. RATIO AU/flt - .2 0 .6 O l — I — 1 — ' — ' — | 0 INTERPRETED PROFILE • ID • 2D 30* Depth Increment i .025 m Max Depth i 29.85 m F i g . 3.4 : T y p i c a l CPTU P r o f i l e at Langley Lower 232 SlHy Cloy O.C. near Surfocs Occasional Sand Lsnss 44 Table 3.5 : S o i l Properties at Langley Lower 232 S p e c i f i c Gravity 2.8 Natural Water Content (%) : Range - Average 45 L i q u i d Limit (%) : Range - Average 40 P l a s t i c L i m i t (%) : Range - Average 20 P l a s t i c i t y Index (%) : Range - Average 19 S e n s i t i v i t y ( f i e l d vane ) : Range 2-19 Average 11 Coef. of Consolidation(cm2/s) : Range .0002-.0003 ( 2 oedometer tes t s ) Average .00025 Permeability ( cm/s ) : 8*10-8 ( 1 BAT inflow t e s t @ 7.3 m ) Table 3.6 : In S i t u Tests Performed at Langley Lower 232 | No. j In S i t u Test J Name In S i t u j Device 1 Date j 1 1 | Seismic Cone Pressuremeter UBC SCP-1 UBC SCP | 10 DEC 87 | 1 2 | Piezocone Penetration CPTU-1 | UBC 4 | 24 NOV 83 | 1 3 | Piezocone Penetration CPTU-2 UBC 6 | 6 JULY 84 j 1 | Piezocone Penetration CPTU-3 j HOG SUPER j 7 NOV 87 | 1 5 | Piezocone Penetration CPTU-4 UBC 7 7 NOV 87 j 1 9 | Seismic Cone Penetration SCPT-l(Acc) j HOG SUPER j 7 NOV 87 | 1 io | F l a t Dilatometer DMT-1 j UBC DMT j 20 JUNE 84 j 1 11 | F i e l d Vane FVT-1 NILC0N | 17 NOV 83 j 1 12 j F i e l d Vane FVT-2 j NILCON j 11 JAN 84 | 1 13 j F i e l d Vane FVT-3 j NILCON j 20 JAN 84 j 1 14 | F i e l d Vane FVT-4 | NILCON j NOV 83 | 15 | F i e l d Vane FVT-5 NILCON 7 NOV 87 CHAPTER 4 THE INTERPRETATION OF THE PRESSUREMETER TEST 4.1 A n a l y t i c a l Approaches to the Pressuremeter Test An advantage of the pressuremeter t e s t i s that i t approximates the plane s t r a i n expansion of an i n f i n i t e l y long c y l i n d e r , a problem which has well defined e l a s t i c and p l a s t i c s o l u t i o n s . One of the f i r s t s o l utions to be applied to t h i s problem was by Bishop, H i l l and Mott (1945) who developed a theory to c a l c u l a t e the pressure required to i n f l a t e a sphere or c y l i n d e r i n an e l a s t i c - p l a s t i c s t r a i n hardening material. Menard i n i t i a l l y attempted to analyze the r e s u l t s of a pressuremeter t e s t i n a pre-bored hole using c a v i t y expansion theories but found that the r e s u l t s were h i g h l y s e n s i t i v e to s o i l disturbance. To overcome the problem of s o i l disturbance, Menard developed standardized t e s t techniques and d i r e c t l y c o r r e l a t e d pressuremeter data to foundation design. Gibson and Anderson (1961) developed an analysis f o r the Menard pressuremeter which assumed that the undrained response of a saturated s o i l could be approximated by a l i n e a r e l a s t i c p e r f e c t l y - p l a s t i c s t r e s s - s t r a i n r e l a t i o n s h i p . For c y l i n d r i c a l c a v i t y expansion, the undrained Young's modulus i n the e l a s t i c region of the pressuremeter t e s t can be obtained using : 46 AP AV E u " 2 - V o < 1 + *u ) 4.1 where 1 - i n i t i a l volume of the probe AV — increment of volume AP — increment of pressure E u,«/ U - undrained Young's modulus and Poisson's c o e f f i c i e n t Once the y i e l d pressure P y - P Q + S u has been reached, the following expression holds : ' G AV AV • 1 + In- 1 _ S V ^ u S u - _ P = P Q + S u 1 + ln\ - 1 — Y . 4.2 where P Q = i n s i t u h o r i z o n t a l stress G / S u - I r - r i g i d i t y index V = V Q + AV — current volumetric s t r a i n In d e r i v i n g equation 4.2, i t i s assumed that at the y i e l d pressure, the v e r t i c a l s t r e s s , az, i s intermediate between the r a d i a l , ar, and c i r c u m f e r e n t i a l ', Og, p r i n c i p a l stresses. The l i m i t i n g pressure at which i n f i n i t e expansion of the c y l i n d r i c a l c a v i t y occurs i s given by : P L " P o + s u I 1 + l n { x r 1 1 Combining equations 4.2 and 4.3 r e s u l t s i n : 4.3 P - P L + S u l n ' AV Vo P Q ' V G 4.4 In d e r i v i n g equation 4.2, Gibson and Anderson also assumed that when the borehole f o r the pressuremeter i s d r i l l e d , the s o i l s t r e s s i s reduced from P Q to q£*z where q£ i s the u n i t weight of the d r i l l i n g f l u i d and z i s the depth below the water table. Linear s o i l unloading i s assumed to occur and subsequent increases i n volume and pressure are 47 measured from t h i s reference state. Windle and Wroth (1977) rederived eq. 4.4 assuming that the pressure and volume i s measured from the i n For a SBPM t e s t i n an approximately e l a s t i c p e r f e c t l y - p l a s t i c s o i l , a p l o t of the pressure versus the na t u r a l logarithm of the current volumetric s t r a i n should y i e l d a s t r a i g h t l i n e r e l a t i o n s h i p from which the average undrained shear strength can be determined. This i s often r e f e r r e d to as the Windle and Wroth average strength method. Another major development i n the analysis of the pressuremeter t e s t i n cohesive s o i l s was by Palmer (1972), Ladanyi (1972) and Baguelin et a l (1972) ( hereafter described as the Palmer,Ladanyi and Baguelin analysis) who independently derived a s o l u t i o n which allowed the undrained s t r e s s - s t r a i n r e l a t i o n s h i p to be derived f o r a saturated s o i l f o r which no p r i o r assumption concerning the s t r e s s - s t r a i n r e l a t i o n s h i p needed to be made. Assuming that every element i n the s o i l follows the same s t r e s s - s t r a i n curve, the shear stress at the c a v i t y w a l l under plane s t r a i n conditions i s given by : s i t u pressure P Q and corresponding volume Vo of the pressuremeter. The following expression i s obtained : 4.5 a r - a 9 eg (1 + eff)(2 + e9) dP r 4.6 2 2 8 48 For small s t r a i n s t h i s equation reduces to : dP T " €g 4.7 dig The s t r e s s - s t r a i n r e l a t i o n s h i p of the s o i l can be d i r e c t l y derived from the pressuremeter t e s t r e s u l t s using a graphical technique often r e f e r r e d to as the "subtangeht method" (Baguelin et al,1972). A more recent trend i s to f i r s t e m p i r i c a l l y smooth or f i t pressuremeter data using a mathematical function such as a polynomial expression (Fyffe et a l , 1986) or hyperbolic expression (Arnold, 1981). A l t e r n a t i v e l y , mathematical expressions which assume a s p e c i f i c s t r e s s - s t r a i n r e l a t i o n s h i p f o r a s o i l can also be f i t t e d to pressuremeter data. Examples are Prevost and Hoeg's (1975) r e l a t i o n s h i p s f o r s t r a i n softening and hardening s o i l s and Denby's (1978) r e l a t i o n s h i p which assumes hyperbolic s t r e s s - s t r a i n s o i l behavior. The SBPM t e s t , which i n theory allows a pressuremeter membrane to be expanded i n a s o i l at close to i t ' s "at r e s t " conditions, i s p a r t i c u l a r l y w e l l s u i t e d f o r analysis by c a v i t y expansion theories. In contrast, the FDPM expansion curve i s d i f f i c u l t to analyze using c a v i t y expansion theory due to e f f e c t s of cone pressuremeter penetration and the complex stress and s t r a i n f i e l d s which are created around the pressuremeter probe. The analysis of the unloading p o r t i o n of the FDPM curve may be one s o l u t i o n to t h i s problem. Houlsby and Withers (1987) present perhaps the f i r s t attempt at developing c a v i t y contraction theory f o r an incompressible l i n e a r l y e l a s t i c p e r f e c t l y - p l a s t i c s o i l . Houlsby and Withers model the i n i t i a l i n s e r t i o n of the cone pressuremeter as an expansion of a c y l i n d r i c a l c a v i t y w i t h i n the s o i l . 49 The expansion phase of the pressuremeter t e s t i s modelled as a continued expansion of the same c y l i n d r i c a l c a v i t y . Expansion i s allowed to continue u n t i l large s t r a i n s and the l i m i t pressure, P^, are reached. Unloading i s assumed to occur from a known state of str e s s and to s i m p l i f y the mathematics, the Hencky or logarithmic d e f i n i t i o n of s t r a i n i s used f o r the c y l i n d r i c a l c a v i t y c o n t r a c t i o n a n a l y s i s . At the s t a r t of contra c t i o n the e n t i r e s o i l mass behaves e l a s t i c a l l y and the unloading curve follows a slope of 2G. Reverse p l a s t i c i t y i n i t i a l l y begins at the ca v i t y wall when the pressure i s equal to (P^ - 2 S U ) . As unloading continues, the p l a s t i c zone' moves outward from the c a v i t y and p l a s t i c unloading occurs along the curve defined by the following equation : S u P - P L - 2S U [ 1 + ln( sinh( e L - e)> - ln{sinh( — )}] 4.8 G where e - ln( 1 + AR/RQ} - l i m i t logarithmic s t r a i n Houlsby and Withers present two techniques to determine the undrained shear strength using the unloading a n a l y s i s . The f i r s t method involves d i f f e r e n t i a t i n g equation 4.8 with respect to e and m u l t i p l y i n g both sides of equation the equation by (e^ " O which r e s u l t s i n : U L - O dP de S u 4.9 where f - 4.10 tanh(£L - e) Since f i s close to one for reasonable values of (e^ - e), an estimate of S u can be made using a graphical technique s i m i l a r to the subtangent 50 method proposed by Baguelin et a l (1972) f o r the analysis of the expansion curve. The second technique involves s i m p l i f y i n g equation 4.8 by recognizing that f o r small values of ( c ^ - e), sinh(e T j - e) w i l l be approximately equal to one. The following equation r e s u l t s : Su P - P L - 2S [ 1 + l n { e L .- e) - ln( — } ] 4.11 G From a p l o t of the pressure, P, against ( - l n f e ^ - e}) a l i n e a r unloading curve with slope equal to 2S U should be obtained. Due to d i f f i c u l t y i n analyzing the FDPM t e s t t h e o r e t i c a l l y , i t i s expected that empirical c o r r e l a t i o n s w i l l be used to a large extent when i n t e r p r e t i n g the FDPM t e s t . One empirical use of FDPM data which has been v a l i d a t e d by f i e l d t e s t s i s the d e r i v a t i o n of the P-Y curve from the pressuremeter expansion curve f o r the purposes of p r e d i c t i n g l a t e r a l load capacity of p i l e s ( Brown, 1985, Robertson et a l , 1983,1986). 4.2 Factors A f f e c t i n g Pressuremeter Test I n t e r p r e t a t i o n 4.2.1 E f f e c t s of Pressuremeter I n s e r t i o n and Relaxation Period The i n s e r t i o n of any pressuremeter probe whether s e l f - b o r i n g or full-displacement w i l l create excess pore pressures. I d e a l l y the i n s e r t i o n of a SBPM should cause a minimal amount of disturbance and only a small excess pore pressure w i l l e x i s t . Canou and Tumay (1986) suggest that a t o t a l pressure or excess pore pressure increase of greater than 50 % over the "at r e s t " conditions during the s e l f - b o r i n g process i s i n d i c a t i v e of s o i l being forced away from the probe. The amount of r e l a x a t i o n time needed to allow pore pressures to come to 51 e q u i l i b r i u m w i l l depend on a s o i l ' s permeability. Several hours r e l a x a t i o n time are often needed even f o r s e l f - b o r i n g i n s e r t i o n performed c a r e f u l l y . The i n s e r t i o n of a cone pressuremeter when compared to SBPM i n s e r t i o n w i l l r e s u l t i n a greater amount of disturbance and la r g e r excess pore pressure. In F i g . 4.1 , Baguelin et a l (1978) compare the pressure expansion curves obtained i n s o f t c l a y from SBPM tes t s performed with no r e l a x a t i o n period and a long r e l a x a t i o n p e r i o d and a FDPM t e s t with no r e l a x a t i o n period. As expected, the FDPM l i f t - o f f pressure i s the highest followed by the SBPM t e s t with no r e l a x a t i o n period or time wait. Both cone pressuremeters used f o r t h i s study d i d not have the c a p a b i l i t y to measure pore pressures at the pressuremeter membrane/soil i n t e r f a c e thereby making a determination of the e f f e c t i v e stress conditions at the beginning and during a t e s t d i f f i c u l t . However, information from the p i e z o - l a t e r a l stress cone, the dilatometer and the piezoblade can a l l provide valuable i n s i g h t s into the t o t a l and e f f e c t i v e s t r e s s conditions present a f t e r cone pressuremeter penetration. Azzouz and Morrison (1988) present data obtained by the Massachusetts I n s t i t u t e of Technology (MIT) p i e z o - l a t e r a l s t r e s s cone (PLS) from te s t s i n lean s e n s i t i v e Lower Boston Blue c l a y and p l a s t i c non-sensitive Lower Empire c l a y . Both clays are l i g h t l y overconsolidated. The pore pressures measured immediately a f t e r cone penetration had stopped were a large percentage of the t o t a l stress ( > 85% f o r Boston Blue c l a y ). Furthermore, the e f f e c t i v e h o r i z o n t a l stress i n i t i a l l y decreased as the pore pressures d i s s i p a t e d and only a f t e r 52 SOFT CRAN CLAY 150 CL 100 V F i g . 4.1 E f f e c t of Pressuremeter In s e r t i o n Method and Relaxation Time on Pressure Expansion Curves ( a f t e r Baguelin et a l , 1978 ) 53 approximately 50 % d i s s i p a t i o n d i d the e f f e c t i v e h o r i z o n t a l stress increase again to the stress measured immediately a f t e r PLS i n s e r t i o n . Although the geometry of the dilatometer and cone pressuremeter are d i f f e r e n t , i t i s reasonable to expect that the e f f e c t s of probe i n s e r t i o n w i l l be s i m i l a r . Comparisons between the dilatometer l i f t - o f f pressure, P Q, and piezoblade pore pressure taken 15 seconds a f t e r penetration has stopped, suggest that the dilatometer P Q value i s dominated by the penetration pore pressures f o r normally consolidated or l i g h t l y overconsolidated clays (Campanella and Robertson,1983, Lutenegger,1988 ; F i g . 4.2). For h e a v i l y overconsolidated s o i l s , the pore pressures created by dilatometer i n s e r t i o n are a much smaller percentage of the dilatometer l i f t - o f f pressures as shown by F i g 4.3. The e f f e c t of varying lengths of r e l a x a t i o n time on l i f t - o f f pressures was assessed for data from Lulu Is.-UBCPRS using the UBC SCP. For the purposes of t h i s research, the r e l a x a t i o n p e r i o d has been defined to s t a r t when the cone t i p passes the s o i l horizon where the pressuremeter t e s t i s performed. However, pore pressures may s t i l l be generated along the c o n e - s o i l i n t e r f a c e . Quick t e s t s were begun 15-30 seconds a f t e r cone pressuremeter penetration stopped r e s u l t i n g i n approximately 1 1/4 to 1 3/4 minutes t o t a l r e l a x a t i o n time. This i s due to the f a c t that the middle of the pressuremeter body i s 1.34 m behind the cone t i p and the cone pressuremeter i s pushed at approximately 2 cm/s. The quick t e s t s were compared to t e s t s at about the same depth with r e l a x a t i o n periods of 7-13 minutes. The r e s u l t s , which are shown i n table 4.1, i n d i c a t e that the l i f t - o f f pressure decreases as the length of r e l a x a t i o n time increases. 54 DMT P 0 ( k Pa ) F i g . 4.2 : Comparison Between Dilatometer P Q and Penetration Pore Pressures from Piezoblade i n Normally Con- s o l i d a t e d and L i g h t l y Overconsolidated Clays ( a f t e r Luttenegger, 1988) DMT P 0 ( k P a ) F i g . 4.3 : Comparison Between Dilatometer P Q and Penetration Pore Pressures from Piezoblade i n Overconsolidated Clays ( a f t e r Lutenegger, 1988) 55 Table 4.1: E f f e c t of Relaxation Time on FDPM L i f t - o f f Pressures. | Depth j L i f t - o f f Pressure j Relaxation Time | j (m) j (kPa) j (min) | 4.8 1 H 7 | < 1 3/4 | | 4.75 1 98 | 7.5 | 1 7.9 1 160 | < 1 3/4 | | 7.75 1 H 2 | 9.7 | | 10.9 | 200 | < 1 3/4 | | 10.75 1 170 | 13 | | 14.0 1 304 | < 1 3/4 | | 13.75 1 »' 1 7.2 j Allowing pore pressures to d i s s i p a t e a f t e r cone pressuremeter penetration has h a l t e d w i l l also cause the s o i l surrounding the probe to consolidate. At Lulu Is.-UBCPRS the permeability of the s o i l i s hig h l y v a r i a b l e . As already ind i c a t e d i n Chapter 3, the time f o r 50 % d i s s i p a t i o n ( t^Q ) of excess pore pressures ranged from 90 to 5000 seconds f o r the pore pressure sensor located at the base of the cone t i p . For some of the FDPM tests with long r e l a x a t i o n periods, i t i s probable that a s i g n i f i c a n t amount of co n s o l i d a t i o n occurred before the te s t s were begun. Figure 4.4 shows t y p i c a l comparisons of quick t e s t s and t e s t s where pore pressure r e l a x a t i o n was allowed to occur. Although the t e s t s were performed at s l i g h t l y d i f f e r e n t s t r a i n rates, the steeper pressure expansion curves and higher l i m i t pressures f o r the tests with longer r e l a x a t i o n periods suggest that c o n s o l i d a t i o n can be of considerable importance when i n t e r p r e t i n g the r e s u l t s of FDPM t e s t s . 56 L U L U IS. U B C P R S P E A T i i i i i i i i i i i i i i i i i i i i i i i i i i i i i ' i i i i i i i i i i i i i i i i i i i | i i i i | i i i i 0 5 10 15 20 25 30 CAVITY STRAIN £ ( s ) L U L U IS. U B C P R S O R G A N I C C L A Y E Y S I L T i t i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i I i i i i I i i i i I i i i i I i i i i I i i i i 0 5 10 15 20 25 30 CAVITY STRAIN £ ( s ) F i g . 4.4 : E f f e c t of Relaxation Time on FDPM Tests at L u l u Is. - UBCPRS 57 In summary, i t i s reasonable to expect that the stress conditions immediately a f t e r cone pressuremeter i n s e r t i o n are dominated by penetration pore pressures. Furthermore, both the l i f t - o f f pressure and shape of the pressuremeter curve w i l l be a f f e c t e d by the changing stress conditions which occur during the r e l a x a t i o n period and therefore standardized t e s t methods should be used. 4.2.2 E f f e c t s of S t r a i n Rate Most c a v i t y expansion theories used to analyze pressuremeter t e s t r e s u l t s i n cohesive s o i l s are based on the assumption that the s o i l remains undrained during a t e s t . However, high gradients of excess pore pressure w i l l cause p a r t i a l c o n s o l i d a t i o n to occur f o r a supposedly undrained t e s t . For t h i s reason, pressuremeter te s t s are run quickly, often several hundred times f a s t e r than laboratory t e s t s . A detrimental e f f e c t of high s t r a i n rates i s that the viscous nature of the s o i l becomes more important. In p r a c t i s e i t i s very d i f f i c u l t to separate c o n s o l i d a t i o n and viscous e f f e c t s . Wroth (1984) conceptually presents how the r e s u l t s of a SBPM tes t i n an e l a s t i c p e r f e c t l y - p l a s t i c s o i l that obeys a Mohr-Coulomb f a i l u r e c r i t e r i o n could be a f f e c t e d by p a r t i a l c o n s o l i d a t i o n . Wroth suggests that p a r t i a l c o n s o l i d a t i o n w i l l increase the e f f e c t i v e stress state of the s o i l and increase the shear stress along the Mohr-Coulomb f a i l u r e surface. This w i l l r e s u l t i n an "undrained" shear strength which i s p r o g r e s s i v e l y increasing as f a i l u r e of the s o i l occurs. Eden and Law (1980) using data from a SBPM equipped with a pore pressure transducer mounted at the center of the pressuremeter membrane, present e f f e c t i v e stress curves from pressuremeter tests which support Wroth's hypothesis. 58 Numerical analysis has also been used Co model the e f f e c t s of p a r t i a l c o n s o l i d a t i o n and creep or viscous e f f e c t s on pressuremeter t e s t r e s u l t s (Anderson et a l , 1987; Baguelin et a l , 1986). Anderson et a l (1982) used a f i n i t e element method analysis and modelled the s o i l using the modified Cam cla y approach. P a r t i a l c o n s o l i d a t i o n was included using a B i o t type a n a l y s i s with pore pressure coupled to the skeleton behavior through the p r i n c i p a l of e f f e c t i v e s t r e s s . The e f f e c t s of d e v i a t o r i c creep were also included i n the a n a l y s i s . Consolidation and creep were analyzed separately and together. Increasing the amount of c o n s o l i d a t i o n during a pressuremeter t e s t r e s u l t e d i n an increase i n the l i m i t pressure and the derived S u using the Palmer, Ladanyi and Baguelin a n a l y s i s described i n se c t i o n 4.1 while increasing the amount of creep during a t e s t reduced the l i m i t pressure and S u. When analyzed together, the e f f e c t s . o f creep and con s o l i d a t i o n tended to cancel each other out. Several f i e l d studies have been done to assess the a f f e c t of s t r a i n rate on S u obtained from SBPM tes t s (Windle and Wroth, 1977; Fahey and Carter,1986 and Benoit and Clough,1986). Windle and Wroth (1977) tested s t i f f Gault c l a y using a four f o l d d i f f e r e n c e i n s t r a i n rate. No di f f e r e n c e i n S u was found using the Windle and Wroth average strength method. The peak Su derived from the Palmer, Ladanyi and Baguelin a n a l y s i s showed an increase of approximately 25 % as the s t r a i n rate was increased. Fahey and Carter (1986) reported that a 2 1/2 f o l d increase i n the s t r a i n rate d i d not change the Su obtained using the Windle and Wroth average strength method. Benoit and Clough (1986) found that f o r stre s s c o n t r o l l e d SBPM t e s t s , the Palmer, Ladanyi and Baguelin peak S u increased approximately 16 % when the stress increments were increased from 6.9 to 47.6 kPa/min 59 I t i s be l i e v e d that s t r a i n rate e f f e c t s w i l l be s i m i l a r f o r SBPM and FDPM t e s t s . One advantage of using the cone pressuremeter i s that 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 a s o i l can be estimated from the pore pressure d i s s i p a t i o n data obtained from the piezocone. I t i s l i k e l y that the e f f e c t s of p a r t i a l c o n s o l i d a t i o n w i l l be s i g n i f i c a n t f o r pressuremeter te s t s performed i n the clayey s i l t s at McDonald Farm and Lulu Is-. -UBCPRS since both piezocone pore pressure d i s s i p a t i o n p l o t s and oedometer tes t s give c o e f f i c i e n t s of co n s o l i d a t i o n which are r e l a t i v e l y high f o r a cohesive s o i l ( see Chapter 3 ). 4.2.3 E f f e c t s of Disturbance The e f f e c t of s o i l disturbance and s o i l remoulding i s of major importance when i n t e r p r e t i n g the r e s u l t s of pressuremeter t e s t s . Baguelin et a l (1978) t h e o r e t i c a l l y analyzed the e f f e c t of a remoulded zone of s o i l around the pressuremeter by modifying the Palmer, Ladanyi and Baguelin analysis so that i t used d i f f e r e n t s t r e s s - s t r a i n properties f o r the remoulded and unremoulded s o i l . The ana l y s i s i n d i c a t e d that although the i n i t i a l slope of the pressure expansion curve w i l l be reduced, the t h e o r e t i c a l l i m i t pressure should not be affe c t e d . For p r a c t i c a l l i m i t s of c a v i t y s t r a i n reached ( approx. 20 % ) , they also concluded that the p r a c t i c a l l i m i t pressure should not be a f f e c t e d when the s e l f - b o r i n g i n s e r t i o n and pressuremeter t e s t are performed with care. The i n s e r t i o n of a cone pressuremeter w i l l create much more disturbance than the proper i n s e r t i o n of a s e l f - b o r i n g probe and therefore, disturbance could p o s s i b l y reduce the p r a c t i c a l l i m i t pressure reached. 60 Disturbance can also s i g n i f i c a n t l y a f f e c t the derived undrained shear strength from a SBPM t e s t . Both Baguelin et a l (1978) and Prevost (1979) t h e o r e t i c a l l y showed that a remoulded zone around a pressuremeter probe w i l l r e s u l t i n a s t r e s s - s t r a i n curve with a higher peak S u. Eden and Law (1980) and Benoit and Clough (1986) showed that a s l i g h t l y oversized SBPM c u t t i n g shoe could cause s o i l s t r e s s r e l a x a t i o n and disturbance leading to an underprediction of the i n s i t u h o r i z o n t a l stress and overprediction of S u. Benoit and Clough found that SBPM tests with an oversized c u t t i n g shoe analyzed using the Palmer, Ladanyi and Baguelin method l e d to undrained shear strengths which were 60 - 100 % higher than S u determined from te s t s using a normal s i z e d c u t t i n g shoe. Wroth (1984) suggested that the Windle and Wroth method of determining the average undrained shear strength i s a s a t i s f a c t o r y method of determining S u and i n f e r s that the Palmer, Ladanyi and Baguelin analysis i s more s e n s i t i v e to the i n i t i a l s t r e s s and s t r a i n datum chosen. The e f f e c t of disturbance on the determination of shear modulus w i l l vary depending on how the shear modulus i s c a l c u l a t e d . Several d i f f e r e n t shear moduli can be obtained from SBPM t e s t r e s u l t s : 1. ) An i n i t i a l tangent or secant modulus can be c a l c u l a t e d from the pressuremeter expansion curve. 2. ) A derived modulus can be c a l c u l a t e d from the derived s t r e s s - s t r a i n curve. 3. ) An unload-reload loop during the loading stage can be used, G u r, or a reload-unload loop during the unloading stage, ^ru; Of these 3 techniques, the unload - reload modulus, G u r, i s considered as the most r e l i a b l e and l e a s t a f f e c t e d by disturbance ( Jamiolkowski et 61 a l , 1985). The i n s e r t i o n of a FDPM probe w i l l create considerably more disturbance that the i n s e r t i o n of a SBPM. Nevertheless, Hughes and Robertson (1985) present G u r values from SBPM and FDPM te s t s i n sand which are i n good agreement suggesting that at l e a s t f o r sands, G u r i s i n s e n s i t i v e to the method of pressuremeter i n s e r t i o n . 4.2.4 E f f e c t s of Pressuremeter L/D Ratio The analysis of pressuremeter t e s t r e s u l t s using c y l i n d r i c a l c a v i t y expansion theory w i l l be somewhat i n erro r due to the f i n i t e length of the pressuremeter. The problem w i l l be magnified f o r expansions taken to large s t r a i n s . For an incompressible e l a s t i c p e r f e c t l y - p l a s t i c s o i l the l i m i t pressure f o r s p h e r i c a l c a v i t y expansion w i l l be : P L - P o + 4/3 S u ( 1 + In I r ) 4.12a which w i l l be somewhat la r g e r than the l i m i t pressure f o r c y l i n d r i c a l c a v i t y expansion : P L ' P o + S u < 1 + l n T r > 4 - 1 2 b Baguelin et a l (1986) analyzed the influence of L/D r a t i o f o r an e l a s t i c p e r f e c t l y - p l a s t i c s o i l by simulating SBPM tes t s using f i n i t e element a n a l y s i s . The derived shear modulus, G, and undrained shear strength, S u, f o r various L/D r a t i o s are compared to Ĝ , and S u o o obtained f o r the i d e a l plane s t r a i n case. The r e s u l t s are given below : 62 Table 4.2 : Numerical Simulation of SBPM Tests with Varying L/D Ratio f o r E l a s t i c P e r f e c t l y - P l a s t i c S o i l ( a f t e r Baguelin et a l , 1986). L/D G/Gw | 1.23 S u / S u » I 1 - 2 2 The r e s u l t s of the numerical analysis i n d i c a t e that f o r a SBPM with L/D of 6, using c y l i n d r i c a l c a v i t y expansion theory w i l l lead to only a s l i g h t o v e r p r e d i c t i o n of G and S u > The influence of f i n i t e L/D r a t i o on FDPM t e s t r e s u l t s i s a f f e c t e d by the i n s e r t i o n of the cone pressuremeter. I f the i n s e r t i o n i s modelled using c y l i n d r i c a l c a v i t y expansion theory, the radius of the p l a s t i c zone f o r an e l a s t i c p e r f e c t l y - p l a s t i c s o i l i s given by Randolph and Wroth (1979) : Rp - r 0 ( I r >'5 4 - 1 3 where r Q = radius of the pressuremeter I r - r i g i d i t y index A t y p i c a l FDPM expansion of approximately 25 % c a v i t y s t r a i n would increase the radius of the e l a s t i c - p l a s t i c boundary to at l e a s t 1.25 r ( I r ) * ^ . In contrast, a t y p i c a l expansion of 15 % c a v i t y s t r a i n f o r a SBPM t e s t would r e s u l t i n a p l a s t i c zone radius of .57r ( I _ ) , ~ ' . r o x r' Table 4.3 compares the radius of the p l a s t i c zone with the length of the pressuremeter probe f o r the FDPM and SBPM probes used f o r t h i s research. Maximum expansions of 15 and 25 % c a v i t y s t r a i n are assumed f o r the SBPM 63 and FDPM probes r e s p e c t i v e l y and the s o i l r i g i d i t y index i s assumed to be equal to 200. Table 4.3 : E f f e c t of In s e r t i o n Method on the Radius of the P l a s t i c Zone f o r an E l a s t i c P e r f e c t l y - P l a s t i c S o i l . PM I I I I I I I | PM | PM | PM | Cavity | Max. Radius | R^ | | j Radius j L/D | Length j S t r a i n j of P l a s t i c j — j I I r I I \ I I P l a s t i c Zone | L | | | ( mm ) | | ( m m ) | ( % ) | P ^ ( m m ) | | UBC SCP | 22 | 5 | 120 | 25 | 389 | 3.24 | FUGRO CP j 22 I 10 j 220 j 25 j 389 j 1.77 | HUGHES SBPM I 37 I 6 I 222 I 15 I 298 I 1.34 I The high RpAp r a t i o f o r the UBC SCP suggests that c y l i n d r i c a l c a v i t y expansion i s not an accurate representation of the actu a l expansion occurring and therefore s p h e r i c a l c a v i t y expansion may be a more appropriate a n a l y s i s to use. 4.3 Comparison of SBPM and FDPM Tests FDPM and SBPM expansion-contraction curves are compared at s i m i l a r depths f o r Lulu Is.-UBCPRS and McDonald Farm i n Figs. 4.5 and 4.6. Si m i l a r s t r a i n rates were used i n a l l cases and unless otherwise noted the te s t s were begun a f t e r a short r e l a x a t i o n period of approximately 1 to 5 minutes duration. Several general observations can be made about the t e s t r e s u l t s . 1.) The shapes of the FDPM and SBPM expansion curves at both s i t e s are s i m i l a r f o r c a v i t y s t r a i n s greater than approxi- mately 5 %. 64 M C D O N A L D F A R M C L A Y E Y S I L T 600 H "i i i i i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i— r SCP 17.0 m UBC SCP 16.75 m HUGHES SBPM € «= 8.5 */min L/D«=5 t - -1 */min L/D-6 a J 1 1 1 i I i i i i |—i—i—i—i—|—i—i—i—i—|—i—i—i—r 0 5 10 15 20 25 CAVITY STRAIN £ ( % ) M C D O N A L D F A R M C L A Y E Y S I L T 900 19.0 m UBC SCP i =9.1 */min L/D=5 18.75 m HUGHES SBPM i =-1 « / m i n L/D=6 19.2 m FUGRO CP t = 5 */min L/D=10 1 1 ' I I I I I I I I I I I I | I I I I I I I I I 0 10 20 30 CAVITY STRAIN £ ( g ) F i g . 4.5a,b : Comparison of FDPM and SBPM Tests at McDonald Farm 65 M C D O N A L D F A R M C L A Y E Y S I L T 1 0 0 0 T—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—j—i—i—i—r a SBPM 22.0 m UBC SCP £ - 8.1 «/min L/D=5 21.75 m HUGHES SBPM i «= 10 «/min L/D=6 5.0 */min L/D=10 22.2 m FUGRO CP £ = 0 1 I I I I I I I I I | I I I I I I I I I | I I I I I I I I I | I I I I 0 10 20 30 CAVITY STRAIN £ ( s ) M C D O N A L D F A R M C U V Y E Y S I L T 1000 o CL 3 00 00 LU or C L i i i i i i i i i i i i i T~ i ~r i I i i r i i •~r ~ b . • - - it**-«*" j a i — / ' •f s ^ — • - - 25.0 m UBC SCP £ • 7.0 */min 24.75 m HUGHES SBPM e =-10 */min L/D=5 L/D=6 i i i i I i 1 1 1 | 1 1 I 1 | 1 I i i I 1 1 1 1 5 1 0 1 5 2 0 CAVITY STRAIN £ ( % ) 2 5 F i g . 4 .5a,b : Comparison of FDPM and SBPM Tests at McDonald Farm 66 LULU IS. UBCPRS PEAT i i i i i i i i i i—i i i i i—i—i i i i i i—i i i—i i i—r a 4.8 m HUGHES SBPM I a 4.3 «/min 4.8 m UBC SCP t = 10.8 %/mm ' I I I I | I I I I | I I I I | I I I I | I I I I | I I I I 0 5 10 15 20 25 30 CAVITY STRAIN 6 ( % ) LULU IS. UBCPRS ORGANIC CLAYEY SILT ' i i i i i i i i i i i i i i i i i i i i i i i i i i i i i b - " i i i i | i i i i | i i i i | i i i i | i i i i | i i i i ( 5 10 15 20 25 30 CAVITY STRAIN 6 ( * ) F i g . 4.6a,b : Comparison of FDPM and SBPM Tests at Lulu Is.-UBCPRS 6 7 LULU IS. UBCPRS ORGANIC CLAYEY SILT 3 0 0 o Q_ £ 1 5 0 - j CO cn LU on a. i i i i i i i i i i i i i i i i i i i i i i i i i i i i i a j 7.9 m UBC SCP fc - 10.6»/min 7.9 m HUGHES SBPM fc - 8.5 */min S C P 0 | I I 1 I | I I I I | I I I I | I I I I | I I I I | I I I 1 0 5 1 0 . 1 5 2 0 2 5 3 0 CAVITY STRAIN £ ( * ) LULU IS. UBCPRS ORGANIC CLAYEY SILT 3 0 0 I I I I I I I I I I I I I I I I I I I I I I I I I I I I I 9.4 m UBC SCP £ = 12.4*/min 9.4 m HUGHES SBPM £ = 12.1*/min S C P I I I ) | I I I I | I I I I | I I I I | I I I I | I I I I 0 5 1 0 1 5 2 0 2 5 3 0 CAVITY STRAIN 6 ( * ) F i g . 4.6a,b : Comparison of FDPM and SBPM Tests at Lulu Is.-UBCPRS 68 2. ) At low s t r a i n s the pressuremeter expansion curves are steeper f o r the SBPM t e s t s . 3. ) At Lulu Is.-UBCPRS, the SBPM expansion pressures are generally s l i g h t l y lower than those obtained f o r the FDPM probe. 4. ) At McDonald Farm, the SBPM expansion pressures are higher than those obtained f o r the FDPM probe. At low s t r a i n s the pressuremeter expansion curves are s i g n i f i c a n t l y steeper f o r the SBPM t e s t s . 5. ) Most of the FDPM expansion curves have a s l i g h t bump f o r c a v i t y s t r a i n s between 0 and 4 %. The probable cause of t h i s e f f e c t i s a combination of pressuremeter s t r a i n arm design , in-accurate zero readings f o r the s t r a i n arms and d i f f i c u l t y i n accurately determining the membrane c o r r e c t i o n at low s t r a i n s . This problem i s covered i n more d e t a i l i n Chapter 2. 6. ) As expected, lower p r a c t i c a l l i m i t pressures are obtained f o r the FUGRO CP with a pressuremeter L/D of 10 as compared to the UBC SCP with a L/D of 5. An i n t e r e s t i n g r e s u l t i s that the expansion pressures obtained f o r the SBPM probe at McDonald Farm are higher than the FDPM pressures but lower f o r tes t s performed at Lulu Is.-UBCPRS. A f a c t o r which may have le d to t h i s r e s u l t i s that the s e l f - b o r i n g procedure at Lulu Is.-UBCPRS probably produced a greater degree of disturbance than the s e l f - b o r i n g at McDonald Farm due to the d i f f i c u l t y encountered i n s e l f - b o r i n g through the fibrous peat and organic clayey s i l t at Lulu Is.-UBCPRS. Furthermore, the organic s i l t at Lulu Is.-UBCPRS i s a moderately s e n s i t i v e clayey s i l t which would be a f f e c t e d by disturbance to a greater degree than the s l i g h t l y s e n s i t i v e clayey s i l t at McDonald Farm. FDPM, SBPM and dilatometer l i f t - o f f pressures are compared f o r a l l three t e s t s i t e s i n F i g . 4.7. The pressuremeter l i f t - o f f pressures f o r a l l t e s t s were obtained by v i s u a l l y determining the l i f t - o f f f o r each s t r a i n arm and then taking the average. Unless otherwise noted, the 15- M C D O N A L D FARM LIFT OFF PRESSURE ( kPa ) 200 400 600 800 1000 i i ,| I i i i I i i i I i i i I • i L U L U IS. U B C P R S LIFT OFF PRESSURE ( kPa ) DILATOMETER PO 20 H 25H UJ Q 30 H 35- * FUGRO CP • UBC SCP ~ 1.5 MIN RELAXATION a HUGHES SBPM • ' ' ' I ' i i i i i i i 20- 100 200 300 ' I i I ' ' ' I i • i ' • 1 400 DILATOMETER PO * UBC SCP -1.5 MIN RELAXATION + UBC SCP~7-13 MIN RELAXATION a HUGHES SBPM ' I ' i i i i ! 5H 10H Q. LU a L A N G L E Y LOWER 2 3 2 LIFT OFF PRESSURE ( kPa ) 150 300 450 600 ' ' I l I I i i I I i • • • l DILATOMETER PO 15-1 v>u. + UBC SCP ~ 7-30 MIN RELAXATION on- I I I I i l I I i i i t I I I I i i • M , F i g . 4.7 : Comparison of FDPM, SBPM and Dilatometer L i f t - o f f Pressures 70 pressuremeter t e s t s were performed a f t e r short r e l a x a t i o n periods of approximately 1 to 5 minutes duration. The SBPM l i f t - o f f pressures are i n general s l i g h t l y lower than the FDPM l i f t - o f f pressures and at McDonald Farm, the SBPM l i f t - o f f pressures are s i g n i f i c a n t l y more v a r i a b l e than the FDPM r e s u l t s . The v a r i a b i l i t y of the SBPM l i f t - o f f pressures and the f a c t that f o r numerous t e s t s the SBPM and FDPM r e s u l t s are almost the same suggests that the i n s e r t i o n of the SBPM may have created a s u b s t a n t i a l amount of disturbance. The dilatometer and FDPM l i f t - o f f pressures are d i f f i c u l t to compare due to the differences i n probe geometry and the way l i f t - o f f pressures are measured. For a l l s i t e s , the dilatometer l i f t - o f f pressures are higher than the FDPM values. This may be due i n part to shorter r e l a x a t i o n period f o r the dilatometer t e s t and smaller amounts of s t r e s s r e l a x a t i o n occurring during dilatometer penetration due to the le s s abrupt change i n geometry between the t i p and blade of the dilatometer. The p r a c t i c a l l i m i t pressure, P^, i s defined as the pressure at 20 % c a v i t y s t r a i n f o r the FDPM probes and 15 % f o r the SBPM probe at Lulu Is.-UBCPRS and 10 % at McDonald Farm. For pressuremeter t e s t s i n which the maximum c a v i t y s t r a i n obtained was s l i g h t l y l e s s than 10,15 or 20 %, the pressuremeter expansion curves were extrapolated to the required s t r a i n by eye. The p r a c t i c a l l i m i t pressure obtained using the FDPM and SBPM and the dilatometer P^ value are compared f o r a l l three s i t e s i n Fig . 4.8. A good comparison between the FDPM and dilatometer i s obtained. M C D O N A L D FARM PRACTICAL LIMIT PRESSURE ( kPa ) 0 300 600 15- 20- 25- 30 35 J I I 1 1 1 L 900 1200 _J I i_ DILATOMETER P1 • P20 FUGRO CP • P20 UBC SCP aP10 HUGHES SBPM i i « I I I 1 1 1 1 L 5- 10- 15- 20- L U L U ISLAND - U B C P R S PRACTICAL LIMIT PRESSURE ( kPa ) 125 250 375 500 ' i i i I i i i ' I i i i i l i i i i —DILATOMETER PI - • P20 UBC SCP *- 1.3 MIN RELAXATION • P20 UBC SCP ~ 7-13 MIN RELAXATION OP15 HUGHES SBPM i i i i i i i i i i i i i i i i I i i L A N G L E Y LOWER 2 3 2 PRACTICAL LIMIT PRESSURE ( kPa ) 0 200 400 600 0-1—I—I—X—I—I I I I I i i I i 5- 10- a. Ld a 15- 20- DILATOMETER PI + P20 UBC SCP 7-30 MIN RELAXATION - I — I — I — I I 1 I • t i t J i F i g . 4.8 : Comparison of FDPM and SBPM P r a c t i c a l Limit Pressures and Dilatometer Values 72 4.4 Parameters Obtained from the Pressuremeter Test The r e s u l t s of FDPM and SBPM tes t s are used to determine four geotechnical parameters: undrained shear strength, shear modulus, i n s i t u h o r i z o n t a l stress and stress h i s t o r y . The main focus of t h i s s e c t i o n of the the s i s i s to ex p l a i n the methods employed and the assumptions made i n determining these parameters. To a l e s s e r extent, a review has been made of comparisons between parameters obtained using the pressuremeter and other i n s i t u and lab t e s t s . 4.4.1 Undrained Shear Strength There are two approaches which can be used to obtain the undrained shear strength from pressuremeter t e s t s ; a t h e o r e t i c a l approach based on c a v i t y expansion or contraction theory or an empirical approach. Both approaches are considered i n t h i s t h e s i s . The undrained shear strength i s t h e o r e t i c a l l y obtained using the following methods : the Windle and Wroth average strength method f or the a n a l y s i s of SBPM and FDPM expansion curves, the Palmer, Ladanyi and Baguelin method using pressuremeter data e m p i r i c a l l y f i t using a hyperbolic equation as suggested by Arnold (1981) f o r the analysis of SBPM expansion curves and the Houlsby and Withers (1987) unloading method f o r the analysis of FDPM contr a c t i o n curves. Since the stress conditions are unknown at the beginning of a FDPM t e s t , s t r i c t l y c a v i t y expansion methods should not be used f o r FDPM t e s t s . Nevertheless, there are i n d i c a t i o n s which suggest that a reasonable estimation of S u can be made despite the disturbance created by FDPM i n s e r t i o n . In s e c t i o n 4.2 , comparisons of SBPM and FDPM tes t s performed at the same depth indi c a t e that the expansion curves are s i m i l a r f o r c a v i t y s t r a i n s greater than 5 73 %. Also encouraging are good comparisons between S u determined from SBPM and PIP tes t s using the Windle and Wroth average strength method (Fyffe et a l , 1982). The Windle and Wroth average strength technique i s shown i n F i g . 4.9 f o r t y p i c a l SBPM and FDPM t e s t r e s u l t s . The current volumetric s t r a i n i s r e l a t e d to the c a v i t y s t r a i n by the following equation : AV 1 1 4.13 V Q + AV (1 + eg)2 The Arnold (1981) type 1 analysis uses a hyperbolic r e l a t i o n s h i p ; €8 P - Q + 4.14 a + beg to e m p i r i c a l l y f i t the pressuremeter curve. The value Q represents the o f f s e t on the pressure axis and i d e a l l y represents the i n s i t u h o r i z o n t a l s t r e s s while the parameters a and b are obtained by a numerical procedure using three points from the experimental expansion curve. The s t r e s s - s t r a i n curve i s derived assuming small s t r a i n s (equation 4.7). The following equation r e s u l t s : aeg T _ 4 1 5 ( a + be& )2 A point which i s often overlooked i s that f o r even r e l a t i v e l y small s t r a i n s equation 4.15 w i l l s i g n i f i c a n t l y underpredict the shear s t r e s s . For example, at 10 % c a v i t y s t r a i n the shear s t r e s s i s underpredicted by approximately 16 %. For t h i s reason the Arnold type 1 analysis has been s l i g h t l y modified to allow the s t r e s s - s t r a i n curve to be derived using 74 HUGHES SBPM Site : Lulu Is. UBCPRS Depth : 6.35 m Dote : 11/2/87 0.1 1 10 100 LOG CURRENT VOLUMETRIC STRAIN x UBC SCP Site : Lulu Is. UBCPRS Depth : 6.35 m Dote : 3/4/87 0.1 1 10 100 LOG CURRENT VOLUMETRIC STRAIN % F i g . 4.9 : Determination of Undrained Shear Strength using the Windle and Wroth Average Strength Method 75 the more accurate equation 4.6. The r e s u l t i n g equation f o r the shear st r e s s i s : ae ( 1 + e ) ( 2 + e ) T 4.16 2 ( a + be ) 2 A SBPM expansion curve f i t t e d using a hyperbolic r e l a t i o n s h i p and the r e s u l t i n g s t r e s s - s t r a i n curve i s shown i n F i g . 4.10. The process of f i t t i n g a hyperbolic curve to the expansion pressure-cavity s t r a i n data i s n a t u r a l l y a subjective process which becomes more d i f f i c u l t as the pressuremeter data deviates from the hyperbolic form. The l a s t t h e o r e t i c a l technique used i s the Houlsby and Withers unloading a n a l y s i s . Figure 4.11 i l l u s t r a t e s how a l i n e a r curve with slope equal to 2S U f o r c y l i n d r i c a l unloading i s obtained when the pressure i s p l o t t e d against ( - l n { e L - e) ), where e L i s the l i m i t s t r a i n . Figure 4.11 also shows how the r i g i d i t y index can be obtained. Two empirical methods are used to determine S u from FDPM and SBPM te s t s . The f i r s t method involves using a r e l a t i o n s h i p often used i n the analysis of Menard pressuremeter data : 4.17 where P^ — l i m i t pressure as defined as the pressure at AV / (V Q + AV) - 1 Amar et a l (1975) reported that a N fa c t o r equal to 5.5 r e s u l t s i n a S u which compares well to f i e l d vane and t r i a x i a l t e s t S u f o r s o f t ( S u < 50 kPa ) cohesive s o i l s . For t h i s research the p r a c t i c a l l i m i t pressure as defined i n se c t i o n 4.2 i s used i n equation 4.17. The N f a c t o r i s found using the f i e l d vane as the reference S . HUGHES SBPM 11/2/87 Lulu Is. UBCPRS Depth = 6.35 m 200 | 190 - ~l 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 2 4 6 B 10 12 U 16 18 Covfty Strain (X) — — Data Points + Arnold Curve Fit F i g . 4.10 : Determination of the S t r e s s - s t r a i n Curve using the Modified Arnold Type 1 Analysis 77 UBC SCP 27/1/87 McDONALD FARM Houlsby Cylindrical Unloading D = 22 m 0 2 4 6 8 10 - l n ( E u - E) E=Natural Strain F i g . 4.11 : Determination of Undrained Shear Strength using the Houlsby Unloading Analysis 78 The second empirical method uses the following expression f o r S u : 4.18 The p r a c t i c a l l i m i t pressure i s again used f o r P^. Although t h i s method i s v i r t u a l l y i d e n t i c a l to the common r e l a t i o n s h i p f o r the piezocone which uses q t i n place of P^ i n equation 4.18, i t i s f e l t that using the FDPM t e s t data may help confirm the S u obtained j u s t using the cone bearing. The v a l i d i t y of t h i s method i s supported by the consistent r e l a t i o n s h i p between q t and P2Q f o r normally consolidated s o i l s as shown i n F i g . 4.12. Ratios ranging from approximately 1.3 to 2.0 were found f o r the three t e s t i n g s i t e s . In general, pressuremeter undrained shear strength obtained using c a v i t y expansion methods are s i g n i f i c a n t l y higher than S u obtained using other i n s i t u or laboratory t e s t s . Table 4.4 i s a comprehensive review of experimental t e s t r e s u l t s comparing the s e l f - b o r i n g pressuremeter to the f i e l d vane and t r i a x i a l t e s t . One r e s u l t f o r a prebored pressuremeter i s also included. For most t e s t comparisons, the pressuremeter S u i s between 1 and 2 times higher than the t r i a x i a l or f i e l d vane. Although not shown i n Table 4.4, the r e s u l t s from the Gothenburg s i t e tested by Wroth and Hughes (1974) and the San Francisco Bay - S i t e 1 tested by Clough and Denby (1980) in d i c a t e that as the clay approaches the normally consolidated c o n d i t i o n at depth, the pressuremeter strength i n c r e a s i n g l y becomes higher than the vane or t r i a x i a l strength. This e f f e c t may be due to s o i l anisotropy. As discussed i n sec t i o n 4.2, co n s o l i d a t i o n e f f e c t s , a remoulded s o i l annulus around the pressuremeter and c a v i t y expansion which i s not 1 MCDONALD FARM J L Qt / P» 1 J I I l_ J I l_ ••••• q, Avg. 8 CPT Teat*. P„ UBC SCP » » > q, Avg. 8 CPT Teat*. P„ Fugro CP —I 1 1 1 I I ' • 1 5H 0 . U J a 1SH 20- LULU IS. - U B C P R S qt / P» J I I L 2 J L .P a :UBC SCP 1.5 MIN RELAXATION +++*+* .Pa) :UBC SCP 7-13 MIN RELAXATION. J l_ J I L J l_ 0.0 10- C L U J O 15H 20- J I LANGLEY LOWER 2 3 2 qt / P» 1.0 2.0 1 1 1 I I u + H + + Sand Layer + q, ,P» .-UBC SCP 7-30 MIN RELAXATION J J I 1 I i i J L F i g . 4.12 : Comparison of Cone Bearing and FDPM P r a c t i c a l Limit Pressure Table 4.4: Comparison of Undrained Shear Strength fron Pressuremeter, F i e l d Vane and T r i a x i a l Teata Slca S o i l Type Type of PH Used Type of PK Teat P l a s t i c i t y Index Msthod of Interpreta- tion Number of PH Tests S u PH S u FV S u PH S u TC (UU) S u PH S u TC (CK0U) Reference Gothenburg Soft Clay Caabrldge Stress Controlled Palmer 6 1.3-2.5 Ulndle & Wroth SBPH 3.45 kPa/30 sec (1974) Cran Soft Clay PAFSOR - 80 • - 1.2 2.0 Anar et a l (1975) Cran Hed. P l a s t i c - 30 - 1.5 1.8 S l i t Plancoet Hed. S i l t - 20 • - .75 1.5 Provlna Soft Clay - 10 • - 1.25 1.67 Provlna A l l u v i a l S i l t • - - • - 1.25 1.67 with Peat Bosse Calln S t i f f Clay * - 80 - .78 Soft Clay * - 80 • - 1 .8 2.25 Lanestar P l a s t i c Clay m - - • .94 Begles Organic m - - - 1.43 • P l a s t i c Saint Andre Peat m Strain * • 5 1.04 Baguelin et a l de Cubzac Controlled (1972) Soft Clay 35 27 1.45 * Canvey Is. Soft S l l t y Cambridge Stress 45 5 1.22 Hughes et a l (1975) Clay SBPH Controlled Hadlngly S t i f f Cault » 44 U&U 18 1.0 Ulndle & Wroth Clay 13 1.3 (1977) Hendon S t i f f Sticky • 40 Clay Palmer NRC Site Soft Senal- • 36 3 1.3 Eden & Law (1980) ( Leda ) tlve Clay 9 .S kPa/aln 1.72 Hatagaml Pl a s t i c Clay • • 34 4 • 9 .8 kPe/mln South Soft Sensi- 29 • 5 1 .8 • Gloucester tive Clay 9.1 kPa/aln San Fran- Soft Clay • 45 Osnby 10 1.14 Clough & cisco S l t e l 3.AS kPa/30 aec Denby (1980) San Fran- Soft Clay m 30-35 • 15 1.43 1.11 • claco alte2 3.45 kPa/30 aac Onsoy Soft Clay • 2B+-8 tf&U 12 1.99 1.72 Lacaase et a l 9.1 kPa/aln (1981) Draoraen P l a s t i c Clay • 30 6 1.92 1.63 • • Porto Tolle S l l t y Clay - 30+-2 a 14 1.15 1.07 Chlonna et al(1981) Panlgaglla S l l t y Clay * - 47+-3 " 12 3-1.2 3.2-1.4 • Taranto S t i f f Hard - 27+-3 m 7 1.25 • Clay Burswood l a Soft Clay Stress Controlled - 12 1.85 Fahey & Carter 20 &. SO kPa/aln (1986) Bangkok Harlne Clay 0Y0 LLT - 60 46 1.20 Bergado & Prebored Khaleque (1986) PH - Pressureaeter Palmer - Derived S u Using Palmer, Ladanyi and Baguelin (1972) Hethod TC - T r i a x i a l Compression W&U - Ulndle and Uroth (1977) Average S u Hethod UU - Unconsolidated Undrained Denby - Denby (1978) S u Hethod Ck 0U - K Consolidated Undrained G&A - Gibson and Anderson (1961) S Hethod 81 t r u l y c y l i n d r i c a l w i l l a l l lead to an overprediction of S u and may be some of the reasons f o r the di f f e r e n c e s observed i n table 4.4. Furthermore, when comparing pressuremeter and t r i a x i a l t e s t s , a much higher s t r a i n rate i s generally used f o r pressuremeter te s t s and t h i s may lead to higher estimates of S u. The measured S u w i l l also be a f f e c t e d by the i n s i t u or laboratory method used and the stress path followed during a t e s t . Wroth (1984) states that the d e f i n i t i o n of S u as h a l f the d i f f e r e n c e between the major and minor p r i n c i p a l s t r e s s does not allow f o r the influence of the intermediate p r i n c i p a l stress and does not d i s t i n g u i s h between d i f f e r e n t types of tes t s which can r e s u l t i n d i f f e r e n t strengths f o r i d e n t i c a l s o i l samples. In an attempt to overcome t h i s problem, Wroth l i n k e d the r e s u l t s of d i f f e r e n t tests by r e l a t i n g S u / < 7 v o ' to the phi angle. For a normally consolidated s o i l he suggested a pos s i b l e p r o f i l e of strength would be as i n d i c a t e d i n F i g . 4.13. Ladd et a l (1979) suggested that the pressuremeter S u should l i e between the r e s u l t s of d i r e c t simple shear and plane s t r a i n compression t e s t s . 4.4.2 Shear Modulus The shear modulus obtained from an unload-reload loop, G u r, performed during the expansion phase of a pressuremeter t e s t appears to be the l e a s t a f f e c t e d by disturbance when compared to other d e f i n i t i o n s of shear moduli ( Jamiolkowski et a l , 1985). Assuming s o i l response i s l i n e a r e l a s t i c , c y l i n d r i c a l c a v i t y expansion theory can be used to obtain the following equation f o r G . 82 a) U k a l y v a r i a t i o n i n u n d r a l n a d b ) U k a l y M a r a r e n y 0 , u r # 3rain«cJ a t r a n g t h r a t i o f o r d i f f a r a n t t t r a n g t n r a t i o f o r d t f f a r a n t t a s t Mtnooa t a a t aatnotis TEST TYPES PH - P r a s s u r a matar K 0TC- K 0 c o n s o l i d a t a d t r i a x i a l comprassfon - P l a i d V a n * OSS - O t r a e t stmpla snaar 4.13 Hierarchy and V a r i a t i o n i n Undrained Strength Ratio f o r Various Test Methods ( adapted from Wroth, 1984) 8 3 AP ( 1 + e ) G u r - 4.19 2 Ae where e m — c a v i t y s t r a i n at the mid point of the unload-reload loop A d e r i v a t i o n of equation 4.19 i s found i n appendix IV. When performing an unload-reload loop, care must be taken not to exceed the " e l a s t i c " l i m i t of the s o i l . For an e l a s t i c p e r f e c t l y - p l a s t i c s o i l the maximum t h e o r e t i c a l amount of unloading which can occur before the i n i t i a t i o n of f a i l u r e at the c a v i t y wall i s AP = 2S U ( Wroth ,1982). In r e a l i t y s o i l behavior i s non l i n e a r even f o r the small s t r a i n increments used f o r unload-reload loops. Jamiolkowski et a l (1985) presented SBPM t e s t r e s u l t s f o r the Porto T o l l e and Panigaglia s o f t clay s i t e s which i n d i c a t e that G u r tends to increase as the s t r a i n increment at the c a v i t y wall decreases. Several researchers have attempted to show how the shear modulus attenuates with increasing shear s t r a i n f o r cohesive s o i l s . Two r e s u l t s are shown i n F i g . 4.14 i n which the shear modulus has been normalized by the dynamic small s t r a i n modulus. The Seed and I d r i s s (1970) average r e l a t i o n s h i p i s based on both c y c l i c and monotonic te s t s while the Kokusho et a l (1982) r e l a t i o n s h i p i s based on c y c l i c t r i a x i a l t e s t s . I t i s not c l e a r why there should be such a large d i f f e r e n c e between the two curves. Based on the data shown here, the r e l a t i o n s h i p between shear modulus and shear s t r a i n appears to be approximate and not w e l l defined. During a pressuremeter unload-reload loop, the s t r a i n increment i s measured at the c a v i t y w a l l . To allow a b e t t e r comparison of G u r with the data shown i n F i g . 4.14, the average s t r a i n increment i n the s o i l 84 SHEAR MODULUS ATTENUATION CURVES 0 . 0 0 0 1 0 . 0 0 1 0 . 0 1 0 . 1 1 1 0 SHEAR STRAIN y ( * ) F i g . 4.14 : Shear Modulus Attenuation Curves i n Cohesive S o i l s 8 5 should be determined. The author i s unaware of any published work which has addressed t h i s d i f f i c u l t problem f o r cohesive s o i l s . The use of G u r i s further complicated by the f a c t that the modulus depends, i n t e r a l i a , on the mean normal e f f e c t i v e stress state of the s o i l at the beginning of and during a t e s t i f drainage occurs. For a SBPM t e s t i n which drainage i s minimal, the e f f e c t i v e s t r e s s during a t e s t w i l l l i k e l y be close to the i n s i t u e f f e c t i v e s t r e s s state. In contrast, the i n s e r t i o n of a cone pressuremeter w i l l create high excess pore pressures and a low e f f e c t i v e s t r e s s state at the c a v i t y w a l l . Some drainage w i l l i n e v i t a b l y occur due the high pore pressure gradients surrounding the pressuremeter and therefore the average e f f e c t i v e stress w i l l be d i f f i c u l t to determine during a FDPM t e s t . For the purposes of t h i s research i t has been assumed that f o r both FDPM and SBPM t e s t s , the mean e f f e c t i v e stress stays approximately constant during a t e s t and i s equal to the i n s i t u e f f e c t i v e s t r e s s . A l l unload-reload loops were performed qu i c k l y with a f u l l loop taking place i n under 5 seconds. Most unload-reload loops were performed with no delay between expansion and the loop. A few tes t s were performed a f t e r a standing period of between 2 and 17 minutes. For the Fugro CP and Hughes SBPM the pressure remained constant during the creep phase while the c a v i t y s t r a i n increased. The opposite e f f e c t took place during the creep phase i n v o l v i n g the UBC SCP probe. The second method of determining the shear modulus involves u t i l i z i n g the r i g i d i t y index obtained using the Houlsby and Withers unloading a n a l y s i s f o r FDPM tests ( F i g . 4.11 ). The shear modulus i s c a l c u l a t e d using the undrained shear strength obtained f o r c y l i n d r i c a l unloading : 86 G u - I r S u 4.20 A drawback of t h i s method i s that i t i s d i f f i c u l t to accurately associate a s t r a i n increment with the modulus obtained. In general, shear moduli computed from SBPM tes t s are higher than those obtained from laboratory t e s t s . In only a few cases has G u r been compared to the r e s u l t s of laboratory t e s t s f o r cohesive s o i l s . Windle and Wroth (1977) and Kay and Parry (1982) compared SBPM G u r to G u r obtained from an unload-reload loop during UU t r i a x i a l t e s t s f o r London and Gault c l a y and found that the SBPM G u r were 2.5 to 3.0 times higher than those obtained during t r i a x i a l t e s t s . The r e s u l t s presented by Windle and Wroth (1977) also i n d i c a t e d that the SBPM Gur i s approximately equal to Gur measured during a pl a t e loading t e s t . Jamiolkowski (1985) compared Gur from SBPM tes t s i n s o f t clays at Porto T o l l e and Panigaglia to G^Q from" CKoU d i r e c t simple shear (DSS) tests and found that the SBPM modulus was approximately 1.5 to 3 times higher than the DSS modulus, the magnitude of the r a t i o being a f f e c t e d by the s i z e of the unload-reload volumetric s t r a i n increment used. Several f a c t o r s which l i k e l y contribute to the large d i f f e r e n c e s i n moduli are the e f f e c t s of c l a y anisotropy, the dif f e r e n c e i n s t r a i n rate or stress paths between SBPM and laboratory tests and the e f f e c t s of disturbance on moduli c a l c u l a t e d from laboratory t e s t s . 4.4.3 Stress H i s t o r y The piezocone has been used to a l i m i t e d extent to estimate the stress h i s t o r y or overconsolidation r a t i o ( OCR - a-p'/avo' ' a p ' = p r e c o n s o l i d a t i o n pressure ) of a cohesive s o i l . Much of the research to date has focused on c o r r e l a t i n g the B parameter : 87 Au B q 4.21 * t " a v o to the overconsolidation r a t i o ( Wroth, 1984; Jamiolkowski et a l , 1985; and Robertson et a l , 1985). S u l l y et a l (1988) proposed a new method to p r e d i c t OCR using the normalized d i f f e r e n c e i n pore pressure measured at the t i p , u^, and d i r e c t l y behind the t i p , U2> as defined by : u l * u2 PPD - : 4.22 u o The new method, c a l l e d the pore pressure d i f f e r e n c e or PPD method, appears to be quite promising f o r overconsolidation r a t i o s l e s s than 15. The author i s unaware of any published research i n which the r e s u l t s of pressuremeter tests are d i r e c t l y c o r r e l a t e d to the stress h i s t o r y of a cohesive s o i l . Two c o r r e l a t i o n methods are proposed which use the data obtained from a cone pressuremeter and seismic piezocone soundings. The f i r s t method r e l a t e s the p r a c t i c a l l i m i t pressure with OCR using the following expression : OCR - f > P L " *vo "vo 4.23 This method i s s i m i l a r to the c o r r e l a t i o n with OCR suggested by Wroth (1988) which uses the piezocone q t i n place of P^ i n equation 4.23. From information reported by Lacasse et a l (1981), Wroth c a l c u l a t e d values of ( q t - avo^/ avo' ^ o r depths of 2 to 20 m at Onsoy and p l o t t e d them against relevant values of OCR from oedometer tests ( F i g . 4.15 ). 88 F i g . 4.15 : V a r i a t i o n i n ( q t - S v o ) / S V Q ' with OCR at Onsoy ( a f t e r Wroth, 1988 ) 89 The r a t i o n a l f o r using equation 4.23 i s i d e n t i c a l to the one given by Wroth (1988) except that i s used i n place of q t since P^ appears to be proportional to q t . By modifying equation 4.23 so that : P L " CTvo P L _ a v o S u S u - N p 4.24 avo' S u Svo' CTvo' a b e t t e r a p p r e c i a t i o n i s given why equation 4.23 should be r e l a t e d to OCR. The undrained shear strength r a t i o S U / C T v o ' v a r i e s with OCR i n a wel l defined way. The r e l a t i o n s h i p between OCR and Np i s s i m i l a r to the r e l a t i o n s h i p between OCR and N^ t as w i l l be shown i n chapter f i v e . The second proposed method c o r r e l a t e s the r i g i d i t y index, I r , against OCR. From a comprehensive review of laboratory data by Wroth et a l (1984a), i t appears that I generally decreases with i n c r e a s i n g OCR. For some tes t s I r i n i t i a l l y increases s l i g h t l y and then decreases with in c r e a s i n g OCR. Figure 4.16 gives the r e l a t i o n s h i p between I r and OCR from CK QU DSS tes t s performed on three c l a y s . The d e f i n i t i o n of I r used i n t h i s research uses the average dynamic shear modulus, G m a x , obtained from dowhhole seismic t e s t i n g and the f i e l d vane S u. Seismic t e s t i n g was performed during some of the UBC SCP t e s t penetrations and during some of the seismic piezocone penetrations adjacent to the cone pressuremeter t e s t holes. The f i e l d vane S u was used since i t was f e l t that the f i e l d vane p r o f i l e s were more comprehensive and r e l i a b l e than the pressuremeter S u p r o f i l e s . The SBPM t e s t has become a w e l l accepted technique of determining the i n s i t u h o r i z o n t a l t o t a l stress of a s o f t cohesive s o i l , afa0, provided that the i n s t a l l a t i o n i s performed c a r e f u l l y and s u f f i c i e n t r e l a x a t i o n time i s allowed f o r stresses around the pressuremeter to Fig. 4.16 : Values of G/Su Plotted Against OCR from CKDU DSS Tests on Three Clays ( after Ladd and Edgers, 1972 ) 91 reach an equilibrium. Experience i n s t i f f clays i s more l i m i t e d ( Jamiolkowski et a l , 1985 ). Several techniques have been proposed f o r evaluating a n o from SBPM and Menard pressuremeter t e s t s . A comprehensive review of these methods are given by Lacasse and Lunne (1983) and Denby and Hughes (1982). Lacasse and Lunne (1983) suggested that the techniques a v a i l a b l e f o r determining a n Q could be divided into three classes of i n t e r p r e t a t i o n methods : approaches r e l a t e d to the d i r e c t measurement of the " i n i t i a l " or " l i f t - o f f " pressure; empirical approaches; and approaches which use the complete pressuremeter curve to determine the i n i t i a l pressure. Of these three classes, only the empirical approach i s v a l i d f o r the tests performed with the UBC SCP and Fugro CP probes because of the short r e l a x a t i o n times used and the large amount of disturbance created during the i n s e r t i o n of these probes. The same r a t i o n a l holds f o r the Hughes SBPM although i t i s l i k e l y that the disturbance created w i l l be le s s severe. The empirical approach i s based on the l i m i t pressure obtained f o r the i n f i n i t e expansion of a c a v i t y i n an e l a s t i c - p e r f e c t l y p l a s t i c s o i l ( Gibson and Anderson, 1961). The i n s i t u h o r i z o n t a l s t r e s s f o r c y l i n d r i c a l c a v i t y expansion i s : aho ' P L ' V 1 + l n { I r > > 4 - 2 5 while the equation f o r s p h e r i c a l c a v i t y expansion i s : aho " P L - 4 / 3 V 1 + l n ( I r ) > 4 - 2 6 The r e s u l t s of FDPM tests are analyzed using both equations 4.25 and 4.26 since i t i s f e l t that because of the e f f e c t s of the f u l l displacement i n s e r t i o n , s p h e r i c a l c a v i t y expansion may more c l o s e l y 92 model the actual expansion process. A drawback associated with the empirical approach i s that e r n o i s s e n s i t i v e to the values of the undrained shear strength and the r i g i d i t y index. For t h i s approach, the i n s i t u h o r i z o n t a l s t r e s s i s c a l c u l a t e d using S u and I r obtained from the Houlsby and Withers unloading analysis and the l i m i t pressure used i s the expansion pressure at 20 % c a v i t y s t r a i n . 93 CHAPTER 5 UNDRAINED SHEAR STRENGTH 5.1 Reference Undrained Shear Strength The f i e l d vane undrained shear strength has been chosen as the reference strength f o r t h i s research. The f i e l d vane t e s t i s c u r r e n t l y the most common i n s i t u method f o r measuring the undrained shear strength and has been proven to be a r e l i a b l e and h i g h l y repeatable t e s t method. There are also several disadvantages with the t e s t . Penetration through coarse grained or s t i f f cohesive s o i l s can damage the vane blades and therefore preboring i s u s u a l l y required through these types of s o i l s . Furthermore, the v e r t i c a l i t y of the vane penetration can not be c o n t r o l l e d or measured. The N i l c o n and Geonor f i e l d vanes used have vane height to diameter r a t i o of 2 as recommended by the standard according to ASTM ( ASTM D2573). The undrained shear strength i s c a l c u l a t e d using the standard expression : S u - 6T/7*D3 5.1 where T - applied torque D - diameter of the vane Several factors such as s o i l anisotropy, s t r a i n rate e f f e c t s , disturbance due to vane i n s e r t i o n and the length of time delay between vane penetration and shearing a l l a f f e c t the measured S u. A comprehensive disc u s s i o n of the importance of these f a c t o r s i s given by Grieg (1985). 94 Researchers such as Bjerrum (1973) and Aas et a l (1986) have proposed c o r r e c t i o n factors f o r f i e l d vane S u based on a review of excavation and embankment f a i l u r e s f o r which f i e l d vane strengths were a v a i l a b l e . They found that the t h e o r e t i c a l f a c t o r of safety d i f f e r e d from 1 and could be c o r r e l a t e d to the p l a s t i c i t y index of the cl a y . No c o r r e c t i o n f a c t o r s have been applied to the f i e l d vane data f o r t h i s research since the undrained shear strength obtained from pressuremeter tes t s i s not corrected. The undrained shear strength from the f i e l d vane and the normalized undrained shear strength p r o f i l e s f o r the three t e s t s i t e s are shown i n F i g . 5.1 and 5.2 r e s p e c t i v e l y . The S U / C T v o ' values at McDonald Farm and at Langley Lower 232 below 16 m are constant and in d i c a t e an approximately normally consolidated s o i l deposit. The small amount of s c a t t e r i n S u at Langley Lower 232 ind i c a t e s a r e l a t i v e l y homogeneous deposit. The S u and S u / c v o ' p r o f i l e s at Lulu Is. - UBCPRS are more d i f f i c u l t to i n t e r p r e t . In Chapter 3 i t was suggested that the s o i l p r o f i l e between 2.5 and 5.0 m consists of h i g h l y organic s i l t or. peat. This would account f o r the high S u's measured at these depths. Both Kaderabek at a l (1986) and Landva (1986) state that the f i e l d vane t e s t i n peat i s d i f f i c u l t to i n t e r p r e t and the S u obtained i s often e r r a t i c and higher than the S u obtained from other i n s i t u t e s t s . The high f i e l d vane undrained shear strength at 13 m depth may have been caused by a t h i n s i l t y sand layer. To help make a more accurate assessment of the reference undrained shear strength at Lulu Is.-UBCPRS, the cone bearing data from f i v e CPTU te s t s i s u t i l i z e d as shown i n F i g . 5.3. A cone f a c t o r of N k t equal to 10 15- MCDONALD FARM Su Field Vane ( kPa ) 25 50 75 i i i i » i i i i .1 i i t i l i i t 100 79 a. UJ a 23 +++++ Fvr-1 • • • • • FVT-2 70 1 1 1 ' ' ' 1 1 1 1 ' ' 1 ' ' ' ' 1 ' ' E . w 1 0 - 1 5 H 20- LULU ISLAND - UBCPRS Su Field Vane ( kPa ) 20 40 60 80 •1 I I I I I I I I I I I . • • • +++++ rvT-i • H 0.0 5H E a 15- 20 H 25- LANGLEY LOWER 2 3 2 Su Field Vane ( kPa ) 20.0 40.0 60.0 - I — I — I I I i i I I I I -R«f. S.-/ • * ••••a FVT— 1 t>i>>>> p/f—2 • o >B> ooooo FVT-3 L ° +++++ FVT-4 • o • ••••• FVT-5 a o - I — l — I — I — l — I — I I ' • • • • Fig. 5.1 : Field Vane Undrained Shear Strength 0.0 MCDONALD FARM Su Ft / Ovo' 0.2 15- 0.4 i i i i i- i i I t i i i i i i I i 0.0 + 20 H + H 25 H (S. / <W)» - 0.33 +++•+ FVT-1 •••••FVT-2 30- Woter Table - 1.0 m + • + + ' ' ' ' ' ' i i i i i i i 5H 10H 13H 20- LULU ISLAND - U B C P R S 1.0 2.0 J 1 1 1 I I i i • (S. / cj)m S 0.4 J •••••FVT-1 Water Table - 1.5 m J 1 1 l i • LANGLEY LOWER 232 s.w / o\.' 0.0 0.5 1.0 1.5 I I ' I I I I I I I I I I I I I 3H 10H O 15H 20 H 25- 2.0 •> • a • O-B OO o o > o O a o •> o •> o o o o aaaao FVT—1 p/T—2 oooooFVT-3 +•+++ FVT-4 ••••• FVT-5 (S. / °J)m - 0.26 J Water Table - 1.0 m i i i i i i i t i t t i i i i • i F i g . 5.2 : Normalized F i e l d Vane Undrained Shear Strength 97 LULU ISLAND - UBCPRS Su ( kPa ) 20 4 0 6 0 8 0 J I L J I L J I L J I L 1 0 - Q_ UJ O 1 5 - + + + + + F I E L D V A N E P R O P O S E D R E F E R E N C E S u A V G . S „ F R O M 5 C P T T E S T S U S I N G S u = ( q t - o \ o ) / N K t ; N „ t = 1 0 2 0 J l I I I I I i i i i ' ' ' ' F i g . 5. 3 : Proposed Reference S u For Lulu I s . UBCPRS 98 i s used to c a l c u l a t e S u since t h i s produced a good match between the f i e l d vane and CPTU data f o r depths greater than 5 meters. Using the combined data from the f i e l d vane and CPTU, a reference undrained shear strength f o r Lulu Is.-UBCPRS i s proposed. 5.2 T h e o r e t i c a l Methods Three t h e o r e t i c a l techniques of obtaining the undrained shear strength o u t l i n e d i n Chapter 4 were u t i l i z e d f o r t h i s study. The Windle and Wroth (1977) average strength and Houlsby and Withers (1987) (Houlsby f o r short) unloading analysis were applied to both FDPM and SBPM t e s t r e s u l t s while the Palmer, Ladanyi and Baguelin analysis using pressuremeter data e m p i r i c a l l y f i t using a hyperbolic equation as suggested by Arnold (1981) was used f o r SBPM t e s t data. A l l p l o t s showing the c a l c u l a t i o n of S u using these techniques are included i n appendices I to I I I . 5.2.1 Windle and Wroth Average Strength Method The undrained shear strength determined from the Windle and Wroth average strength technique i s shown i n F i g . 5.4. Unless otherwise indicated, a l l te s t s were performed with short r e l a x a t i o n periods equal to 1 to 5 minutes duration. At McDonald Farm the pressuremeter S u i s approximately 1.25 to 2.25 times higher than the reference S u. The superscript s i s used to d i s t i n g u i s h t e s t s run at approximately 5 to 10 % s t r a i n per minute from tes t s where the s t r a i n rate i s less than or equal to 2 %/min. I t appears that the slower tests r e s u l t i n a higher S u p o s s i b l y due to con s o l i d a t i o n occurring during the t e s t . The SBPM and FDPM undrained MCDONALD FARM S„ ( kPa ) 15- i i 50 I I I I 100 150 ' • t i l l 20- 25- 30- R«f. S. rv aooaaUBC SCP »*>»>»•»> FUGRO CP + • + • + H u g h 6 » SBPM SUPERSCRIPT S INDICATES TEST PERFORMED SLOWLY WITH A STRAIN RATE < 2 %/nin 35- • » • • • J I I I I I L U L U ISLAND - U B C P R S S„ ( kPa ) 0 25 50 75 100 p. | - 1 i i i I i i i i I I 1 i i I I I I I 5- 10- 15- 20- Re'* ^*/anm aooaaUBC SCP 1.5 min RELAXATION ••••• UBC SCP 7-13 min RELAXATION ••+++HughM SBPM i i i i i i i i i i i i ^ 5- 10- I us o 15- LANGLEY LOWER 2 3 2 S,, ( kPa ) 20 40 60 1 1 1 1 1 1 1 I 1 1 1 I 1 • • \ • ; R«f. S»iv-A • : SCP~7-30 min RELAXATION - i i i i i • i i i i i i i F i g . 5.4 : FDPM and SBPM Undrained Shear Strength from Windle and Wroth Average Strength Method 100 shear strengths are s i m i l a r and appear to increase at the same rate as the reference undrained shear strength. Furthermore, the s c a t t e r f o r the pressuremeter t e s t r e s u l t s i s s i m i l a r to that obtained f o r the f i e l d vane. At Lulu Is.-UBCPRS, the FDPM tests performed with short r e l a x a t i o n periods and the majority of the SBPM tes t s r e s u l t i n undrained shear strengths which are close to the reference S u. The low SBPM undrained shear strengths c a l c u l a t e d at depths equal to 9.4, 10.9 and 12.4 m were po s s i b l y caused by a r e l a t i v e l y greater amount of s o i l disturbance created by the i n s e r t i o n of the SBPM. As already noted i n Chapter 3, the organic nature of the s o i l deposit at Lulu Is.-UBCPRS makes the j e t t i n g technique of SBPM i n s e r t i o n d i f f i c u l t to accomplish without clogging of the s e l f - b o r i n g c u t t i n g shoe. I t appears that allowing a longer period of r e l a x a t i o n between penetration and actual t e s t i n g r e s u l t s i n higher undrained shear strengths f o r the FDPM t e s t . Furthermore, f o r several t e s t s a d d i t i o n a l problems i n i n t e r p r e t a t i o n were created by the period of creep allowed before an unload-reload loop was performed. I d e a l l y , no unload-reload loops should be performed f o r t e s t s i n which obtaining the undrained shear strength i s the primary objective. The measured undrained shear strengths at Langley Lower 232 are approximately twice as high as the reference undrained shear strength. The d i f f e r e n c e between the pressuremeter and reference S u would l i k e l y have been l e s s i f shorter r e l a x a t i o n periods had been used f o r the FDPM t e s t s . 101 5.2.2 Arnold Curve F i t t i n g Method The SBPM undrained shear strength c a l c u l a t e d using the Arnold curve f i t t i n g technique modified to allow f o r a more accurate d e r i v a t i o n of S u ( as discussed i n sec t i o n 4.4.1 ) i s shown i n F i g . 5.5. Comparative values of the modified and unmodified Arnold undrained shear strength can be found i n appendices I and I I . On average, the unmodified undrained shear strengths are approximately 5 % lower than the modified values. The S u obtained using the Windle and Wroth average strength technique i s included to allow a comparison of the two methods. At McDonald Farm and Lulu Is.-UBCPRS the modified Arnold method r e s u l t s i n undrained shear strengths which are generally s l i g h t l y higher than the Windle and Wroth method. This trend i s reversed f o r a few tests at shallow depths at Lulu Is.-UBCPRS. In general a good agreement was obtained between the two methods. At McDonald Farm, the curve f i t t i n g of the pressure-cavity s t r a i n data was made more d i f f i c u l t by the small number of data points acquired due to the l i m i t a t i o n s of the data a c q u i s i t i o n system used. Nevertheless, i t i s f e l t that the subjective process of the curve f i t t i n g leads to range of undrained shear strengths which i s no greater than 5 % of the given S u f o r most t e s t s . 5.2.3 Houlsby Unloading Method The undrained shear strength c a l c u l a t e d using the Houlsby c y l i n d r i c a l a n alysis of the FDPM unloading curve i s shown i n F i g . 5.6. At McDonald Farm and Lulu Is.-UBCPRS, the Houlsby undrained shear strength i s 55 to 75 % of the reference S u while at Langley Lower 232 the percent r a t i o ranges from 65 to 110 %. Furthermore, the Houlsby S u f o r McDonald Farm and Lulu Is.-UBCPRS increases with depth at a s i m i l a r MCDONALD FARM Su ( kPa ) 0 50 100 150 1 S | i i i i I i i i i I i i i i I. 20- 25 30- 35 +++++Windle and Wroth Avg. S, ••••• Arnold Curve Fit S» (modified) SUPERSCRIPT S KJtCATES TEST PERFORMED SUmY WITH A STRAIN RATE < 2 u/rrin i « I l l I I I 5- 10- 15- 20- LULU ISLAND - UBCPRS S„ ( kPa ) 25 50 75 100 i i-i i I i i i i I i i i i I i i i i Ref. Safv/tow - +•••• windle and Wroth Avg. S. ••••• Arnold Curve Fit S, (modified) l l • ' ' ' ' • ' i i ' ' F i g . 5.5 : SBPM Undrained Shear Strength from Arnold Curve F i t t i n g Method 15- McDONALD FARM S„ ( kPo ) 25 50 75 100 I I I I I > I I I » I I I I I I t L I 20- I 25- 30- • Ref. S, »y . 35- aaaaaUSC SCP e>**M> FUGRO CP i ' « l i t LULU ISLAND - UBCPRS S« ( kPa ) 0 20 40 60 i i i I i i i I i i i i i i 5- 10- 15- o o if a R«f. S, ft/tarn 80 LANGLEY LOWER 232 Su ( kPa ) oooooUBCSCP 1.5 min RELAXATION •••••UBC SCP 7-13 mln RELAXATION I i i i i i i i i i i i 5- 10- 15- 20- 20 40 60 J I I I I I I I I I I I • / : • / Ref. S , w • • \ - 1 1 1 i . l l l l .1. .1., i i I . . F i g . 5.6 : FDPM Undrained Shear Strength from Houlsby Unloading Method i 104 rate to the reference S u. In contrast, the Houlsby S u p r o f i l e at Langley Lower 232 does not have a s i m i l a r shape to the reference S u. For the te s t s near the ground surface at Langley Lower 232, the d i s - s i m i l a r shape may have i n part been caused by the d i f f i c u l t y i n estimating the S u due the non-linear nature of the unloading curve using the method ou t l i n e d i n Chapter 4 ( also see appendix III ). The generally low undrained shear strength from the Houlsby unloading a n a l y s i s can perhaps be a t t r i b u t e d to the s t r e s s paths followed during the t e s t . During unloading, the r a d i a l t o t a l stress r a p i d l y decreases and quickly becomes l e s s than the t a n g e n t i a l t o t a l s t r e s s . This i s somewhat analogous to the s t r e s s conditions during a t r i a x i a l extension t e s t and may explain why the Houlsby unloading undrained shear strengths are low. The r e s u l t s from a l l three s i t e s showed l e s s s c a t t e r than the reference S u from the f i e l d vane t e s t . This trend may have been caused by a p a r t i a l l o s s i n s o i l heterogenity during the loading p o r t i o n of the t e s t . Also i n t e r e s t i n g to note i s that i t appears that the amount of r e l a x a t i o n time before a t e s t i s performed does not s i g n i f i c a n t l y a f f e c t the undrained shear strength measured. 5.3 Empirical Methods The pressuremeter factors obtained using the f i r s t empirical method described i n s e c t i o n 4.4.1 are shown i n F i g . 5.7. The following equation was used to c a l c u l a t e N : S u - < P L - P o > / N 4-!7 P L - p r a c t i c a l l i m i t pressure S u •= reference Su 0.0 MCDONALD FARM N 2.0 4.0 6.0 8.1 I I I I I I ' • • I i • • »3 ooooo UBC SCP p-fft-f FUGRO CP ++•++ Hughes SBPM N - (P»-PJ N - (P»-PJ N - (V,»-PJ/ SUPERSCRIPT S INDICATES TEST PERFORMED SLOWLY WITH A STRAIN RATE ^ 2 a/mln J I J U J I I I I l _ 0.0 0 I ' 1 5- 1 0 - o. LU Q 1 5 - 2 0 - LULU IS. U B C P R S N 2.0 4.0 6.0 J I I I I I I I u a a *> • a + + a + a + o + a a + « aaaaa UBC SCP N - (P»-P.)/S. „/wm 1.5 min REUOGATION UBC SCP. N - (P»-P.)/S.r//w« 7-13 min RELAXATION +++•+Hughes SBPM N =• (PiB-Pj/S. „w J I I I L _L 0.0 0 - L - L 5- 10- 15- LANGLEY LOWER 2 3 2 N 2.5 5.0 7.5 i I i i i i I i i i i I i i i i 10.0 ••••• UBC SCP N - (P»-P.)/S, „ 7 - 3 0 min RELAXATKJN 2Q 1 1 1 1 1 1 I I I I I I I I F i g . 5.7 : FDPM and SBPM Pressuremeter Factor N - ( P L - P Q ) / S U R E F vs Depth 106 Assuming that the pressuremeter l i m i t pressure and the reference S u can be r e l a t e d using the above equation, i . e . , N i s independent of other s o i l c h a r a c t e r i s t i c s such as OCR, the i d e a l c o r r e l a t i o n would r e s u l t i n a N f a c t o r e x h i b i t i n g a minimal amount of sc a t t e r and remaining constant with depth. At McDonald Farm the c o r r e l a t i o n obtained using the UBC SCP i s quite good with a N value ranging between 2.5 and 3.0. The range f o r the Fugro CP i s 2.2 to 3.5. The SBPM N values show considerably more sc a t t e r then the FDPM N values at McDonald Farm. At Lulu Is.-UBCPRS, the les s homogeneous s o i l deposit r e s u l t s i n a N p r o f i l e with a l o t of sc a t t e r and a range from 2.25 to 5.25. The r e s u l t of varying amounts of r e l a x a t i o n time i s also quite noticeable f o r the tes t s with the UBC SCP. A poor c o r r e l a t i o n i s also obtained at Langley Lower 232 where N ranges from 4.5 to 8.5. The poor c o r r e l a t i o n over the f i r s t several meters at Langley Lower 232 i s perhaps due to the f i s s u r e d and p a r t i a l l y saturated nature of the overconsolidated s o i l i n h i b i t i n g the generation of large pore pressures and hence P2Q values. The r e s u l t s of the second empirical technique are shown i n F i g . 5.8. The q u a l i t y of the c o r r e l a t i o n between the pressuremeter and the reference undrained shear strength i s perhaps s l i g h t l y poorer than the f i r s t empirical method presented. The most consistent c o r r e l a t i o n i s f o r the FDPM tes t s at McDonald Farm where Np range from 3.4 to 4 f o r the Fugro CP and 4.2 to 5.1 f o r the UBC SCP. At Lulu Is.-UBCPRS the range i s between 3.7 and 6. Again a poor c o r r e l a t i o n i s obtained at Langley Lower 232 where Np ranges from 5 to 11.5. The r e s u l t s of the second empirical method at Lulu Is.-UBCPRS appear to in d i c a t e that t h i s method i s les s a f f e c t e d by the amount of 15- McDONALD FARM NP 0.0 2.0 4.0 6.0 8, I I I I I I I L_l I I I I 1 20- 25- UJ a 30- 8 s + +• DOODOUBC SCP » » » » » FUGRO +++++ Hughei SBPM fl, - (PV£)/SL w 35- SUPERSCRfT S INDICATES TEST PERFORMED SUDWLY WITH A STRAIN RATE 4- 2 */ndn I I I I I I I I I I I I I 5- 10- 0. U l Q 15- 20- LULU IS. UBCPRS 2 4 6 I I I I I I I I I i_ 4- a oaaaa UBC SCP 1.5 min RCI N.-(PJD-< lELAXATION - O / s . . E n/oam ••••• UBC SCP N,=(P»-0/S. FVAXXC 7-13 min RELAXATION +++++Hugh«9 SBPM N,=(Pi8-o«)/S, nr/tac I I I I I I I I I I I I I l 0.0 3- 10- 15- 20- LANGLEY LOWER 232 3.0 6.0 9.0 J I L. 12.0 UBC SCP N, - (Pa-oJ/S, n 7-30 min RELAXATION J I I l_ J I l_ o F i g . 5.8 : FDPM and SBPM Pressuremeter Factor N p - ( P L - a v o ) / S u vs Depth REF 108 r e l a x a t i o n time allowed when compared to the f i r s t e mpirical method. For both methods, standardizing the amount of r e l a x a t i o n time before a t e s t i s performed would make the i n t e r p r e t a t i o n of the t e s t s l e s s d i f f i c u l t . An advantage of the cone pressuremeter i s that the cone bearing and excess pore pressure measured during cone pressuremeter penetration can also be used to estimate the undrained shear strength. The t r a d i t i o n a l empirical expression f o r the undrained shear strength of cohesive s o i l s uses a bearing capacity type equation of the form : 1 c - S u N k + * v o 5 - 2 where q c - cone bearing - cone f a c t o r With the advent of the piezocone, the cone bearing i s u s u a l l y corrected f o r unequal end area e f f e c t s . The corrected cone bearing and corresponding cone f a c t o r are designated as q t and N̂ -p. r e s p e c t i v e l y . The cone f a c t o r w i l l depend on the type of t e s t used to obtained the reference undrained shear strength and the c h a r a c t e r i s t i c s of the cohesive s o i l tested. A wide range of values are reported i n the l i t e r a t u r e . From a review of the a v a i l a b l e l i t e r a t u r e , Greig (1985) suggests that there appears to be a general trend of decreasing cone f a c t o r with increasing p l a s t i c i t y index. For a given p l a s t i c i t y index, i t also appears that increases with increasing s e n s i t i v i t y . A more recent proposed method of c o r r e l a t i o n involves using the excess pore pressure i n the following equation ( Robertson et al,1985): N A u = A u / S u 5 - 3 where Au «- u - u Q 109 The N^ u measured w i l l depend on the l o c a t i o n of the pore pressure element on the cone and the s t i f f n e s s , s e n s i t i v i t y and s t r e s s h i s t o r y of the s o i l being tested. The values of and N^ u c a l c u l a t e d f o r t h i s study are shown i n f i g u r e 5.9 and 5.10. The N^ u c o r r e l a t i o n uses the excess pore pressure, U2, measured j u s t behind the cone t i p . The best and N^ u c o r r e l a t i o n s are obtained at McDonald Farm. The cone f a c t o r s are approximately constant with depth and are w i t h i n a narrow range. At Langley Lower 232 the and N^ u values show a moderate amount of s c a t t e r but vary considerably with depth i n approximately the same manner as the pressuremeter f a c t o r s N and Np do. At Lulu Is.-UBCPRS, the values vary over a large range. In contrast, the N^ u values are much more c l o s e l y spaced with the exception of the N^ u obtained from the UBC SCP probe at several depths. The d i f f e r e n c e i n q u a l i t y between the two c o r r e l a t i o n s can probably be p a r t i a l l y a t t r i b u t e d to the f a c t that i n the s o f t organic clayey s i l t the pore pressure transducer i s operating at 20 to 30 % f u l l output while the load c e l l measuring cone bearing i s operating at l e s s than 1 % f u l l output and therefore i s l e s s r e l i a b l e . The undrained shear strength e m p i r i c a l l y c a l c u l a t e d using the FDPM fa c t o r N and the cone f a c t o r are compared to the reference undrained shear strength i n F i g . 5.11. The FDPM N values are the c a l c u l a t e d average values from the p r o f i l e s i n F i g . 5.7. The r e s u l t s at McDonald Farm in d i c a t e an e x c e l l e n t c o r r e l a t i o n between the FDPM, cone and reference S u. At Lulu Is.-UBCPRS, a constant N^ t equal to 10 produces a cone S u p r o f i l e with a wide range. The c o r r e l a t i o n between the l i m i t e d number of FDPM S u's and the reference S u appears to be s l i g h t l y better. 15- 20- 25- McDONALD FARM N M J I L 10 I I I I 30- ooooo CPTU—1 O O O D O CPTU—2 - *>»»-»-»> CPTU-3 ooooo CPTU-4 ft**** CPTU-5 4 4 4 4 4 CPTU-6 KKKKM CPTU—7 ••••• CPTU-B <x»a*+ • ot>D •> O O D 4 «Oft>«- X o » a • 0*>D*» •>*•• + o Ma + o >a+ •> o ota + o NO+ o »• o ft* o »•» + o •*» + 15 ( Qt - or» ) - i r* 35- • ' i I I I I I I I I — I — I — L 5- i a 10- 15- 20- LULU IS. UBCPRS N« 5 10 15 20 25 I I I I I I I I I I 1 I I I I L I I I I I I I I > a •+ • a o » > <m 4 • >a o • + t>a o 4 • Oft- o • 4 a « *• a fto+ • a o i> • • •• «o+ a *• 4 o o • 4 oooaa CPTU—1 fr>>t>t» CPTU—2 ooooo CPTU-3 4 4 4 4 4 CPTU-4 UBC SCP-2 ' • ' ' ' • ' ' • • ' ' ' ' ' • ' i ' i i i i i 5- E a. Id a is- 20- 25- I I LANGLEY LOWER 232 Nkt 5 10 15 ' i I ' ' ' ' I i ' i ' l • 20 I I aaaaa CPTU-1 »>»>»>B>e> CPTU-2 ooooo CPTU-3 ••••• CPTU-4 4 4 4 4 4 UBC SCP • • +0-O a «+ o > > o> 4 0 >B> • 4 O + 0 • OH> + I I I I I I «•> t> + «a o*. • <11> 4 • a> ©• 4 • o-oa •> a + B>4H- 4 mo 4 o n of av • Oft- a « 4 4 - '''''' F i g . 5.9 : Cone Factor N k t - ( q t - * v o ) / S u R E F vs Depth 1 15- 20 H 25H 30 H MCDONALD FARM ( Ni„ >2 5 10 J I I I I i i I i 1 t t i • o» <•<><*• ••a ot> • « Ofr • •W O * • -K> <X> •+o <» •fa e * o » o * o » o •+ o +o « > •B «• HO l> 15 ooooo CPTU—1 O O O O D CPTU—2 SE™-? (N*)« - flu, / s,w •CPTU-4 ••••• CPTU-6 ••••• CPTU-8 35- J i_ -I I L -I I I I I L I O 15- 20- LULU ISLAND - U B C P R S 5 (N*j)2 i—i—i l i i u LANGLEY LOWER 2 3 2 10 J 1 I I I L 15 *> • » o « >•>• AU, tan- • M + o • • O O O D CPTU—1 »»»»» CPTU-2 ooooo CPTU-3 +++++ CPTU-4 •••••UBC SCP-2 J I I I I I I I I I I I I L 0 5 Q I I I I I I I 5-H 10H u 15H 20 H 25- (N«u)l 10 I I I 15 20 .1 I I I I i.i QWs - a o >• D O -a o - • t» oa - • t> o o - • i> oo - • t> oa - I> o • - • > «l - AU, - Sg PV o t» a - o a -o t> a -aaaaa CPTU-1 e»*e>t»t> CPTU-2 • CPTU-3 UBC SCP i i ' i » i wo • O I I I I I I I F i g . 5.10 : Cone Factor N A u - Au/S u R E F vs Depth 1 MCDONALD FARM S„ ( kPa ) 25 15 20- i a 25- 30- 35- 50 75 100 i i » ' I i i i i I i i i i I i i t i I Ref. S» n/ - RANGE OF S. FROM 8 CPT TESTS USING Ni •* 7.9 DDOQO t>t>t>»-t> UBC SCP SB-(P1»-P0/N : N-2.80T FUGRO CP S.=»(P,o-Pl;/N ; N»2.89. i i ' i i i i t i i i i i i i i i i i i 3- 10- LU a 13- 20- LULU IS. U B C P R S S„ ( kPa ) 20 40 60 _J I I I I i i i I LANGLEY LOWER 2 3 2 80 RANGE OF S, FROM 3 CPTU TESTS USING S» - (p,-a J/H, : NM - ID Ref. S« n/oom •DODO UBC SCP 5, - (P.-PJ/N ;N=>2.85 1.5 min RELAXATION UBC SCP S» - (P«,-P-)/N :N-4.5 7-13 min RELAXATION i - i.. i i i i i i i i i i i 0 0 I ' • 5- & a 10- 15- 20- S„ ( kPa ) 20 40 ' ' • • ' 60 I I I I -Ref. S. n RANGE OF S. FROM 5 CPTU TESTS USING S, - (q, - aJ/N*, ; Ntt a 13 ••••• UBC SCP S. - (P.-PJ/N ;N=6.44- 7-30 min RELAXATION J—I I—I l I I I i i t i t F i g . 5.11 : Comparison of S u using FDPM Factor N and Cone Factor N| I 113 At Langley Lower 232, a f a i r c o r r e l a t i o n i s obtained between the FDPM, cone and reference S u but unfortunately the pressuremeter and cone S u p r o f i l e does not follow the same trend as the reference S u. 5.4 Conclusions In general, the undrained shear strength obtained using the Windle and Wroth average strength method ranged from being approximately equal to the f i e l d vane S u at Lulu Is.-UBCPRS to 1.25 to 2.25 times higher at McDonald Farm and Langley Lower 232. A good comparison was obtained between FDPM and SBPM tests using the Windle and Wroth average strength a n a l y s i s . The pressuremeter undrained shear strength f o r McDonald Farm, when compared to the reference Su, follows the same trend with depth and has a s i m i l a r amount of s c a t t e r . At Lulu Is.- UBCPRS the s c a t t e r i n the data i s l i k e l y due to s o i l v a r i a b i l i t y . When tests were performed using v a r i a b l e s t r a i n rates, the slow tests r e s u l t e d i n higher undrained shear strengths which were l i k e l y caused by c o n s o l i d a t i o n during the t e s t s . Furthermore, when r e l a x a t i o n times p r i o r to a t e s t were increased, the undrained shear strength also increased s i g n i f i c a n t l y . In summary, the Windle and Wroth average strength method appears to be a reasonably v a l i d method when used f o r the analysis of FDPM despite the f a c t that t h e o r e t i c a l l y c a v i t y expansion methods should not be used when the i n i t i a l s t r e s s conditions are not known. The Houlsby unloading analysis r e s u l t e d i n S u values which were generally l e s s than the reference S u. When compared to the r e s u l t s of the Windle and Wroth average strength method, the r e s u l t s showed les s s c a t t e r which may be due to a loss of s o i l heterogenity during the loading p o r t i o n of the pressuremeter t e s t . 1 14 An ex c e l l e n t c o r r e l a t i o n was obtained between the t r a d i t i o n a l empirical method of c a l c u l a t i n g the undrained shear strength and reference S u f o r McDonald Farm with N fa c t o r s ranging between approximately 2.2 and 3.0 f o r tes t s were conducted using s i m i l a r s t r a i n rates. At Lulu Is. - UBCPRS and Langley Lower 232 the N fa c t o r s were more v a r i a b l e . The poor c o r r e l a t i o n near the ground surface at Langley Lower 232 was l i k e l y a r e s u l t of the overconsolidated and f i s s u r e d nature of the s o i l crust. When compared to the cone parameters and N^ u, the pressuremeter parameters N and Np appear to e x h i b i t the same dependence on s o i l c h a r a c t e r i s t i c s . In summary, the empirical methods presented are a u s e f u l means of estimating S u provided that standard t e s t procedures are followed and c o r r e l a t i o n s are l i m i t e d to l o c a l i z e d areas. 1 15 CHAPTER 6 SHEAR MODULUS AND RIGIDITY INDEX 6.1 Shear Modulus The unload-reload shear modulus, G u r, and the shear modulus, GJJ, c a l c u l a t e d using the r i g i d i t y index and undrained shear strength from the Houlsby c y l i n d r i c a l unloading analysis i s presented i n F i g . 6.1. The shear modulus i s not adjusted f o r varying stress or s t r a i n l e v e l s . Plots showing the c a l c u l a t i o n of the shear modulus can be found i n appendices I to I I I while a summary of the shear modulus values are i n appendix V. The r e s u l t s at McDonald Farm in d i c a t e that the shear modulus i s approximately constant with depth and that the G u r and G^ values are s i m i l a r . The high unload-reload shear moduli obtained at 16.2 m depth with the Fugro CP can be a t t r i b u t e d to the small s t r a i n increments used f o r the unloading loops. At 27.5m the high G u r and GJJ values c a l c u l a t e d f o r the UBC SCP are most l i k e l y caused by the c o n s o l i d a t i o n of the s o i l around the pressuremeter probe during a 17 min creep phase before the unload-reload loop was performed. Since no pore pressure measurements were made during a pressuremeter t e s t , no attempt was made to correc t f o r changes i n the e f f e c t i v e stress state of the s o i l surrounding the probe. For several other unload-reload tests short periods of creep ranging from 2 to 5 minutes were allowed to occur before the unload- reload loop was performed. The short periods of creep appear not to s i g n i f i c a n t l y a f f e c t the shear modulus obtained. The shear moduli at Lulu Is. -UBCPRS vary over a wide range and ind i c a t e a s o f t e r s o i l than the s o i l tested at McDonald Farm. The MCDONALD FARM SHEAR MODULUS ( MPa ) 0 10 20 30 40 15 I i ' ' i I i ' ' i J i i i i I i » i 2 0 - 25- CL UJ a 3 0 - 35- D t>tr a > aaaaa UBC SCP GH Houlsby Unloading >t,t>» UBC SCP C +++++ FUGRO CP GH Houlsby Unloading ••••• FUGRO CP C _ l_ I I I I I I I I I I I I I I 5 - fc Q 10 - 15 - 20- LULU IS. U B C P R S SHEAR MODULUS ( MPa ) 2 4 6 a * oa a * # 0 * oo * a * * * > ° o * * 0 * » o° * * - DDOOD UBC SCP GH Houlsby Unloading " UBC SCP Gl ***** Hughes SBPM G» . . l . J 1 1 1 1 1 1 1 1 1 1 1 LANGLEY LOWER 2 3 2 SHEAR MODULUS ( MPa ) 0 1 2 3 4 5 1 i 1 I 1 1 1 l i 1 i I 1 1 1 I 1 1 1 5- fc a 10- 15- 20- DOOOO UBC SCP GH Houlsby Unloading 1 1 1 1 1 1 1 1 1 1 1 1 1 Fig . 6.1 : Unload-Reload, G u r , and Houlsby Unloading, G H , Shear Modulus vs Depth 1 17 Houlsby unloading shear moduli appears to be on average s l i g h t l y higher than the unload-reload modulus. At Langley Lower 232 the GJJ values i n d i c a t e a s o i l which appears to have approximately the same s t i f f n e s s as the Lulu Is.-UBCPRS s o i l deposit. Unfortunately, unload-reload shear moduli are not a v a i l a b l e f o r t h i s s i t e . Although the equation f o r the unload-reload shear modulus ( eq. 4.19 ) Is derived using a l i n e a r e l a s t i c s o i l model, i n r e a l i t y s o i l behavior i s non-linear even f o r the small s t r a i n increments used f o r the unload-reload loops. Therefore a b e t t e r understanding of the shear modulus can be obtained by normalizing G U R with respect to the dynamic small s t r a i n modulus, G m a x and p l o t t i n g the r a t i o against the c a v i t y shear s t r a i n increment. This has already been done f o r shear moduli from c y c l i c and monotonic lab tests i n F i g . 4.14. An approximate average G M A X p r o f i l e at each s i t e used f o r the normalization of G U R i s found i n F i g . 6.2. At McDonald Farm and Lulu Is.-UBCPRS below 5 meters, Gmax appears to increase l i n e a r l y with depth while at Langley Lower 232, a non l i n e a r increase of G F F L A X i s observed with depth. Also i n t e r e s t i n g to note are the extremely low G M A X values i n the organic clayey s i l t or peat at Lulu Is.-UBCPRS between 3 and 5 meters depth. The normalized unload-reload shear modulus p l o t t e d against the shear s t r a i n increment f o r McDonald Farm and Lulu Is.-UBCPRS i s shown i n Fi g s . 6.3 and 6.4. The Houlsby unloading shear moduli are not analyzed i n t h i s manner due to d i f f i c u l t y i n accurately determining a s t r a i n l e v e l f o r the shear modulus. I t should be emphasized that the shear s t r a i n increment from an unload-reload loop i s the s t r a i n increment at the c a v i t y wall and not the average s t r a i n increment i n the s o i l . MCDONALD FARM Gmax ( MPa ) 50 100 i b i i I L_ Avg. Gmax J l L 150 Gmax - pV. V. - Shear Wave , Velocity J ••••• SCPT--1 Acc] ••••+ SCPT-•2 Geo ooooo SCPT--3 Ace] SCPT-•4 Ace, oaooo SCPT--5 Geo ooooo SCPT-•6 'Geo, -I I L -I L -I I L 5-̂ 10H 15H 20- L U L U I S . U B C P R S Gmax ( MPa ) 20 40 J 1 1 i i i i Gmax - pV, V, - Shear Wove Velocity Avg. Gmax ••••• SCPT-1 (Acc) +++++UBC SCP-2 (Acc oooooUBC SCP-2 (Acc UBC SCP-2 (Acc aoooa UBC SCP-2 (Acc' _ l _ L A N G L E Y L O W E R 2 3 2 Gmax ( MPa ) 0 20 40 Q I I I t I I I I I I I I I I I I I I 3H i a 10H 1SH 20- Gmax - pV.* V, - Shear Wave Velocity Avg. Gmax ••••• SCPT-1 (Geo) +•+•• UBC SCP-1 (Acc) UBC SCP-1 (Acc) I i i i i i i i i i i i i i i i i • i F i g . 6.2 : Dynamic Small S t r a i n Shear Modulus, G . vs Deoth ' max' r 119 M C D O N A L D F A R M o.o -j 1 1—i i i i i 11 1—i—i I I I I 11 1—I—I I I I I 11 0.01 0.1 1 10 SHEAR STRAIN y = 2e„ ( % ) F i g . 6.3 : G /G vs Shear S t r a i n at McDonald Farm 120 LULU IS. UBCPRS 0-00 -j 1 1—i i i i i 11 1 1—i I I i i 11 1—i—i i i i i 11 0.01 0.1 1 - 10 SHEAR STRAIN y = 2zv ( % ) F i g . 6.4 : G /G vs Shear S t r a i n at Lulu Is.-UBCPRS 121 Therefore, a d i r e c t comparison between the pressuremeter unload-reload r e s u l t s and the Seed and I d r i s s and Kokusho shear modulus attenuation curves reproduced from F i g . 4.14 can not be made. Nevertheless, a q u a l i t a t i v e comparison can be made r e a l i z i n g that the average s t r a i n increment w i l l l i k e l y be a constant r a t i o of the s t r a i n increment at the c a v i t y w a l l . At McDonald Farm, the normalized G u r / G m a x values are between .08 and .65 with most points f a l l i n g between .08 and .24. The normalized G u r attenuates with increasing shear s t r a i n i n a manner s i m i l a r to the behavior f o r Teganuma s o f t clay. At Lulu Is.-UBCPRS, the GI1T./G values are between .07 and .22. A good comparison i s obtained \JL JL H i d A . between G u r/ Gmax from the FDPM and SBPM tests and the normalized G u r again attenuates i n a s i m i l a r manner to Teganuma s o f t clay. 6.2 R i g i d i t y Index The r i g i d i t y index, I r , was c a l c u l a t e d i n three d i f f e r e n t ways, the f i r s t two methods shown i n F i g . 6.5. The f i r s t method uses parameters derived from the Houlsby unloading analysis while the second method uses the r a t i o of the G u r and the f i e l d vane undrained shear strength. The r i g i d i t y index i s not adjusted f o r varying s t r a i n l e v e l s . Furthermore, the reference S u from the f i e l d vane i s used with the unload-reload shear modulus since i t i s f e l t that the reference S u i s more consistent and r e l i a b l e than S u obtained using the pressuremeter. At McDonald Farm I r f o r most tes t s ranges between 80 and 220. The r i g i d i t y index i s approximately constant below a depth of 20 m. For most test s the Houlsby unloading I r i s s l i g h t l y higher than I r c a l c u l a t e d using G MCDONALD FARM RIGIDITY INDEX ( lr ) 200 400 600 i i i I I I i I I I — I — L + • • • + ooooo UBC SCP lr Houlsby Unloading ••••^ UBC SCP \r=G„/Su mr ry +++++ FUGRO CP lr Houlsby Unloading • ••••FUGRO CP l r =G„/S u mr ry _ l _ J I I I I I I I I L LULU IS. U B C P R S RIGIDITY INDEX ( l r ) 0 50 100 150 200 5H I a 15H 20- J u -I I i L * o o * » u «> o J »a' ooooo UBC SCP lr Houlsby Unloading UBC SCP Ir-Ggr/S, mr rv/eac »»»>»» Hughes SBPM I^Ctj/S pv/eaw _ l _ 5H & a 10- 15H LANGLEY LOWER 2 3 2 RIGIDITY INDEX ( l r ) 50 100 1 150 _ L _ 200 ooooo UBC SCP L Houlsby Unloading J 20 J ' >- J I I L F i g . 6.5 : G u r/S u R E p and Houlsby Unloading I f vs Depth 1 23 At L u l u Is.-UBCPRS the r i g i d i t y index v a r i e s over a wide range. The r i g i d i t y index c a l c u l a t e d using G u r f o r the SBPM and FDPM are s i m i l a r and vary between 20 and 135 while the Houlsby unloading I r ranges between 65 and 210. At Langley Lower 232 the Houlsby r i g i d i t y index ranges from 85 to 140. Although above 7 m depth the p r o f i l e i s not consistent, below 7 m I r increases c o n s i s t e n t l y with depth. Figure 6.6 shows the t h i r d method of obtaining the r i g i d i t y index using the average G m a x and the reference S u. At McDonald Farm the r i g i d i t y index i s approximately constant with depth which i s to be expected f o r a normally consolidated s o i l . At Lulu Is.-UBCPRS the r e s u l t s are somewhat unexpected since below approximately 6 to 7 m, the s o i l deposit i s be l i e v e d to be close to normally consolidated and above t h i s only l i g h t l y overconsolidated. Furthermore, since the p l a s t i c i t y index and s e n s i t i v i t y are beli e v e d to be f a i r l y constant with depth one would expect l e s s of a change i n I r with depth. The low r i g i d i t y indices obtained near the surface are l a r g e l y due to the extremely low shear v e l o c i t i e s and therefore G m a x obtained i n the organic clayey s i l t or peat. Even below 5 m the organic nature of the deposit may have had a s l i g h t e f f e c t on G m a x > The r i g i d i t y index could also be s l i g h t l y i n err o r due to i n c o r r e c t s o i l d e n s i t i e s assumed i n the c a l c u l a t i o n of the G values. max At Langley Lower 232 the r i g i d i t y index i s quite low at shallow depths and increase to a maximum at 8 m depth and then s l i g h t l y decreases at lower depths. The change i n r i g i d i t y index i s to be expected since the degree of overconsolidation i s decreasing with depth. I t i s also i n t e r e s t i n g to note that the r i g i d i t y index p r o f i l e from the MCDONALD FARM RIGIDITY INDEX ( I, ) 0 250 500 750 1000 15 I i i i i I i i i i I i i i i I i i i i I | 20 25 H Q. UJ Q 30 H 35- Avg. Gmax lr = Ref. S u FV/OONE ' ' i ' ' ' ' i ' • ' i i i i 0 O-i-L. i a 10H 13H 20- L U L U I S . U B C P R S RIGIDITY INDEX ( lr ) 200 400 600 800 ' I i i i I » i i ' ' • i ' • - • I, = Avg. Gmax Ref. Su FV/OONE •' 1 ' 1 1 LANGLEY LOWER 2 3 2 RIGIDITY INDEX ( l f ) 0 250 500 750 1000 0 I i i i I i i i i I i i i i I i • • • | , 5H icH Q. UJ a 15H Ir = Avg. Gmax Ref. S„ rv/coNE ?Q.I I I I I I I I I I t l i l i i i i i i M F i g . 6-6 : G m a x / S u R E p vs Depth 125 Houlsby unloading analysis i n F i g . 6.5 i s unlike the p r o f i l e obtained using G m a x and the reference S u. The dif f e r e n c e i n the two p r o f i l e s near the ground surface may i n part r e s u l t from the d i f f i c u l t y i n estimating the l i n e a r p o r t i o n of the Houlsby unloading curve ( see s e c t i o n 5.2.3 ). Consequently, the Houlsby S u may have been underpredicted leading to an overprediction of the r i g i d i t y index. The r i g i d i t y index defined as G u r/S u gj-p i s p l o t t e d against the shear s t r a i n increment f o r McDonald Farm and Lulu Is.-UBCPRS i n Figs. 6.7 and 6.8. The Seed and I d r i s s r e l a t i o n s h i p i s included to provide a q u a l i t a t i v e comparison between the r e s u l t s of pressuremeter and laboratory t e s t s . At both McDonald Farm and Lulu Is. -UBCPRS the r i g i d i t y index attenuates with increasing shear s t r a i n i n a manner s i m i l a r to the Seed and I d r i s s r e l a t i o n s h i p . At Lulu Is.-UBCPRS a good comparison between SBPM and FDPM r e s u l t s are obtained. 6.3 Conclusions A good comparison was obtained between the r e s u l t s of the Houlsby unloading shear modulus analyzed using c y l i n d r i c a l unloading and the unload-reload modulus. A l i m i t e d amount of data from McDonald Farm showed that f o r both methods a long creep phase before a t e s t r e s u l t e d i n higher values, l i k e l y a r e s u l t of consolidation. An ex c e l l e n t comparison was obtained between FDPM and SBPM G u r values. The unload- reload modulus was normalized with respect to G m a x and was shown to attenuate as the magnitude of the c a v i t y s t r a i n increased. The normalized unload-reload data was found to be between the laboratory attenuation curves by Seed and I d r i s s (1970) and Kokusho et a l (1982). 126 M C D O N A L D F A R M 1000- X LxJ Cr: 100 - 10 0.0001 f IIIIIIII I IIIIIIII 1 | | | | | | | | i 1 1 1 l l l| 1  1 1 1 II! * Gmax/Su REF FV — Avg. Relationship for Cohesive Soil6 f Seed and Idriss, 1970 ) > -t- + • M in i i I I I • •••a UBC SCP +++++ FUGRO CP 'r = G u r/S u REF Ir = G u r/S u REF FV FV - l M i l l l i | I l i i i l i i | i 1 1 1 1 III] 1 1 111 11) 1 i i 11 in 0.001 0.01 0.1 1 SHEAR STRAIN y = 2t9 { % ) 10 F i g . 6.7 : G u r / S u R £ F vs Shear S t r a i n at McDonald Farm 1 27 LULU IS. UBCPRS SHEAR STRAIN y = 2ev ( % ) F i g . 6.8 : G u r / S u R £ F vs Shear S t r a i n at Lulu Is.-UBCPRS 1 28 However, i t should be emphasized that the pressuremeter shear s t r a i n i s the s t r a i n at the c a v i t y w a l l and not the average s t r a i n increment i n the s o i l . Three d i f f e r e n t d e f i n i t i o n s of the r i g i d i t y index were compared. The Houlsby unloading r i g i d i t y index and I r c a l c u l a t e d using G u r d i v i d e d by the reference S u ranged between 75 and 200 f o r most FDPM t e s t . On average the Houlsby unloading I r was s l i g h t l y higher than I r c a l c u l a t e d using G u r and the reference S u. The r i g i d i t y index c a l c u l a t e d using G m a x and the reference S u produced values ranging from approximately 100 near the ground surface at Lulu s.-UBCPRS to 1000 at Langley Lower 232 and McDonald Farm. The r i g i d i t y index c a l c u l a t e d using G m a x appears to be in v e r s e l y p r o p o r t i o n a l to the organic content and overconsolidation r a t i o . At McDonald Farm , the normally consolidated s o i l i s r e l a t i v e l y homogeneous over the depth range tested with I r constant and approximately equal to 1000. The r i g i d i t y index c a l c u l a t e d using G u r and the reference S u was shown to attenuate with increasing shear s t r a i n i n a s i m i l a r manner to the Seed and I d r i s s (1970) average r e l a t i o n s h i p f o r cohesive s o i l s . An ex c e l l e n t comparison was obtained between the SBPM and FDPM I r values at Lulu Is.- UBCPRS. 129 CHAPTER 7 STRESS HISTORY AND IN SITU HORIZONTAL STRESS 7.1 Reference Overconsolidation Ratio The r e s u l t s of laboratory t e s t s (Ladd et a l , 1977) and c r i t i c a l s tate s o i l mechanics concepts have shown that the normalized undrained shear strength can be r e l a t e d to the overconsolidation r a t i o ( OCR ) using the following expression : ( S / e r ' j - ( S /cr ' ) * OCRA 7.1 v w vo 'oc v u' vo 'nc ' The OCR r a t i o i s defined i n terms of e f f e c t i v e v e r t i c a l stress ( OCR = crp'/ C T v o' ) a n d A i s the p l a s t i c volumetric s t r a i n r a t i o . For t h i s study the reference OCR i s obtained by matching f i e l d vane data to the r e s u l t s of oedometer te s t s on tube samples as shown i n F i g . 7.1. For the Lower Langley 232 s i t e a p l a s t i c volumetric s t r a i n r a t i o of A - 0.9 produces a good f i t between the f i e l d vane and oedometer r e s u l t s . This i s a reasonable value when compared to a review of nine w e l l documented clays by Jamiolkowski et a l (1985) which i n d i c a t e d that fo r f i e l d vane shear conditions, A ranges between 0.77 and 1.51 with a mean of 1.03. 7.2 Stress History The reference OCR i s c o r r e l a t e d against the r e s u l t s of FDPM and seismic piezocone t e s t s at the Lower Langley 232 s i t e between the depths of 2 and 13 m. The v a r i a t i o n i n G m a x / S u with OCR i s shown i n F i g . 7.2 130 LANGLEY LOWER 232 OCR 5 J L 10 J L J L 5 H 1(H x i— CL 20 H 25 « > > * # « « « * « * * _L_ OCR > » » OEDOMETER TESTS * * * * * FIELD VANE SANDY SILT LAYER I (s>;)J (S«/a w) M =.26,A = 0.9 J I L J L F i g . 7.1 : Stress Hi s t o r y from F i e l d Vane at Lower Langley 232 131 while the v a r i a t i o n i n the normalized l i m i t pressure and cone bearing with OCR i s shown i n F i g . 7.3. In F i g . 7.2 the r i g i d i t y index i s c a l c u l a t e d by using the average dynamic small s t r a i n shear modulus, G m a x , and the average undrained shear strength, S u. The f i e l d vane S u i s used since i t i s f e l t to be more r e l i a b l e and consistent than the l i m i t e d number of FDPM S u values obtained. The r i g i d i t y index i n i t i a l l y increases s l i g h t l y and then decreases i n a l i n e a r fashion as the OCR increases. This r e s u l t i s s i m i l a r to the trend observed f o r Boston Blue c l a y i n F i g . 4.16. In F i g . 7.3 , the c o r r e l a t i o n between ( ^20'ffvo ) / a V o ' o r ( q t - a v o ) / < 7 v o ' a * i d OCR are compared. I t i s apparent that the FDPM c o r r e l a t i o n increases l e s s r a p i d l y than the CPT c o r r e l a t i o n and appears to l e v e l o f f as the OCR increases. The CPT c o r r e l a t i o n increases i n a consistent manner except f o r a s l i g h t dip at an OCR of approximately 2.8. Also included f o r comparison purposes i s the curve produced using N^ t*S u/<7 v o' where S u i s from the f i e l d vane. A good comparison i s obtained except that the p l o t of N^ t*S u/a V Q' i s more concave up shaped. 7.3 Reference In S i t u Horizontal Stress The determination of the i n s i t u h o r i z o n t a l s t r e s s , ^ n o , using i n s i t u t e s t methods i s a challenging task. In s o f t clays, the SBPM t e s t i s perhaps the most promising method of determining a n Q . Unfortunately, high q u a l i t y SBPM tes t s were not performed during t h i s research. The dilatometer t e s t also y i e l d s reasonable values of K Q and hence a n o i n s o f t and medium non-cemented clays ( Jamiolkowski et a l , 1985 ). Since several dilatometer t e s t p r o f i l e s were made at the research s i t e s , the 132 LANGLEY LOWER 232 1200 C/? 900- x o E UJ 1 — 'T 1 - I 1 I I " • * S„ FROM FIELD VANE * * * * * • /(Su/oW)oo> OCR = U S u / O n J ^ I ( S „ / O n e = .26. A = .9 a OCR • t 7 • • 10 F i g . 7.2 : V a r i a t i o n i n Gmax/Su with OCR at Langley Lower 232 15- 0- } 10- b -g 5- i t) LANGLEY LOWER 232 » 12.5 1~ + ***** {jX~0^)/0^o » "ao UfcJU S O r Tests OCR ~i—i—r 7 8 9 10 F i g . 7.3 V a r i a t i o n i n (P 2 0- Svo>/ Svo' a n d <*t- Svo>/ Svo' w i t h OCR at Langley Lower 232 133 dilatometer K Q and hence a n Q was chosen as the reference cr^o' Marchetti's (1980) c o r r e l a t i o n : K Q - ( KD/1.5 ) 0 - 4 7 - 0.6 7.2 i s used to c a l c u l a t e K Q. Brooker and Ireland's c o r r e l a t i o n between K Q obtained during c o n s o l i d a t i o n tests and OCR and p l a s t i c i t y index i s also included f o r comparison purposes. 7.4 In S i t u Horizontal Stress The i n s i t u h o r i z o n t a l stress and therefore K Q c a l c u l a t e d from FDPM te s t s i s shown i n F i g . 7.4. The K Q values are obtained using the empirical approach as suggested by Lacasse and Lunne (1983). The p r a c t i c a l l i m i t pressure i s defined as the expansion pressure at 20 % c a v i t y s t r a i n and S u and I r are from the Houlsby Unloading a n a l y s i s . Several observations can be made : 1. ) The FDPM K Q values are i n general much too high. 2. ) The FUGRO CP with a pressuremeter L/D of 10 produced K Q values which were lower than the UBC SCP with a L/D of 5. 3. ) The FDPM K Q values are hig h l y s e n s i t i v e to the S u used. The K Q values are i n part too high because of the low S u obtained using the Houlsby Unloading analysis ( see Chapter 5 for d e t a i l s ). The r e s u l t s also appear to indic a t e that s p h e r i c a l expansion theories may be more appropriate f o r the analysis of FDPM tes t s with low L/D r a t i o s . The same technique i s used to obtain K Q from SBPM tes t s except that the f i e l d vane S u and a constant I r equal to 200 are used. The r e s u l t s f o r McDonald Farm i n F i g . 7.5 indic a t e a f a i r l y good c o r r e l a t i o n between MCDONALD FARM K. 0.0 0.5 1.0 15 _l I I I i I I J i I L 1.5 0.0 20- Q 25- 3 0 - 35- J I l_ UBC SCP CYLINDRICAL UBC SCP SPHERICAL oaaaa FUGRO CP CYLINDRICAL »»t>t>» FUGRO CP SPHERICAL DILATOMETER Morchetti flflBO) Brooker ft Irelartd(l965). PI=1S. OCR-1 — I — I I—I I I I I I I I I I t 5- i 10" 15- LULU IS. U B C P R S 1.0 2.0 _ l _ I I I I I I I L 0.0 + + • • ••••• UBC SCP CYLINDRICAL +++++UBC SCP SPHERICAL DILATOMETER Brooker ft Morchetti (1980) lreland(1965). PI -21 . OCR-1 J I I I I 1 I i ' 5- 10- 15- 20- LANGLEY LOWER 2 3 2 K. 1.0 i 2.0 I I I 3.0 L_L_ 4.0 20- FDPM K, - — PL-^CZ+mJ/J^Cl+tnLj-u, Ir and S, Houlsby Unloading , m - 1 CYLINDRICAL m - 2 SPHERICAL Ko\ 0 4 7 Brooker and Ireland (1965). PI-20 •••••UBC SCP CYLINDRICAL t i n t UBC SCP SPHERICAL DILATOMETER MarchetM (1980) - J — I — I — I I I—I I I I I I I I I DILATOMETER K» - —̂j - 0.6 u F i g . 7.4 : FDPM K Values Obtained Using Empirical Method \ 135 M C D O N A L D F A R M K 0 0.0 0.5 1.0 15 2 0 - 2 5 - Q_ Lul Q 30 35 J I I I I I I 1 I I I I I I 1.5 *#*#• Hughes SBPM CYLINDRICAL DILATOMETER Morchetti (1980) Brooker & lreland(1965;. Pl=15. 0CR=1 J I I I I I I ' ' ' i i i i SBPM Ko • — ; a*' = P L-S u*(1+lnl r)-u 0 . If=200 . S U-FV / K \ 0 4 7 DILATOMETER - f — J - 0.6 F i g . 7.5 : SBPM K Q Values Obtained Using Empirical Method at McDonald Farm 136 the dilatometer and SBPM. When t h i s same technique i s used f o r SBPM te s t s at the Lulu Is.-UBCPRS extremely low or negative values of K Q are obtained. I t i s l i k e l y that the low SBPM p r a c t i c a l l i m i t pressures obtained at Lulu Is.-UBCPRS are the major cause of the poor r e s u l t s . The r e s u l t s i n d i c a t e that the empirical method of determining K Q i s a poor one. This same conclusion was reached by Lacasse and Lunne (1983) when they compared the r e s u l t s of the empirical method to other techniques f o r high q u a l i t y SBPM t e s t s . Another technique which may be bett e r s u i t e d to determining the i n s i t u h o r i z o n t a l stress from FDPM tes t s i s shown i n F i g . 7.6. The dilatometer and FDPM are compared using i d e n t i c a l equations f o r and K p M. From the r e s u l t s at McDonald Farm and the Lulu Is.-UBCPRS, i t appears that Kp^ could be c o r r e l a t e d to K Q i n a s i m i l a r manner to K D. A poorer comparison of the K D and Kp M p r o f i l e s at the Lower Langley 232 s i t e could be i n part due to the long r e l a x a t i o n times employed during t e s t i n g at t h i s s i t e . Another f a c t o r which could cause a di f f e r e n c e i n the dilatometer and FDPM t e s t p r o f i l e s i s that l e s s s t r e s s r e l a x a t i o n l i k e l y occurs during dilatometer penetration due to l e s s abrupt change i n geometry between the t i p and blade of the dilatometer. 7.5 Conclusions Two methods were presented which r e l a t e parameters obtained from a seismic cone pressuremeter sounding to stress h i s t o r y . An ex c e l l e n t c o r r e l a t i o n was obtained between the r i g i d i t y index defined as G ° J max div i d e d by the f i e l d vane S u and the OCR. The second method involved c o r r e l a t i n g the normalized cone bearing and the pressuremeter p r a c t i c a l l i m i t pressure to the OCR. The normalized cone bearing and to a l e s s e r MCDONALD FARM LULU IS. U B C P R S LANGLEY LOWER 2 3 2 Ko & KPM KD & Km Ko & KPM 10 2.0 3.0 0.0 1.0 2.0 3.0 4.0 0.0 Jn an nn DILATOMETER K D = (P0-U0)/<J„' FDPM Kp*, = (P0-u0)/o", F i g . 7.6 : Comparison of Dilatometer K D and FDPM K p M Values 138 extent the p r a c t i c a l l i m i t pressure showed a f a i r l y consistent increase as the OCR increased. Both techniques are promising and should be inve s t i g a t e d further. The determination of i n s i t u h o r i z o n t a l s t r e s s i s d i f f i c u l t . Using the "empirical" method described by Lacasse and Lunne (1983) , the a n Q was estimated f o r FDPM t e s t r e s u l t s assuming both c y l i n d r i c a l and s p h e r i c a l c a v i t y expansion theory. The method has several drawbacks i n that i t i s s e n s i t i v e to the S u and I r chosen. Furthermore, the expressions f o r c a v i t y expansion are based on the assumption that the stres s conditions are known at the beginning of a t e s t . When compared to laboratory and dilatometer K Q values, the FDPM K Q r e s u l t s f o r c y l i n d r i c a l c a v i t y expansion and to a l e s s e r extent s p h e r i c a l c a v i t y expansion are much higher. In summary, the r e s u l t s i n d i c a t e that the "empirical" method of c a l c u l a t e d the i n s i t u h o r i z o n t a l s t r e s s i s a poor technique f o r FDPM t e s t s . 139 CHAPTER 8 CONCLUSIONS AND RECOMMENDATIONS The main objective of t h i s research was to i n t e r p r e t and evaluate the r e s u l t s of FDPM tests performed as part of a cone pressuremeter sounding. The following sections summarize the most s i g n i f i c a n t findings of t h i s research. 8.1 Factors A f f e c t i n g the Int e r p r e t a t i o n of the FDPM Test FDPM t e s t r e s u l t s are influenced by both the design and performance of the pressuremeter and the procedures used during an ac t u a l t e s t . Important equipment r e l a t e d considerations which were discussed are compliance, s t r a i n arm design and c a l i b r a t i o n s , membrane c o r r e c t i o n curves and pressuremeter L/D r a t i o . Compliance r e s u l t i n g from the compression of the lanter n s t r i p s and rubber membrane was inves t i g a t e d f o r the UBC SCP by i n f l a t i n g the pressuremeter ins i d e a 44 mm diameter s p l i t c y l i n d e r . I t was shown that although the actual d e f l e c t i o n s due to compression are small, the s t r a i n s recorded are s i g n i f i c a n t because of the small diameter of the UBC SCP. Despite the p o t e n t i a l problems i n i n t e r p r e t a t i o n which compliance can cause, i t i s f e l t that i n cohesive s o i l s , compliance has only a minor e f f e c t on t e s t r e s u l t s due to e f f e c t i v e stress conditions which remain approximately constant throughout a t e s t . The design of the pressuremeter s t r a i n arms can have a s i g n i f i c a n t e f f e c t on e s p e c i a l l y the i n i t i a l p o r t i o n of the pressuremeter expansion curve. For the UBC SCP, an improvement i n the design of the s t r a i n arms appeared to eliminate apparent outward d e f l e c t i o n s f o r a f u l l y d e f l a t e d 140 pressuremeter thereby allowing a more r a t i o n a l i n t e r p r e t a t i o n of the pressuremeter expansion curve. The importance of the L/D r a t i o was discussed i n Chapter 4. Comparisons of the l i m i t pressures from te s t s with the Fugro CP having a L/D r a t i o of 10 and the UBC SCP having a L/D r a t i o n of 5 i n d i c a t e d that higher l i m i t pressures are obtained with the UBC SCP. This i s to be expected since according to c a v i t y expansion theory, the l i m i t pressure f o r s p h e r i c a l c a v i t y expansion i s greater than that f o r c y l i n d r i c a l c a v i t y expansion. I t was also postulated that the i n s e r t i o n of a FDPM w i l l create a zone of f a i l e d s o i l surrounding the probe which w i l l r e s u l t i n a subsequent pressuremeter expansion which shows a greater d e v i a t i o n from the i d e a l c y l i n d r i c a l expansion when compared to a SBPM probe with an i d e n t i c a l L/D r a t i o i n s e r t e d with l i t t l e disturbance. Several important considerations which r e l a t e to t e s t procedures are the amount of r e l a x a t i o n time allowed before a pressuremeter t e s t i s performed, the disturbance created during pressuremeter i n s e r t i o n and the s t r a i n rate employed during a pressuremeter t e s t . The amount of r e l a x a t i o n time allowed has a s i g n i f i c a n t e f f e c t on the measured l i f t - o f f pressure f o r FDPM tests due to high excess pore pressures and subsequent high pore pressure gradients created by the i n s e r t i o n process. I t was shown f o r a l i m i t e d number of tes t s with the UBC SCP that the l i f t - o f f pressure decreased s u b s t a n t i a l l y as the length of r e l a x a t i o n time was increased. The shape of the pressuremeter expansion curve also appears to be a f f e c t e d by the length of r e l a x a t i o n time allowed. For tes t s with r e l a t i v e l y longer r e l a x a t i o n periods, the pressure expansion curves are steeper p o s s i b l y being a r e s u l t of co n s o l i d a t i o n occurring before a t e s t i s started. 141 A s u b s t a n t i a l but repeatable amount of disturbance i s created by FDPM i n s e r t i o n . A v a r i a b l e amount of disturbance often r e s u l t s from SBPM i n s e r t i o n due to the d i f f i c u l t y i n i n s e r t i n g the SBPM probe without d i s t u r b i n g the surrounding s o i l . In general, the v a r i a b i l i t y of the SBPM l i f t - o f f pressures were much greater than the FDPM r e s u l t s suggesting that the degree of disturbance created by SBPM i n s e r t i o n was v a r i a b l e . Also i n t e r e s t i n g to note were the good comparisons obtained between dilatometer and FDPM l i f t - o f f pressures and the FDPM p r a c t i c a l l i m i t pressure and the dilatometer P^ pressure. Most i n t e r p r e t a t i v e methods used to analyze the pressuremeter t e s t i n cohesive s o i l s are based on the assumption that the s o i l remains undrained during a t e s t . For the r e l a t i v e l y permeable cohesive s o i l s tested f o r t h i s research, i t i s f e l t that the high gradients of excess pore pressure created some p a r t i a l c o n s o l i d a t i o n during a t e s t . The r e s u l t s of pressuremeter tests at McDonald Farm appear to confirm t h i s i n that slower tests r e s u l t e d i n a higher undrained shear strengths f o r te s t s analyzed using Windle and Wroth's average strength method. A l i m i t e d number of t e s t r e s u l t s also ind i c a t e that the unload-reload modulus increases i n proportion to the length of the creep phase before the unload-reload t e s t i s begun. 8.2 Parameters Obtained From FDPM Tests 8.2.1 Undrained Shear Strength A good comparison was obtained between FDPM and SBPM undrained shear strength values analyzed using the Windle and Wroth average strength a n a l y s i s of the pressuremeter expansion curve. For most tes t s the pressuremeter produces higher Su values than the f i e l d vane. I t 142 should be noted that i n a s t r i c t sense, the use of c a v i t y expansion theory f o r the analysis of FDPM tests i s i n c o r r e c t due to the unknown stre s s conditions caused by s o i l disturbance. A l i m i t e d number of FDPM te s t s performed a f t e r a r e l a t i v e l y long period of r e l a x a t i o n a l l r e s u l t e d i n much higher Su values i n d i c a t i n g that the d i s s i p a t i o n of excess pore pressures has a s i g n i f i c a n t e f f e c t on the c a l c u l a t i o n of FDPM undrained shear strengths using c a v i t y expansion theory. The Houlsby analysis of the contraction curve i n general r e s u l t s i n undrained shear strengths which are generally lower than the f i e l d vane S u. Compared to the other t h e o r e t i c a l methods, the Houlsby S u values are le s s v a r i a b l e and e x h i b i t l e s s s c a t t e r . The merits of the a n a l y t i c a l techniques used to c a l c u l a t e the undrained shear strength are d i f f i c u l t to assess since S u w i l l be af f e c t e d to varying degrees by the factors discussed i n s e c t i o n 8.1 as wel l as the technique chosen. The Windle and Wroth average strength method appears to be a reasonably sound method of c a l c u l a t i n g S u f o r the foll o w i n g reasons ; the SBPM and FDPM r e s u l t s are s i m i l a r , and the reference and FDPM S u values e x h i b i t s i m i l a r amounts of s c a t t e r and trends with depth. The Houlsby unloading technique appears somewhat promising i n that i t provides a conservative estimate of S u which does not appear to be a f f e c t e d by the length of r e l a x a t i o n time allowed. A moderately good c o r r e l a t i o n was obtained between the t r a d i t i o n a l empirical method f o r c a l c u l a t i n g the pressuremeter S u and the f i e l d vane S u i n normally consolidated s o i l s . At McDonald Farm and Lulu Is.-UBCPRS the FDPM N value c a l c u l a t e d using the following equation : N - ( P 2 Q - P Q ) / S u pv 8.1 143 ranged between approximately 2.25 and 3.75 f o r tes t s with short r e l a x a t i o n periods. The average N value was 2.8 f o r McDonald Farm and 2.9 f o r Lulu Is.-UBCPRS. The dependence of N on s o i l c h a r a c t e r i s t i c s i s thought to be s i m i l a r to that shown f o r and N^ u. 8.2.2 Shear Modulus and R i g i d i t y Index An ex c e l l e n t comparison between FDPM and SBPM unload-reload shear moduli were obtained. The unload-reload shear modulus was normalized with respect to G m a x and was shown to attenuate as the magnitude of the c a v i t y s t r a i n increment increased. A good comparison was also obtained between the Houlsby unload shear modulus and G u r. A drawback with the Houlsby shear modulus i s that i t i s d i f f i c u l t to associate a s t r a i n increment l e v e l with the shear modulus. Three d i f f e r e n t d e f i n i t i o n s of r i g i d i t y index were compared. The Houlsby unloading r i g i d i t y index f o r most FDPM tes t s ranged between 75 and 200 and on the average was s l i g h t l y higher than I r c a l c u l a t e d using G u r d i v i d e d by the f i e l d vane S u. The r i g i d i t y index c a l c u l a t e d using Gmax di v i d e d by the f i e l d vane S u produced values as high as 1000 at McDonald Farm and Langley Lower 232. A l l d e f i n i t i o n s of the r i g i d i t y r e s u l t e d i n h i g h l y v a r i a b l e r e s u l t s at Lulu Is.-UBCPRS and to a l e s s e r degree at Langley Lower 232. 8.2.3 Stress H i s t o r y and In S i t u Horizontal Stress The overconsolidation r a t i o was c o r r e l a t e d to both the pressuremeter p r a c t i c a l l i m i t pressure and the cone bearing f o r data at Langley Lower 232 using the following expression : OCR - f ( (q f c or P 2 0 - a V Q ) / a V Q ' ) 8.2 144 The normalized cone bearing and to a l e s s e r extent the normalized p r a c t i c a l l i m i t pressure showed a f a i r l y consistent increase as the OCR increased. An ex c e l l e n t c o r r e l a t i o n was obtained between the r i g i d i t y index defined as the dynamic small s t r a i n shear modulus di v i d e d by the f i e l d vane S u and the OCR. The r i g i d i t y index increased s l i g h t l y and then decreased s t e a d i l y as the OCR increased. The i n s i t u h o r i z o n t a l stress and hence K Q was estimated using the equation f o r the l i m i t pressure assuming both c y l i n d r i c a l and s p h e r i c a l c a v i t y expansion theory. The method has several drawbacks i n that i t i s s e n s i t i v e to the value of the l i m i t pressure and the undrained shear strength used. Furthermore, the expressions f o r s p h e r i c a l and c y l i n d r i c a l c a v i t y expansion are based on known str e s s conditions at the beginning of a t e s t . The Houlsby unloading undrained shear strength and r i g i d i t y index was used f o r the estimation of the i n s i t u h o r i z o n t a l stress f o r FDPM t e s t s . Spherical c a v i t y expansion theory r e s u l t e d i n the most reasonable values of K Q when compared to dilatometer K Q values using Marchetti's (1980) c o r r e l a t i o n . 8.3 Recommendations The cone pressuremeter i s a promising new i n s i t u t e s t i n g device which has great p o t e n t i a l . A comprehensive amount of data i n c l u d i n g f u l l displacement pressuremeter, piezocone and seismic data can be obtained during a cone pressuremeter sounding. Recommendations f o r furthe r research deal with equipment design, t e s t procedures and i n t e r p r e t a t i v e methods. 145 1) The cone pressuremeter should have a pore pressure sensor next to the probe. This w i l l allow a bet t e r estimation of the str e s s conditions p r i o r to a t e s t . 2) Consideration should be given to constructing a cone pressuremeter with a low L/D r a t i o and using s p h e r i c a l expansion to analyze the r e s u l t s . 3) The e f f e c t of varying lengths of r e l a x a t i o n time p r i o r to a t e s t should be furth e r investigated. This i s important f o r both t h e o r e t i c a l l y and e m p i r i c a l l y based i n t e r p r e t a t i v e methods. I t may be b e n e f i c i a l to e s t a b l i s h guidelines f o r the length of r e l a x a t i o n time p r i o r to a FDPM t e s t s i m i l a r to those f o r a dilatometer t e s t . 4) Further research should be d i r e c t e d towards t r y i n g to quantify the e f f e c t s of co n s o l i d a t i o n and s t r a i n rate on FDPM curves. 5) The Houlsby unloading analysis appears to be a very promising method of determining both the undrained shear strength and shear modulus. Further work should be done i n a v a r i e t y of cohesive s o i l s to v a l i d a t e t h i s method and to compare the r e s u l t s to undrained shear strengths obtained using other i n s i t u and laboratory methods. 6) Further research should be d i r e c t e d towards t r y i n g to e s t a b l i s h FDPM c o r r e l a t i o n s using parameters s i m i l a r to those used f o r the dilatometer t e s t . 7) Further research should focus on r e l a t i n g the unload-reload shear modulus to a s t r a i n increment l e v e l and to compare G u r to the r e s u l t s of other c y c l i c and monotonic laboratory t e s t s . The r e l a t i o n s h i p between G u r and G m a x should also be established f o r overconsolidated s o i l s . 146 REFERENCES Aas.G.,' Lacasse,S., Lunne,T. and Hoeg.K. (1986): "Use of InSi t u Tests f o r Foundation Design on Clay". 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Presented to AGO Symp. on Advances i n Hydraulic Testing and Tracer Methods, San Francisco. 150 Prevost.J.H. (1979): "Undrained Shear Tests on Clays". Journal of the Geotechnical Engineering D i v i s i o n , ASCE, Volume 105, No.GTl, pp. 49-64. Prevost.J.H. and Hoeg.K. (1975): "Analysis of Pressuremeter i n S t r a i n - softening S o i l " . Journal of the Geotechnical Engineering D i v i s i o n , ASCE, Vol. 101, No. GT8, pp. 717-732. Rice,A.H. (1984): "The Seismic Cone Penetrometer". M.A.Sc. Thesis, Department of C i v i l Engineering, U n i v e r s i t y of B r i t i s h Columbia. Robertson,P.K., Hughes,J.M.O., Campanella,R.G., Brown,P. and McKeown.S. (1986): "Design of L a t e r a l l y Loaded P i l e s using the Pressuremeter". The Pressuremeter and I t s Marine Applications, Second Int. Symp. : ASTM STP 950, J.L. Briaud and J.M.E. Audibert, Eds. American Society f o r Testing and Materials.21 Robertson,P.K. and Campanella,R.G. 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(1970): " S o i l Moduli and Damping Factors for Dynamic Response Analysis". Report No. EERC 70-10, College of Engineering, U n i v e r s i t y of C a l i f o r n i a at Berkeley, December. Sully,J.P., Campanella,R.G. and Robertson,P.K. (1988): "Inte r p r e t a t i o n of Penetration Pore Pressures to Evaluate Stress H i s t o r y i n Clays". Proc. of the F i r s t I nternational Symposium on Penetration Testing, ISOPT-1, Orlando, March, Volume 2, pp. 993-1000. Suyama.K., Imai.T., and Ohya.S. (1982): "Development of LLT and Its A p p l i c a t i o n i n P r e d i c t i o n of P i l e Behavior Under Horizontal Load". Proc. Symposium on the Pressuremeter and I t s Marine Applications, Pa r i s , pp. 61-67. Windle,D. and Wroth,CP. (1977): "The Use of the Self-Boring Pressuremeter to Determine the Undrained Properties of Clays". Ground Engineering, September, pp. 37-46. Wroth,CP. (1988): "Penetration Testing - A More Rigorous Approach to Int e r p r e t a t i o n " . 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Wroth,CP. and Hughes,J.M.O. (1973): "An Instrument f o r the In s i t u Measurement of the Properties of Soft Clays". 8th ICSMFE, Moscow. APPENDIX I PRESSUREMETER TEST DATA AT MCDONALD FARM 1*3 S i t e : McDonald Farm Date : 27/1/87 Pressuremeter : UBC SCP On S i t e Location : JAN27 Comments : No piezocone or seismic measurements S t r a i n c o n t r o l l e d t e s t Depth S t r a i n Rate Approx. Relaxation ( m ) ( %/min ) Period ( min ) 17.0 8.5 1.5 19.0 9.1 1.5 22.0 8.1 1.5 25.0 7.0 1.5 27.5 7.2 1.5 30.0 7.6 1.5 UBC SCP 27/1/87 REPLOT 27/10/87 S D Q. £ n n £ •o a> +> o © k. «~ o o 6 0 0 500 H 4 0 0 3 0 0 H 2 0 0 H 100 McDonald F a r m - 1 7 . 0 m - 1 0 0 Average Strain % Cavi4y -Strain UBC SEISMIC CONE PRESSUREMETER Site : McDonald F a r m - In f Depth : 17 .0 m Date : 2 7 / 1 / 8 7 LOG CURRENT VOLUMETRIC STRAIN 600 500 H 400 300 200 H UBC SCP 27/1/87 Houlsby Unloading Cyi McDonald Farm—17 .0m 5 ^ = 24x5 kPa 100 2 i 1 — r 6 T 8 10 —ln(eo — e ) ©=ncrtural strain U B C S C P 2 7 / 1 / 8 7 R E P L O T 2 7 / 1 0 / 8 7 o Q. O i_ n ro £ U O -M O © l _ 1 . 0 O 7 0 0 600 H 5 0 0 H 4 0 0 H 3 0 0 4 2 0 0 H 100 -4 McDonald Fa rm—Depth=19 .0m - 1 0 0 Average Strain (%) i <5<d> UBC SEISMIC CONE PRESSUREMETER Site : McDonald Form -Inf Depth : 19.0 m Date : 27/1/87 700 650 600 550 500 450 1 10 10* LOG CURRENT VOLUMETRIC STRAIN UBC SCP 27/1/87 McDONALD FARM Houlsby Unloading Cyl D = 19 .0m 100 - i o r 1 1 1 1 1—1 1 - i i I 0 2 4 6 8 10 - l n ( E 0 - E) E=Natura l Strain UBC SCP 27/1/87 REPLOT 28/10/87 McDonald Farrn-Depth==22.0rn 800 -i r ~ioo H 1 r - — i 1 1 T 1 1 — — i 1 1 r -2 2 6 10 14 18 22 Average Strain (%) Cav/i-Vy 5+rain. 16\ UBC SEISMIC CONE PRESSUREMETER Site : McDonald F a r m - l n f Depth : 2 2 . 0 m Date : 2 7 / 1 / 8 7 0 £ 3 B n e O O 8 0 0 7 0 0 4 6 0 0 4 5 0 0 4 0 0 4 3 0 0 4 2 0 0 4 100 4 UBC SCP 27/1/87 McDONALD FARM Houlsby Unloading Cyl D=22.0M T 2 T = 46.1 IcPa S a s r k - 3 4 S Vft ^ 4 u . - 1 3 4 6 , - 134*5^1 -4.18 MPa 4 6 - I n ( E 0 - E) E=Notura l Strain 8 10 0 n 0 0 o o 7 5 0 7 4 0 7 3 0 7 2 0 7 1 0 7 0 0 690 6 8 0 6 7 0 6 6 0 6 5 0 6 4 0 6 3 0 6 2 0 6 1 0 6 0 0 5 9 0 5 8 0 5 7 0 5 6 0 5 5 0 UBC SCP - 27/1/87 McDonald F a r m — 2 2 . 0 m - 2 l o o « 5 . o 5 M P . If 2 2 N«Ki«4 Strain Data Points UBC SCP 27/1/87 REPLOT 28/10/87 McDonald F a r m - D e p t h = 2 5 . 0 m 9 0 0 n r— — Average strain (%) Cavity S+rain UBC SEISMIC CONE PRESSUREMETER Site : McDonald F a r m - I n f Depth : 25.CV m Date : 2 7 / 1 / 8 7 1 10 10 2 LOG CURRENT VOLUMETRIC STRAIN \6£ UBC SCP - 27/1/87 McDonald Farm — 2 5 . 0 m - 1 1 3 5 7 9 11 13 15 17 19 N o v . W < 0 Strain - Data Points Average Strain {%) Cav/rq "Strain. UBC SCP 2 7 / 1 / 8 7 McDONALD FARM Houlsby Unloading Cyl D = 2 7 . 5 m 1 6 ~240*Su«jl« H-ZMPJ 8 10 - l n ( E 0 - E) E=Notura l Strain Natural Strain C o r r e c t e d P r e s s u r e ( k P a ) UBC SCP- 27/1/87 REPLOT 28/10/87 McDonald F a r m - D e p t h = 3 0 . 0 m o Q_ x © L. 3 (D 0) £ Q. © O © I- L . 0 o 1100 1000 H 9 0 0 -\ 8 0 0 H 7 0 0 H 6 0 0 4 5 0 0 -4 400 Cavil j 5^31 A Average Strain (%) UBC SEISMIC CONE PRESSUREMETER Site : McDonald F a r m - I n f Depth : 3 0 . 0 m Date : 2 7 / 1 / 8 7 1 10 1 0 2 LOG CURRENT VOLUMETRIC STRAIN UBC SCP 27/1/87 Houlsby Unloading Cyi McDonald F a r m — D e p t h = 3 0 . 0 m - l n ( E O - E) E=Naturol Strain U B C S C P 2 7 / 1 / 8 7 M C D O N A L D FARM D=3O.O m C a v i t y Strain % Data Points 1 ^5 Site Date Pressuremeter On Site Location Comments McDonald Farm 7/11/85 FUGRO CP N0V7 No piezocone measurements Quasi- s t r a i n c o n t r o l l e d t e s t Depth S t r a i n Rate Approx. Relaxation ( m ) ( %/min ) Period ( min ) 16.2 1.1 1-5 18.2 1.9 1-5 19.2 - 1-5 20.2 5.2 1-5 22.2 5.0 l'-5 1 0 0 0 86/01/10 DEPTH = 16.2 m. McDONALD FARM CORRECTED FOR MEMBRANE 3 0 4 0 C A V I T Y STRAIN (%) FUGRO CONE PRESSUREMETER Site : McDonald F a r m Depth : 16.2 m Date : 1 0 / 1 / 8 6 L O G C U R R E N T V O L U M E T R I C S T R A I N S 86/01/10 DEPTH=16.2 m. McDONALD FARM fugro 16 17 18 19 2 0 CAVITY STRAIN % o Q. \ ^ hi OH D V) in hi a: o. Q hi hi OH OH O O 86/01/10 DEPTH=16.2 m. McDONALD FARM fugro 20hl.|oc66-ln I-W61 G u r - 130 2t In l.03*Mn 103381 8 -41 T - 10 CAVITY STRAIN % 86/01/10 DEPTH=16.2 m. McDONALD FARM FUGRO HOULSBY UNLOADING CYL 0 2 4 6 8 10 - l n £ o - € ) r £ = NATURAL STRAIN ' 86/01/10 DEPTH=18.2 m. McDONALD FARM Corrected for Membrane 1000 — — — " 9 0 0 - 8 0 0 - CAVITY STRAIN (%) FUGRO CONE PRESSUREMETER Site : McDonald F a r m Depth : 18.2 m Date : 1 0 / 1 / 8 6 6 0 0 H i 1 1—i i i i i | 5.303 I 1 1—ryi i i i 1 1- 'i i i i i 1 10 LOG CURRENT VOLUMETRIC STRAIN S 10 •Z3\ o Q. hi or D (/) V) bJ Q. 86/01/10 DEPTH=18.2 m. McDONALD FARM Corrected for Membrane i 1 r~ 2 1 . 4 21 . 8 2 3 T T ~ 2 3 . 4 i I CAVITY STRAIN % 86/01/10 DEPTH-18.2 m. McDONALD FARM Corrocted for Membrane CAvrrr STRAIN % 86/01/10 DEPTH=18.2 m. McDONALD FARM FUGRO HOULSBY UNLOADING CYL 4 , 1 1 r — 1 H 1 1 1 1 0 2 4 6 8 10 - I n (EO - E) E=NATURAL STRAIN C A V I T Y STRAIN (%) ( 8 ^ FUGRO CONE PRESSUREMETER Site : McDONALD FARM Depth : 19 .2 m Date : 1 0 / 1 / 8 6 7 0 0 6 5 0 D CL 6 0 0 LxJ cr § 5 5 0 LU CcL CL j< 5 0 0 H O r - 4 5 0 H 4 0 0 i 1 1—i i 1 1—i i i i Sg= 584-40O - 8ao kfk 2-303 T 1 1 1 l l l l | i b L O G C U R R E N T V O L U M E T R I C S T R A I N S T 1 1 I I I I I 10 8 6 / 0 1 / 1 0 DEPTH-19.2 M McDONALD FARM FUGRO HOULSBY UNLOADING CYL 100 -] o _j j 1 -j [ — r 1 1 1 0 2 4 6 8 —LN(EO - E) E=NATURAL STRAIN 1000 900 - 800 - 700 - C A v i T Y STRAIN (%) I 3 o FUGRO CONE PRESSUREMETER Site : McDona ld F a r m Depth : 2 0 . 2 m Date 7 0 0 6 5 0 o CL •* 6 0 0 a: § 5 5 0 LLI a: Q - ^ 5 0 0 o 4 5 0 g l a r e d - 4 O Q + + + • + 4 0 0 - j 1 10 LOG CURRENT VOLUMETRIC STRAIN CORRECTED PRESSURE ( kPa ) o II Z I XI f 73 > 8 6 / 0 1 / 1 0 DEPTH=22.2m McDONALD FARM Corrected for Membrane MF3V2r~U 2 0 0 - 1 0 0 - 0 _ T _ . . 1 0 .... f " 1 2 0 ' " I " 3 0 (CAVITY STRAIN (%) FUGRO s f t e : McDonald F a r m CONE PRESSUREMETER Date : 1 0 / 1 / 8 6 Depth 22.2 m LOG CURRENT VOLUMETRIC STRAIN * 0 D E P T H = 2 2 . 2 m McDONALD FARM FUGRO HOULSBY UNLOADING CYL 5 u 5 p U =- 33.8 IcPa I 61 - I36*5ucyl =6.12 Nfli 4 6 _! j 8 10 —LN(E0 - E) E=NATURAL STRAIN 86/01/10 DEPTH=22.2m McDONALD FARM FUGRO 560 550 540 530 - i 520 -1 510 \ / \ / l^icAA^= .23% r — [ — 3.6 ~ i r 3.8 T 1 T " 4 4.2 CAVITY STRAIN % o Q. hi tY. D U) V) hi tn CL Q Id LJ a: or o o 710 700 -} 690 "1 680 -t 670 H 86/01/10 DEPTH=22.2m McDONALD FARM FUGRO 660 " i — i — r — r I \ l \ i V Hnl.2274-Wil.725ll -13.6 MPa ? A ^ A j - 0.29% /1 / 22 _ _ 1 j r . . _ f ; j 1 r 1 j 22.2 22.4 22.6 22.8 23 23.2 23.4 23.6 23.8 24 CAVITY STRAIN % Site : McDonald Farm Date : 18/10/83 Pressuremeter : Hughes SBPM On Site Location : 0CT18 Comments : S t r a i n rate i s rough approximation Stress Controlled Test Depth S t r a i n Rate Approx. Relaxation ( m ) ( %/min ) Period ( min ) 16.75 1 1-5 17.75 1 1-5 18.75 1 1-5 19.75 10 1-5 20.76 1 1-5 21.76 10 1-5 22.76 1 1-5 23.76 10 . 1-5 24.76 10 1-5 25.76 1 1-5 McDONALD FARM Hughes SBPM D= 16.75 rn CAVITY STRAIN ( % ) 1 9 9 H U G H E S S B P M 1 0 / 1 8 / 8 3 McDONALD FARM D « 16.75 m ++++ +++ ++ (5,= 3 ? k 3 * .02.38 T 1 1 1 1 i 1 1 1 1—i 1—i 1 1 1 1 1 r 10 1 2 14 16 18 2 0 O Data Points Cavfty Strain (SQ + Arnold Curv» FH fro H U G H E S S B P M 1 8 / 1 0 / 8 3 Mod Arnold McDONALD FARM D" 16.75 m Cavtty Strain W SELF - BORING PRESSUREMETER Site : McDonald Farm - JH Depth : 16.75 m Date : 10/18/83 1 10 10* LOG CURRENT VOLUMETRIC STRAIN % McDONALD FARM SBPM Feb. /84 D« 16.75 m Houlsby Unloading Cyl o a. (0 CO tt. 600 500 - 4 0 0 H 300 ~t 200 100 - 5 8 o S u ^ l - 583 ka P j 560- C-^ - 32 -2̂ 4 6 o 8 - l n ( E 0 - E) E«Natural Strain McDONALD FARM Hughes SBPM D= 17.75 m T 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1! 0-j—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i 0 5 10 15 2 0 CAVITY STRAIN ( % ) 800 H U G H E S S B P M 1 0 / 1 8 / 8 3 McDONALD FARM D = 17.78 m 700 H 600 H 500 H 400 H 300 Jf 200 . 4 . ^ + 4-+ + + + + + + + ^ + + + + ° ° cS^ 4It 5 « l a - .CM5Z. ~ i — i — i — i — i — i — i — i — i — i — i — i — i — i — i — i — i — r 2 4 6 8 10 12 14 16 18 20 D Dote Points Cavtty Strain (*) 4- Arnold Curv* Fit Cavfty Strain (X) 10<o SELF - BORING PRESSUREMETER Site : McDonald Farm - JH Depth : 17.75 m Date : 10/18/83 LOG CURRENT VOLUMETRIC STRAIN % McDONALD FARM SBPM FEB. /84 D = 17.75 m Houlsby Unloading Cyl £43 o o. 0 / 2 4 6 8 10 - l n ( E 0 - E) E=NAtural Stra in McDONALD FARM Hughes SBPM D= 18.75 m o O 200 ~i—i—i—i—j—i—i—i—i—1—i—i—i—i I " ' 1 r 5 10 15 CAVITY STRAIN ( % ) 900 HUGHES SBPM 10/18/83 McDONALD FARM D = 18.75 m 800 H 700 600 500 H 400 H 300 ++++ a - O i l ! b= .C.G2-T- —t— 10 —r - 12 —r— U 16 -r 0 2 D Data Points T 4 - r 8 18 20 CavHy Strain (*) + Arnold Curve Fit Covfty Strain (X) 9-w 1 10 10* LOG CURRENT VOLUMETRIC STRAIN * o 0- 2 B 0) 2 Q. 900 800 700 600 500 H 400 H 300 200 4 100 -4 McDONALD FARM SBPM FEB. / 8 4 D= 18.75 m Houlsby Unloading Cyl 823 - + V P Cwo = 8 Z ! ^ 4^> 8 -ln(E0 - E) E=NaturaI Strain McDONALD FARM Hughes S B P M D= 19 .75 m 1 0 0 0 - i — - | — i — i — i — i — i — i — i — i — i — r — i — i — i — i — i — i — i — i — I 0 f i—i—i—i—I—i—r—i—i—|—~i—i—i—i—j—i—i—i—i— I 0 5 1 0 1 5 2 0 CAVITY STRAIN ( % ) 3-\4 a & I 3 a L. 8 900 800 700 H 600 H 500 H 400 300 HUGHES SBPM 10/18/83 McDONALD FARM D » 19.76 m ++++ <5V= 640 I K o ^ e A /Wold ^Ll^ax" 101 K P a -r- 2 4. - r 8 -T— 10 — i — r 12 1+ 16 - 1 — r 18 20 • Data Polnta Cavity Strata ( X ) + Arnold Curve Fit  SELF - BORING PRESSUREMETER Site : McDonald Form - JH Depth : 19.76 m Date : 10/18/83 550 H 1 1—i i i i i i | 1—-i » i i i ' i ' 1 10 1 LOG CURRENT VOLUMETRIC STRAIN % McDONALD FARM SBPM FEB. / 8 4 D=19.76 m Houlaby Unloading Cyl o H —i 1 1 — : — i — — i 1 1 1 r 1 0 2 4 6 8 10 - l n ( E 0 - E) E=Natura l Strain  9 1 5 o I I £ 3 • 0 o 900 800 700 -4 600 500 H 400 41 300 HUGHES SBPM 10/18/83 McDONALD FARM D => 20.76 m +++ + + ^ +  + + ~ 1 1 1 b- -0022_ 6) = 4to T 1 1 1 1 1 1 1 1 1 1 1—1 1 1 1 1 1 r 2 4 6 8 10 12 14 16 18 20 D Data Points Cavity Strain (%) + Arnold Curve Fit 7.7-0 Ccvhy Strain (X) SELF - BORING PRESSUREMETER Site : McDonald Farm - JH Depth : 20.76 m Date : 10/18/83 850 i 1—I—T—rr -n o or ZD CO CO Ld cr a. Q 800 H - t H j 750- i 700 H 450 10 1 0 2 LOG CURRENT VOLUMETRIC STRAIN % McDONALD FARM SBPM FEB. / 8 4 D=20.76 m Houlsby Unloading Cyl 0 2 4 6 8 —ln(EO — E) E=natura l strain <rc£ 2 l A 900 800 -\ 700 4 600 500 400 H 300 HUGHES S B P M 1 0 / 1 8 / 8 3 McDONALD FARM D = 21.76 m +++++ \o =- .00:14 Arnold . S c W * 100^3 - i — i — i — i — i — i — r — i — i — ' — ' — 1 1 r 2 4 6 8 10 12 1 + 16 1 — i — r 18 20 D Data Pointa Cavity Strain (X) +• Arnold Curva Fit 1%Z o 92 HUGHES SBPM 18/10/83 Mod Arnold McDONALD FARM D-21.76 m Covtty Strain (X) SELF - BORING PRESSUREMETER Site : McDonald Farm - JH Depth : 21.76 m Date : 10/18/83 1 T [ - T / T T T T 900 850 —i T — — i 1—r-i i i n -t 800 H : -1 D CL H -j 750 3 LU J cr: 4 i —« co 7 0 0 -CO LU or Q_ 6 5 0 - < h- o — r— 600 - i 550-i 500 T — r ~ T ~ m r r i — i — i r r r r , 10 1 0 2 LOG CURRENT VOLUMETRIC STRAIN % 900 McDONALD FARM SBPM FEB. / 8 4 D=21.76 m Houlsby Unloading Cyl 833 800 700 4 Q . l_ 3 CO Of) (9 1_ Q. 600 500 400 4 300 200 4 C f h p . g33-(~54) -54 z - 3eo KPa 5 100 2 4 6 8 - l n ( E 0 - E) E=Natura l Strain McDONALD FARM Hughes SBPM D=20.75 m i — i — i — i — i — i — i — i — i — i — i — i — i — i — i — i — i — i — i — i 1 i i i i i i — i — i — i — | — i — i — i — i — | — i — i — i — i — j O 5 10 15 20 CAVITY STRAIN ( % ) I a 0. 5 900 800 H 700 600 500 400 300 HUGHES SBPM 10/18/83 McDONALD FARM D - 22.76 m ++ + +. + + + qi + + + + 6 5 - 840 £ 3 = I Z •wax (3r- k P d 150 K P a T 1 1 1 1 1 1—1—1 1 1 1 1 1 1 1 1 1 r~ 2 4 6 8 10 12 14 16 1B 20 • Data Polnta Covfty Strain (X) + Amotd Curve Fit S13 0 HUGHES SBPM 18/10/83 Mod McDONALD FARM D=22-76 m SELF - BORING PRESSUREMETER Site : McDonald Farm - JH Depth : 22.76 m Date : 10/18/83 LOG CURRENT VOLUMETRIC STRAIN % McDONALD FARM SBPM FEB 84 0=22.76 m HouW3byJJrac^^ _ln(EO - E) E=NoturaI Strain McDONALD FARM Hughes SBPM D=23.75 m 1000 -1—i—i—i—i—i—i—i—i—i—i—> « 1 1 1 1 1 1 r~I o CL LU cn ZD to CO LU cr: Q. c r o o 800 H 600 H 400 200 -t 0 a l_l I • I a. HUGHES SBPM 10/18/83 Vk DONALD FARM D « 23.76 m 300 H 200 4 ioo H b = .-O0Z2. 1 2 ++++ + +-4- + + + + S + H o c k W A r n o l d 12.0 KPa n Data Points Cavity Strain (X) + Arnold Curve Frt ^ 3 ^ HUGHES SBPM 18/10/83 Mod Arnold McDONALD FARM D=23.76 m 130 -i 0 -j 1 1 1 1 1 1 1 j 1 1 1 1 1 r 1 T 0 2 + 6 8 10 12 U 16 CovHy Strain (5Q SELF - BORING PRESSUREMETER Site . . M c D o n a l d Farm - JH Depth : 23.76 m Date : 10/18/83 900 I T 1 1 T r T T T J ~i 1—i7-T-n-r-rrj 850 H o CL 800- i 4 6u 7 5 0 ^ -^3.9 - 500 - 1 l < U k & LU cr: 3 CO 700 co LU cr: CL . 650 H 4 3 o Q. CD i _ 3 01 0) CP l_ CL MCDONALD FARM SBPM FEB 84 D=23.76 m Houlsby Unloading Cyl 8 3 6 900 -• 800 - + 700 - / + 600 - 500 - F 400 - 300 - 200 - 100 - n -—-A- r— 1 • —, 1 1 ~ i r— 8 - l n ( E 0 - E) E=Natura l Strain <b<ct 2 3 9 HUGHES SBPM 1 0 / 1 8 / 8 3 McDONALD FARM D - 24.76 m 1 "I II 1—i—i : i — i — i — i — i — i — i — i — i — i — i — i — i — i — i — r 0 2 4 6 8 10 12 14 16 18 D Data Points Cavity Strain (*) + Arnold Curve Fit  SELF - BORING PRESSUREMETER ,u Depth : 2 4 . 7 6 m Date : 10/18/83 Site : McDonald Farm - JH Depth 1000-r i T T T \ 1 0 * ' L 0 G CURRENT VOLUMETRIC STRAIN % McDONALD FARM SBPM feb 84 D=24.76 m Houlsby Unloading Cyl 481 left. 2 4 - l n ( E O - E) E=Natura l Strain T 6 McDONALD FARM Hughes SBPM D=25.75 m i — i — i — i — | — i — i — i — i — | — i — i — i — i — | — i — i — i — r 5 10 15 20 CAVITY STRAIN ( * ) . •MA HUGHES SBPM 10/18/83 McDONALD FARM D - 25.76 m 0.9 H 0.8 H 0.7 H 0.6 -1 0.5 H 3 3 0.4 + + + + +•+ © > 68a 62.= 833 ^ 4 b - .0019 T — 1 1 1 1 1 — 1 1 — 1 1 1 1 1 1 1 — i 1 1 r 2 4 6 8 10 12 U 16 18 20 • Data Points Covfty Strain (X) + Arnold Curve Fit SELF - BORING PRESSUREMETER Site : McDonald Farm - JH Depth : 25.76 m Date : 10/18/83 HUGHES SBPM 18/10/83 Mod Arnold McDONALD FARM D=*25.76 m . Pressure ( kPa ) (Thousands) £ 4 T APPENDIX I I PRESSUREMETER TEST DATA AT LULU IS. - UBCPRS £ 4 6 S i t e : Lulu Is - UBCPRS Date : 3/4/87 Pressuremeter : UBC SCP On S i t e Location : APR3 Comments : No seismic or piezocone data S t r a i n C o n t r o l l e d Test Depth S t r a i n Rate Approx. Relaxation ( m ) ( %/min ) Period ( min ) 3.0 11.1 1.5 4.0 11.2 1.5 4.8 10.8 1.5 6.35 10.6 1.5 7.9 10.6 1.5 9.4 12.4 1.5 10.9 10.3 1.5 12.4 10.3 1.5 14.0 9.3 1.5 UBC SCP 3/4/87 REPLOT 2 6 / 1 0 / 8 7 D=3.0 M Lulu Ts - U B C P R S ^7~V .++ +rH+ 4f»-+ + + + + + T ~ r 8 12 T 1 - 16 20 C-/VMTY STRAIN % UNCOR + COR COR PRESSURE (kPa) a ARM1 + ARM2 • ARM3 9.5 \ UBC SEISMIC CONE PRESSUREMETER Site : LuluB-UBCPRS- Inf Depth : 3.0 m Date : 3 / 4 / 8 7 S t r a i n UBC SCP 3/4/87 HOULSBY UNLOADING CYL 0 2 4 8 8 10 -ln(E0 - E) E»Notura! Strain 0 CD i _ m m CD i _ Q. 300 2 5 0 ~\ 2 0 0 -j 150 H 100 50 H -50 UBC SCPM 3/4/87 REPLOT 26/10/87 Annacis Pile D=4 .0 m AnnSc^ Pile <= U d a T s - O B C P f ^ uncor Infinitesimal Strain % + c o r 18 2 2 7J UBC SCPM 3/4/87 REPLOT 2 6 / 1 0 / 8 7 Annacis Pile D=4.0 m -40 0 40 80 120 160 Cor Pressure (kPa) • arm1 + arm2 O arm3 UBC SEISMIC CONE PRESSUREMETER Site : Annacis Pile - Inf Depth : 4.0 m Date : 3/4/87 10 ~1 1 10 10 s LOG CURRENT VOLUMETRIC STRAIN +  UBC SCPM 3/4/87 REPLOT 2 6 / 1 0 / 8 7 A N N A C I S PILE D = 4 . 8 M A N N K I 5 P I L £ ~ Lu luXs-UBcP^ 2 6 o -. • , - 6 0 H 1 r , 1—-1 1 1 1 1 1 1 r 0 4 8 1 2 1 8 2 0 2 4 INFINITESIMAL S T R A I N % C C A V I T V ) U N C O R + C O R UBC SCPM 3/4/87 REPLOT 2 6 / 1 0 / 8 7 ANNACIS PILE D=4 .8 M i t > w-» >• S o I - I I I I I I I I 1 1 I I I 1 1 1 1 1 i - 5 0 - 3 0 - 1 0 10 3 0 5 0 7 0 9 0 110 130 150 COR P R E S S U R E (KpA) O ARM1 + ARM2 • ARM3 UBC SEISMIC CONE PRESSUREMETER Site : Annacis Pile - Inf Depth : 4.8 m Date : 3/4/87 10 " 1 1 10 1 0 2 LOG CURRENT VOLUMETRIC STRAIN + Cor rec ted Pressure ( kPa ) - i M U > 0 l O l M 0 0 t D O ~ ' M 0 i f O I 0 1 v J C 0 ( O O o o o o o o o o o o o o o o o o o o o o o o hi (Z D V) in u tr o. UBC SCPM 3/4/87 REPLOT 2 6 / 1 0 / 8 7 ANNACIS PILE D=6.35M AWNAC15 P l l _ £ - L u l u I < S U S C P R S INFINITESIMAL STRAIN % Ccavi+j) UNCOR + COR <5̂ E E c o o e Q 0.5 0.4 4 0.3 4 0.2 4 0.1 4 -0.1 UBC SCPM 3/4/87 REPLOT 2 6 / 1 0 / 8 7 Annacis Pile D=6.35 M 1° - 4 0 0 O arm1 40 80 120 160 Cor Pressure (kPa) arm2 • arm3 *> c • * •4J 2 ^ 3 UBC SEISMIC CONE PRESSUREMETER Site : Annacis Pile - Inf Depth : 6.35 m Date : 3/4/87 10 - 1 1 10 1 0 2 LOG CURRENT VOLUMETRIC STRAIN + Average Strain + Corrected Navfu-ral S + r a i n UBC SCPM 3/4/87 HOULSBY UNLOADING CYL AN NAC IS PILE D=>6.35M 20 4 0 -J , 1 1 1 1 f 1 1 1 1 0 2 4 6 8 10 -ln(E0 - E) E=NATURAL STRAIN UBC SCPM 3/4/87 REPLOT 2 6 / 1 0 / 8 7 uncor Infinitesimal Strain % + cor E E c o o H— o Q 0.5 0.4 0.3 - i 0.2 0.1 0 > 0 ' - 0 . 1 UBC SCPM 3/4/87 REP LOT 2 6 / 1 0 / 8 7 ANNACiS PILE D=7 .9m / 4/ M - ... H — .... /// ii! St-. a ^ ~ 4 i -40 4 0 80 120 ~r ft ft *̂ 3 IS — • arm1 Corrected Pressure kPa + a r m 2 O ARM3 160 O UBC SEISMIC CONE PRESSUREMETER Site : Annacis Pile - Inf Depth : 7.9 m Date : 3/4/87 1 0 - 1 1 10 1 0 2 LOG CURRENT VOLUMETRIC STRAIN + UBC Seismic Cone Pressuremeter-3/4/87 Annacis Pile Sfte-Depth=7.9m 240 -, : 230 -j 160 4 1 1 1 1 1 1 1 1 6 7 8 9 10 Average Strain (%) + Corrected NaWral S+rain* UBC SCPM 3/4/87 HOULSBY UNLOADING CYL Annacis Pile D«=7.9 m o H 1 r~ 1 1 1 r— 1 1 1 1 0 2 4 6 8 1 0 -!n(EO - E) E=Noturol Strain UBC SCPM 3/4/87 REPLOT 26/10/87 ANNACIS PILE D=9.4m 400 —i 0 4 8 12 18 20 24 Infinitesimal Strain % UNCOR + COR UBC SCPM 3/4/87 REPLOT 26/10/87 ANNACIS PILE D=9.4 m IP—B—~_ ;P  K- - - . , . / ^ - * / 1 r - . — — H i 1 1 1 1 1 1 1 1 - 1 1 - 4 0 0 4 0 8 0 120 1 6 0 * 2 0 0 • ARM1 COR P R E S S U R E (KpA) .+ ARM2 O ARM3 2 . 7 - 3 UBC SEISMIC CONE PRESSUREMETER Site : Annacis Pile - Inf Depth : 9.4 m Date : 3/4/87 LOG CURRENT VOLUMETRIC STRAIN + UBC SCPM 3/4/87 HOULSBY UNLOADING CYL Annacis Pile D=9.4 m S u - \A>°S Vfo spk 6 10 -ln(E0 - EO) E=Notural Strain U N C O R Infinitesimal Strain % + COR UBC SCPM 3/4/87 REPLOT 2 6 / 1 0 / 8 7 ANNACIS PILE D= 10 .9m 0.5 0.4 - 0.3 0.2 - 0.1 0.0 - 0 . 1 - 4 0 120 • ARM1 COR P R E S S U R E (KpA) + ARM2 O ARM3 UBC SEISMIC CONE PRESSUREMETER Site : Annacis Pile - lnf Depth : 10.9 m Date : 3/4/87 i — r i i i i T — i — I I I I 1 10 1 0 * LOG CURRENT VOLUMETRIC STRAIN C o r r e c t e d P r e s s u r e ( k P a ) 500 UBC SCPM 3/4/87 HOULSBY UNLOADING CYL Armada Pile Stte—Depth=10.9m 400 4 /->» o ft 3 m ? Q. O o 300 H 200 4 100 4 -In(E0 - E) E»Natural Strain UBC SCPM 3/4/87 REPLOT 2 6 / 1 0 / 8 7 ANNACIS PILE D=»12.4 M 600 -T -100 H 1 1 1 1 1 — l r — — i — — I 1 r T" 0 4 8 12 16 20 24 Infinitesimal Strain % UNCOR + COR UBC SCPM 3/4/87 REPLOT 2 6 / 1 0 / 8 7 ANNACIS PILE D«12.4 m 2 Z o § u Q 0.5 0.4 4 0.3 0.2 4 0.1 4 0.0 -0.1 • ARM1 200 COR PRESSURE (KpA) + ARM2 • ARM3 au OJ OS CP ^ 8 Z UBC SEISMIC CONE PRESSUREMETER Site : Annacis Pile - Inf Depth : 12.4 m Date : 3/4/87 1 10 1 0 2 LOG CURRENT VOLUMETRIC STRAIN UBC Seismic Cone Pressuremeter—3/4/87 Annacla Pile Sfte-Depth=12.4m Average Strain (%) Natural Strain 500 400 H o CL O L. 3 S) n CL 300 200 -i 100 4 UBC SCPM 3/4/87 HOULSBY UNLOADING CYL ANNACIS PILE D=12.4 U 5u- 3-lQ kfo 5* • left qpk CO 2 - r 4 6 8 10 -ln(E0 - E) E=Notural Strain Inftnlteatlmal Strafn ( % ) UNCOR 4- COR UBC SCPM 3/4/87 REPLOT 17/12/87 ANNACIS PILE D=14.0 M to 0̂ 0 200 400 • arm1 CORRECTED PRESSURE ( kPa ) + drm2 • arm3 UBC Seismic Cone Pressuremeter-3/4/87 Annacis Pile Stte-Depth«= 14.0m CO +-4- PM Average Strain (%) Natural S+rain« UBC SEISMIC CONE PRESSUREMETER % Site : Annacis Pile - Inf Depth : 14.0 m Date : 3/4/87 500-j 1 1—i—i—i i i i | -j 1—i—i—i t i i i LOG CURRENT VOLUMETRIC STRAIN % UBC SCPM 3/4/87 HOULSBY UNLOADING CYL Annaci8 Pile D=14.0 m 50 4 0 H 1 r~ 1 1 1 1 1 1 1 1 0 2 4 6 8 10 -ln(E0 - E) E=Natural Strain S i t e Date Pressuremeter On S i t e Location Comments Lulu Is - UBCPRS 8/1/88 UBC SCP JAN8 S t r a i n C o n trolled Test Depth S t r a i n Rate Approx. Relaxation ( m ) ( %/min ) Period ( min ) 4.75 14.7 7.5 7.75 13.4 9.7 10.75 12.9 13 13.75 12.9 7.2 Cavity Strain [%] Avg. of arms 1-2—3 SCPM 8/1/88 Annacfs Pile D=4.75 m 1 0.5 • Arm #1 . A r m Deflection [mm] + Arm #2 <• Arm #3 ^ 9 3 UBC SEISMIC CONE PRESSUREMETER Site : Annacis Pile 300 250 H D Q_ LU m § 2 0 0 LU cr: CL o r - 150 H 100 Depth : 4.75 m Date : 8/1/88 i i i i i i i n 1 1—l— I I i i r 5 a = 172-loo , 3 / . 5 k f t 2.303 + + , + + + + + + T I I I l l l l | -1 1 1 1 | | | | 10 1 0 8 LOG CURRENT VOLUMETRIC STRAIN % SCPM 8/1/88 Houlsby Unloading Cyl Annacis Pile D=4.75 m -j , 1_, , , , , j j j j j 0 2 4 6 8 10 -ln(E0 - E) E=Natural Strain 2 0 0 SCPM 8/1/88 Annacis Pile D=7.75 m J 0.5 • Arm #1 Arm Deflection [ m m ] + Arm #2 • Arm #3 2 9 6 UBC SEISMIC CONE PRESSUREMETER Site : Annacis Pile Depth : 7.75 m Date : 8/1/88 Seismic Cone Pressuremeter 8/1 / 8 8 Annacis Pile D=7.75 m 5 7 9 11 13 15 Cavity Strain [%] Avg. of arms 1 - 2 - 3 s c r M a/i/oo H o u l s b y U N i o a d i n g uyi Annacis Pile D=7.75 m 0 2 4 6 8 -ln(E0 - E) E=Natural Strain Seismic Cone Pressuremeter 8/1/88 Annacis Pile D= 10.75 m i—i—i—i—i—T—i—i—i—i—i—i—i—i—i—i—r 3 5 7 9 11 13 15 17 19 Cavity Strain [%] — Avg. of arms 1-2-3 o CL © L. 3 a n £ Q. 2 6 0 2 4 0 - 2 2 0 - 2 0 0 180 160 140 120 - 100 - 80 - 60 4 0 - 2 0 - 0 - 2 0 - 0 . 1 • Arm #1 SCPM 8/1/88 Annacis Pile D = 10.75 m r~ 0.1 0.3 Arm Deflection [mm] + Arm #2 o Arm #3 3 o i UBC SEISMIC CONE PRESSUREMETER Site : Annacis Pile Depth : 10.75 m Date : 8/1/88 SCPM 8/1/88 Houlsby Unloading Cyl Annacis Pile D= 10.75 m 400 - i ~ln(E0 - E) E=Natural Strain Seismic Cone Pressuremeter 8/1/88 Annocl8 Pile D=13.75 m 1 1 r— i i i 1 1 j 1 1 j , , , r 3 7 9 11 13 15 Cavity Strain \%] Avg. of arms 1 - 2 - 3 SCPM 8/1/88 • Arm #1 Arm Deflection [mm] + Arm #2 O A r m #3 UBC SEISMIC CONE PRESSUREMETER Site : Annacis Pile Depth : 13.75 m Date : 8/1/88 LOG CURRENT VOLUMETRIC STRAIN s C o r r e c t e d P r e s s u r e [ k P a ] S i t e : Lulu Is - UBCPRS Date : 11/2/87 Pressuremeter : Hughes SBPM On Si t e Location : FEB11 Comments : Quasi-Strain C o n t r o l l e d Test S t r a i n range i s the range i n c a v i t y s t r a i n over which the s t r a i n rate has been c a l c u l a t e d . Depth S t r a i n Rate S t r a i n Range Approx. Relaxation ( m ) ( %/min ) ( % ) Period ( min ) 4.8 4.3 0-9.5 1-5 6.35 8.1 0-16 1-5 7.9 8.5 0-16.9 1-5 9.4 6.4 0-13.3 1-5 10.9 8.0 0-16.4 1-5 12.4 2.6 0-16.4 1-5 0 Q. X £ 3 n m © Q- "O O +> o £ L. 0 o 10 0 Self-Boring Pressuremeter-11/2/87 UJ«* I * - U8CPRS-Depth:4 .8m F t b U . O c f l •1 &ur * 0 .7Z MPa • A * * 3 . 3 % . 3 V . Arnold S t W = Zl.3kP<i | ModtW Arnold S u ^ - Hi kPa 5 0 4 0 3 0 2 0 -ffi <3 •, •= O.fMPa a - i o 2 . * VJ& 0 0 0 — — T" 4 T " 6 8 "1 10 12 • Measured + Average Strain (%) Arnold "fype-l Stress-Strain Na+ur-al 6-V Curve Ft+ 0 CD Self-Boring Pressuremeter-11/2/87 Lulu, 35-U6CPfS-Depth:4.8m 120 160 200 240 Pressure (kPc) — Arm 2 Arm 3 3 l o SELF - BORING PRESSUREMETER Site : Lulu Is-UBCPRS Depth ; 4 .8 m Date : 11/2/87 1 10 1 0 * LOG CURRENT VOLUMETRIC STRAIN Self-Boring Pressuremeter—1 LUIIA Hi-UBCpR5-.Depth:6.35m / 2 / 8 7 Fcbll.oo3 Arnold S u ^ - 23.0 kPa ModrrVa A^old 5u^ K = 24.4 k P a . 6 t - 1.1 MPa W 05 A 0 0 o o 0 7 p r j r 6 8 10 12 T 1 - 14 " 7— r 16 18 Measured Average Strain (%) Arnold Ttjpe. V <> S t r e s s - S t r a i n Self-Boring Pressuremeter- i i / ^ / " ' LuAu I s - U&CPKS-Depth:6.35m lur-0.62Hfa Arm 1 "120 160 Pressure (kPa) Arm 2 Arm 3 SELF - BORING PRESSUREMETER Site : Lu lu Is-U8CPR5> Depth : 6.35 m Date : 11/2/87 LOG CURRENT VOLUMETRIC STRAIN Self-Boring Pressuremeter-11 / 2 / 8 7 Lulu I*.-uecpRS -Depth:7.9m 1 , 0 0 4 0 2 4 6 8 10 12 14 16 18 20 Average Strain (%) C Measured + Arnold Type 1 O Stress-Strain Cu»*ve F I T 3 a o © CM a a 4- SBPM 11/2/87 ARNOLD TYPE 1 lu lu l3-UBCPR5D=7 .9m SUavg=23.4 em«=10 Natural Strata % Strain 2\Tr SELF - BORING PRESSUREMETER Site : Lulu T s - UBCPRS Depth : 7.9 m Date : 11/2/87 SBPM 11/2/87 Houlsby Unloading Cyl La\ul6-U8CPR5 -Depth:7.9m 1 1 1 1 1 1 1 1 1 1 1 0 2 4 6 8 10 ~ln(E0 - E) E=Natural Strain o n 2 0) n £ Q. 3 0 0 2 8 0 - 2 6 0 - 2 4 0 - 2 2 0 - 2 0 0 - 180 - 160 - 140 120 - 100 - 8 0 60 4 0 2 0 - - o Self-Boring Pressuremeter-11 / 2 / 8 7 febli.ooS Uiu Ts - UBCPRS - D e p t h : 9 . 4 m I54 T 1 1 1 1 r 4 6 8 ~i r 10 12 T r- 14 Measured Average Strain (%) (Mature, l ) + Corrected o C L X © n m © t_ D. •u <D +-> O © 0 o 260 240 - 220 - 200 180 H 160 140 120 - 100 - 80 60 40 20 H Self-Boring Pressuremeter-11 / 2 / 8 7 UIUJA- UBCPRS -Depth:9.4m I64" tnf ja^orx d z - l 8 3 1.9? b« .OMZ-33 6 u - W Hfe Arno ld S i w * 22 kPa M o d i W 5 I A ^ X - Z3.I kPa Thi* (t> a lovv Su.J fo55iblu 3 S^eMr cksfu.r\)eA 4^5f «' 2 4 - Measured T 6 8 10 12 - r - 14 Average Strain (%) ( Natura l ) + Arnold Type I Curve. F I T Self-Boring Pressuremeter-11 / 2 / 8 7 0 40 80 120 160 200 240 280 Arm 1 Pressure (kPa) Arm 2 Arm 3 SELF - BORING PRESSUREMETER Site : La lu I s - U6CPRS Depth : 9.4 m Dote ; 11 /2/87 Cor rec ted Pressure ( k P a ) Self-Boring P.M., 11/2/87 Lulu I5- OBCPRS -Depth:10.9m F t B U-OOfi Average Strcfn (%) (KJaKxral — - Co rr. Press. (kPa) Self-Boring Pressuremeter-11/2/878 Lulu T s - U8CPR5 -Depth: 10.9m ro 2 5 0 2 4 0 - 2 3 0 - 2 2 0 - 2 1 0 - 0 Q. 2 0 0 190 _ 0 i_ 180 es si  170 — C o r P r 160 150 — i 140 130 - 120 - 110 - 100 SBPM 11/2/87 ARNOLD TYPE 1 LuluXs.UBCPR5D=10.9 m S U m a x = 2 4 . 3 kPA + + + Arwold Sawv^^ 24.3 kPa Modrpfed A*>o The. SM. ob+ai^cl Is |otO. 5ome, disWbance w a y U a v c occurred. A U o p l̂onaexJl pttn'cdj of" Creep before J t W w/ r ( ° 0 p*- do KO+ KVTSIPC- 4WS -res)-- VRKJ 5cLikbW. -for C^CLLISTIUÎ  5tt-; ~ r 2 6 8 I 10 12 14 16 18 Natural Strain % Data Points VP (T SBPM 11/2/87 ARNOLD TYPE 1 L u K u f t l P R S D=10.9 m SUavg=19.7 kPa em=10 Natural Strain % Strain 3 2 8 SELF - BORING PRESSUREMETER Site : LJIU I s - U B C P R S Depth : 10.9 m Dote : 11/2/87 1 10 1 0 * LOG CURRENT VOLUMETRIC STRAIN 500 400 -4 300 200 "4 100 -j Self-Boring P.M., 11/2/87 Lulu lb.-UBCPR5 -Depth: 12.4m f e b l l . O O ^ Corr. Pressure kPa H 18 Average Strain (%) ( N J a W a f ) 22 C 20 19 18 17 16 15 H 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Self-Boring Pressuremeter-11 / 2 / 8 7 Lulu 36.-UBCPRS -Depth:12.4m Po = 255 K?3 This Po -i3 considerable hfcjW 4han +V\c Po calculated TTO'VA ploh of -Hit co/vee-fed pressure, vs average plof on "Hoc ' previous pagc.Tl'ii*. oonjd otcW +o stale af u/U f court (* puffed, A U P M £ P o J f 23o is Ta^cio TO be Corvttk 0 200 400 Arm 1 Pressure (kPa) Arm 2 Arm 3 o Q. o l _ ZJ n m v Q. i _ 0 O 3 6 0 3 5 0 3 4 0 3 3 0 3 2 0 3 1 0 3 0 0 2 9 0 2 8 0 2 7 0 2 6 0 2 5 0 2 4 0 2 3 0 2 2 0 - 1 SBPM 11/2/87 ARNOLD TYPE 1 ANNACIS D=12 .4 m S U m a x = 3 2 . 1 kPA MfltltfW Arnold * 3 2.1 fcPa. Th& "6u is low. Some Dr-s-K^kance- 1 o-p c r e e p mr| v w a k d . 4U15 £3 3 11 13 15 17 Natural Strain % Data Points 0» V>3 Natural Strain % Strain 3 ^ 3 SELF - BORING PRESSUREMETER Site : U U I s - O B c P R S Depth : 12.4 m Date : 11/2/87 T i i i i i i | 1 1—~i—I I I I I I i i i i i i i i | 1 1 1—i i i i i 1 1 10 1 0 2 LOG CURRENT VOLUMETRIC STRAIN 33 <4 S i t e : Lulu Is - UBCPRS Date : 19/2/87 Pressuremeter : Hughes SBPM On S i t e Location : FEB19 Comments : Quasi- S t r a i n Controlled Test S t r a i n range i s the range i n c a v i t y strainover which the s t r a i n rate has been calc u l a t e d . Depth S t r a i n Rate S t r a i n Range Approx. Relaxation ( m ) ( %/min ) ( % ) Period ( 4.9 4.3 0-18.5 1-5 6.3 2.8 0-3.5 1-5 7.9 9.5 0-19.2 32 9.4 6.4 0-13.3 1-5 10.7 4.2 0-12 1-5 12.5 2.1 0-17.4 1-5 14.0 2.5 0-17.4 1-5 260 SBPM 19/2/87 REPLOT 28/10/87 l ukxXs ,- U B C P R S -Depth:4.9m TeB\9.0tfL o 0. m m © Q. •o 9 IS I O O 20 Average Strain (%) — Cavi+w strain Self-Boring Pressuremeter-19/02/87 Lulu l3.~U8CPGS-Depth:4.9m.SBPM#3 — Arm 1 " p r y ^ r 120 160 200 Pressure (kPo) Arm 2 Arm 3 240 o CM E <5 o O Q O CM CM O CM O O CM O O) O 00 O o CO o lO o SBPM 19/2/87 ARNOLD TYPE 1 D=43 m SUavg=17.9kPa em=10 Cavjiti^ Strain % • Strain SELF - BORING PRESSUREMETER Site : Lulu X 5 - U B C P R S Depth : 4.9 m Date : 19/2/87 o Q. 3 to 0) "8 -f-> o © b o o SBPM 19/2/87 REPLOT 2 9 / 1 0 / 8 7 Lulu. Tjs.- 06CPR5 -Depth:6.3m 0. -Cawrtij Strain 8 10 12 Average Strain (%) 3*1 ' T SBPM 19/2/87 ARNOLD TYPE 1 b l u I D - U B C P R S D=6.3M SUmax=20.0 kPa v a. 3 « m CL "O 9 +» o P. 0 o C^avi+ij Data Points Strafn X SBPM 19/2/87 ARNOLD TYPE 1 T I I I 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 3 5 7 9 11 1 3 1 5 1 7 1 9 2 1 CavHHj Strain % Strain 344 SELF - BORING PRESSUREMETER Site : LoUX^- U B C P R S Depth : 6.3 m Date : 19/2/87 200 H o Lul or z> 00 CO Ld 150 OL o r - 100 T 1—I I I I 1 11 —I 1—I I I ITT] 1 1—nTTTTT 5u.~ r7B,6-t54 10 1 1—I TTTTTp ' ' I 1—I I I I M | - 1 1 10 —r—i—i I I I I I 1 0 * L O G C U R R E N T V O L U M E T R I C STRAIN 34 5" Self — Boring Pressuremeter—TS/ 7 26 24 LuW T s - U B C P R S -Depth:7.9m "1 D •*-> 22 20 18 16 14 12 10 8 6 4 2 0 P.*l3H 134+ 14?* 143Kfe 100 Arm 1 200 Pressure (kPa) Arm 2 Arm 3 300 400 SELF - BORING PRESSUREMETER Site : L u k l s - U J & P R S Depth ; m Date : 19/2/87 ouu- I I I I 1 l I 1 [ i i J y I i T T " 8. / \ PR ES SU RE  ro  O  t i i I i /?\1 " J < 200- £ ; II 150- 2 3 0 3 ^ 45A IcPa 100 - - 1 WW i i 1 I 1 1 1 I | • i i i J i i r 1 10 10 LOG CURRENT VOLUMETRIC STRAIN SeIf~3or!ng Pressuremeter-19/02/87 Lulu Is-UBCFRs ~Depth:7.9m(repeat) 5fc-iYrfl&koM R-b |$.005" T ~ T ~ " ~ T— r 4 6 ~ r 8 10 12 14 16 -T" 18 20 Average Strcfn (J5) c 2 OT 20 19 — 18 17 - 16 - 15 14 13 12 - 11 - 10 - 9 ... 8 - 6 - 5 4 - 3 - 2 - 1 - 0 0 Self-Boring Pressuremeter-19/02/87 Lulu Is- UBCPRS~Depth:7.9m(repect) £ e _ ,v,ftah Arm 1 Pressure (kPa) Arm 2 • Arm 3 —I— 280 Self-Boring Pressuremeter— 19/2/87 Lota I s - ~Depth:9.4 m Feb 19-006 Average Strain {%) (̂ MaKtral SBPM 19/2/87 ARNOLD TYPE 1 Lulu Is-UBCH^ D=9.4m SUavg=32.2kPa em=10 % i r 1 1 1 1 1 r — i 1 T 3 5 7 9 11 Natural Strain % Strain 20 — 19 -18 i 17 -j 16 -j 15 4 u —| 13 H 12 4 11 -j 10 -4 9 4 8 H i ' ^ 6 4 5 4 4 4 3 4 ! 2 -1 1 I o 4 Self-Boring Pressuremeter-19/2/87 Lulu Is - UBCPRS -Depth:9.4 m // / / f / //^7 / ft / •?/ / / / . / 100 ' 200 3 - Mo ttk _ 300 j 400 — Arm 1 Pressure (kPa) Arm 2 Arm 3 SELF - BORING PRESSUREMETER : b k I s - UBCPR5 Depth : 9.4 rn Date : 19/2/87 Self-Boring Pressuremeter-19/2/87 Average Strain (%) (rOaW&l^ . Self Boring Pressuremeter— 19/2/87 Lola Hs-UBCFfcS ~-Dopth:10.7 m 3 / f . = I 4 S | c p 8 / / / / / S^ZJhf I / '7 40 80 ~ Arm 1 120 160 200 Pressure (kPa) 240 - Arm 2 Average Strain (%) Self-Boring Pressuremeter-19/2/87 Ulul6-u8CP£S-Depth:12.5 m 600 -r — 500 - 1 I I I 1 r — I — l — I — 1 1 1 1 1 1 1 1 j 1 1 0 2 4 6 8 10 12 14 18 18 20 Average Strain (%) C NaWa I s ) Strain ( « ) 0 - » M ( d ^ W O I M f f l ( 0 0 - ' M O l ^ O l O ) M 0 1 f f l O 500 400 - » 4> 300 - 200 - 100 - Self-Boring Pressuremeter-19/2/87 U I u. J s - 06C PRS -Depth:!4.0 m Correced Pressure Average Strain (%) ( Ma+uraf) +• Arnold SBPM 19/2/87 ARNOLD TYPE UUts-u&CPKS. D= 14.0m SUavg=41.4 kPa em=10 ^ j r - - - i j 1 1 - - 1 r~ 4 . 6 8 10 12 Natural Strain % Strain Self-Boring Pressuremeter-19/2/87 L o k X s -OBCPRS -Depth: 14.0 m Pressure (kPa) Arm 2 Arm 3 SELF - BORING PRESSUREMETER Site : Lu\u I S - ( J B £ P R 5 Depth : 14.0 m Date : 19/2/87 • 500 -i T 1—i J- I T r r i 1 r — 1 I T T T T ] 1 10 1 0 * LOG CURRENT VOLUMETRIC STRAIN % 3 ^ 3 APPENDIX III PRESSUREMETER TEST DATA AT LANGLEY LOWER 232 36n Site : Langley Lower 232 Date : 10/12/87 Pressuremeter : UBC SCP On Si t e Location : DEC10 Comments : St r a i n C o n trolled Test Depth Str a i n Rate Approx. Relaxation ( m ) ( %/min ) Period ( min ) 1.0 11.5 >20 2.0 8.3 >20 3.0 12.6 18 5.0 12.2 8.3 7.0 12.3 9.6 9.0 12.3 7.0 11.0 12.1 10.3 13.0 12.0 8.0 14.1 10.2 >30 16.0 11.4 >30 SCPM 10/12/87 Langley Lower 232 D=1.0 m 350 i • — Cavity Strain ( % ) SCPM 10/12/87 Langley Lower 232 D=1.0 m -0.1 0 0.1 Arm Deflection [mm] • Arm #1 + Arm #2 O Arm #3 UBC SEISMIC CONE PRESSUREMETER Site : Langley Lower 232 Depth : 1.0 m Date : 10/12/87 LOG CURRENT VOLUMETRIC STRAIN s SCPM 10/12/87 Lower Langley 232 Houlsby Unloading Cylindrical D=1.0 m 0 2 4 6 8 10 -ln(E0 - E) E=Natural Strain SCPM 10/12/87 Langley Lower 232 D=2.0 m 200 - i r 190 - Cavity Strain [%] Avg. of arms 1—2—3 SCPM 10/12/87 • Arm #1 Arm Deflection [mm] + Arm #2 O Arm #3 3 * 1 UBC SEISMIC CONE PRESSUREMETER Site : Langley Lower 232 Depth : 2.0 m Date : 10/12/87 1 ~ r r -T— r - r r -n r r ~ - r — r - T - r T T 1 1 10 1 0 2 LOG CURRENT VOLUMETRIC STRAIN % 0 a. x i—i I 3 O a I Q. © 0 © t 0 O SCPM 10/12/87 Lower Langley 232 Houlsby Unloading Cylindrical D=2.0 m "T 2 l .9 l MPa -ln(EO ~ E) E=Natural Strain UBC SCPM 10/12/87 HOULSBY UNLOADING CYL Langley Low 232 D=2.0 m SU=16.6 kPa 120 -i 0 2 4 6 8 10 Natural Strain % Data Points UBC SCPM 10/12/87 Houlsby Unloading Cyl Langley Low232 D=2.0 m Natural Strain % Strain SCPM 10/12/87 Langley Lower 232 D=3.0 m 300 1 : 280 -I 260 - 240 - Cavfty Strain [X] Avg. of arms 1-2-3 • Arm #1 Arm Deflection [mm] + Arm #2 O Arm #3 I—I o 0. X I I £ 0) 0) o D. •D 0 +> o £ L. 0 o 260 240 - 220 - 200 - 180 - 160 - 140 - 120 - 100 80 - 60 40 - 20 - 0 SCPM- 10/12/87 Lower Langley 232 Houlsby Unloading Cylindrical D=3.0 m 8 + 10 -ln(E0 - E) E=Natural Strain + EO = .1716 SCPM 10/12/87 Lower Langley 232 ~ln(E0 - E) E=Natural Strain + EO = .174 Cavity Strain [%] Avg. of arms 1-2-3 SCPM 10/12/87 Langley Lower 232 D=5.0 m 260 -i j : -0.1 0.1 0.3 Arm Deflection [mm] • Arm #1 + Arm #2 O Arm #3 3© i UBC SEISMIC CONE PRESSUREMETER Site : Langley Lower 232 Depth : 5.0 m Date : 10/12/87 350 - i 1 1—i—i i i i i i 1 1—i—> i i i i i LOG CURRENT VOLUMETRIC STRAIN * SCPM 10/12/87 Langley Lower 232 Houlsby Unloading Cylindrical D-5.0 m »ln(E0 - E) E=Natural Strain 0 n PI © © o © 0 o UBC SCPM 10/12/87 HOULSBY UNLOADING CYL Langley Low 232 D=5,0 m SU=21.3 kPa "Hviptrl?olcc Curve f r r CP 8 10 Natural Strain % Data Points UBC SCPM 10/12/87 Houlsby Unloading Cyi Langley Low232 D«5.0 m Natural Strain % Strain 400 350 300 J 250 -\ 200 150 - i 100 50 -I SCPM 10/12/87 Langley Lower 232 D=7.0 m o 4 Arm 1 3 Arm Deflection [mm] Arm #2 ~ Arm #3 400 SCPM 10/12/87 Lower Langley 232 D=7.0 m 350 - o Q . £ 3 n 0) £ D_ © o £ 0 o 300 - 250 - 200 - 150 J 100 - CO 50 - _ l — n , , , 1 1 1 1 1 1 1 i i r i i r~ 2 4 6 8 10 12 14 16 18 20 Cavity Strain [%] Avg. of arms 1-2—3 Pressure [kPa] > -i 3 ho o o 5* •1 i i > i 04 3 6 © UBC SEISMIC CONE PRESSUREMETER Site : Langley Lower 232 Depth : 7.0 m Date : 10/12/87 1 10 1 0 * LOG CURRENT VOLUMETRIC STRAIN x 0 Q. 2 3 n 0) e Q. •o © o 2 i _ o o 350 300 -\ 250 -4 200 -4 150 -4 100 -4 50 ~\ SCPM 10/12/87 Lower Langley 232 Houlsby Unloading Cylindrical D=7.0 m +++ 6/^-87 8 -ln(E0 - E) E=NaturaI Strain + E0 = .1596 SCPM 10/12/87 Lower Langiey 232 Houlsby Unloading Cylindrical D=7.0 m + + + + I — -ln(E0 - E) E=Natural Strain EO = .162 SCPM 10/12/87 Lower Langley 232 Houlsby Unloading Cylindrical D -7 .0 m -ln(E0 -- E) E=Natural Strain + EO = .164 UBC SCPM 10/12/87 HOULSBY UNLOADING CYL Langley Low 232 D=7.0 m SU=22.0 kPa 150 - i _ _ _ _ _ ... 0 2 4 6 8 Natural Strain % Data Points /-s O Q. I UBC SCPM 10/12/87 Houteby Unloading Cyl Langley Low232 D=7.0 m Natural Strain % Strain SCPM 10/12/87 400 350 H Langley Lower 232 D=9.0 m 300 250 ~\ 200 -\ 150 H 100 -\ 50 -i* Cavity Strain [%] Avg. of arms 1-2-3 SCPM 10/12/87 • Arm #1 Arm Deflection [mm] + Arm #2 O Arm #3 334 UBC SEISMIC CONE PRESSUREMETER Site : Langley Lower 2 3 2 Depth : 9 .0 m Date : 1 0 / 1 2 / 8 7 4 0 0 - j - r 1—i—i I I I I I i 1—i—i i i / i r 3 5 0 -A o CL lxl Dd tf> 3 0 0 CO 1x1 on a. 2 5 0 2 0 0 5.i~3oa .4- l o o 1 r — i — i i i i i' LOG CURRENT VOLUMETRIC STRAIN * 10 1 0 Q. i i c _ 9) n c Q. © © b o o 400 350 H 300 H 250 200 150 100 -f SCPM 10/12/87 Lower Langley 232 Houlsby Unloading Cylindrical 0=9.0 m 50 H + + -ln(E0 - E) E=Natural Strain EO = .1642 8 o Q . X _ 3 0) V) £ C L •o 0 +» o _ O o 400 350 H 300 -4 250 -i 200 -\ 150 -4 100 -4 50 SCPM 10/12/87 Lower Langley 232 Houlsby Unloading Cylindrical D=9.0 m + + CP 8 -In(E0 - E) E=Ncrtural Strain 4- E0 = .164 UBC SCPM 10/12/87 HOULSBY UNLOADING CYL Langley Low 232 D=9.0 m SU=21.0 kPa 1 1 1 1 1 1 1 1 1 1 1 0 2 4 6 8 10 Natural Strain % Data Points UBC SCPM 10/12/87 Houlsby Unloading Cyl Langley Low232 D=9.0 m 2 6 —J : _ _ 0 2 4 6 8 10 Natural Strain % Strain Cavity Strain [%] Avg. of arms 1-2-3 SCPM 10/12/87 Langley Lower 232 D=11.0 m ' n ~1 1 1 1 1 1 1 1 1 r -0.1 0.1 0.3 0.5 0.7 0.9 Arm Deflection [mm] • Arm #1 + Arm #2 • Arm #3 UBC SEISMIC CONE PRESSUREMETER Site : Langley Lower 232 Depth : 11.0 m Date : 10/12/87 LOG CURRENT VOLUMETRIC STRAIN % o Q. a a 9 •o 9 +> o I v_ O O 400 350 -\ 300 H 250 -4 200 -4 150 4 100 4 50 4 SCPM 10/12/87 Lower Langley 232 Houlsby Unloading Cylindrical D=11.0 m + + + 2 T " 4 -ln(E0 - E) E=Notural Strain 6 8 UBC SCPM 10/12/87 HOULSBY UNLOADING CYL Longley Low 232 D-f1.0 m SU=23.4 kPa Natural Strain % Data Points Natural Strain % Strain 500 SCPM 10/12/87 Langley Lower 232 D=13.0 m 400 -4 o a. © L. 3 0) n _ Q. •o © O I 0 o 300 -4 200 H 100 -4 Cavity Strain [%] Avg. of arms 1-2-3 S C P M 1 0 / 1 2 / 8 7 Langley Lower 232 D=13.0 m 450 - 1 ~0.1 0.1 0.3 Arm Deflection [mm] O Arm #1 + Arm #2 • Arm #3 Ao<=\ UBC SEISMIC CONE PRESSUREMETER Site : Langley Lower 232 Depth : 13.0 m Date : 10/12/87 0 D_ X 3 0) 0) c Q. •o 0 L. 0 o 500 400 -\ 300 ^ 200 H SCPM 10/12/87 Houlsby Unloading Cyl Langley Lower 232 D=13.0 m + + - 3.3 8 HPa. o 100 H 4- T 4 6 8 10 -lnn(E0 - E) E=Natural Strain o 0_ X £ n n £ Q. •o <D +> 0 £ _. o o 200 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 0 UBC SCPM 10/12/87 HOULSBY UNLOADING CYL Langley Low 232 D=13.0 m SU=25.6 kPa Crr UftlracUtAj 'Curve 4- 4 ~T~ 6 T 8 10 Natural Strain % Data Points UBC SCPM 10/12/87 Houlsby Unloading Cyl Langley Low232 D=13.0 m Natural Strain % Strain 700 SCPM 10/12/87 Langley Lower 232 D=14.1 m 600 0 + - 1 Pressure [ k P a ] Cavity Strain [%] Avg. of arms 1 —2—3 500 400 H !p0-&9- left o Q . £ m n £ Q . 300 -i 200 -4 100 -i -0.1 SCPM 10/12/87 Langley Lower 232 D=16.0 m 0.1 0.3 0.5 Arm Deflection [mm] Arm #2 O Arm #3 UBC SEISMIC CONE PRESSUREMETER Site : Langley Lower 232 Depth : 16.0 m Date : 10/12/87 1 10 1 0 * LOG CURRENT VOLUMETRIC STRAIN % C o r r e c t e d P r e s s u r e [ k P a ] A\9- APPENDIX IV DERIVATION OF UNLOAD RELOAD SHEAR MODULUS DE-RWATiON Op EQUATION F o R 6ur I n chapW 'Tour m ec^. A.-Y) fs vie a — ̂ ( S u r = A P T i-i-sOi -fhe d.er(\/a4fovi i s a s 4ollov/us : CCovi^icler -file, expans ion ° r wlvacdiow o*f a o^i^cWfcal C-ui-Vtj in IjiAeav C ^ 3 5 T ( C 9 Viowio^t^eoas 3 n d \5oWop\c rviedi.ui/n. S t r e s s e 5 3,4 Ec^ A i U b Poydiv/e, c©/vn press statuses a^d ctj(i/dvica\ o f spta«nca\ ̂ ip- d m a T e s £ l'S&->:0 are, u sed . For strnsll dd-forwad Cons 3»od culin drfCol cavi-tâ  exp&wsicm 4ke ^ O I I O U ^ V K J 6^u.a-rio/\ results • . OV -6e _ O A4. I 5 + ram's The, Caujcla^ cU-f ivnvliov^ 0-f 5-Vram i*5 Ul^ed . Bon^axion 1-5 pos- t-h'v/e. '_Kvd -ovyj-racTiovo vnegs4we. TV»e ec|a_rVioms - T D V r a d i a l avA " tar^cnTial -5-Vra'm as -fo l lows *. U + du - d r —AX- A.. . £r - 22 =- _ _ _ A 4.2, dr d r These. e^uaTior\s spp]u ov\lu JXJV ^ m a l l 5 r r a m s a n d >u. d e - n o t e s 4W <d»'5p)ace^v\€^-T a-f r a d i u m s r. Cpi^5-TiTiAT\\ye Elgi^a-hon, As/Su^imc^ a Co\r\d'\\'\o\a of radial p\awe $4rai^-,4Ue pr inci - p a l 6-WaiV\ direc4coiAS are r a d i a l 0 Ta\/^e»/vria.I a n d w a i . £r - ± far - »Ad&-JJ Ad^) " Ee - x^AcTe - i>&6r -2>k6^) A 4.5 = ( l - i ^ r - ^ O + ^ f r A 4.8 E £ * ~ 0-^L\<5* - J > ( a A 4 . 9 - S u b s T i T u r c e a u a l f o ^ s A 4 . 2 3IACJ, A 4 . 3 in eou3T-fo Ms A 4 . 0 A M . 9 ' o n e O W B . ^ S : 5uiWli-U.-\-(n^ An.10 B^d A 4 . U i M o A4.1 re^l-fe i/i r " 2 d i L L t- YCLL - - o A4.IZ S o l y / i i A ^ -\-Ue_ L m e a y ELVa^Tfc P r o b l e m 5oUin^ fo<- 4lrte câ e o*f a cult/id/real cav/"4-uj wi-rU \»oi4ral radium f o 4̂ >e. general UXlOVl |<> The. tau^lav^ co\nA\\\ov\<> srl- 4"Ue U / 3 I I o £ 4 W cavf-kj 3rd. 6 V - P f o - . ^ / f , , •awd ck^ <5& . T V w e W fX equals O . 42/2L A4 4he wall crF 4W C a u d a = r G 4 Ue re-fore. 8 = >Ooro= To"1. 3 C^O/nb^ina e-_.u.a-f<"oins A4-Z au\d A^-IO Ovid A4-II O ^ . £ e -4-v»decrial -5"W<9ivi _4 4Vie. 6 - 4civvdjevi-lial s4v<_fn r _ c v - P o -f £_c_v P o + Ack AT 4 W vvjall of 4V\e cayrV^ r*2-- Vo 7- _^d. £ & - W ° / r _ p = p 0 -t 2 < _ ^ A 4 ( 8 for 3 pre^5u.r-ery\eT-er unload / reload \t$\ T^e radius Q4 fWe. CBvi-ru^ VAJBW f>W>v*m \wv ecj. A4.18 *5 KVO4 Psdvu.5 _rf ~f^e <Drtssuve welter in 4Ue. J-ullu defla.+ecl po5\Vioi/\# T y ^ e a d i4 dke radius <g-P 4-Ke, /vwddle <--r +W unload/ r&loadi loop. 42^ fuJIij (de-fU-red ^oe-'iTi'ov^ i-5 de-Pmed a s 3o , The . 6ar - P-?c 257 A4. I5 1 1 Au "Sf Au 0 _ 2L £ » - €«. 2. where, AP= Po-Po 6^ - (£. + £0/z "Hoe unload/^e[oadl 3 hear modulus can si so be oWaf U 6 i ^ m s T u r a l S4VSM6 w<dv\ 4-W -fallowing ecjua-Won ' AP Ifeiflcj +He Mada^riVs S e r i e s W +W ina+ural sfraivi one. 42.4 l«0+*J4.")- & £ p - ~ . Z 3 2 . 3 4 * • * 4V\eiA e<\u£-l-iem r \4-22 3 iimpU-$ne£ +o AC* - £)-£i -42-5" APPENDIX V SHEAR MODULUS VALUES SHEAR MODULUS FROM HOULSBY CYLINDRICAL UNLOADING ANALYSIS Sit e : McDonald Farm Date : 27/1/87 Pressuremeter : UBC SCP On Si t e Location : JAN27 Comments : No piezocone or seismic measurements St r a i n c o n t r o l l e d t e s t Depth G H (Houlsby) GH/ s u REF  1r < H o u l s b y ) ( m ) ( MPa ) 17.0 10.63 185.0 325 19.0 7.62 122.1 207 22.0 6.18 88.0 134 25.0 8.59 110.1 164 27.5 14.18 167.8 240 30.0 6.78 74.5 105 Si t e : McDonald Farm Date : 7/11/85 Pressuremeter : FUGRO CP On Site Location : JAN27 Comments : No piezocone measurements Quasi-strain c o n t r o l l e d t e s t Depth G R (Houlsby) GH/ S U REF X r ( H o u l s b y ) ( m ) ( MPa ) 16.2 10.10 183.3 221 18.2 7.07 117.2 185 19.2 7.03 112.7 179 20.2 6.23 95.1 159 22.2 6.13 86.7 136 Sit e : Lulu Is - UBCPRS Date : 3/4/87 Pressuremeter : UBC SCP On Site Location : APR3 Comments : St r a i n Controlled Test Depth G H (Houlsby) GH/ s u REF I r ( H o u l s b y ) ( m ) ( MPa ) 3.0 2.40 60.4 122 4.0 1.58 52.0 83 4.8 1.58 61.5 109 6.35 2.36 88.4 165 ATI- 7.9 3.72 126.1 197 9.4 2.91 90.1 146 10.9 5.50 155.8 209 12.4 3,85 79.1 104 14.0 3.89 79.9 148 Sit e Date Pressuremeter On Si t e Location Comments : : Lulu Is - UBCPRS 8/1/88 : UBC SCP : JAN8 St r a i n c o n t r o l l e d t e s t Depth G H (Houlsby) ( m ) ( MPa ) V S u REF X r (Houlsby) 4.75 7.75 10.75 13.75 1.35 3.54 5.25 4.05 52.1 121 150.3 85.6 95 178 199 157 S i t e : Langley Lower 232 Date : 10/12/87 Pressuremeter : UBC SCP On S i t e Location : DEC10 Comments : S t r a i n c o n t r o l l e d Depth G H (Houlsby) G H / S U REF ( » ) ( MPa ) 2.0 1.91 72.1 3.0 2.36 102.6 5.0 2.25 118.4 7.0 2.14 115.7 9.0 2.01 98.0 11.0 2.36 ' 96.3 13.0 3.38 112.7 16.0 4.59 I r (Houlsby) 90 142 121 87 92 101 117 131 UNLOAD RELOAD SHEAR MODULUS Si t e : McDonald Farm Date : 27/1/87 Pressuremeter : UBC SCP On S i t e Location : JAN27 Comments : No piezocone or seismic measurements St r a i n c o n t r o l l e d t e s t Depth G u r Cavity S t r a i n Time Wait G u r / S u REF ( m ) ( MPa ) Increment (%) ( sec ) 22 5.58 .97 79.5 22 9.03 .57 128.6 25 6.96 1.02 89.2 25 9.72 .69 124.6 27.5 6.98 .81 82.6 27.5 8.19 1.14 96.9 27.5 16.9 .34 1040 200 30 7.19 .79 79 30 8.96 1.03 98.5 Si t e : McDonald Farm Date : 7/11/85 Pressuremeter : FUGRO CP On Si t e Location : NOV7 Comments : Unload reload loops are very small and poor q u a l i t y Q u a s i - s t r a i n c o n t r o l l e d t e s t Depth G u r Cavity S t r a i n Time Wait G u r / S u REF ( m ) ( MPa ) Increment (%) ( sec ) 16.2 13.4 .40 200 243. 2 16.2 35.7 .072 200 647. 9 16.2 21.7 .22 300 393. 8 18.2 7.84 .58 380 130 18.2 9.72 .40 230 161. 2 Site Date Pressuremeter On Si t e Location Comments : Lulu Is - UBCPRS 3/4/87 UBC SCP APR3 S t r a i n c o n t r o l l e d t e s t Depth G u r Cavity S t r a i n Time Wait G u r / S u REF ( m ) ( MPa ) Increment (%) ( sec ) 6.35 1.1 2.14 41.2 7.9 1.32 3.63 44.7 10.9 2.79 1.02 79.0 10.9 3.65 1.21 103.3 12.4 2.94 2.21 60.4 14.0 3.38 1.72 73.3 14.0 3.30 2.14 71.6 Si t e Lulu Is - UBCPRS Date : 11&19/2/87 Pressuremeter : Houghes SBPM On S i t e Location : FEB11 & FEB19 Comments : Quasi-strain c o n t r o l l e d t e s t Depth G u r Cavity S t r a i n Time Wait G u r / S u REF ( m ) ( MPa ) Increment (%) ( sec ) 4.8 .72 3.49 28.0 6.35 .57 7.89 21.3 7.9 1.38 2.17 46.9 10.9 .91 5.72 125 25.8 10.9 1.6 3.0 125 45.3 12.4 1.37 4.91 200 28.1 6.3 1.1 5.04 315 43.1 7.9 2.5 1.06 84.7 9.4 1.62 4.17 50.2 10.7 .89 4.43 25.5 10.7 2.9 2.0 220 83.2 12.5 2.91 3.2 59.4 12.5 6.1 .91 150 124.5 14 6.5 .58 141.0 14 4.5 2.17 97.6 APPENDIX VI IN SITU TEST LOCATIONS 224 J N GZAVBL General Area for UBC SCP tests srztL 3 B£FtUNl£ tox>T 2 1 General Area for- Fugro CP tests General Area f o r Hughes SBPM tests 8- I 4 M LEGEND • PIEZ0UZ7EJL COhlt T£6T m *AT WE: 0tLATOM£IBt. TEST fsiOTE '• A L L L P C A T t o j ? SITE PLAN OF McDONALD * s FARM m DIKE ROAD FRASER RIVER © © © © © 0 © VO MO MO VO I I -& 4 1 3 0 0 1 3 0 0 LEGEND i P/£ZOCOM£ TEST I I DMT-2 DKT-1 r UBC SCP-1J t I R l UBC SCP-2 4 L S C P T . -0 X - F V T - l l(Acc) •© •© •© SCALE 1 : 50 LULU IS.-UBCPRS SITE PLAN 43B> FVT-4 1 CPTU-3 - fr-FVT-5 A /-CPTU-4 - SCPT-1 (Acc)-1 UBC SCP-1 MoT T O M O T E . A_ P i fcfcO C O »vJT£

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