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Interface strength of various geosynthetics and soils from ring shear tests Effendi, Rustam 1995

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INTERFACE STRENGTH OF VARIOUS GEOSYNTHETICS AND SOILS FROM RING SHEAR TESTS by R U S T A M  E F F E N D I  B . S c . (Ir.), U n i v e r s i t y o f L a m b u n g M a n g k u r a t Indonesia, A THESIS  SUBMITTED  1989  I N PARTIAL FULFILLMENT  T H E R E Q U I R E M E N T S F O R T H E D E G R E E M A S T E R  O F A P P L I E D  O F  S C I E N C E  in T H E F A C U L T Y O F G R A D U A T E  S T U D I E S  Department of Civil Engineering The University of British Columbia  W e accept this thesis as  conforming  to the required standard  T H E U N I V E R S I T Y O F B R I T I S H February,  1995  © RUSTAM EFFENDI  C O L U M B I A  O F  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 C I V I L  6AJ^[NBB^NQ-  The University of British Columbia Vancouver, Canada Date  DE-6 (2788)  FP&rWtfl>f  1,  IQQCJ  ABSTRACT I n t e r f a c e s t r e n g t h is o n e o f t h e m a j o r p a r a m e t e r s c o n t r o l l i n g g e o t e c h n i c a l  construc-  tions that i n c o r p o r a t e g e o s y n t h e t i c s . H o w e v e r there are, at the t i m e o f w r i t i n g , f e w d a t a o n the interface strength o f v a r i o u s g e o s y n t h e t i c s w i t h soils. O n o c c a s i o n , s l o p e failures  have  b e e n a t t r i b u t e d t o a l a c k o f k n o w l e d g e o n t h i s p a r a m e t e r . T h e m a i n o b j e c t i v e o f t h i s t h e s i s is to contribute to the available database o n the interface strength o f geosynthetics, with  em-  phasis o n the implications for design a n d c o n s t r u c t i o n o f w a s t e c o n t a i n m e n t facilities. p r o g r a m o f laboratory tests w a s used to observe a n d interpret the mobilization o f strength. Limitations o f the direct shear apparatus for simulating the large  A  shear  displacements  c o m m o n l y exhibited in the field led to the selection o f the U B C ring shear device for testing. M o s t tests w e r e p e r f o r m e d at a strain rate o f 0.04 m m / s , for n o r m a l stresses in the g e n e r a l range 50 to 200 kPa. T w o types o f geosynthetic, g e o m e m b r a n e s a n d geotextiles, a n d  two  t y p e s o f soils, a c o m p a c t e d clay a n d O t t a w a sand, w e r e e x a m i n e d in the p r o g r a m o f testing. A m a r k e d sensitivity o f the interface strength o f the c o m p a c t e d clay-geosynthetic v a r i a t i o n s o f m o u l d i n g w a t e r c o n t e n t i n t h e r e c o n s t i t u t e d c l a y is a p p a r e n t f r o m t h e  to  results.  Clay samples c o m p a c t e d to a moisture content o f 2 6 % and 2 7 % , w h i c h are nominally  1%  and 2 % wet o f o p t i m u m exhibited residual shear strengths of approximately 75 k P a and 50 k P a respectively. Results for the various geosynthetic-compacted  ii  clay interfaces  gave  residual strengths ranging from 13% to 95% of that for the compacted clay alone, which was assumed to have 0 = 23.9° and c = 20.9 kPa. The interface strength of the Ottawa sand and various geomembranes is generally governed by the stiffness, hardness, and texture of a geomembrane and by imposed stress level. It was found that the residual interface friction angles, ^  r e s i d u a  i , for the interfaces varied from  10.5° to 29.1°. The lower value is for a smooth HDPE, while the higher value is mobilized by a soft PVC at higher stresses. The Ottawa sand/nonwoven geotextile interface strength varied from 24° to 27.8° and appeared to be controlled primarily by the type and the arrangement of fibres composing the fabric. Values of <5  id  , for the geomembrane-geotextile interfaces were found to be inde-  pendent of stress level. They vary widely from 6.1° to 33.8°, and are controlled mainly by the texture and stiffness of geomembranes, and the types and arrangement of filaments composing the geotextile. The lower value is for a smooth HDPE with a geotextile comprising glossierfilaments,while the higher value is mobilized by the textured HDPE against a geotextile withfilamentsthat are best-interwoven. Of all interface combinations, the ring shear tests with a smooth HDPE geomembrane always resulted in lowest residual interface strengths.  iii  CONTENTS Page ABSTRACT  ii  LIST O F TABLES  vii  LIST O F FIGURES  x  L I S T O F S Y M B O L S  xv  A C K N O W L E D G E M E N T  xvi  CHAPTER 1 INTRODUCTION CHAPTER 2 P U B L I S H E 2.1 2.2 2.3 2.4 2.5  1  D D A T A O N S O I L / G E O S Y N T H E T I C I N T E R F A C E S T R E N G T H General Compacted Clay-Geosynthetics Ottawa Sand-Geosynthetics Nonwoven Geotextiles-Geomembrane Summary  CHAPTER 3 R I N G S H E A R T E S T I N G P R O G R A M S 3.1 T h e U B C R i n g S h e a r D e v i c e 3.2 Materials 3.2.1 C o m p a c t e d C l a y 3:2.2 O t t a w a S a n d 3.2.3 G e o m e m b r a n e s 3.2.4 Geotextiles 3.3 S a m p l e P r e p a r a t i o n 3.3.1 P l a c e m e n t o f the C l a y 3.3.2 Placement of the S a n d 3.3.3 P l a c e m e n t of the Geosynthetics 3.4 Testing Procedures  iv  4 4 5 9 11 15  16 16 20 20 22 23 24 24 27 30 31 32  Page CHAPTER 4 C O M P A C T E D C L A Y 4.1 G e n e r a l 4.2 C o m p a c t e d 4.2.1 C o 4.2.2 C o 4.3 C o m p a c t e d 4.4 S u m m a r y  G E O S Y N T H E T I C T E S T R E S U L T S A N D A N A L Y S I S Clay-Geomembranes mpacted Clay-Smooth HDPE mpacted Clay-Textured HDPE Clay-Geotextile  CHAPTER 5 O T T A W A S A N D - G E O S Y N T H E T I C T E S 5.1 G e n e r a l 5.2 O t t a w a S a n d - G e o m e m b r 5.2.1 O t t a w a S a n d - S m o o t h 5.2.2 O t t a w a s a n d - V L D P E 5.2.3 O t t a w a S a n d - P V C 5.2.4 O t t a w a s a n d - T e x t u r e d 5.3 O t t a w a S a n d - G e o t e x t i l e s 5.4 S u m m a r y CHAPTER 6 G E O M E M B R A 6.1 6.2 6.3 6.4 6.5 6.6 CHAPTER  T R E S U L T S A N D A N A L Y S I S anes HDPE  HDPE  N E - G E O S Y N T H E T I C T E S T R E S U L T S A N D A N A L Y S I S General VLDPE-Geotextiles Smooth HDPE-Geotextiles PVC-Geotextiles Textured HDPE-Geotextiles Summary  33 33 38 38 43 47 50  52 52 56 56 60 64 70 73 77  78 78 79 84 87 92 96  7  C O N C L U S I O N S  98  R E F E R E N C E S  102  APPENDIX A T E S T D A T A O N C O M P A C T E D C L A Y - G E O S Y N T H E T I C I N T E R F A C E S I. C O M P A C T E D CLAY  104  v  Page I I .C O M P A C T E D C L A Y - S M O O T H H D P E I I I . C O M P A C T E D C L A Y - T E X T U R E D H D P E I V .C O M P A C T E D C L A Y - G E O T E X T I L E ( P O L Y F E L T T S 5 5 0 )  1 0 6 I l l 1 1 4  APPENDIX B T E S T D A T A O N O T T A W A S A N D - G E O S Y N T H E T I C I N T E R F A C E S I.OTTAWA SAND I I .O T T A W A S A N D - S M O O T H H D P E III. OTTAWA SAND-VLDPE IV.OTTAWA SAND-PVC V. OTTAWA SAND-STEEL V I . O T T A W A S A N D - T E X T U R E D H D P E VII.OTTAWA SAND-TREVTRA 1120 VIII. O T T A W A S A N D - P O L Y F E L T T S 5 5 0  116 1 2 0 124 129 133 1 3 5 138 141  APPENDIX C T E S T D A T A O N G E O M E M B R A N E - G E O T E X T I L E I N T E R F A C E S I. VLDPE-TREVIRA 1120 II.VLDPE-POLYFELT TS 550 III. SMOOTH HDPE-TREVIRA 1120 IV. SMOOTH HDPE-POLYFELT TS 550 V. PVC-TRIVERA 1120 VI. PVC-POLYFELT TS 550 VII.TEXTURED HDPE-TREVIRA 1120 VIII. T E X T U R E D H D P E - P O L Y F E L T T S 5 5 0  144 148 151 155 157 160 163 166  vi  L I S T O F  T A B L E S  Page Table 3.1. D r y density a n d moulding water content o f the compacted  clay  f r o m the S t a n d a r d P r o c t o r c o m p a c t i o n tests  21  T a b l e 3.2. Properties o f g e o m e m b r a n e s (after G F R : Specifier's G u i d e 1 9 9 3 )  23  Table 3.3. M e c h a n i c a l properties o f Trevira 1120 a n d Polyfelt T S 550 (after G F R : Specifier's G u i d e , 1993) Table 4.1. Test c o d e f o r ring shear tests o n the c o m p a c t e d clay w i t h different geosynthetics  24 34  Table 4.2. S u m m a r y o f shear strengths f r o m ring shear tests o n the c o m p a c t e d clay  35  Table 4.3. S u m m a r y o f shear strengths f r o m ring shear tests o n compacted clay-smooth HDPE  39  Table 4.4. S u m m a r y o f shear strengths f r o m ring shear tests o n compacted clay-textured H D P E  43  Table 4.5. S u m m a r y o f shear strengths TS 550  from  ring shear tests o n c o m p a c t e d  clay-Polyfelt 47  Table 5.2. Test c o d e f o r ring shear tests o n the O t t a w a sand w i t h different geosynthetics  53  Table 5.2. S u m m a r y o f internal friction angles f r o m ring shear tests o n the O t t a w a sand  54  Table 5.3. S u m m a r y o f interface friction angles a n d efficiency ratios f r o m ring s h e a r t e s t s o n O t t a w a s a n d - s m o o t h H D P E  57  Table 5.4. S u m m a r y o f interface friction angles a n d efficiency ratios f r o m ring shear tests o n O t t a w a s a n d - V L D P E  61  vii  Page Table 5.5 S u m m a r y o f interface friction angles a n d efficiency ratios ring shear tests o n O t t a w a s a n d - P V C  from  T a b l e 5 . 6 . S u m m a r y o f i n t e r f a c e friction a n g l e s a n d e f f i c i e n c y r a t i o s ring shear tests o n O t t a w a sand-soft steel  from  64  68  Table 5.7. S u m m a r y o f the interfacel friction angles a n d efficiency ratio from ring shear tests o n O t t a w a sand-textured H D P E  70  Table 5.8. S u m m a r y o f the interface friction angles a n d efficiency ratios f r o m ring shear tests o n O t t a w a sand-Trevira 1 1 2 0  73  Table 5.9. S u m m a r y o f the interface  friction  angles a n d efficiency ratios  f r o m ring shear tests o n O t t a w a sand-Polyfelt T S 5 5 0  74  Table 6.1. Test c o d e f o r ring shear tests o n g e o m e m b r a n e s with geotextiles Table 6.2. S u m m a r y VLDPE-Trevira Table 6.3. S u m m a r y VLDPE-Polyfelt  o f i n t e r f a c e friction a n g l e s f r o m r i n g s h e a r t e s t s o n 1120 o f i n t e r f a c e f r i c t i o n a n g l e s from r i n g s h e a r t e s t s o n T S 550  Table 6.4. Effect o f rate o f strain o n residual interface friction angles ring s h e a r t e s t s o n V L D P E - T r e v i r a 1 1 2 0 Table 6.5. S u m m a r y o f interface smooth HDPE-Trevira 1120  friction  79  81 81 from 82  a n g l e s f r o m ring s h e a r t e s t s o n 86  T a b l e 6 . 6 . S u m m a r y o f i n t e r f a c e f r i c t i o n a n g l e s f r o m ring s h e a r t e s t s o n smooth HDPE-PolyfeltT S 550  86  Table 6.7. S u m m a r y o f interface PVC-Trevira 1120  89  friction  angles  from  ring shear tests o n  T a b l e 6 . 8 . S u m m a r y o f i n t e r f a c e f r i c t i o n a n g l e s f r o m ring s h e a r t e s t s o n PVC-geotextiles  viii  89  Page Table 6.9. S u m m a r y o f interface friction angles f r o m ring shear tests o n textured HDPE-Trevira 1120  93  Table 6.10. S u m m a r y o f interface friction angles f r o m ring shear tests o n textured HDPE-Polyfelt T S 550 .  94  ix  L I S T O F  F I G U R E S  Page F i g u r e 2.1. S c h e m a t i c o f M o d i f i e d K a r o l - W a r n e rdirect shear d e v i c e a n d s a m p l e c o n f i g u r a t i o n (after M i t c h e l l et al. 1 9 9 0 )  6  F i g u r e 2.2. E f f e c t o f fast strain rate o n shear strengths: r i n g shear tests o n K a l a b a g h D a m , P a k i s t a n (after S k e m p t o n , 1 9 8 5 )  7  F i g u r e 2.3. S c h e m a t i c o f pullout b o x using X - r a y  technique  (after Karchafi a n d Dysli, 1993)  8  F i g u r e 2.4. S c h e m a t i c o f direct shear device (after Martin, 1984)  9  F i g u r e 2.5. S c h e m a t i c o f pullout b o x (after M i t c h e l l , 1990)  12  F i g u r e 2.6. M o d i f i e d D i r e c t S h e a r D e v i c e (after W i l l i a m s a n d H o u l i h a n , 1986)  13  F i g u r e 2.7. S h a k i n g - T a b l e Facility, (a) S e t u p f o r static tests. (b) S e t u p for d y n a m i c tests (after Y e g i a n a n d Lahlaf, 1992)  14  F i g u r e 3.1 T h e U B C ring shear device  16  F i g u r e 3.2. M a j o r c o m p o n e n t s a n d data acquisation system o f the U B C ring shear device F i g u r e 3.3. Relationship b e t w e e n d r y density a n d m o u l d i n g w a t e r content  17 from  the S t a n d a r d P r o c t o r c o m p a c t i o n tests  21  F i g u r e 3.4. Particle distribution o f O t t a w a C - l 0 9 s a n d  22  F i g u r e 3.5. (a) A l t e r n a t i v e setups o f soils s a m p l e for the r i n g shear tests, (b) S e t u p for tests o n (c) P h o t o g r a p h o f a g e o m e m b r a n e s p e c i m e n F i g u r e 3.6. S p e c i m e n s o f (a) g e o m e m b r a n e s a n d annular steel platens using e p o x y resin  25  and geosynthetic specimens geotextile-geomembrane interface. in the lower confining rings (b) geotextiles g l u e d o n  26  Page F i g u r e 3.7. C o m p a c t o r a n d top confining ring assembly  27  F i g u r e 3.8. S c h e m a t i c d i a g r a m o f t h e c o m p a c t o r a n d its t r a c e s o n t h e (a) S e c t i o n v i e w o f c o m p a c t o r ; (b) P l a n v i e w o f c o n f i n i n g rings  sample. 28  F i g u r e 3.9. Relationship b e t w e e n d r y density a n d m o u l d i n g w a t e r content f r o m compaction in the ring shear device  29  Figure 3.10. R e m o v a l o f surplus o f sand using a v a c u u m device to level the sample  31  F i g u r e 4.1. Variation o f shear strength with displacement f r o m a test o n compacted clay (CLAY50C)  35  F i g u r e 4.2. R e s i d u a l shear strengths f r o m ring shear tests o n the c o m p a c t e d clay  36  F i g u r e 4.3. Effect of m o u l d i n g water content o h the residual shear strength of compacted clay F i g u r e 4.4. V a r i a t i o n o f shear strength w i t h displacement f r o m a test o n the compacted clay-smooth H D P E ( C H D S 5 0 S )  37  F i g u r e 4 . 5 . R e s i d u a l s h e a r s t r e n g t h s f r o m ring s h e a r t e s t s o n t h e clay-smooth H D P E  compacted 40  F i g u r e 4.6. Effect of m o u l d i n g water content o n the residual interface of compacted clay-smooth HDPE F i g u r e 4.7. Interface strength ratios f r o m ring shear tests o n the clay-smooth H D P E  strength  xi  41  compacted 42  F i g u r e 4.8. V a r i a t i o n o f shear strength w i t h displacement f r o m a test o n c o m p a c t e d textured H D P E ( C H D T 5 0 S ) F i g u r e 4 . 9 . R e s i d u a l s h e a r s t r e n g t h s f r o m ring s h e a r t e s t s o n t h e clay-textured H D P E  40  clay44  compacted 45  Page Figure 4.10. Effect of moulding water content on the residual interface strength of compacted clay-textured HDPE  45  Figure 4.11. Interface strength ratios from ring shear tests on the compacted clay-textured H D P E ,  46  Figure 4.12. Variation of shear strength with displacement from a test on compacted clay-Polyfelt TS 550 (CPF50S)  48  Figure 4.13. Residual shear strengths from ring shear tests on the compacted clay-Polyfelt T S 550  49  Figure 4.14. Interface strength ratios from ring shear tests on the compacted clay-Polyfelt TS 550...  50  Figure 5.1. Variation of internal friction angle with shear displacement from a test on Ottawa sand (SAND200S)  55  Figure 5.2. Residual interface friction angles from ring shear tests on the Ottawa sand... 56 Figure 5.3. Variation of interface friction angle with shear displacement from a test on Ottawa sand-smooth HDPE (HDSP50B)  58  Figure 5.4. Residual interface friction angles from ring shear tests on Ottawa sand-smooth H D P E  59  Figure 5.5. Efficiency ratio of Ottawa sand-smooth H D P E  60  Figure 5.6. Variation of interface friction angle with shear displacement from a test on Ottawa sand-VLDPE (VLSP50B)  61  Figure 5.7. Residual interface friction angles from ring shear tests on Ottawa sand-VLDPE  62  Figure 5.8. Efficiency ratio of Ottawa sand-VLDPE  63  Figure 5.9. Variation of interface friction angle with shear displacement from a test on Ottawa sand-PVC (PVSP50)  65  xii  Page Figure 5.10. Residual interface friction angles f r o m ring shear tests o n Ottawa sand-PVC  66  Figure 5.11. Efficiency ratio o f O t t a w a s a n d - P V C  67  F i g u r e 5.12. S k e t c h o f shearing b e h a v i o u r at the interface o f the O t t a w a s a n d - P V C  68  Figure 5.13. C o m p a r i s o n o f interface behaviour for various f r o m ring shear tests  69  materials  Figure 5.15. Residual interface friction angles f r o m ring shear tests o n Ottawa sand-textured H D P E  71  Figure 5.14. Variation o f interface friction angle with shear displacement f r o m a test o n O t t a w a sand-textured HDPE ( H D T S P 5 0 )  71  Figure 5.17 Sketch o f the interface shearing behaviour for O t t a w a sandtextured H D P E :  72  Figure 5.16. Efficiency ratio o f O t t a w a sand-textured H D P E  72  Figure 5.18. Variation o f interface friction angle with shear displacement from a test o n O t t a w a sand with Trevira 1120 a n d Polyfelt T S 5 5 0  74  Figure 5.19. Residual interface friction angles f r o m ring shear tests o n O t t a w a sand with Trevira 1120 a n d Polyfelt T S 550  75  F i g u r e 5.20. Efficiency ratios for the tests o n the interface o f O t t a w a sand with Trevira1120 a n d Polyfelt T S 550 Figure 6.1. Variation o f interface on the VLDPE-geotextiles  friction  angle with displacement  from  :. 7 6  tests 80  F i g u r e 6.2. Effect o f rate o f strain o n residual interface friction angles f r o m ring shear tests o n VLDPE-Trevira 1120  82  Figure 6.3. Residual interface friction angles f r o m ring shear tests o n VLDPE-geotextiles  83  xiii  Page Figure 6.4. Variation o f interface friction angle with displacement tests o n s m o o t h H D P E - g e o t e x t i l e s  from 85  F i g u r e 6.5. Residual interface friction angles f r o m ring shear tests o n smooth HDPE-geotextiles  87  Figure 6.6. Variation o f interface friction angle with displacement f r o m tests o n PVC-geotextiles  88  Figure 6.7. Residual interface friction angles  from  ring shear tests o n  PVC-geotextiles  90  F i g u r e 6.8. A r r a n g e m e n t o f the ring shear test o n O t t a w a s a n d - g e o t e x t i l e - P V C F i g u r e 6 . 9 . V a r i a t i o n o f i n t e r f a c e friction a n g l e w i t h d i s p l a c e m e n t from t e s t s on Ottawa sand-Trevira 1120-PVC and Ottawa sand-Trevira 1120 F i g u r e 6 . 1 0 . V a r i a t i o n o f i n t e r f a c e friction a n g l e w i t h d i s p l a c e m e n t from tests o n textured H D P E - g e o t e x t i l e s Figure 6.11. Residual interface friction angles textured HDPE-geotextiles  xiv  from  91  92 94  ring shear tests o n 95  L I S T O F  <j) <|) (b 8 5  internal friction angle o f soil average internal friction angle .. , r e s i d u a l i n t e r n a l f r i c t i o n a n g l e residual  T  av  ^residual  x x  a v  residuai  x  E c  S Y M B O L S  interface friction angle average interface friction idual interface friction shear strength o f soil or o average shear strength of  r e s  °  angle angle f geosynthetic/soil interface soil or of geosynthetic/soil interface  i d u a l shear strength o f soil or o f geosynthetic/soil efficiency ratio cohesion intercept  r e s  xv  interface  A C K N O W L E D G E M E N T S  I a m deeply indebted to m y thesis supervisor D r . R . J. F a n n i n for his unfailing support, advice a n d engineering j u d g e m e n t throughout the study. W i t h o u t his patience a n d understanding, this research project w o u l d not have b e e n possible. I w o u l d like to express m y sincere thanks to D r . Y . R Vaid for his advice a n d suggestions regarding use o f the U B C ring shear apparatus in this thesis w o r k , a n d also for providing a data acquisition s y s t e m for the apparatus. H i s review c o m m e n t s o n this m a n u s c r i p t are very m u c h appreciated. Special thanks to D r . W . D . Liam Finn for his invaluable assistance a n d advice d u r i n g m y  first  year o f study.  G e n u i n e appreciation to M r . Harald S h r e m p p and M r . D i c k P o s t g a t e , talented machinists at the civil engineering w o r k s h o p , U B C , for their assistance w i t h the apparatus. Many  thanks to M r . N o r m a n F. R i n n e o f Trans M o u n t a i n Pipe Line C o . L t d . for their  contribution to u p g r a d i n g o f the apparatus, a n d also for his explanation about the data acquisition  system. Finally, I wish to convey m y sincere gratitude to m y wife Fachrinawaty for her constant  support a n d patience throughout the thesis w o r k . T h i s r e s e a r c h is f u n d e d b y a s c h o l a r s h i p f r o m t h e S i x U n i v e r s i t i e s D e v e l o p m e n t Rehabilitation (SUDR),  and  Indonesia. I wish to express m y thanks for the financial support  provided.  xvi  CHAPTER 1 I N T R O D U C T I O N  I n t e r f a c e s t r e n g t h is o n e o f t h e m a j o r p a r a m e t e r s c o n t r o l l i n g d e s i g n u s i n g g e o s y n t h e t i c materials such as g e o m e m b r a n e s a n d geotextiles in geotechnical, transportation, a n d environmental constructions. A n improper selection o f interface strength values for combinations o f geosynthetics, a n d g e o s y n t h e t i c s a n d soils, m a y lead to u n d e s i r a b l e d e f o r m a t i o n s  of  t h e s t r u c t u r e d u r i n g a n d p o s t - c o n s t r u c t i o n . N e v e r t h e l e s s , t h e u s e o f g e o s y n t h e t i c s is g r o w ing b e c a u s e o f material availability, cost-benefits and, m o r e recently, e n v i r o n m e n t a l regulations. Serious environmental concerns have led several countries to enable regulations  that  m a n d a t e the u s e o f g e o m e m b r a n e s for w a s t e landfill facilities, in c o n j u c t i o n w i t h a  com-  p a c t e d clay, as materials for the l o w h y d r a u l i c c o n d u c t i v i t y liner. I n the P r o v i n c e o f British C o l u m b i a , as a follow-up to the Pollution Control A c t o f 1967 a n d a n inquiry b y the Ministry o f Environment, W a t e r Resources Service, the Waste M a n a g e m e n t A c t o f 1982 and Special W a s t e Regulations o f the A c t (1988) provide standards for the prevention a n d 1  the con-  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 1—2  trol o f pollution. Liners must be constructed o f impervious materials either using  synthetic  liners or clayey materials. A l t h o u g h , and in contrast to the a p p r o a c h o f the U . S .  Environ-  m e n t a l P r o t e c t i o n A g e n c y ( U S E P A ) , t h e u s e o f g e o m e m b r a n e s is n o t m a n d a t e d , t h e i r b e n efits are explicitly r e c o g n i z e d . G i v e n the n e e d for d r a i n a g e layers a n d filters w i t h i n the liner s y s t e m , it is c l e a r t h a t t h e c o m b i n a t i o n s o f m a t e r i a l s u s e d i n  construction may  comprise  m a n y t y p e s o f g e o s y n t h e t i c s a n d soils. R e c e n t l y , s e v e r a l f a i l u r e s h a v e b e e n a t t r i b u t e d t o al o w i n t e r f a c e s t r e n g t h b e t w e e n different t y p e s o f g e o s y n t h e t i c s a n d the adjacent soils. T o s o m e extent, the failures arise f r o m a lack o f k n o w l e d g e the interface strength and factors influencing behaviour o f the materials in shear. A w e l l - d o c u m e n t e d failure w a s the slippage at the K e t t l e m a n Hills landfill facility , C a l i f o r n i a ( S e e d et al., 1988; M i t c h e l l et al, 1 9 9 0 ) . T h e n i n e t y - f o o t h i g h , 1 5 - a c r e  hazardous  w a s t e landfill slid w i t h a lateral displacement u p to 35 feet. F o r e n s i c observations a n d l a b o r a t o r y tests i n d i c a t e d failure p r o b a b l y o c c u r r e d a l o n g aw e a k interface w i t h i n the liner system. To date, f e w comprehensive studies have been carried out o n the interface strength geosynthetic materials w i t h various soils c o m m o n l y u s e d in construction applications. leads to a difficulty in selecting values to use for preliminary design calculation.  of  This  Several  series o f tests w e r e therefore performed using the U B C ring shear device o n combinations  of  g e o s y n t h e t i c / s o i l interfaces. T h e m a i n p u r p o s e o f this w o r k is t o c o n t r i b u t e o f t h e l i t e r a t u r e o n interface strength and to assess the implications for optimization o f materials for construction. T h e decision use to a ring shear device in this study w a s taken to benefit f r o m  its  capacity to shear a sample to unlimited displacement in one direction. This shearing behaviour is e x p e c t e d t o c l o s e l y s i m u l a t e c o n d i t i o n s i n t h e  field  where failure occurs through  large  Interface Strength of Various Geosynthetics and  SoilsfromRing Shear Tests: CHAPTER 1  d i s p l a c e m e n t s a n d u s u a l l y i n o n e d i r e c t i o n : t h e m i n i m u m s t r e n g t h o r t h e r e s i d u a l s t r e n g t h is r e a c h e d at this failure condition. T h e ring shear tests c o n d u c t e d in this p r o g r a m address combinations o f the interfaces: 1. c o m p a c t e d  clay-geomembrane;  2. c o m p a c t e d  clay-geotextile;  3. O t t a w a  sand-geomembrane;  4. O t t a w a s a n d - g e o t e x t i l e ; a n d 5.  geomembrane-geotextile.  following  CHAPTER 2 P U B L I S H E D  2.1  D A T A  O N  S O I L / G E O S Y N T H E T I C S T R E N G T H  I N T E R F A C E  General To date there are a relatively few published data pertaining to the interface strength  of  g e o s y n t h e t i c s w i t h soils. S i n c e n o testing p r o c e d u r e h a s b e e n s t a n d a r d i z e d , the testing m e t h ods e m p l o y e d a n d the apparatuses used vary. A review o f the published data f r o m tests o n the interface o f geosynthetics w i t h various soils follows, w i t h e m p h a s i s o n the ring  shear  device and the direct shear box, the pullout box, and other specially designed pieces  of  equipment. G i v e n the objective o f this thesis, the r e v i e w addresses tests o n the f o l l o w i n g interface c o m b i n a t i o n s , as u s e d in this thesis p r o g r a m : - compacted clay with: - smooth H D P E geomembrane; - textured H D P E geomembrane; - n o n w o v e n geotextiles.  4  Interface Strength of Various Geosynthetics and  Soils from Ring Shear Tests: CHAPTER  - Ottawa sand with: - smooth H D P E geomembrane; - textured H D P E geomembrane; - V L D P E geomembrane; - P V C geomembrane; - nonwoven  geotextiles.  - n o n w o v e n geotextiles with - smooth H D P E geomembrane; - textured H D P E geomembrane; - V L D P E geomembrane; - P V C geomembrane. 2.2  Compacted Clay-Geosynthetics I n a back-analysis o f the failure o f the liner s y s t e m at the K e t t l e m a n Hills h a z a r d o u s -  w a s t e landfill, S e e d et al. ( 1 9 8 8 ) a n d M i t c h e l l et al. ( 1 9 9 0 ) p r e s e n t e d a p a p e r r e p o r t i n g their investigation o f interface strength characteristics o f the material combinations used in the liner system.  T h e y examined combinations of compacted clay with a smooth HDPE  and  with a geotextile. T h e clay w a s the mixture of onsite claystone, siltstone, a n d sandstone w i t h a p p r o x i m a t e l y 5 % bentonite. Its plasticity i n d e x v a r i e d b e t w e e n 2 2 % a n d 4 6 % . T h e a p p a r a tus used in the observation was a modified Karol-Warner  direct shear device; a  schematic  d i a g r a m o f t h e a p p a r a t u s is i l l u s t r a t e d i n F i g u r e 2.1. T h e m a x i m u m d i s p l a c e m e n t a c h i e v e d is very small w h e n c o m p a r e d with that o f the ring shear device. In their investigation o f the compacted clay with the HDPE  interface, tests w e r e c o n d u c t e d a c c o r d i n g to t w o  methods:  the s a m p l e s w e r e sheared as c o m p a c t e d without soaking, a n d after being s o a k e d for  24  hours. N o r m a l stresses used w e r e 158.7, 317.3, a n d 480.8 k P a , a n d the rates o f displace-  Interface Strength of Various Geosynthetics and SoilsfromRing Shear Tests: CHAPTER 2—6  APPLIED V E R T I C A L LOAD  APPLIED SHEAR 4 LOAD Bollom Somple Bottom Ploten -A  F i g u r e 2.1. Schematic o f M o d i f i e d K a r o l - W a r n e rdirect shear device s a m p l e c o n f i g u r a t i o n (after M i t c h e l l et al. 1 9 9 0 )  ment ranged  from  and  0 . 1 2 7 m m / m i n t o 1.27 r r r x r i / m i n . It w a s f o u n d that t h e r a t e s o f d i s p l a c e -  m e n t did not affect the m e a s u r e d shear strengths o f any liner interface combinations. independence o f shear strength  from  This  rate o f strain w a s also f o u n d b y S k e m p t o n ( 1 9 8 5 ) in his  observations o n the clay o f the K a l a b a g h D a m , Pakistan, using aring shear device. H e  ob-  Interface Strength of Various Geosynthetics and  served that rate o f strains  from  Soils from Ring Shear Tests: CHAPTER  0.01 m m / m i n to 10 m m / m i n h a d n o significant influence  the shear strength o f the clay, w h i c h h a d L L = 45 a n d P I = 22, a n d w a s classified as a p l a s t i c i t y clay. It c a n b e s e e n strength obtained  from  from  F i g u r e 2.2 that the c u r v e o f n o n - d i m e n s i o n a l i z e d  on low  shear  s t r a i n r a t e s u p t o 1 0 0 m m / m i n i s r e l a t i v e l y flat. F o r t h e c l a y s h e a r e d  as c o m p a c t e d , M i t c h e l l et al. ( 1 9 9 0 ) m e a s u r e d p e a k a n d r e s i d u a l  friction  angles in the range  1 3 . 6 ° ± 2 . 4 ° a n d 1 2 . 4 °± 1 . 1 °respectively. U n d e r the p r e s o a k e d condition, the v a l u e s o f p e a k a n d residual interface strengths w e r e 48.3 ± 6.2 k P a a n d 43.8 ± 4 . 1 k P a respectively.  F i g u r e 2.2. Effect o f fast strain rate o n shear strengths: r i n g shear tests o n K a l a b a g h D a m , P a k i s t a n (after S k e m p t o n , 1 9 8 5 )  This  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 2—8  presoaked condition w a s also applied to the interface o f the c o m p a c t e d clay with the  geotextile,  a n d the resulting values o f interface friction angles w e r e in excess o f 2 4 ° . N o tests  were  p e r f o r m e d o n t h e c o m p a c t e d c l a y / g e o t e x t i l e i n t e r f a c e f o r t h e as compacted c o n d i t i o n s . Karchafi a n d D y s l i ( 1 9 9 3 ) c o n d u c t e d aseries pullout tests to d e t e r m i n e interface frict i o n v a l u e s b e t w e e n an o n w o v e n g e o t e x t i l e a n d a  fine-grained  s o i l , am o i s t silt. A n  X-ray  technique w a s u s e d to determine the displacement o f the soil a n d the strain o f the reinforcement, see F i g u r e 2.3. A l t h o u g h the soil they used in the investigation w a s not a c o m p a c t e d c l a y — t h e m a i n p u r p o s e o f the discussion in this s e c t i o n — t h e y c o n c l u d e d that the r a t i o ( t a n o V t a n <p) o f t h e n o n w o v e n g e o t e x t i l e a n d a useful data point for comparison with other  fine-grained  soil w a s 0.6, w h i c h serves  results.  Experimental set-up: side view.  .vi,iy Utt*  /  Jick  GcotMDk umple wiih lead i h o u  / Diiplacantni  (••inducer  efficiency  Mewl d a m n  eeotexile MHKhutrm  Eipcrimcnuil scl-up: horizontal section ul Hie level ul (lie ttcotcxtile.  F i g u r e 2.3. S c h e m a t i c o f pullout b o x using X - r a y technique (after K a r c h a f i and Dysli, 1993)  as  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 2—9  2.3 Ottawa Sand-Geosynthetics Several researchers have reported the interface strength o f O t t a w a sand with various t y p e s o f geosynthetics. T h e w e l l - r e f e r e n c e d d a t a are t h o s e r e p o r t e d b y M a r t i n et al. ( 1 9 8 4 ) f r o m their investigation o n various geosynthetics  a n d soils u s i n g a m o d i f i e d direct  shear  apparatus, as illustrated schematically in F i g u r e 2.4. T h e stress levels u s e d in the tests r a n g e d from  13.8 k P a to 103.5 kPa. T h e y f o u n d the interface friction angles o f the O t t a w a  w i t h as m o o t h H D P E  sand  g e o m e m b r a n e and a n o n w o v e n C Z 600 were 1 8 ° a n d 2 6 ° respectively.  U s i n g the U B C r i n g s h e a r d e v i c e , N e g u s s e y et al. ( 1 9 8 8 ) c o n d u c t e d atest o n t h e interface between an HDPE  g e o m e m b r a n e and O t t a w a sand. A t an o r m a l stress o f 50 k P a , they  observed that the interface exhibited apeak friction angle o f 1 7 . 6 ° a n d aresidual value 1 5 ° . T h e p e a k v a l u e s e e m s to a g r e e w i t h that f o u n d b y M a r t i n et al. ( 1 9 8 4 ) , h o w e v e r  NORMAL STRESS  F i g u r e 2.4. S c h e m a t i c o f direct shear d e v i c e (after M a r t i n ,  1984)  of the  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 2—10  r e s i d u a l v a l u e d o e s not. R i n n e ( 1 9 8 9 ) o b s e r v e s that M a r t i n et al. ( 1 9 8 4 ) p o s s i b l y failed to simulate large displacements by reversing the direction o f shearing in their direct shear b o x . T h i s c o m m e n t m i g h t b e t r u e since M a r t i n et al. ( 1 9 8 4 ) d i d n o t m e n t i o n t h e m a x i m u m disp l a c e m e n t obtained in testing. In his study, R i n n e ( 1 9 8 9 ) f o u n d that the residual interface strengths o f the O t t a w a sand with smooth H D P E  a n d with P V C w e r e dependent o n stress  levels. F o r n o r m a l stresses o f 100 a n d 750 k P a , he m e a s u r e d the residual friction angle of the Ottawa sand with smooth HDPE  as 1 4 ° a n d 1 8 ° respectively. T h e s e f i n d i n g s a r e a little  different to, b u t i n r e a s o n a b l e a g r e e m e n t w i t h , t h o s e o f N e g u s s e y et al. ( 1 9 8 8 ) . T h e v a r i a t i o n might arise f r o m different properties of the HDPE  geomembranes used: detailed properties  of the g e o m e m b r a n e s used in these studies are not provided. In the tests o n the interface o f PVC  with the O t t a w a sand, R i n n e (1989) found residual interface friction angles b e t w e e n  28° a n d 2 9 ° for stress levels o f 100 a n d 500 k P a : these values are the s a m e as those obtained f r o m tests o n the O t t a w a sand alone. D r u s c h e l et al. ( 1 9 9 0 ) a n d D r u s c h e l a n d R o u r k e ( 1 9 9 1 ) r e p o r t tests o n 4 5 0  geomem-  b r a n e - s a n d interfaces, u s i n g a6 0 - m m - s q u a r e s h e a r b o x w i t h as t r a i n e d - c o n t r o l l e d d i s p l a c e m e n t system. A c c o u n t i n g for the l o w stresses that are typical in covers o f w a s t e i m p o u n d m e n t facilities, the tests w e r e c o n d u c t e d at n o r m a l stresses r a n g i n g b e t w e e n 3.5 a n d 3 5 k P a . F o u r s a n d s w e r e u s e d in the tests; o n e o f t h e m w a s O t t a w a sand. T h e g e o m e m b r a n e s  were  s m o o t h H D P E (pipe a n d lining), M D P E , a n d P V C (pipe a n d lining) polymers. T h e y f o u n d 0 = 3 5 ° a n d (5 = 1 9 ° ( p e a k v a l u e s ) f o r t h e t e s t s o n t h e O t t a w a s a n d a l o n e a n d t h e i n t e r f a c e s the O t t a w a sand either with the s m o o t h H D P E  lining or with the smooth HDPE  of  pipe respec-  tively. A higher p e a k friction angle o f 3 0 ° w a s f o u n d o n the interface o f the P V C liningO t t a w a sand; o n the other hand, ap e a k 6 =1 7 ° w a s observed for the test o n P V C pipeO t t a w a sand. T h e y further observed the effect of surface hardness o n the ratio of interface to  Interface Strength of Various Geosynthetics and  SoilsfromRing Shear Tests: CHAPTER  t h e s a n d f r i c t i o n a n g l e ((5/0): f o r t h i s p u r p o s e t h e y a l s o i n c l u d e e p o x y a n d p l e x i g l a s a c r y l i c . T h e y f o u n d that the ratio w a s dependent o n the surface hardness of the g e o m e m b r a n e s ;  the  harder materials exhibited l o w e r ratios. 2.4  Nonwoven Geotextiles-Geomembrane M a r t i n et al. ( 1 9 8 4 ) , in a d d i t i o n to the series o f tests o n t h e interface o f soils  with  g e o m e m b r a n e s a n d with geotextiles, also performed tests investigating the interface strength b e t w e e n g e o m e m b r a n e s a n d geotextiles. F o r each test o n a P V C g e o m e m b r a n e w i t h a n o n w o v e n C Z 6 0 0 g e o t e x t i l e , b o t h s i d e s o f t h e P V C s p e c i m e n w e r e u s e d s i n c e it w a s  rougher  o n o n e s i d e . T h e y f o u n d t h a t t h e r o u g h e r s i d e e x h i b i t e d a h i g h e r f r i c t i o n a n g l e (<5 = 2 3 ° ) t h a n t h e o t h e r s i d e (d = 2 1 ° ) . A v e r y l o w f r i c t i o n a n g l e o f 8 ° w a s m e a s u r e d i n a CZ 600 with a smooth HDPE observed an even  test o n  the  g e o m e m b r a n e . I n a n o t h e r i n v e s t i g a t i o n , N e g u s s e y et al. ( 1 9 8 8 )  lower frictional resistance to be mobilized with a Texel 7612  geotextile  (d = 6 . 5 ° ) . T h e s e v a r i a t i o n s m i g h t r e s u l t f r o m d i f f e r e n c e s i n t h e t e s t d e v i c e s t h a t s h e a r  the  specimens in dissimilar ways, or c o u l d be material specific. H o w e v e r , the c o n c l u s i o n that the interface o f n o n w o v e n geotextiles with a smooth HDPE  results i n a l o w f r i c t i o n a n g l e is a l s o  a s s e r t e d b y t h e f i n d i n g s o f M i t c h e l l et al. ( 1 9 9 0 ) . W i t h a d i r e c t s h e a r d e v i c e a n d a p u l l o u t b o x ( s e e F i g u r e 2 . 5 ) , t h e y f o u n d v a l u e s o f ^ siduai  =  t0  re  1 2 . 5 ° and 9 . 5 ° for the  respective  devices. In earlier observations, Williams a n d H o u l i h a n (1986) also f o u n d a similar interface friction angle o f 9 ° f r o m a direct shear test o n a n o n w o v e n geotextile a n d s m o o t h  HDPE.  W i l l i a m s a n d H o u l i h a n (1986) further p r o v e d , using a modified direct shear as s h o w n  in  F i g u r e 2.6, that friction resistance exhibited at the interface o f g e o m e m b r a n e s w i t h g e o t e x tiles is d e p e n d e n t o n t h e m a t e r i a l s u s e d . T h e y o b s e r v e d  d = 1 0 ° for the tests o n a  smooth  H D P E geomembrane with a T r e v i r a2125 n o n w o v e n geotextile and 6 = 1 2 ° for smooth H D P E  2—  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 2—12  ^ — R e o c t i o n Top Plote  I I I I f II  II  I I M  PNEUMATIC  PRESSURE  (Confined  within Air Bog)  I I I I  P  F i g u r e 2.5. S c h e m a t i c o f pullout b o x (after M i t c h e l l ,  1990)  with Trevira 1135. This variation might have resulted f r o m the different properties o f the g e o t e x t i l e s . T h e T r e v i r a 2 1 2 5 is a n o n w o v e n , n e e d l e p u n c h e d , a n d s t a p l e p o l y e s t e r tile; w h e r e a s t h e T r e v i r a 1 1 3 5 is an o n w o v e n , n e e d l e p u n c h e d , c o n t i n u o u s  filament  geotexpolyester  geotextile. T h e grab tensile strengths w e r e 25 k N / m a n d 60 k N / m respectively. Realizing that the published data for the d y n a m i c interface strength properties o f g e o m e m branes and geotextiles are very limited, Yegian and Lahlaf (1992) a n d Lahlaf a n d Y e g i a n ( 1 9 9 3 ) r e p o r t tests u s i n g a s h a k e table facility. T h e y u s e d a s m o o t h H D P E  geomembrane  Interface Strength of Various Geosynthetics and  Soils from Ring Shear Tests: CHAPTER  F i g u r e 2.6. M o d i f i e d D i r e c t S h e a r D e v i c e (after W i l l i a m s a n d Houlihan, 1986)  ( G u n d l e H D 6 0 ) and a n o n w o v e n geotextile (Polyfelt T S 700) in both dry a n d  submerged  conditions. T h e y also c o n d u c t e d static shear tests o n the s a m e interface, a n d p r e p a r e d c o n ditions u n d e r n o r m a l stresses varying  from  3.4 to 34 k P a for c o m p a r a t i v e purpose. T h e rate  o f shear d i s p l a c e m e n t in the static tests w a s a p p r o x i m a t e l y 1.27 m m / m i n . T h e s e t u p s f o r b o t h static a n d d y n a m i c interface strength tests are s h o w n in F i g u r e 2.7. A residual friction  2—13  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 2—14  angle of 1 0 ° and 8.5° was found  from  static tests f o r the d r y a n d s u b m e r g e d  conditions  respectively. T h e d y n a m i c tests triggered with 2to 10 H z resulted in residual d y n a m i c friction angles o f 1 0 . 7 ° and  9 . 6 ° at the first o b s e r v a t i o n o f sliding, f o r d r y a n d  submerged  c o n d i t i o n s respectively. B o t h static a n d d y n a m i c tests s e e m s to g i v e ag o o d a g r e e m e n t , g e s t i n g t h e r e is little d i f f e r e n c e b e t w e e n interface sliding and those  from  friction  angles m e a s u r e d at the onset  static tests.  9 9.  Concilia Mock, (ma*) labia, 0*>*d «**MQMt fl<gid i l M l column v*iiato* loading (••• tfawos Proving »mg Gaoiaalto Goorntfflb'iiM liaad IO lh« lal Hwifonlal disptacanwnl itai  10 Clamp  (a)  vifWAHON EXCHEH  (b) Figure 2.7. Shaking-Table Facility, (a) Setup for static tests, (b) Setup for dynamic tests (after Yegian and Lahlaf, 1992)  sugof  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 2—15  2.5 Summary T h e general implications o f the literature review are that the methods, apparatus, a n d sample dimensions in tests vary widely. C o m p a r i s o n s b e t w e e n studies reveal that tests o n similar materials give reasonably g o o d agreement. H o w e v e r , the reported data currently a v a i l a b l e a r e still i n a d e q u a t e . T h e m a i n o b j e c t i v e o f this t h e s i s p r o g r a m is t o c o n t r i b u t e g o o d d a t a f r o m r i n g s h e a r tests t o t h e e x i s t i n g b u t l i m i t e d d a t a b a s e . A r i n g s h e a r d e v i c e is p r e f e r e n t i a l l y s e l e c t e d f o r t h e t e s t i n g p r o g r a m b e c a u s e o f its ability t o s h e a r a s a m p l e t o u n l i m i t e d d i s p l a c e m e n t i n o n e d i r e c t i o n , w h i c h is s i m i l a r t o t h e c o n d i t i o n s i n t h e f i e l d : o t h e r a p p a r a tuses d o not satisfy this condition.  CHAPTER 3 RING SHEAR TESTING PROGRAMS  3.1 T h e U B C R i n g S h e a r D e v i c e The tests discussed throughout this thesis program were conducted using the UBC  ring  shear device as shown in Figure 3.1. It was originally designed by Bosdet (1980) and used to  Figure 3.1 The UBC  ring shear device 16  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 3—  HORIZONTAL LOAD CELL 2  Figure 3.2. Major components and data acquisation system of the U B C ring shear device  measure the strength of fine-grained soils. Its basic features are illustrated in Figure 3.2. In order to measure the constant volume of friction angle for cohesionless materials, Wijecwickreme (1986) then modified the device. He altered the upper confining rings (see Figure 3.2) which were originally fixed to the moment transfer arms, so that granular soil sample could also be prepared by pluviation. Another multipurpose modification was the inclusion of a bolt to connect the bottom load cell to the bottom base plate, in order to measure the upward load caused by dilation during tests on granular materials such as sand. The modifications also include an upgrading of the gearhead and the chain drive to cope with the high friction that can develop during shear of granular materials. Negussey et al (1989)  Interface Strength of Various Geosynthetics and  Soils from Ring Shear Tests: CHAPTER  a n d R i n n e (1989), in separate studies, used the device to investigate the behaviour a n d interface strength between granular materials and geosynthetics. T h e c u r r e n t a r r a n g e m e n t o f t h e U B C r i n g s h e a r d e v i c e is s h o w n s c h e m a t i c a l l y i n F i g ure 3.2, together w i t h the data acquisition system. T h e m a j o r c o m p o n e n t s o f the device are u s e d to i m p o s e n o r m a l stresses a n d rates o f strain, a n d m o n i t o r the horizontal forces  and  vertical displacements that develop with increasing radial displacement. N o r m a l loads  are  i m p o s e d f r o m air pressure in a c h a m b e r m o u n t e d o n top o f the apparatus, a n d transmitted t h r o u g h a p i s t o n a n d l o a d i n g y o k e to t h e s a m p l e . T h e m a g n i t u d e o f n o r m a l l o a d is c o n t r o l l e d b y a regulator a n d r e c o r d e d w i t h a load cell located o n the top o f the l o a d i n g yoke.  To  monitor any load that might be developed by friction b e t w e e n the outer a n d the inner surface o f the sample a n d the u p p e r confining rings, the so-called b o t t o m load cell w a s installed. T h e n e t n o r m a l l o a d is t h e d i f f e r e n c e b e t w e e n t h e r e a d i n g o f t h e t o p l o a d c e l l a n d t h e b o t t o m l o a d cell. N o r m a l s t r e s s is d e t e r m i n e d k n o w i n g t h e n e t l o a d a n d t h e c r o s s - s e c t i o n a l a r e a o f t h e s a m p l e . T h e c a p a c i t y o f e a c h l o a d cell u s e d i n this o b s e r v a t i o n is 1 0 0 0  lbs.  T h e confining rings comprise t w o parts: the u p p e r rings a n d the l o w e r rings. B o t h parts can be rotated using a m o t o r with a speed regulator. M o m e n t transfer arms are fixed to the u p p e r rings (inner a n d outer rings) a n d bear u p o n a pair o f horizontal l o a d cells (see  Fig-  u r e 3.1), e a c h w i t h a c a p a c i t y o f 5 0 lbs. T h e l o w e r rings are c o n n e c t e d to a t u r n t a b l e a n d c a n b e c o n t i n u o u s l y r o t a t e d at s e l e c t e d , c o n s t a n t rate. T h e s a m p l e is u s u a l l y a c c o m m o d a t e d  in  b o t h parts. T h e loads carried b y the m o m e n t arms are a result o f shearing resistance across the failure plane o f the sample. A specific rate o f rotation, herein called rate o f strain, c a n be attained b y adjusting the speed regulator. T h e rates o f strain that can be achieved range f r o m 2.8 x 10" m m / s t o 3.43 x 10" m m / s . Radial d i s p l a c e m e n t s are d e t e r m i n e d f r o m the l e n g t h o f 6  1  d i s p l a c e m e n t at the center o f the a n n u l a r s a m p l e in the c o n f i n i n g rings u s i n g a n  LVDT;  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 3—19  vertical displacements are recorded with an LVDT  from  m o v e m e n t s o f the loading piston.  T h e w o r k i n g r a n g e o f t h e t r a n s d u c e r u s e d to m e a s u r e v e r t i c a l d i s p l a c e m e n t is ± 1 2 . 7 m m ; w h i l e t h a t f o r r a d i a l d i s p l a c e m e n t is a p p r o x i m a t e l y 9 3 9 m m . A d e t a i l d e s c r i p t i o n o f t h e d e v i c e is g i v e n b y B o s d e t ( 1 9 8 0 ) . Data  from  all t r a n s d u c e r s w e r e transferred t h r o u g h a n A . D . c o n v e r t e r to a p e r s o n a l  c o m p u t e r . T h e y w e r e t h e n m a n i p u l a t e d b y ac o m p u t e r p r o g r a m t o d e t e r m i n e v a l u e s o f n o r mal stress, shear stress, radial displacement, vertical displacement a n d friction. T h e friction angle and the shear strength were calculated  from  the following equations (Bosdet,  B i s h o p et al. 1 9 7 1 ) : M o m e n t ( M )  = T x s a m p l e a r e a xm o m e n t a r m r.  = / (cr t a n 0X2^rrdr)(r) r,  [3.1]  [3.2] r,  = 2jta a tn 0  ,3\  [3.3]  Therefore:  tan.0 =  3 M 2jra(r -r, ) 3  3  [3.4]  2  s i n c e t a n 0 = r/a  r =  3 M 2jr(r 3  2  3 r i  )  [3.5]  1980;  Interface Strength of Various Geosynthetics and  Soils from Ring Shear Tests: CHAPTER 3—  where 0 = internal friction angle o f the soil o r interface friction angle (<5) o f i n t e r f a c i a l m a t e r i a l s , x = shear stress, o~ = n o r m a l s t r e s s , n  M=  s u m o f m o m e n t s over the shear plane as m e a s u r e d b y horiz o n t a l l o a d cells, o r = 0.1372(HL1 + H L 2 ) N-m.*  Tj = i n n e r r a d i u s o f s a m p l e / s p e c i m e n = 4 . 4 5  c m  r = outer radius o f sample/specimen = 7.00  cm.  2  3.2 M a t e r i a l s T h e materials u s e d in this study c o m p r i s e t w o t y p e s o f soils: a c o m p a c t e d clay a n d the Ottawa C - l 0 9 sand; four geomembranes: V L D P E , P V C , smooth and textured H D P E ; two geotextiles: Trevira 1120 and Polyfelt T S 3.2.1 C o m p a c t e d  and  550.  Clay  T h e clay originates  from  the H a r t l a n d landfill project, at V i c t o r i a , B C . It h a s t h e f o l l o w -  i n g A t t e r b e r g limits: P L = 3 0 % a n d L L = 5 4 % . It is classified, a c c o r d i n g t o t h e U n i f i e d S o i l Classification System (ASTM  D - 2 4 8 7 ) , a s CH  or a n inorganic clay o f h i g h plasticity.  T o  m e e t the requirements o f the l o w hydraulic conductivity barrier in the liner system o f the l a n d f i l l , it is i n t e n d e d t o p l a c e it at a b o u t 2 % w e t o f t h e o p t i m u m m o i s t u r e c o n t e n t  * Length of each moment arm from horizontal load cells  is 27.43 cm.  HL1  and  HL2  are  forces (in  Newton) measured  OMC.  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 3—21  S e v e r a l S t a n d a r d P r o c t o r c o m p a c t i o n tests w e r e m a d e o n t h e soil: t h e results a r e r e p o r t e d i n T a b l e 3.1 a n d p r e s e n t e d i n F i g u r e 3.3. T h e O M C is t a k e n t o b e am o u l d i n g content o f approximately  25%.  Table 3.1. D r y density a n d moulding water content o f the c o m p a c t e d c l a y from t h e S t a n d a r d P r o c t o r c o m p a c t i o n t e s t s No.  Name of test  CD  Pd  (%)  (Mg/m3)  1  SPC1  17.12  1.47  2  SPC2  18.50  1.52  3  SPC3  19.77  1.55  4  SPC4  21.11  1.57  5  SPC5  22.16  1.58  6  SPC6  23.40  1.61  7  SPC7  32.05  1.40  8  SPC8  30.71  1.45  Note: O) = moulding water content pd  = dry density  15  20 25 30 Moulding water content (%)  3  Figure 3.3. Relationship between d r y density a n d m o u l d i n g water content f r o m the Standard Proctor c o m p a c t i o n tests  water  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 3—22  3.2.2 Ottawa Sand T h e granular material used in the study was the O t t a w a C - l 0 9 sand. A particle d i s t r i b u t i o n c u r v e f r o m s i e v e a n a l y s i s o f t h e s a n d is s h o w n i n F i g u r e 3.4. T h e c o e f f i c i e n t uniformity C and coefficient o f curvature C u  according to the USCS  c  (ASTM  f o r the s a n d a r e 1.6 a n d 0.9  size of  respectively;  D - 2 4 8 7 ) , t h e s o i l i s c l a s s i f i e d a s SP, a p o o r l y o r u n i f o r m l y  graded sand .  100  Particle diameter (mm) F i g u r e 3.4. Particle distribution o f O t t a w a C - 1 0 9  sand  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 3—  3.2.3  G e o m e m b r a n e s S i n c e t h e m a i n o b j e c t i v e o f t h e s t u d y is t o b e t t e r u n d e r s t a n d t h e b e h a v i o u r a n d i n t e r f a c e  strength o f v a r i o u s g e o s y n t h e t i c s a n d soils, f o u r n o n - r e i n f o r c e d g e o m e m b r a n e s w i t h different characteristics w e r e extensively used in testing. T h e y are a s m o o t h polyvinyl chloride (PVC), smooth very low-density polyethylene (VLDPE), high-density polyethylene (HDPE).  and both smooth and  textured  A l t h o u g h t h e P V C is d e s c r i b e d a s h a v i n g a s m o o t h s u r -  f a c e , i n f a c t it h a s s l i g h t l y r o u g h e r s u r f a c e t h a n t h e o t h e r s m o o t h m a t e r i a l s . I n a d d i t i o n , it c o u l d also b e classified as the m o s t flexible material o f all g e o m e m b r a n e s u s e d in the test program. In comparison, the VLDPE  is stiffer a n d s m o o t h e r ; it is c l a s s i f i e d a s a s e m i f l e x i b l e  material. Yet, o f all a b o v e - m e n t i o n e d g e o m e m b r a n e s , the s m o o t h H D P E  is t h e  smoothest,  t h e stiffest, a n d the h a r d e s t material. In contrast, as s o - n a m e d , the t e x t u r e d H D P E r o u g h e s t surface, b u t is o f a s i m i l a r stiffness a n d h a r d n e s s t o t h e s m o o t h H D P E .  has  the  T h e texture  p r o t r u d e d r a n d o m l y a b o u t 1.5 t o 2 m m i n a b o v e t h e s u r f a c e o f t h e s h e e t . M a t e r i a l p r o p e r t i e s for all o f the g e o m e m b r a n e s are d o c u m e n t e d in T a b l e 3.2.  T a b l e 3.2. Properties o f g e o m e m b r a n e s (after G F R : Specifier's G u i d e  Manufacturer  Product name  Polymer Thickness ^ Texture type mm  1993)  Specific  Pucture  gravity  resistance  ASTM D792 FTMS 101C kN (lb)  Columbia Geosystem Inc.  HDPE 80 mil  HDPE  Columbia Geosystem Inc.  60 mil VLDPE  VLDPE PVC  2.03  Canadian General Tower Ltd. Geoliner60 National Seal Co.  Friction Seal HD HDPE-T  *)ASTMD751, except Geoliner60: D1593  2.03  smooth  0.940  0.40 (90)  1.52  smooth  0.915  0.35 (78)  1.52  smooth  1.238  0.44  (100)  textured  0.940  0.46  (104)  Interface Strength of Various Geosynthetics and  3.2.4  Soils from Ring Shear Tests: CHAPTER 3—  Geotextiles T h e t w o types o f geotextiles used in testing w e r e a n o n w o v e n Trevira 1120 a n d n o n -  w o v e n P o l y f e l t T S 5 5 0 . T h e f o r m e r is m a d e o f p o l y e s t e r t o a t h i c k n e s s a n d m a s s p e r u n i t a r e a o f 1.9 m m a n d 193 g / m  is 0 . 2 1 m m .  The  P o l y f e l t is m a d e o f p o l y p r o p y l e n e , w i t h a t h i c k n e s s a n d m a s s p e r u n i t a r e a o f 1.5 m m  and  1 7 0 g / m . T h e AOS 2  r e s p e c t i v e l y . I t s a p p a r e n t o p e n i n g s i z e AOS  2  o f this g e o t e x t i l e is 0 . 3 0 m m . M e c h a n i c a l p r o p e r t i e s f o r b o t h g e o t e x t i l e s  are r e p o r t e d in T a b l e 3.3. B o t h geotextiles h a v e v e r y similar properties; h o w e v e r visual o b servations revealed that the diameter o f fibres c o m p o s i n g the Trevira w a s slightly  smaller  than that constituting the Polyfelt. M o r e o v e r , the  slightly  fibres  o f the Trevira seemed to be  less glossy. Table 3.3. M e c h a n i c a l properties o f Trevira 1120 T S 550 (after G F R : Specifier's G u i d e , 1993) Puncture  Product name  Trevira  1120  Polyfelt TS  550  and  Polyfelt  Mullen burst  Trapezoid tear Grab tensile/ strength elongation ASTM D4833 ASTM D3786 ASTM D4533-85 ASTM D4632-86 kN(lb) kPa (psi) kN (lb) % WM(lb) 0.386  (80)  1896(275)  0.267  (60)  0.711  0.311  (70)  1379(200)  0.267  (60)  0.578(130)50  (160)60  3.3 S a m p l e P r e p a r a t i o n T h e general a r r a n g e m e n t o f a soil sample a n d a geosynthetic s p e c i m e n for a ring shear test a r e i l l u s t r a t e d i n F i g u r e 3.5a. It s h o w s t h e s a m p l e p l a c e d i n t h e u p p e r o r t h e t o p c o n f i n ing rings a n d the s p e c i m e n g l u e d to a n annular steel base (see F i g u r e 3.6) in the  bottom  confining rings. In the case o f tests o n soil alone, the geosynthetic s p e c i m e n w a s r e p l a c e d b y the g i v e n soil. F o r tests o n a g e o m e m b r a n e - g e o t e x t i l e  interface, the top confining ring as-  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 3—  sembly was modified, as shown in Figure 3.5b, with the geotextile specimen glued on an annular steel platen fixed to the loading yoke.  Load Cell Loading yoke semi permanent marks  semipermanent marks  outer confining rings  ribbed platei Compacted clay or Ottawa sand  geotextiles  geomembranes or geotextiles BOTTOM CONFINING RING ASSEMBLY  rigid t (steel)  (b)  (a)  (c) Figure 3.5. (a) Alternative setups of soils sample and geosynthetic specimens for the ring shear tests, (b) Setup for tests on geotextile-geomembrane interface, (c) Photograph of a geomembrane specimen in the lower confining rings  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 3—26  F i g u r e 3.6. S p e c i m e n s o f ( a ) g e o m e m b r a n e s a n d ( b ) g e o t e x t i l e s g l u e d o n annular steel platens using e p o x y resin.  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 3—2 7  3.3.1 P l a c e m e n t o f t h e C l a y The target moulding water content for compacted clay samples in the ring shear tests about 27%, that is 2% wet of OMC, Although most attempts were successful, occasionally some samples failed to meet this value. The reason that some samples were reconstitute to water contents slightly lower than 27% was the difficulty of controlling the water contents of the mixture during preparation. Before a compaction, the mixture was sealed with a plastic wrap and covered with a damp towel. It was then left to cure for at least 24 hours in a controlled humidity room. Most specimens were prepared for geosynthetic-compacted clay tests. Compaction of the clay involved placing the mixture directly in the top (upper) confining ring assembly in an upside-down position, and compacting it using a specially-made steel compactor. Figure 3.7 shows a photograph of the compactor and the top confining ring assembly; and Figure 3.8 illustrates the schematics of the compactor details and the traces of compaction effort on the  Figure 3.7. Compactor and top confining ring assembly  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 3-  Figure 3.8. Schematic diagram of the compactor and its traces on the sample, (a) Section view of compactor; (b) Plan view of confining rings.  Interface Strength of Various Geosynthetics and  Soils from Ring Shear Tests: CHAPTER 3—  clay in the u p p e r confining rings. E a c h sample w a s c o m p a c t e d to 48 b l o w s per layer  of  1.24 c m . T h e weight a n d the d r o p height o f the c o m p a c t o r w e r e 14 N a n d 10 c m ; they  were  selected to replicate the c o m p a c t i v e effort i m p a r t e d in the S t a n d a r d P r o c t o r test. A  very  g o o d agreement w a s achieved b e t w e e n densities o f the test samples a n d those f r o m S t a n d a r d P r o c t o r tests, as s h o w n in F i g u r e 3.9. T o m i n i m i z e friction b e t w e e n the  the  samples  a n d the u p p e r confining rings, a small a m o u n t o f glycerine w a s applied to the walls o f the rings before p l a c e m e n t a n d c o m p a c t i o n . F o r this series o f tests, the thickness o f e a c h  sample  w a s 1 c m . T o obtain this finished thickness, a circumferential s e m i p e r m a n e n t m a r k w a s inscribed o n the inside wall o f the u p p e r confining ring. T h e b o t t o m edge o f the rib platen that was  fixed  t o t h e l o a d i n g y o k e ( s e e F i g u r e 3 . 5 . a ) w a s s l o w l y p u s h e d t o a l i g n w i t h it, a n d  surplus clay w a s then t r i m m e d with a wire saw. Finally the sample w a s installed over  the  geosynthetic (fixed to a n annular steel base in the l o w e r confining rings). T o a v o i d friction  15  17  19  21 23 25 27 29 Moulding water content  31  33  35  (%)  F i g u r e 3.9. Relationship b e t w e e n d r y density a n d m o u l d i n g w a t e r c o n t e n t from c o m p a c t i o n i n t h e r i n g s h e a r d e v i c e .  Interface Strength of Various Geosynthetics and  Soils from Ring Shear Tests: CHAPTER 3—  b e t w e e n the u p p e r a n d the lower confining rings, a gap o f 0.02 m m w a s created b y raising the adjustable shaft c o n n e c t i n g the u p p e r confining rings to the b o t t o m l o a d cell. A g a u g e w a s u s e d to m o n i t o r this g a p  dial  adjustment  S o m e tests w e r e carried out o n c o m p a c t e d clay alone. In this case the sample preparation i n v o l v e d a t w o - l a y e r c o m p a c t i o n , e a c h o f 1.24 c m thickness in the t o p confining ring assembly, again w i t h the assembly held u p s i d e - d o w n . A s e m i p e r m a n e n t m a r k (see F i g u r e 3.5a) was also inscribed to determine the  final  thickness o f the sample, w h i c h was 2 c m  pushing and trimming the sample in the top assembly. T o place the sample in the  after lower  confining rings to a height o f 1 c m , both the upper a n d lower confining rings w e r e  then  connected with t w o pairs o f pins. This allowed the sample to be p u s h e d d o w n into the lower confining rings which had already been smoothened with glycerine, creating a sample equal thickness in the top and bottom halves o f the device. Finally the pins w e r e  of  released,  a n d a g a p o f 0.02 m m again created b e t w e e n the u p p e r a n d l o w e r confining rings as before. 3.3.2  Placement of  the  Sand  For the tests o n the O t t a w a sand-geosynthetic, the sand w a s p r e p a r e d b y air pluviation into the u p p e r confining rings that w e r e aligned a n d connected with t w o pairs o f pins to the lower confining rings. A s mentioned in the previous section a n d illustrated in F i g u r e 3.5a, the geosynthetic specimens w e r e setup o n the bottom confining ring assembly. A i r pluviation w a s s e l e c t e d b e c a u s e t h e soil is u n i f o r m l y g r a d e d a n d t h e t e c h n i q u e g e n e r a t e s  repeatable  samples. T o replicate densities for all tests, the p l u v i a t i o n d r o p height w a s m a i n t a i n e d approximately  at  1 c m . L e v e l l i n g (see F i g u r e 3.10) o f the soil s a m p l e w a s carried out u s i n g a  v a c u u m device, to siphon off the surplus soil to the targeted thickness o f 1 c m . Final steps in the preparation routine w e r e installing the loading y o k e with a ribbed p o r o u s platen  (see  Interface Strength of Various Geosynthetics and  Soils from Ring Shear Tests: CHAPTER  Figure 3.10. R e m o v a l o f surplus o f sand using a v a c u u m to level the sample.  device  F i g u r e 3.2 o r F i g u r e 3.5) a n d r e m o v a l o f the pins that w e r e u s e d to connect the u p p e r a n d lower confining rings during pluviation. T o avoid friction between the upper a n d the  lower  confining rings during testing, the u p p e r confining rings w e r e raised to create a g a p o f about 0.03 m m . T h i s g a p w a s set f r o m a c o n s i d e r a t i o n o f the particle size o f the O t t a w a s a n d  (see  F i g u r e 3.3), in o r d e r to m i n i m i z e loss o f particles. T h e s a m e procedures w e r e applied to tests o n the O t t a w a sand alone. T h e w a s that the lower confining rings w e r e also the lower confining rings, the 3.3.3 P l a c e m e n t o f the  final  fil ed  difference  with sand. A g a i n with a height o f 1 c m in  thickness o f the sample was 2 c m .  Geosynthetics  T h e setup for tests o n a geomembrane-geotextile interface w a s achieved out b y gluing a geotextile s p e c i m e n o n the annular steel platen  fixed  to the loading y o k e and a g e o m e m b r a n e  3  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 3—32  specimen on the base platen in the lower confining rings. This setup enabled the upper confining rings to be taken off, thereby avoiding friction between the annular steel platen and the walls o f the upper confining rings, as illustrated schematically in Figure 3.5b.  3.4 Testing Procedures Interface strength was examined at different values of normal stress, and with reference to rate of shear. Normal stresses used in this program of testing ranged generally from 50 kPa to 200 kPa; lower stresses o f 10 to 25 kPa or higher stresses to 400 kPa were occasionally applied. T o more efficiently understand the residual strength of a given interface, multistage tests that had stepwise increments of normal stresses were used to optimize the value o f each set-up. Unless stated otherwise, a rate o f shear o f 0.04 mm/s or 2.4 mm/min was selected for all tests in this investigation. For tests involving the compacted clay, this selection falls into the range of the findings o f Skempton (1985), as discussed in the previous chapter, in which it is believed the strength remains independent of rate of strain when compared with that resulting from a very slow rate o f strain of 0.01 mm/min. Furthermore, the above rate o f strain was found by Negussey et al.(1988) and Rinne (1989), using the same U B C ring shear device, not to affect the interface friction angle of Ottawa sand and geomembranes.  CHAPTER 4 C O M P A C T E D  4.1  C L A Y - G E O S Y N T H E T I C T E S T R E S U L T S A N A L Y S I S  A N D  General  T h e use o f compacted clay and geosynthetics  — s u c h as g e o m e m b r a n e s a n d geotex-  t i l e s — i n liner s y s t e m s led to three series o f ring shear tests o n c o m b i n a t i o n s o f the soil w i t h t w o types o f g e o m e m b r a n e s a n d a geotextile. T h e g e o m e m b r a n e s u s e d w e r e a s m o o t h a n d a textured HDPE,  a n d the geotextile w a s a n o n w o v e n Polyfelt T S 550. T h e d a t a f o r all tests  discussed in this chapter are enclosed in A p p e n d i x A . U n l e s s stated otherwise, the rate o f s h e a r u s e d t h r o u g h o u t this r e s e a r c h p r o g r a m is 0 . 0 4  rarn/s  or 2.4 m m / m i n . T h e selection  of  the rate w a s b a s e d o n the findings o f S k e m p t o n (1985), as m e n t i o n e d in the p r e v i o u s c h a p ter. T a b l e 4.1 illustrates a c o d e u s e d for e a c h test r e p o r t e d in this chapter. T h e first a n d s e c o n d c o l u m n represent the materials u s e d in a test, a n d the third c o l u m n d e n o t e s the a p p r o x i m a t e n o r m a l stresses in k P a . T h e fourth a n d the fifth c o l u m n s describe the p r o c e d u r e o f  33  Interface Strength of Various Geosynthetics and  Soils from Ring Shear Tests: CHAPTER 4—  Table 4.1. Test c o d e for ring shear tests o n the c o m p a c t e d with different geosynthetics 2  1  3  clay  5  4  50 CLAY C  HD  100  HDT  150  PF  200  B S  C D  loading (S = multistage loading) a n d the sequence of tests respectively (for those tests that w e r e repeated). T h e materials, as listed in the T a b l e 4.1, are CLAY  = c o m p a c t e d clay (soil only, w i t h n o geosynthetic),  C = c o m p a c t e d clay (used as a n interface material), HD  = smooth  HDPE,  HDT  = textured HDPE,  PF  = Polyfelt T S  and  550.  In order to better understand the nature of the interface strength of the c o m p a c t e d claygeosynthetics, a n d provide a basis for comparison, three tests w e r e p e r f o r m e d o n the  com-  p a c t e d clay alone. T w o of t h e m w e r e multistage tests a n d the third a singlestage, see T a b l e 4.2. The n o r m a l stress used in the testing ranged f r o m 50 k P a to 150 k P a . The samples w e r e generally compacted to a m o u l d i n g water content about 2 7 % , is n o m i n a l l y 2 % w e t o f t h e o p t i m u m m o i s t u r e c o n t e n t . T h e t y p i c a l r e l a t i o n s h i p  which between  s h e a r s t r e n g t h a n d d i s p l a c e m e n t is illustrated i n F i g u r e 4.1. A p e a k s t r e n g t h is m o b i l i z e d at d i s p l a c e m e n t s b e t w e e n 5 m m a n d 1 0 m m , a n d it g r a d u a l l y r e d u c e s t o a c o n s t a n t o r r e s i d u a l v a l u e at a d i s p l a c e m e n t o f a p p r o x i m a t e l y 60 m m . A  s u m m a r y plot o f residual  shear  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 4—35  Table 4.2. Summary of shear strengths from ring shear tests on the compacted clay  No  1  Name of test  CLAY50S  2  CLAY100S  3  C L A Y 100  water content  Tpeak  ^residual  (kPa)  (kPa)  (kPa)  (%)  50  74.1  40.7  27.13  103  NP  57.7  27.13  108  90.3  72.1  26.81  150  NP  84.1  26.81  104  90.2  78.0  26.55  Note: NP=no peak  20  40  60  80  100  Shear displacement (mm)  Figure 4.1. Variation of shear strength with displacement from a test on compacted clay (CLAY50S)  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 4—36  strength (r  r e s i d u a l  ) , w i t h a p p l i e d n o r m a l s t r e s s e s (a) is g i v e n i n F i g u r e 4.2. T h e l i n e a r r e l a -  t i o n s h i p i n d i c a t e s t h e c o m p a c t e d s o i l e x h i b i t s a c o h e s i o n ( c ) a n d i n t e r n a l f r i c t i o n a n g l e (<p)  of  about 20.9 k P a a n d 23.9° respectively. 150  -  100 •o  CO  50 —\ Best fit: r  r e s i d u a  |  =  0  4  4  3  ^  a  <p = 23.9°  1  i 50  1  r~ 100  I 150  '  I 200  +  2  o. 5 8  c = 20.9 kPa  '  I ' 250  300  (kPa)  F i g u r e 4.2. R e s i d u a l shear strengths f r o m r i n g shear tests o n the compacted clay S o m e s c a t t e r is o b s e r v e d i n t h e m e a s u r e d r e s i d u a l s t r e n g t h at n o r m a l s t r e s s e s o f a p p r o x i m a t e l y 1 0 0 k P a . T h i s is a t t r i b u t e d t o different w a t e r c o n t e n t s i n t h e r e c o n s t i t u t e d  soil  samples. F i g u r e 4.3 s h o w s the scattered residual strengths w i t h their m o u l d i n g w a t e r  con-  tents. A reduction in strength with increasing m o u l d i n g water content a b o v e the  optimum  m o i s t u r e c o n t e n t ( O M C ) w a s o b s e r v e d . T h i s f i n d i n g is c o n s i s t e n t w i t h t h a t o f M i t c h e l l et a l ( 1 9 6 5 ) f o r a c o m p a c t e d silty clay u s i n g three different m e t h o d s o f c o m p a c t i o n — s t a t i c ,  vi-  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 4—37  100  75  ro  03  50  O  Q  n  = 103 - 108 kPa  25  26  27  28  Moulding water content (%)  F i g u r e 4.3. Effect o f m o u l d i n g w a t e r content o n the residual shear strength o f compacted clay  b r a t o r y , a n d k n e a d i n g m e t h o d s . It is b e l i e v e d t h e l o w e r s t r e n g t h w i t h i n c r e a s i n g w a t e r c o n t e n t o n t h e w e t s i d e o f t h e O M C is a result o f p a r t i c l e a l i g n m e n t f r o m a f l o c c u l a t e d t o a parallel arrangement (Mitchell, 1965; Skempton, 1985). This p h e n o m e n o n might be a consequence o f the higher pore pressure developed in sample with higher water contents.  Since  the ring shear apparatus does not have any means to observe pore pressures, the  measured  s t r e n g t h s a r e i n t e r p r e t e d i n t e r m s o f total stresses. It is i n t e r e s t i n g t o n o t e t h a t  Skempton  (1985) f o u n d that a strain rate  from  0.01 m m / m i n , at w h i c h a test c a n b e c o n s i d e r as a  drained condition, to 10 m m / m i n did not exert any significant variation in the s t r e n g t h s f o r t h e CL c l a y o f K a l a b a g h D a m , P a k i s t a n .  measured  Interface Strength of Various Geosynthetics and  Soils from Ring Shear Tests: CHAPTER 4—  K n o w i n g t h e r e s i d u a l s h e a r s t r e n g t h o f t h e c o m p a c t e d c l a y (f  c l a y  ),  a ratio f o rthe strength  o f a n y i n t e r f a c e C^residual) t o t h a t o f t h e c l a y c a n b e e s t a b l i s h e d ; c o n s e q u e n t l y , t h e n a t u r e o f s h e a r i n g b e t w e e n t h e soil a n d g e o s y n t h e t i c is easier t o c o m p a r e a n d contrast. T o o b t a i n t h e s t r e n g t h r a t i o (r id ai/ ciay)> t h e b e s t fit l i n e i s e s t a b l i s h e d f r o m F i g u r e 4 . 2 a s : T  res  U  Residual = 0 - 4 4 3 O  n  + 20.85 k P a  [4.1]  4.2 C o m p a c t e d C l a y - G e o m e m b r a n e s 4.2.1 C o m p a c t e d C l a y - S m o o t h  H D P E  Test conditions a n dinterface strengths f r o m nine ring shear tests o n t h e c o m p a c t e d clay with a smooth HDPE  g e o m e m b r a n e are reported in Table 4.3. M o s t o f the tests w e r e con-  d u c t e d b y m e a n s o f multistage tests. N o r m a l stresses applied i n t h e tests w e r e generally f r o m 1 0 k P a t o 2 0 0 k P a . A t y p i c a l c u r v e f o r t h e t e s t CHDS50S i s s h o w n i n F i g u r e 4 . 4 . A  distinct  p e a k strength is d e v e l o p e d at a relatively small displacement o f a b o u t 1 m m . Figure 4.5 summarizes the residual shear strengths f r o m ring shear tests o n the pacted clay-smooth HDPE  interface. Different symbols a r e used to d e n o t e different  comwater  c o n t e n t s of the c o m p a c t e d clay. Scatter i n t h e data a r e attributed t o t h e differences i n w a t e r c o n t e n t . I n d e e d , w h e n a b e s t fit l i n e i s p l o t t e d a m o n g t h e s a m e w a t e r c o n t e n t s , a n d t h e samples having water content o f approximately 2 7 % a r e t h e m a i n objective i n this research p r o g r a m , a g o o d l i n e a r r e l a t i o n s h i p i s o b s e r v e d . T h e v a l u e s o f residual i n d i c a t e a  strong  d e p e n d e n c y o n s t r e s s l e v e l , a n d a s t r e n g t h e n v e l o p e g i v e n b y (j>= 4 ° a n d a c o h e s i v e i n t e r c e p t of3.6kPa. The interface strength behaviour of the compacted clay-smooth HDPE  c a nbe described  w i t h respect t o t h e m o u l d i n g water content. F i g u r e 4.6 illustrates t h e resulting  interface  shear strengths o f the compacted clay-smooth HDPE  contents,  at various moulding water  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 4—39  T a b l e 4.3. S u m m a r y o f shear strengths f r o m ring shear tests o n c o m p a c t e d H D P E  No  Name of test  2 3  4 5  6  CHDS10S  CHDS25S CHDS25SB  CHDS50S  f residual  (kPa)  (kPa)  (%)  10  4.5  1.6  24.80  NA  25  6.1  5.6  24.80  NA  51  12.7  11.7  24.80  NA  100  24.9  22.6  24.80  NA  203  48.8  35.4  24.80  NA  24  10.4  5.2  25.46  NA  59  13.4  13.4  25.46  0.13  CHDS50SC  26  5.1  4.1  50  NP  5.7  27.21  0.13  99  NP  8.4  27.21  0.13  148  NP  11.9  27.21  0.14  199  NP  14.9  27.21  0.14  28  7.8  5.0  26.94  0.15  51  NP  6.2  26.94  0.14  9.0  26.89  0.21  11.7  103  NP  15.6  26.89  0.23  148  NP  18.2  26.89  0.21  50  7.4  5.8  27.40  0.13 0.17  107  12.7  11.5  27.40  154  14.5  14.2  27.40  0.16  9.4  26.90  0.14  7  CHDS100  100  8  CHDS100B  101  13.2  11.2  27.30  0.17  9  CHDS100S  100  21.0  12.3  27.58  0.19  148  15.0  14.6  27.58  0.17  200  17.2  16.8  27.58  0.15  Note: NP=  NA  27.21  49  CHDS50SB  water content ^residual^clay  Tpeak (kPa)  1  clay-smooth  no peak  NA=  not available  NP  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 4—40  2a  10  20  40  30  50  Shear displacement (mm)  Figure 4.4. Variation o f shear strength w i t h displacement f r o m a test o n the c o m p a c t e d clay-smooth H D P E ( C H D S 5 0 S )  150  T  T  Water contents:  100  A  24.8%  •  25.5%  O  2 CO « CL  Best fit: r  26.9%-27.6%  r e s i d u a  |  =  0  .07 a  tb = 4°  n  • 3.57  c = 3.6 kPa  50 —\  50  100  150  200  250  300  (kPa)  Figure 4.5. Residual shear strengths f r o m ring shear tests o n the compacted clay-smooth H D P E  Interface Strength of Various Geosynthetics and  Soils from Ring Shear Tests: CHAPTER  Stress level:  A  24  26  99-  107  49  - 59  kPa kPa  28  Molding water content  30 (%)  F i g u r e 4.6. Effect o f m o u l d i n g w a t e r content o n the interface strength o f compacted clay-smooth FfDPE  residual  u n d e r stress levels o f about 50 k P a and 100 k P a . In addition to s h o w i n g the d e p e n d e n c y interface strength o n stress levels, the F i g u r e also s h o w s that the strength decreases increasing water content  of with  a b o v e the o p t i m u m m o i s t u r e content (about 2 5 % ) f o r these soils  w h i c h w e r e sheared immediately after c o m p a c t i o n . In t w o series o f direct shear tests o n the interface o f a s m o o t h H D P E - c o m p a c t e d clay, a p p l y i n g the s a m e stress levels, S e e d et al. ( 1 9 8 8 ) a n d M i t c h e l l et al. ( 1 9 9 0 ) o b s e r v e d that the strengths o f the c o m p a c t e d c l a y for 24 hours were lower than those  from  the same clay sheared immediately after  soaked compac-  tion. A l t h o u g h the clay w a s reconstituted to the same water content in each case, the soaking o f the clay must have resulted in an increase in degree o f saturation , and in turn, water  Interface Strength of Various Geosynthetics  and Soils from Ring Shear Tests: CHAPTER  4—42  content o f the clay. T h e interface strengths obtained f r o m the p r e s o a k e d clay w e r e i n d e p e n dent o f stress level, unlike t h o s e f r o m the other clay. T h i s p h e n o m e n o n implies that the m o r e w a t e r c o n t a i n e d i n t h e soil, t h e less f r i c t i o n a l r e s i s t a n c e is e x h i b i t e d at t h e i n t e r f a c e . Visual inspection o f the test specimens in these ring shear tests revealed a trace shearing o n the surface o f the g e o m e m b r a n e and the c o m p a c t e d clay; polishing w a s  of  appar-  ent o n b o t h surfaces. T h e trace observation confirms that shearing t o o k place at the interface. T h e t e s t d a t a f o r OJ = 2 6 . 9 % - 2 7 . 6 %  are non-dimensionalized with respect to  the  residual strength o f the clay alone, see F i g u r e 4.7. T h e resulting ratios s e e m to b e i n d e p e n d e n t o f stress level a n d , f o r as a m p l e s w i t h aw a t e r c o n t e n t o f a p p r o x i m a t e l y 2 7 % , v a r y  from  0.13 to 0.23. T h e ratio suggests that the available interface strength o f the c o m p a c t e d claysmooth HDPE  g e o m e m b r a n e is a p p r o x i m a t e l y 13 t o 2 3 % o f t h e c l a y itself.  1.0  Water contents: O  26.8%-27.6%  0.5  O 0.0 50  100  150  200  250  300  (kPa)  F i g u r e 4.7. Interface strength ratios the compacted clay-smooth H D P E  from  ring shear tests  on  Interface Strength of Various Geosynthetics and  4.2.2  Soils from Ring Shear Tests: CHAPTER 4—  C o m p a c t e d Clay-TexturedH D P E A l l ring shear tests o n the c o m p a c t e d clay-textured H D P E  specimens were performed  as multistage tests. T h e applied n o r m a l stresses r a n g e d f r o m a p p r o x i m a t e l y 2 5 k P a to  200  kPa. D a t a f r o m 5 multistage tests, i n c l u d i n g p e a k a n d residual shear strengths, w a t e r  con-  t e n t s , a n d s t r e n g t h r a t i o s a r e s u m m a r i z e d i n T a b l e 4.4.  T h e relationship b e t w e e n interface  s t r e n g t h a n d s h e a r d i s p l a c e m e n t i s p r e s e n t e d f o r t e s t CHDT50S i n F i g u r e 4.8.  Av e r y stiff  r e s p o n s e is e v i d e n t f r o m t h e p e a k strength m o b i l i z e d at t h e b e g i n n i n g o f t h e test, contrasts m a r k e d l y w i t h the equivalent test o n a s m o o t h H D P E  ( s e e F i g u r e 4.4).  which  T h e com-  plete test r e c o r d is s h o w n i n A p p e n d i x A .  T a b l e 4.4. H D P E No  S u m m a r y o f s h e a r s t r e n g t h s from r i n g s h e a r t e s t s o n c o m p a c t e d  On  Name of test  ^peak  (kPa) 1  2  3  4  5  CHDT25S  (kPa)  22  no  17.5  26.94  0.57  26.94  0.68  106  NP  56.7  26.94  0.84  214  NP  99.5  26.94  0.86  26  21.9  20.2  27.56  0.63  61  NP  35.7  27.56  0.74  106  NP  48.6  27.56  0.71  49  47.8  28.5  27.35  0.67  27.35  0.87  27.35  0.89 0.90  67  NP  44.0  107  NP  60.4  209  NP  102.4  27.35  49  47.8  40.5  24.44  NA  110  NP  79.7  24.44  NA  151  NP  104.9  24.44  NA  105  102.2  68.8  25.47  NA  202  NP  103.8  25.47  NA  CHDT50SB  NA=  (%)  30.8  CHDT50S  peak  (kPa)  NP  Note: NP=  water content ^residual^clay  55  CHDT25SB  CHDT100  26.7  ^residual  clay-textured  not  available  .  Interface Strength of Various Geosynthetics and  90  —  80  —  70  —  60  —  0  20  40  SoilsfromRing Shear Tests: CHAPTER 4—  60  Shear displacement  80  100  (mm)  F i g u r e 4.8. V a r i a t i o n o f s h e a r s t r e n g t h w i t h d i s p l a c e m e n t a test o n c o m p a c t e d clay-textured H D P E ( C H D T 5 0 S )  Values of T  residual  d o c u m e n t e d in Table 4.4 for the tests with various water contents are  s h o w n in F i g u r e 4.9. A s f o u n d HDPE,  from  from  the previous tests o n the c o m p a c t e d clay w i t h the  smooth  t h e s c a t t e r i n t h e F i g u r e 4 . 9 is a t t r i b u t e d t o d i f f e r e n t w a t e r c o n t e n t s i n t h e r e c o n s t i -  t u t e d c l a y s p e c i m e n s . A g a i n , t h e r e is a l i n e a r fit t o t h e v a l u e s o f T w a t e r c o n t e n t s o f a p p r o x i m a t e l y 27%,  for the clay with  f o r w h i c h c = 9 k P a a n d 0 = 23.8°. F i g u r e 4 . 1 0  the effect o f m o u l d i n g water contents o n the mobilized r is s i m i l a r t o t h e c o m p a c t e d c l a y - s m o o t h H D P E decreases with increasing water  residual  content.  r e s i d u a l  shows  . A b e h a v i o u r is e v i d e n t  interface in this series o f tests: the  that  strength  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 4—45  Water contents: A  0  24.44%  50  100  150  200  250  300  (kPa)  F i g u r e 4.9. R e s i d u a l shear strengths f r o m ring shear tests o n the compacted clay-textured H D P E  100  24  25  26  27  28  Moulding water content (%)  Figure 4.10. Effect o f m o u l d i n g water content o n the residual interface strength o f compacted clay-textured HDPE  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 4—46  T h e shearing b e h a v i o u r at the interface o f the c o m p a c t e d clay w i t h the t e x t u r e d  HDPE  is i l l u s t r a t e d i n F i g u r e 4.11 e x p r e s s e d as a r e l a t i o n s h i p b e t w e e n r e s i d u a l s t r e n g t h r a t i o a n d n o r m a l stress. O n l y the results f r o m samples w i t h water contents f r o m 2 6 . 9 % to 2 7 . 6 %  are  reported. A t n o r m a l stresses f r o m 22 k P a to 214 kPa, the strength ratios vary f r o m 0.57  to  0 . 9 . T h e s t r e n g t h r a t i o o f 0 . 5 7 f o r t e s t CHDT25S a t a n o r m a l s t r e s s o f 2 2 k P a i n d i c a t e s t h a t the residual strength o f the interface was only 5 7 % o f the x  residual  o f t h e c o m p a c t e d clay. It is  a p p a r e n t that the ratios are d e p e n d e n t o n stress level. R a t i o s o f a l m o s t unity, at stresses greater than 2 0 0 k P a , suggest that the surface o n w h i c h shearing t o o k place w a s likely within the clay samples. Visual inspection revealed that the textures o f g e o m e m b r a n e w e r e fully  2.0 Water contents:  O  26.9%-27.6%  ro 1.0  0.0 0  50  100  150  200  250  300  (kPa)  Figure 4.11. Interface strength ratios the compacted clay-textured H D P E  from  ring  shear tests o n  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 4—47  e m b e d d e d into the clay for the tests t e r m i n a t e d at an o r m a l stress greater t h a n 2 0 0 k P a : the textures o f the HDPE  g e o m e m b r a n e p r o t r u d e b e t w e e n 1.5 m m t o 2 m m a b o v e t h e  geomem-  b r a n e sheet. In addition, the fact that n o s c o u r w a s evident o n the surface o f the clay at h i g h e r n o r m a l stresses further c o n f i r m e d that the shearing o c c u r r e d w i t h i n the c l a y . I n c o n t r a s t , f o r t e s t CHDT25SB  samples  compacted  w h e r e the final stage o f the test w a s at a = 106 k P a ,  s o m e circumferential g r o o v e s w e r e observed o n the surface o f the c o m p a c t e d clay. T h e r e f o r e it is b e l i e v e d t h e s m a l l e r r a t i o s o b s e r v e d at l o w e r s t r e s s e s a r e a n i n d i c a t i o n t h a t s h e a r i n g w a s m o b i l i z e d , at least i n p a r t , a l o n g t h e i n t e r f a c e itself, l i k e l y a s ar e s u l t o f t h e t e x t u r e s fully p e n e t r a t i n g into the clay at these stress  not  levels.  4.3 C o m p a c t e d C l a y - G e o t e x t i l e D a t a o n interface strengths obtained f r o m t w o multistage a n d single stage test o n the c o m p a c t e d clay a n d n o n w o v e n geotextile (Polyfelt T S 550) are reported in T a b l e 4.5. A r e p r e s e n t a t i v e t e s t CPF50S, u n d e r a s t a g e d n o r m a l s t r e s s o f 4 3 k P a a n d 1 0 0 k P a , i s s h o w n i n Table 4.5. S u m m a r y o f shear strengths f r o m ring shear tests o n c o m p a c t e d TS 550 No  1  2  3  Name of test  CPF50S  CPF100S  CPF200  Note: NP=no peak  clay-Polyfelt  water content ^residual/^clay  Tp k  ^residual  (kPa)  (kPa)  (kPa)  (%)  43  37.0  32.1  26.85  0.80  100  0.86  e a  NP  56.0  26.85  170  NP  75.2  26.85  0.78  201  NP  94.5  26.85  0.86  251  NP  110.6  26.85  0.84  92  69.8  58.8  27.10  0.95  148  NP  72.7  27.10  0.84  200  NP  90.2  27.10  0.82  191  94.8  90.4  26.94  0.86  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 4—48  F i g u r e 4.12, i n d i c a t i n g as m o o t h r e s p o n s e a n d aslight p e a k s t r e n g t h at the  first  stage; h o w -  ever, n o p e a k s t r e n g t h is o b s e r v e d at t h e s e c o n d stage. T h e p e a k i n t e r f a c e s t r e n g t h o f t h e c o m p a c t e d c l a y w i t h t h e g e o t e x t i l e is m o b i l i z e d at d i s p l a c e m e n t s b e t w e e n 5 m m a n d 7 m m . Fibres pulled  from  the geotextile w e r e f o u n d adhering to the surface o f the c o m p a c t e d clay.  A s a consequence o f the pulled  fibres  t h e s u r f a c e o f t h e g e o t e x t i l e w a s o b s e r v e d t o b e shaggy  i n v i s u a l i n s p e c t i o n s a f t e r testing. It w o u l d a p p e a r t h a t b e f o r e t h e c o n s t a n t v a l u e s o f t  r e s  j  d u a l  100 90 —| 80 70 —| 60 S3  50 40 — 30 — 20 — 10 0 20  40  60  80  100  Shear displacement (mm)  Figure 4.12. Variation o f shear strength with displacement a test o n c o m p a c t e d clay-Polyfelt T S 550 ( C P F 5 0 S )  were developed, the  fibres  from  o f t h e g e o t e x t i l e h a d first t o b e p r e f e r e n t i a l l y a l i g n e d i n t h e d i r e c -  tion o f shear. F i g u r e 4.13 illustrates the relationship b e t w e e n T in Table 4.5. T h e  figure  r e s i d u a  s u g g e s t s as t r o n g d e p e n d e n c y o f T  i a n d stress level, as r e s i d u a  documented  i o n stress level, a n d a linear  Interface Strength of Various Geosynthetics and  Soils from Ring Shear Tests: CHAPTER 4—49  Figure 4.13. Residual shear strengths f r o m ring shear tests o n the compacted clay-Polyfelt T S 550  b e s t fit t o t h e r e s u l t s g i v i n g 0 = 1 9 . 9 ° a n d c = 1 9 . 5 k P a . T h e v a l u e s o f t h e a n g l e o f f r i c t i o n a n d the intercept for this interface are close to t h o s e for the clay at the s a m e w a t e r  content,  w h i c h a r e <p = 2 3 . 9 ° a n d c = 2 0 . 9 k P a . T h e h i g h s t r e n g t h s e x h i b i t e d a t t h e i n t e r f a c e r e s u l t e d from the  fibres  e m b e d d i n g in the top surface o f the clay. T h e a p p a r e n t o p e n i n g size ( A O S ) o f  t h e g e o t e x t i l e o f 0 . 3 0 m m , w h i c h is m u c h l a r g e r t h a n c l a y particles, a l l o w e d t h e c l a y t o squeeze t h r o u g h the openings u n d e r the influence o f the applied n o r m a l stresses. T h e v a r i a t i o n o f strength ratio w i t h a p p l i e d n o r m a l stress, see F i g u r e 4.14, s h o w s  a  r a t i o t h a t v a r i e s f r o m 0 . 7 8 t o 0 . 9 5 a n d is i n d e p e n d e n t o f n o r m a l stress. T h e r e s u l t s i m p l y t h a t  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 4—50  the shearing action m i g h t h a v e tended to develop within the c o m p a c t e d clay at the surface o f the geotextile.  T Water contents: O 26.85%-27.1%  (0 •g 'GO  TT  o  D  50  100  -e-  150  -o  o  200  250  300  (kPa) Figure 4.14. Interface strength ratios f r o m ring shear tests o n the compacted clay-Polyfelt T S 550  4.4 Summary Analysis o f results f r o m ring shear tests o n ac o m p a c t e d clay with b o t h as m o o t h textured HDPE •  and  g e o m e m b r a n e , a n d an o n w o v e n geotextile, suggest: residuai  T  level.  is d e p e n d e n t o n s t r e s s l e v e l : it i n c r e a s e s w i t h a n i n c r e m e n t o f s t r e s s  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 4—57  •  residuai  T  is s e n s i t i v e t o m o u l d i n g w a t e r c o n t e n t o f t h e r e c o n s t i t u t e d  com-  p a c t e d clay. • t h e r a t i o s T siduai/ ciay f o r a l l t e s t s a b o v e a r e g e n e r a l l y l e s s t h a n u n i t y . T h e y r  re  are independent o f stress level for the tests o n the combinations - the compacted clay with the smooth H D P E  geomembrane  - t h e c o m p a c t e d c l a y w i t h t h e P o l y f e l t T S 550 n o n w o v e n • the ratios T  residua  i/T  clay  0,  c, a n d  T  r e s i d u a  i/r i c  a y  - t h e s m o o t h H D P E : 0 = 4°, c = 3.6 k P a , residua./ clay = 0.13 t o 0.23 T  - t h e t e x t u r e d H D P E : 0 = 25°, c = 11.2 k P a , 7  residual  /T  clay  = 0.57 t o 0.90  - t h e P o l y f e l t T S 550:  0=  19.9°,  *residual/*clay = 0-?8 t o 0.95  geomembrane  for the geosynthetic  strength with c o m p a c t e d clay are as follows:  T  geotextile  are dependent o n stress level for the tests o n  - the compacted clay with the textured H D P E • measured values of  of  c = 19.5 k P a ,  interface  CHAPTER 5 O T T A W A  5.1  S A N D - G E O S Y N T H E T I C T E S T R E S U L T S A N A L Y S I S  A N D  General A l t h o u g h t h e r e is a g r o w i n g b o d y o f d a t a o n t h e i n t e r f a c e s t r e n g t h o f  geosynthetics  w i t h g r a n u l a r soils, f e w d a t a are p u b l i s h e d f r o m r i n g shear tests at large d i s p l a c e m e n t .  In  c o m p a r i n g results f r o m this w o r k o n O t t a w a sand w i t h other studies, n o r m a l i z e d values  of  the interface friction angles to that o f the given soil are used, resulting in a n o n - d i m e n s i o n a l factor k n o w n as the efficiency ratio, E = -^  [5.1]  a t n 0  where E  = efficiency ratio,  d  = interface  (f)  = internal  friction friction  angle b e t w e e n geosynthetic a n d soil (°), angle o f soil (°).  V a l u e s o f 0 r e s i d u a ) f o r d e r i v i n g t h i s r a t i o i n e a c h t e s t a r e b a s e d o n b e s t fit l i n e t o from  tests o n the O t t a w a sand alone.  52  data  Interface Strength of Various Geosynthetics and  Soils from Ring Shear Tests: CHAPTER 5—  In the following presentation o f test data o n residual interface friction angles, a n d in order to better appreciate the interface behaviour, the discussion of each geosynthetic interf a c e is u s u a l l y p r e c e d e d b y a t y p i c a l r e l a t i o n s h i p b e t w e e n i n t e r f a c e f r i c t i o n a n g l e s a n d s h e a r d i s p l a c e m e n t . A c o m p l e t e s e r i e s o f d a t a f o r all t e s t s is g i v e n i n A p p e n d i x B . As described in the previous chapter, the tests reported in the thesis are assigned a c o d e r e p r e s e n t i n g the c o n d i t i o n s o f the test, see T a b l e 5.1. T h e c o d e s a n d the relevant are: SAND  = O t t a w a sand (soil only, n o geosynthetic),  HD  = smooth  VL  =  PV  = P V C ,  HDT  = textured  TR  =Trevira  PF  = Polyfelt T S 550,  SP  = O t t a w a sand, as a n interfacing material.  HDPE,  VLDPE,  HDPE, 1120, and  T a b l e 5.2. T e s t c o d e f o r ring shear tests o n the O t t a w a sand with different geosynthetics. 1  2  3  SAND  50  HD  100  VL  150  PV  SP  200  HDT  250  TR  300  PF  4  5  B S  C D  materials  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 5—54  S i n c e t h e c o d e SAND  o n l y r e p r e s e n t s t h e t e s t o n O t t a w a s a n d a l o n e , it d o e s n o t n e e d  the  code in the second column. A s explained in the previous chapter, the third, fourth, a n d the fifth  c o l u m n s d e s i g n a t e t h e s t r e s s l e v e l s i n k P a , am u l t i s t a g e l o a d i n g ( S ) , a n d t h e s e q u e n c e  t e s t s r e s p e c t i v e l y . H e n c e t h e c o d e HDSP100SB m e a n s t h a t t h e s e c o n d t e s t o n t h e HDPE-Ottawa  of  smooth  sand interface w a s p e r f o r m e d b y applying staged stress levels initiated f r o m  approximately 100 kPa. A d e t e r m i n a t i o n o f E i n e q u a t i o n [5.1] r e q u i r e s av a l u e o f « 7 > f o r t h e O t t a w a s a n d . M o bilized values o f 0 u n d e r stress levels f r o m about 100 k P a to 4 0 0 k P a are r e p o r t e d in T a b l e 5 . 2 . A t y p i c a l c u r v e r e l a t i n g <p t o s h e a r d i s p l a c e m e n t , f r o m o n e o f t h e t e s t s o n O t t a w a s a n d , i s p r e s e n t e d i n F i g u r e 5 . 1 . A p e a k o f (j> i s m o b i l i z e d a t a d i s p l a c e m e n t o f a p p r o x i m a t e l y 2 m m ; a c o n s t a n t v a l u e of0, k n o w n a s t h e r e s i d u a l i n t e r f a c e f r i c t i o n a n g l e , g e n e r a l l y i n i t i a t e s f r o m adisplacements o f about 10 to 20  mm.  T a b l e 5.2. S u m m a r y o f internal friction angles f r o m r i n g tests o n the O t t a w a sand No  Name of test  On  0peak  0residual  (kPa)  o  o  209  33.7  28.6 28.5  1  SAND200S  156  NP  2  SAND250  255  33.2  28.5  3  SAND250S  241  34.6  28.6  173  NP  28.8  4  SAND200  205  32.2  28.7  5  SAND200SB  211  32.7  28.9  301  NP  28.7  217  30.2  28.7  402  NP  28.5  6  SAND200SC  Note: NP= no peak  shear  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 5—55  10 —\  0  20  40  60  80  100  Shear displacement (mm) F i g u r e 5.1. V a r i a t i o n o f internal friction angle w i t h shear d i s p l a c e m e n t f r o m atest o n O t t a w a s a n d ( S A N D 2 0 0 S )  F i g u r e 5.2 illustrates the values o f from 28.5°  0  residual  listed in the T a b l e 5.2. T h e values  to 28.9°, showing ag o o d agreement with values for O t t a w a sand f o u n d  W i j e w i c k r e m e (1986) and R i n n e (1989) o f 29.9° and 2 9 ° respectively,  vary by  for similar stresses  using the s a m e device. T h i s finding verifies the repeatability a n d the reliability of the a p p a r a tus. T h e results indicate that values o f 0  residua  i are essentially independent of stress level, for  t h e r a n g e u s e d i n t e s t i n g . T h e l i n e o f b e s t fit t o t h e r e s u l t s is g i v e n b y Residua.  = 28.8°.  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 5—56  40  i  30  •C  1  r  i  •  eo  <W) c o — ©  r  o  20  10 Best fit :0 = 2 8 . 8 ° 0 100  200  300  400  500  (kPa) F i g u r e 5.2. R e s i d u a l interface friction angles f r o m r i n g s h e a r tests o n the O t t a w a sand  5.2 Ottawa Sand-Geomembranes G e o m e m b r a n e s u s e d in this series o f tests w e r e s m o o t h H D P E , textured HDPE.  VLDPE,  P V C , and  T o a l l o w c o m m e n t o n the effect o f stiffness a n d h a r d n e s s o f the specimens,  a series of tests w e r e also p e r f o r m e d o n a n O t t a w a sand-steel interface. 5.2.1 Ottawa Sand-Smooth HDPE R i n g shear tests o n the O t t a w a sand-smooth H D P E mal stresses b e t w e e n 4 6 k P a a n d 295 k P a in  five  interface were performed for nor-  single stage tests, a n d f r o m 5 2 k P a to  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 5—57  4 0 8 k P a i n o n e m u l t i s t a g e test, see T a b l e 5.3. A t y p i c a l result is s h o w n i n F i g u r e 5.3.  The  interface exhibits am a x i m u m friction angle at ad i s p l a c e m e n t o f a b o u t 2 m m a n d g r a d u a l l y d e v e l o p s residual friction thereafter.  T a b l e 5.3. S u m m a r y o f interface friction angles a n d efficiency ratios shear tests o n O t t a w a sand-smooth HDPE No  Name of test  (5peak  On  ^residual  from  E  o  o  1  HDSP50  54  12.0  11.6  0.37  2  HDSP50B  46  13.2  11.4  0.37  3  HDSP50S  52  12.6  10.5  0.34  105  NP  11.0  0.35  204  NP  12.0  0.39  (kPa)  ring  301  NP  13.1  0.42  408  NP  14.0  0.45  104  14.8  12.9  0.42  4  HDSP100  5  HDSP200  195  13.6  11.8  0.38  6  HDSP300  295  13.9  12.6  0.41  Note: NP=  no peak  Values of 6  r e s i d u a  |, as r e p o r t e d in T a b l e 5.3, are plotted in F i g u r e 5.4. T h e y v a r y  10.5° to 1 4 ° . a n d r e v e a l ad e p e n d e n c y o f <5  r e s i d u a l  from  o n stress l e v e l : ag r e a t e r f r i c t i o n a n g l e is  exhibited at h i g h e r stress levels. Aresidual interface friction o f 1 5 ° w a s f o u n d b y N e g u s s e y et al ( 1 9 8 8 ) , u s i n g the s a m e U B C r i n g shear device, f o r a6 0 - m i l H D P E - O t t a w as a n d u n d e r a n o r m a l s t r e s s o f 5 0 k P a . A g a i n , u s i n g t h e s a m e d e v i c e , R i n n e ( 1 9 8 9 ) o b s e r v e d a<5 14° a n d 1 8 ° for stress levels o f 100 k P a a n d 750 k P a respectively for tests o n 20 to HDPE  r e s i d u a l  of  100-mil  w i t h O t t a w a s a n d . W i l l i a m s a n d H o u l i h a n ( a f t e r I n g o l d , 1 9 9 1 ) f o u n d <5 = 1 9 °  from  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 5—58  40  30 —  oo  20 —  C  10 —\  0 0  20  40  60  80  100  Shear displacement (mm) F i g u r e 5.3. V a r i a t i o n o f interface friction angle w i t h displacement f r o m a test o n O t t a w a s a n d - s m o o t h (HDSP50B)  shear HDPE  their test o n H D P E - O t t a w a sand. U s i n g a m o d i f i e d direct shear a p p a r a t u s , Martin et al ( 1 9 8 5 ) o b s e r v e d d= 1 8 ° from t h e i r t e s t o n O t t a w a s a n d w i t h a 2 0 - m i l H D P E , u n d e r n o r m a l stresses varying  from  13.8 to 103.5 k P a .  U n f o r t u n a t e l y , ad e t a i l e d c o m p a r i s o n o f r e s u l t s is p r e c l u d e d , b e c a u s e n o i n f o r m a t i o n is reported o n m e c h a n i c a l properties of the other g e o m e m b r a n e s such as p u n c t u r e Greater ^  res  ,  dual  resistance.  are anticipated w h e n higher n o r m a l stresses are applied, as aresult of m o r e  s c o u r o n the surface o f g e o s y n t h e t i c s p e c i m e n at higher stress levels.  Interface Strength of Various Geosynthetics and  Soils from Ring Shear Tests: CHAPTER 5—59  40  30  —  20  O  (5)  10  100  200  300  400  500  (kPa)  F i g u r e 5.4. R e s i d u a l interface friction a n g l e s tests o n O t t a w a sand-smooth HDPE  from  ring shear  A d e t e r m i n a t i o n o f efficiency ratios s h o w s t h e m to b e less t h a n unity, see F i g u r e 5.5. T h e ratios,  from  0.34 to 0.46, i m p l y that the s h e a r i n g o c c u r r e d at the interface. M a r t i n et al.  ( 1 9 8 4 ) r e p o r t E = 0 . 6 4 s m a l l d i r e c t s h e a r b o x tests. H o w e v e r it is b e l i e v e d t h i s h i g h e r r a t i o may stem  from  an inability to achieve a true residual friction angle b y repeated reversals in  the direction o f shearing. In contrast, R i n n e (1989) implies that E = 0.45 for O t t a w a sand with a smooth HDPE  at a n o r m a l stress o f 100 k P a .  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 5—60  I  m  1  1  1  1  '  1  1  (§  0  8  I  I  0  100  ) ®  ®  I  I  200  o  I  300  400  500  °n (kPa)  F i g u r e 5.5. E f f i c i e n c y ratio o f O t t a w a s a n d - s m o o t h  HDPE  5.2.2 Ottawa sand-VLDPE N i n e ring shear tests w e r e conducted o n an O t t a w a s a n d - V L D P E  interface with n o r m a l  stresses in the range 50 k P a to 2 0 0 k P a . F i g u r e 5.6 s h o w s a typical c u r v e o f interface friction a n g l e v e r s u s s h e a r d i s p l a c e m e n t f r o m t h e t e s t VLSP50B. A n o t i c e a b l e p e a k v a l u e o f 6 i s f o u n d at a d i s p l a c e m e n t o f 2 to 3 m m , decreasing to aconstant, residual v a l u e at a p p r o x i mately 20  m m .  A s u m m a r y o f r e s u l t s f o r f5 a n d t h e c o r r e s p o n d i n g e f f i c i e n c y r a t i o s a r e r e p o r t e d i n T a b l e 5.4. V a l u e s o f <5  r e s i d u a l  are plotted against n o r m a l stress in F i g u r e 5.7: t h e y v a r y f r o m  1 3 . 5 ° to 1 7 . 9 °d e p e n d i n g o n the applied stress level. A t a b o u t 50 k P a , the interface exhibited  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 5—61  T a b l e 5.4. S u m m a r y o f interface friction a n g l e s a n d efficiency ratios f r o m ring shear tests o n O t t a w a sand-VLDPE No  Name of test  On  (5peak  (kPa)  ^residual  E  0  o  1  VLSP50  48  NP  14.3  0.46  2  VLSP50B  53  19.7  16.0  0.52  3  VLSP50C  49  17.6  13.5  0.44  4  VLSP100  103  19.6  16.5  0.54  5  VLSP100B  105  NP  17.8  0.58  6  VLSP100C  97  NP  15.8  0.51  7  VLSP100D  102  21.4  16.7  0.55  8  VLSP100E  97  21.0  17.9  0.59  9  VLSP200  NP  17.8  0.58  197  Note: NP=  no peak  30 —\  10 —\  0  20  40  60  80  100  Shear displacement (mm)  F i g u r e 5.6. V a r i a t i o n o f interface friction angle w i t h shear displacement f r o m a test o n O t t a w a sand-VLDPE ( V L S P 5 0 B )  Interface Strength of Various Geosynthetics and  Soils from Ring Shear Tests: CHAPTER 5—62  40  30  —  20 CO  10  100  300  200  400  500  (kPa)  F i g u r e 5.7. R e s i d u a l interface friction a n g l e s tests o n O t t a w a s a n d - V L D P E  a <5  r e s i d u a l  from  ring shear  o f 1 4 . 6 °in average, increasing to 1 7 ° and 1 7 . 8 °for n o r m a l stresses of about 100 k P a  a n d 2 0 0 k P a respectively. T h e d e p e n d e n c y o f <5  r e s i d u a  . o n s t r e s s l e v e l is a t t r i b u t e d t o  the  s o m e w h a t softer surface of the specimens and the consequent susceptibility of the specimens to scour. D e e p e r circumferential grooves w e r e found o n the surface o f the  geomembrane  after the c o m p l e t i o n o f e a c h test at higher n o r m a l stresses. C o m p a r e d w i t h the h a r d surface of the smooth HDPE,  that of the VLDPE  is slightly softer, a n d h e n c e m o r e p r o n e t o s c o u r . I n  tests o n a combination o f O t t a w a sand and an EPDM  g e o m e m b r a n e , M a r t i n et al ( 1 9 8 4 )  f o u n d t h a t t h e v a l u e o f (5 w a s 2 0 ° a t n o r m a l s t r e s s e s v a r y i n g f r o m 1 3 . 8 t o 1 0 3 . 5 k P a : i t i s  Interface Strength of Various Geosynthetics and  Soils from Ring Shear Tests: CHAPTER 5—63  likely there w a s a stress d e p e n d e n c y in those results, but the a u t h o r p r o v i d e s n o Similar values could be achieved b y the O t t a w a sand-VLDPE  details.  at interface h i g h e r n o r m a l  stresses. E f f i c i e n c y ratios ( E ) o f the interface are s h o w n in F i g u r e 5.8, a n d the v a l u e s are s e e n to vary f r o m 0.43 to 0.59. A g a i n they are well b e l o w unity, a n d suggest that the shearing action is d e v e l o p e d at t h e interface.  2  1  o  o 0  100  200  300  400  0~n (kPa)  F i g u r e 5.8. E f f i c i e n c y ratio o f O t t a w a  sand-VLDPE  500  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 5—64  5.2.3 Ottawa Sand-PVC M e a s u r e d v a l u e s o f i n t e r f a c e f r i c t i o n a n g l e s (d) f r o m o n e t e s t o n O t t a w a s a n d - P V C , a g a i n a t 50 k P a , a r e s h o w n i n F i g u r e 5.9. T h e p e a k v a l u e s o f d, s e e a l s o A p p e n d i x B f o r t h e r e m a i n i n g t e s t s a t n o r m a l s t r e s s e s r a n g i n g f r o m 50 t o 300 k P a , w e r e g e n e r a l l y f o u n d a t d i s p l a c e m e n t s o f 2t o 3 m m . Ab e h a v i o u r t h a t is s i m i l a r t o t h e p r e v i o u s t e s t s o n O t t a w a s a n d w i t h o t h e r g e o m e m b r a n e s is e v i d e n t , w i t h ac o n s t a n t v a l u e o f d m o b i l i z e d at a d i s p l a c e m e n t o f a b o u t 20 m m . T h e r e a f t e r t h e v a l u e s r e m a i n c o n s t a n t t o t h e e n d o f a t e s t , t y p i c a l l y a t a d i s p l a c e m e n t o f m o r e t h a n 300 m m . A s u m m a r y o f o n e m u l t i s t a g e t e s t a n d 5 s i n g l e s t a g e t e s t s i s g i v e n i n T a b l e 5.5, a n d t h e r e s i d u a l v a l u e s , <5 o f <5  residua  residual  , a r e p l o t t e d a g a i n s t s t r e s s l e v e l i n F i g u r e 5.10. A g a i n , a d e p e n d e n c y  i o n s t r e s s l e v e l is e v i d e n t . T h i s c a n b e c o n c l u d e d f r o m t h e i n c r e a s e i n v a l u e s  of  c5residual f r o m 21° t o 28.1° w i t h i n c r e a s i n g n o r m a l s t r e s s e s f r o m 50 t o 223 k P a . I n g o l d (1991) r e p o r t s f i n d i n g s  from  t h e o b s e r v a t i o n s o f W i l l i a m s a n d H o u l i h a n (1987): t h e f r i c t i o n  T a b l e 5.5 S u m m a r y o f i n t e r f a c e f r i c t i o n a n g l e s a n d e f f i c i e n c y r a t i o s f r o m ring shear tests o n O t t a w a s a n d - P V C No  Name of test  On  (kPa)  (5peak  ^residual  E  0  0  1  PVSP50  50  23.4  21.8  0.73  2  PVSP50B  50  24.2  21.0  0.70  3  PVSP50S  74  27.4  25.8  0.88  104  NP  26.3  0.90  202  NP  26.9  0.92  4  PVSP100  119  28.6  27.8  0.96  5  PVSP100B  125  29.3  27.9  0.96  6  PVSP200  223  30.0  28.1  0.97  Note: NP= no peak  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 5—65  40  30 —\  OO  C  20  —I  10 —\  0 0  20  40  60  80  100  Shear displacement (mm) F i g u r e 5.9. V a r i a t i o n o f interface friction angle w i t h shear d i s p l a c e m e n t f r o m atest o n O t t a w a s a n d - P V C ( P V S P 5 0 )  a n g l e m o b i l i z e d at t h e i n t e r f a c e o f P V C w i t h O t t a w a s a n d is 2 6 ° w h i c h still falls i n t o r a n g e o f t h e results i n this t e s t i n g p r o g r a m . H o w e v e r , t h e a p p l i e d s t r e s s l e v e l is n o t  the men-  tioned in the paper. U s i n g the same U B C ring shear device, R i n n e (1989) c o n d u c t e d tests o n the interface o f the s a m e soil w i t h a similar (but not identical) P V C . H e f o u n d values «3residual o f a p p r o x i m a t e l y 2 9 ° u n d e r n o r m a l s t r e s s e s o f 1 0 0 a n d 5 0 0 k P a , w h i c h a r e t h e  of  same  as his tests o n the O t t a w a sand. A similar b e h a v i o u r w a s o b s e r v e d in this testing p r o g r a m : the v a l u e s o f <5  r e s i d u a l  at h i g h stress levels are e q u a l to t h o s e o b t a i n e d for the O t t a w a sand,  F i g u r e 5.11, s h o w i n g the efficiency ratio with  see  applied stress levels. T h e ratios at stresses  Interface Strength of Various Geosynthetics and  Soils from Ring Shear Tests: CHAPTER 5—66  40  30 o  oo !C  20  —  10  —  o  CO  0  100  200  300  400  500  (kPa)  F i g u r e 5.10. R e s i d u a l interface friction angles f r o m ring shear tests o n O t t a w a s a n d - P V C  f r o m 104 k P a to 223 k P a v a r y b e t w e e n 0.90 a n d 0.97, w h i c h are almost unity. A ratio o f 0.9 is r e p o r t e d b y M a r t i n et a l ( 1 9 8 4 ) f r o m t h e i r t e s t s o n t h e i n t e r f a c e o f P V C sand. In another investigation using a specially constructed B a t e r e a u (1987) c o n d u c t e d tests o n the interface o f P V C  film  flat  with  concrete  shear device, Weiss  and  with sand, a n d obtained ratios  f r o m 0.5 to 0.6 for l o w stress levels f r o m 5 k P a to 50 k P a . T h e possibility o f gaining the s a m e ratios c a n be implied f r o m the trend in F i g u r e 5.11. A f t e r e a c h test, visual inspection r e v e a l e d the P V C s p e c i m e n s d i d n o t s h o w a n y signs o f scour like that f o u n d o n the s m o o t h H D P E -  or the VLDPE-the  Ottawa sand. Neverthe-  Interface Strength of Various Geosynthetics and  I  W  Soils from Ring Shear Tests: CHAPTER 5—67  '  I  I  1  1 o  -  -  I  0  l  100  l  l  200  300  l  400  500  (kPa)  F i g u r e 5.11. Efficiency ratio o f O t t a w a  sand-PVC  less, the v e r y h i g h friction w a s believed to be a result o f softness o f the m a t e r i a l — i t w a s  the  softest g e o m e m b r a n e u s e d t h r o u g h o u t this p r o g r a m o f testing. A t h i g h stress levels the grains o f s a n d t e n d e d t o p r e s s d o w n i n t o t h e P V C s p e c i m e n , s e e F i g u r e 5 . 1 2 , a n d it is b e l i e v e d t h i s p h e n o m e n o n c a u s e d t h e s h e a r i n g a c t i o n t o o c c u r w i t h i n t h e s a n d itself. T o better appreciate the influence o f stiffness a n d h a r d n e s s o f the g e o m e m b r a n e m e n s o n <5  r e s i d u a l  , several ring shear tests w e r e p e r f o r m e d o n a n O t t a w a sand-steel  speci-  interface.  T h e results are r e p o r t e d in T a b l e 5.6. A c o m p a r i s o n o f the residual interface friction angles with those and PVC—is  from  the previous tests o n the three g e o m e m b r a n e s — s m o o t h H D P E ,  VLDPE,  presented in F i g u r e 5.13 in t e r m o f efficiency ratio a n d stress level. T h e data  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 5—  jnormal load shearing direction  PVC  specimen  F i g u r e 5.12. S k e t c h o f shearing b e h a v i o u r at the o f the O t t a w a s a n d - P V C  interface  T a b l e 5.6. S u m m a r y o f interface friction angles a n d efficiency ratios f r o m ring shear tests o n O t t a w a sand-soft steel  Name of test  No  1 2  3  STEEL STEELS  STEELSB  Note: NP= no peak  On  (5peak  ^residual  (kPa)  0  o  E  NP  18.1  0.60  58  NP  18.1  0.60  108  NP  18.1  0.60  198  NP  18.0  0.59  289  NP  18.0  0.59  66  NP  18.1  0.60  58  NP  17.9  0.59  108  NP  17.9  0.59  209  NP  17.9  0.59  298  NP  17.9  0.59  304  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 5—69  T  T  T  Best fit: —£s— Ottawa sand-PVC -0—  Ottawa sand-VLDPE  -G—  Ottawa sand-Smooth HDPE Ottawa sand-Soft Steel  W  1  T 0  T 100  T 200  T  T 300  400  T 500  T 600  700  T 800  900 1000  On (kPa)  Figure 5.13. C o m p a r i s o n o f interface b e h a v i o u r for materials f r o m ring shear tests  for the O t t a w a s a n d - P V C and the O t t a w a sand-VLDPE  various  s h o w asimilar trend: b o t h lines are  steeper than that for the interface o f the O t t a w a sand-smooth HDPE.  It c a n b e  concluded  t h a t t h e s o f t e r s p e c i m e n , t h e g r e a t e r t h e i n c r e a s e o f d w i t h n o r m a l s t r e s s . T h e b e s t fit l i n e f o r the O t t a w a sand-steel d a t a — t h e steel w a s the hardest s p e c i m e n u s e d in  testing—further  c o n f i r m s t h i s r e s p o n s e . T h e r e is n o v a r i a t i o n o f d w i t h n o r m a l stress. T h e e f f i c i e n c y r a t i o is relatively high c o m p a r e d to that o f the s m o o t h polyethylene g e o m e m b r a n e s VLDPE).  (HDPE  and  T h i s is a t t r i b u t e d t o t h e r o u g h n e s s o f t h e steel s u r f a c e , a n d w a s v e r i f i e d b y v i s u a l  inspection using a microscope. Rinne (1989) has documented the influence of surface roughness of prepared steel specimens o n interface friction with different sands.  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 5—70  5.2.4 O t t a w a s a n d - T e x t u r e d  HDPE  M e a s u r e d interface friction angles a n d efficiency ratios f r o m aseries of ring shear tests o n the interface of O t t a w a sand with the textured HDPE  are r e p o r t e d in T a b l e 5.7. O w i n g to  the g o o d repeatability of the residual test data, the series of four single stage tests w a s  con-  sidered adequate to describe the of interface friction behaviour. A typical curve showing the variation ofd with shearing displacement  from  t e s t HDTSP50  is p r e s e n t e d i n F i g u r e 5.14. A d i s t i n c t p e a k v a l u e o f d is e n c o u n t e r e d at a d i s p l a c e m e n t  of  a p p r o x i m a t e l y 2 m m ; it d e c r e a s e s r a p i d l y t o a c o n s t a n t v a l u e at t h e d i s p l a c e m e n t o f a b o u t 1 0 m m . T h e v a r i a t i o n i n p e a k v a l u e s b e t w e e n tests, w h i c h is n o t e v i d e n t i n t h e r e s i d u a l v a l u e s , is a t t r i b u t e d t o d i f f e r e n c e s i n t h e initial d e n s i t y o f t h e p l u v i a t e d s a n d T h e v a l u e s o f <5 vary  from  r e s i d u a  samples.  i, see F i g u r e 5.15, a p p e a r to b e i n d e p e n d e n t o f stress level.  2 8 . 1 °to 29.1°, and are similar in magnitude to those obtained f r o m the  They  previous  tests o n the O t t a w a sand alone. R i n n e (1989) reports similar results ranging f r o m 2 8 ° to 3 0 ° . The efficiency ratios are essentially equal to unity, see T a b l e 5.7 a n d F i g u r e 5.16,  implying  t h a t s h e a r i n g h a s o c c u r r e d w i t h i n t h e p a r t i c l e s o f t h e s a n d . T h i s p h e n o m e n o n is i l l u s t r a t e d schematically in F i g u r e 5.17. T h e heights o f the texture o f the H D P E  are generally  from  1.5 m m t o 2 m m . S i n c e t h e a v e r a g e d i a m e t e r o f t h e g r a i n s i z e o f t h e O t t a w a s a n d u s e d i n t h e T a b l e 5.7. S u m m a r y o f the interfacel friction angles a n d efficiency ratio ring shear tests o n O t t a w a sand-textured HDPE  No  Name of test  On  Opeak  ^residual  (kPa)  (°)  0  E  1  HDTSP50  47  37.0  28.1  0.97  2  HDTSP50B  50  35.0  29.0  1.00  3  HDTSP100  101  29.8  28.7  0.99  4  HDTSP150  149  34.0  29.1  1.01  from  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 5—71  to  C  20  Shear displacement (mm)  F i g u r e 5.14. Variation o f interface friction angle w i t h shear displacement f r o m a test o n O t t a w a sand-textured H D P E ( H D T S P 5 0 )  100  200  300  400  500  (KPa)  Figure 5.15. Residual interface friction angles f r o m ring shear tests o n O t t a w a sand-textured HDPE  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 5—72  2  1  ^  1  '  r)  ^  1  1  1  i  1  1  -  0  i  0  |  i  100  i  200  i  300  |  I  400  500  (kPa)  Figure 5.16. Efficiency ratio o f O t t a w a sand-textured  FfDPE  textures  textured H D P E s p e c i m e n  Figure 5.17 Sketch of the interface shearing behaviour for O t t a w a sand-textured H D P E  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 5—73  tests w a s approximately 0.35 m m , the particles o f sand tend to fill the gap, stacking to the m a x i m u m height o f the texture. Consequently the specimen w a s then covered with  sand  p a r t i c l e s , a n d t h e p l a n e o f s h e a r i n g w a s f o r c e d i n t o t h e s a n d itself. 5.3 O t t a w a  Sand-Geotextiles  T h e Trevira 1120 a n d Polyfelt T S 550 w e r e used in the ring shear test p r o g r a m for investigating the interface friction behaviour o f O t t a w a sand a n d n o n w o v e n geotextiles. T h r e e single stage tests w e r e  p e r f o r m e d at stress levels o f a p p r o x i m a t e l y 50, 100, a n d 1 5 0 k P a ,  a n d o n e multistage test w a s c o n d u c t e d at stress levels r a n g i n g f r o m a b o u t 4 5 k P a to 2 0 0 k P a , for b o t h geotextiles. T h e results are r e c o r d e d in T a b l e s 5.8 a n d 5.9. T o illustrate the m o b i l i zation o f interface friction angle («5)w i t h displacement, results  from  t e s t s TRSP50 a n d PFSP50  are plotted i n F i g u r e 5.18. A t this l o w n o r m a l stress o f 4 4 k P a , the O t t a w a s a n d - T r e v i r a 1120 interface seems to exhibit am a x i m u m resistance almost immediately, while the interface  of  the O t t a w a sand-Polyfelt T S 550, at an o r m a l stress o f 4 8 k P a , m o b i l i z e s am a x i m u m resis-  T a b l e 5.8. S u m m a r y o f the interface friction angles a n d efficiency ratios ring shear tests o n O t t a w a sand-Trevira 1120  Name of test  No  <5peak  ^residual  (kPa)  0  0  E  1  TRSP50  44  29.7  25.4  0.86  2  TRSP50S  45  32.8  25.6  0.87  106  '  NP  25.7  0.88  151  NP  25.9  0.88  205  NP  26.3  0.90  3  TRSP100  99  28.3  25.1  0.85  4  TRSP150  150  34.2  27.8  0.96  Note: NP=  On  no peak  from  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 5—  T a b l e 5.9. S u m m a r y o f the interface friction angles a n d efficiency ratios ring shear tests o n O t t a w a sand-Polyfelt T S 550  Name of test  No  E  ^residual  (5peak  On  from  0  o  1  PFSP50  48  32.3  24.0  0.81  2  PFSP50S  48  34.1  25.1  0.85  99  NP  25.6  0.87  152  NP  25.9  0.88  200  NP  25.8  0.88  (kPa)  3  PFSP100  98  30.8  25.5  0.87  4  PFSP150  145  32.3  25.4  0.86  Note: NP= no peak  40  -A  30  (O  C  20  10  Name of test:  20  40  60  A  TRSP50  Q  PFSP50  80  100  Shear displacement (mm)  F i g u r e 5.18. Variation o f interface friction angle with shear d i s p l a c e m e n t from a t e s t o n O t t a w a s a n d w i t h T r e v i r a 1 1 2 0 and Polyfelt T S 550  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 5—75  tance at a relatively small d i s p l a c e m e n t o f a p p r o x i m a t e l y 2 m m . A similar b e h a v i o u r  also  o c c u r r e d w i t h b o t h interfaces u n d e r multistage tests initiated w i t h stress levels o f a p p r o x i m a t e l y 5 0 k P a . H o w e v e r , the p h e n o m e n o n w a s not a p p a r e n t at h i g h e r stresses: the values for b o t h geotextiles w e r e , as s h o w n in A p p e n d i x B , generally f o u n d at  peak  displacements  between 3m m and 5 m m . F i g u r e 5.19 s h o w s aslight d e p e n d e n c y o f <5 A l t h o u g h the v a l u e s o f <3  r e s j d u a l  r e s i d u a )  o n stress levels for b o t h  seem to coincide, the values  from  geotextiles.  the tests using Trevira  1120  a r e t y p i c a l l y h i g h e r : this b e h a v i o u r o f T r e v i r a 1 1 2 0 is a t t r i b u t e d t o t h e l e s s g l o s s y s u r f a c e o f the geotextile fibres in this material. T h e values v a r y f r o m 2 5 . 1 ° to 27.8°; in contrast 40  30 —  (/) o  20 —\  10 —\ A  Ottawa sand-Trevira 1120  O  Ottawa sand-Polyfelt TS 550  0 0  100  300  200  400  500  (kPa)  F i g u r e 5.19. R e s i d u a l interface friction angles f r o m ring shear tests o n O t t a w a sand with T r e v i r a 1120 a n d Polyfelt T S 550  those  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 5—76  m o b i l i z e d at the interface o f the O t t a w a sand w i t h Polyfelt T S 5 5 0 r a n g e f r o m 2 4 ° to 2 5 . 9 ° . These values appear consistent with the  finding  o f M a r t i n et al ( 1 9 8 4 ) w h i c h is 2 6 ° , f r o m a  m o d i f i e d direct shear test o n the interface o f O t t a w a sand w i t h n o n w o v e n geotextile C Z Efficiency ratios derived  from  the m e a s u r e d <5  5.9 are presented in F i g u r e 5.20. T h e ratios 0.96; those for the Polyfelt T S 550 vary  from  from  r e s i d u a l  , as d o c u m e n t e d in T a b l e s 5.8  the tests o n Trevira 1120 v a r y  from  0.85  0.81 to 0.88. Karchafi a n d Dysli ( 1 9 9 3 )  g e s t a n e f f i c i e n c y r a t i o o f 0.8 is a p p l i c a b l e t o n o n w o v e n g e o t e x t i l e s . T h i s v a l u e s e e m s agree with the m i n i m u m ratio obtained  0  100  from  the tests with the Polyfelt geotextile.  200  O  Ottawa sand-Polyfelt TS 550  A  Ottawa sand-Trevira 1120  300  400  500  (kPa)  F i g u r e 5.20. Efficiency ratios for the tests o n the interface Ottawa sand with Trevira 1120 and Polyfelt T S 550  of  600. and to sugto  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 5—77  5.4 Summary Analysis o f results f r o m ring shear tests o n O t t a w a sand with three s m o o t h a n d  one  textured geomembrane, and with two n o n w o v e n geotextiles, suggests: •  d  r e s i d u a l  f o r the O t t a w a s a n d w i t h the s m o o t h g e o m e m b r a n e s is  dependent  o n stress level: the values increase w i t h higher stress levels. •  <5  r e s i d u a l  for the O t t a w a sand with the textured HDPE  g e o m e m b r a n e is i n d e -  p e n d e n t o f stress level: shearing t o o k place within the s a n d •  ^ siduai re  f °  r t n e  Ottawa sand with two nonwoven geotextiles—Trevira  1120  a n d P o l y f e l t T S 5 5 0 — i s s l i g h t l y d e p e n d e n t o n s t r e s s l e v e l . T h e g l o s s i e r fibers of the Polyfelt t e n d e d to exhibit aslightly l o w e r interface friction angle. • <5  r e s i d u a  . f o r t h e O t t a w a s a n d a n d t h e g e o s y n t h e t i c s is m a i n l y c o n t r o l l e d b y : - stiffness, hardness a n d texture o f the - type of  •  T h e values of d  fibers  geomembranes;  composing the geotextiles. , with efficiency ratios in parentheses, for O t t a w a sand  r e s i d u a l  (at n o r m a l stresses f r o m 4 4 k P a to 4 0 8 k P a ) w i t h the v a r i o u s g e o s y n t h e t i c s are as follows. - smooth H D P E :  10.5° to 1 4 . 0 ° (0.34 to  0.45)  - V L D P E:  13.5° to 1 7 . 9 °(0.44 to  0.59)  - P V C :  21.0° to 2 8 . 1 °(0.70 to  0.97)  - texturedH D P E :  28.1° to 2 9 . 1 °(0.97 to  1.01)  - T r e v i r a1120:  25.1° to 27.8° (0.85 to  0.96)  - Polyfelt T S  24.0° to 25.9° (0.81 to  0.88)  550  CHAPTER 6 G E O M E M B R A N E - G E O S Y N T H E T I C A N A L Y S I S  6.1  T E S T R E S U L T S  A N D  General T h e use o f geotextiles in construction applications, in some cases to protect a  geomem-  b r a n e f r o m d a m a g e t h r o u g h direct contact w i t h adjacent soils, l e d to several series o f r i n g shear tests o n a geomembrane/geotextile VLDPE,  interface. G e o m e m b r a n e s u s e d in the tests  P V C ,and both the smooth and textured H D P E ; the geotextiles were the  were  nonwoven  Trevira 1120 a n d Polyfelt T S 550. N o r m a l stresses applied in the testing p r o g r a m ranged f r o m about 50 k P a to 300 k P a : again s o m e tests w e r e p e r f o r m e d in multistages o f n o r m a l stress. U n l e s s stated otherwise, all tests w e r e p e r f o r m e d at a rate o f shear o f 0.04  mm/s.  M o s t results a r e p r e s e n t e d i n t e r m s o f r e s i d u a l i n t e r f a c e f r i c t i o n a n g l e s , w i t h e m p h a s i s o n its v a r i a t i o n w i t h n o r m a l stress. T h e m o b i l i z e d interface friction angles a n d the a p p l i e d stresses w i t h shear d i s p l a c e m e n t f r o m all tests are e n c l o s e d in A p p e n d i x C . E a c h test is d e s c r i b e d b y a c o d e that r e p r e s e n t s t h e m a t e r i a l , t h e s t r e s s level,  multistage  (if a p p r o p r i a t e ) , a n d the o r d e r o f e a c h test. A s d e s c r i b e d i n the p r e v i o u s chapters, a n d illustrated in T a b l e 6.1, the c o d e refers to: 78  Interface Strength of Various Geosynthetics and  VL = PV  Soils from Ring Shear Tests: CHAPTER 6—79  VLDPE, = P V C ,  HD  = smooth  HDPE,  HDT  = textured  TR  = Trevira  PF  = Polyfelt T S 550,  HDPE, 1120, and  S = multistage test. T h e last t w o c o l u m n s designate the a p p r o x i m a t e n o r m a l stress in k P a a n d the s e q u e n c e  of  the tests.  T a b l e 6.1. Test c o d e for ring shear tests geomembranes with geotextiles 1  2  VL  3  5  50  PVC  TR  100  HD  PF  200  HDT  4  on  300  B S  C D  6.2 V L D P E - G e o t e x t i l e s T w o c u r v e s i l l u s t r a t e s t h e c h a n g e i n m o b i l i z e d i n t e r f a c e f r i c t i o n a n g l e (d) displacement for the VLDPE  with  shear  g e o m e m b r a n e w i t h e a c h geotextile, at a n o r m a l stress o f a p -  p r o x i m a t e l y 5 0 k P a , see F i g u r e 6.1. A slight p e a k strength w a s m o b i l i z e d at relatively s m a l l displacements b e t w e e n 2 m m to 5 m m for the Trevira 1120 a n d the T S 550; the strength r e m a i n e d constant after about 15 m m o f displacement.  interface  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 6—80  40  30 —\  OO  C  20 —  10 —  Test:  A ~o 0  20  40 60 Shear displacement (mm)  -©—  VLPF50  -A—  VLTR50  80  F i g u r e 6.1. V a r i a t i o n o f interface friction angle displacement f r o m tests o n the V L D P E - g e o t e x t i l e s  T a b l e s 6.2 a n d 6.3 s u m m a r i z e  100 with  the peak and the residual interface friction angles ob-  tained f r o m 10 tests: 6tests o n VLDPE-Trevira  1120 a n d 4tests o n VLDPE-TS  effect o f rate o f shear o n the interface friction w a s investigated b y applying rates from  -  550.  The  ranging  0 . 0 4 m m / s t o 0 . 1 5 m m / s i n t w o s t a g e d t e s t s o n t h e T r e v i r a U20-—VLTR200 a n d  VLTR200S — a t n o r m a l s t r e s s e s o f a p p r o x i m a t e l y 2 0 0 k P a . T h e r e s u l t i n g v a l u e s o f < 3  r e s i d u a l  a r e listed i n T a b l e 6.4 a n d a r e d e p i c t e d i n F i g u r e 6.2. A l t h o u g h t h e r e is g o o d r e p e a t a b i l i t y , a n o n - l i n e a r r e l a t i o n s h i p is o b s e r v e d t o o c c u r at t h e i n t e r f a c e d u e t o t h e v a r y i n g rates. values of f5  r e s i d u a l  The  i n c r e a s e slightly w i t h i n c r e a s i n g r a t e o f s h e a r , a n d a c h i e v e an e a r l y c o n s t a n t  v a l u e of a p p r o x i m a t e l y 1 9 ° at a rate of strain of 0.15 m m / s . T h e r e a s o n that m o s t tests in this s e r i e s w e r e still p e r f o r m e d at a strain r a t e o f 0 . 0 4 m m / s w a s t o m a i n t a i n a c o n s i s t e n t test  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 6—81  Table 6.2. S u m m a r y o f interface friction angles f r o m ring shear tests o n V L D P E - T r e v i r a 1120  Name of test  No  On  (kPa)  <5peak  (°)  ^residual  O  1  VLTR50  48  19.0  15.7  2  VLTR50B  59  16.2  15.8  3  VLTR100  95  17.8  15.5  4  VLTR100B  99  16.9  15.4  5  VLTR200  195  19.5  16.1  6  VLTR200S  193  17.5  15.9  301  NP  16.5  Note: NP=no peak  Table 6.3. S u m m a r y o f interface friction angles f r o m ring shear tests o n V L D P E - P o l y f e l t T S 5 5 0  No  Name of test  1  VLPF50  2  VLPF50S  On  <5peak  ^residual  (kPa)  o  (°)  49  15.9  14.2  52  16.5  14  115  NP  13.7  155  NP  13.5  213  NP  14.1  3  VLPF100  99  15.6  13.8  4  VLPF150  149  15.8  13.5  Note: NP=no peak  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 6—82  T a b l e 6.4. Effect o f rate o f strain o n residual interface friction angles f r o m ring shear tests o n VLDPE-Trevira 1120  N a m e of test  No  R a t e of strain  VLTR200  1  VLTR200S  2  <5 residual  (mm/s)  n  0.04  16.1  0.06  16.7  0.08  18.3  0.12  19.0  0.15  19.3  0.04  15.9  0.06  16.9  0.08  17.4  0.12  18.3  0.15  19.0  30  20  10 Trevira 1120 - VLDPE  T  T 0.02  0.04  T 0.06  VLTR200S  A  VLTR200  T  T 0.08  O  0.10  0.12  0.14  0.16  0.18  0.20  Rate of strain (mm/s)  Figure 6.2. Effect o f rate o f strain o n residual interface friction a n g l e s from r i n g s h e a r t e s t s o n V L D P E - T r e v i r a 1120  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 6—83  m e t h o d throughout the p r o g r a m of work. Values of ^  r e s  i  d u a  im o b i l i z e d at 0.04 m m / s , as listed  i n T a b l e s 6.2 a n d 6.3, are plotted in F i g u r e 6.3 together w i t h s o m e o f t h e s e a d d i t i o n a l data. T h e results s u g g e s t that <5  r e s i d u a  . is d e p e n d e n t o n t h e rate o f strain, b u t is i n d e p e n d e n t  of  stress level. T h e v a l u e s o f <5 siduai d e v e l o p e d a t t h e i n t e r f a c e o f t h e V L D P E - T r e v i r a re  greater than those achieved by the VLDPE-TS  1120 tend to be  550. T h e former ranges f r o m 1 5 . 4 °to 16.5°,  w h e r e a s t h e l a t t e r v a r i e s f r o m 1 3 . 5 ° t o 1 4 . 2 ° . M a r t i n et al ( 1 9 8 4 ) r e p o r t av a l u e o f « 3 = 1 5 ° f o r the interface o f an E P D M - n o n w o v e n geotextile ( C Z 600) using  a modified direct  apparatus with n o r m a l stresses varying f r o m 13.8 to 103.5 k P a . In another  investigation  35 30 25 -  o  TS  550-VLDPE  A  Trevira 1120-VLDPE 6= 0.04 mm/s  A  Trevira 1120-VLDPE E= 0.15 mm/s  -  —  —  20 CO  A A  15 -  ZA O  O  O  OO  10 —| 5 0 200  100  shear  300  (kPa)  F i g u r e 6.3. R e s i d u a l interface friction angles f r o m r i n g shear tests o n V L D P E - g e o t e x t i l e s  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 6—84  W e i s s a n d B a t e r e a u ( 1 9 8 7 ) , u s i n g a s p e c i a l l y c o n s t r u c t e d flat s h e a r d e v i c e a n d n o r m a l s t r e s s e s f r o m 5to 50 k P a , measured values o f 6ranging ylene ( P E ) w i t h an o n w o v e n  from  11° to 1 4 ° o n the interface o f polyeth-  geotextile.  Visual observations, after each test w a s completed, revealed the fibres o f b o t h geotextiles s e e m e d to slightly pull out d u r i n g shear. T h e values o f r5  p e a k  for each test (see  Fig-  u r e 6.1) are attributed to a r e a l i g n m e n t o f the fibres at the surface o f the geotextile d u r i n g the beginning o f shear. O n c e the pulling o f the fibres w a s fully d e v e l o p e d a n d aligned to  the  d i r e c t i o n o f s h e a r i n g , ac o n s t a n t interface friction angles w a s established. T h i s i m p l i e s that at large displacements the values o f 8 the  fibres  r e s i d u a  .  from  the tests w e r e affected b y the smoothness  o f t h e g e o t e x t i l e s . T h e l o w e r v a l u e s o f <5 j i o b t a i n e d f r o m t h e t e s t s o n r e s  VLDPE-Polyfelt T S 550 could have resulted  from  the  d u a  fibres  of the  o f that geotextile being glossier  (from visual observation) than those o f Trevira 1120. 6.3 Smooth HDPE-Geotextiles T h e test series for the s m o o t h H D P E - g e o t e x t i l e s c o m p r i s e d 6tests o n s m o o t h  HDPE-  Trevira 1120 a n d 3 tests o n s m o o t h H D P E - P o l y f e l t T S 550. T h e tests w e r e c o n d u c t e d stress levels f r o m 50 k P a to 200 k P a . A multistage test w a s also p e r f o r m e d o n the HDPE-Trevira  at  smooth  1120 using confining stresses f r o m approximately 50 k P a to 300 k P a . Typi-  cal c u r v e s for b o t h interface c o m b i n a t i o n s u n d e r an o r m a l stress o f a b o u t 5 0 k P a are  shown  i n F i g u r e 6.4. N o n o t i c e a b l e p e a k a n g l e o f i n t e r f a c e f r i c t i o n is e v i d e n t i n e i t h e r o f t h e tests. T h i s is a l s o t h e c a s e f o r t h e rest o f tests, see A p p e n d i x C . A s u m m a r y o f t h e t e s t s is g i v e n i n T a b l e s 6.5 a n d 6.6 , a n d d e p i c t e d in F i g u r e 6.5.  A g a i n the values o f <5  r e s i d u a l  seem  indepen-  dent o f stress level for both geotextiles. A l s o the tendency o f the Trevira 1120 to mobilize a h i g h e r f r i c t i o n t h a n P o l y f e l t T S 5 5 0 is a p p a r e n t , t h o s e less s o t h a n w i t h t h e s m o o t h  VLDPE.  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 6—85  40 Test:  30 —  tvO  C  -e-  -  HDPF50  -A-  -  HDTR50  20 —  10 —\  0 0  20  40 60 Shear displacement (mm)  80  F i g u r e 6.4. V a r i a t i o n o f interface friction a n g l e displacement f r o m tests o n s m o o t h H D P E - g e o t e x t i l e s  T h e v a l u e s o f <5  r e s i d u a l  100  with  d e v e l o p e d at the interface o f t h e s m o o t h H D P E - T r e v i r a  ranged  f r o m 7 . 2 ° to 7 . 7 ° a n d t h o s e at the s m o o t h H D P E - P o l y f e l t v a r i e d f r o m 6 . 1 ° to 6 . 7 ° . T h i s r e s p o n s e is a g a i n a t t r i b u t e d t o the less g l o s s y s u r f a c e o f t h e  fibres  composing the Trevira  fabric. A n interface friction a n g l e o f 8 ° w a s o b s e r v e d b y M a r t i n et al ( 1 9 8 4 ) f o r the interface o f a n H D P E - n o n w o v e n g e o t e x t i l e ( C Z 6 0 0 ) . It a g r e e s v e r y w e l l w i t h t h o s e o b t a i n e d f r o m the tests o n the HDPE-Trevira.  M i t c h e l l et al ( 1 9 9 0 ) u s e d a m o d i f i e d K a r o l - W a r n e r d i r e c t  shear device to test the interface o f aso-called polished HDPE-Trevira and found 6 ranging  from  Spunbond No.  1145  8 . 5 ° to 1 0 . 5 ° . T h e y also observed 6 o f 8 ° for the s a m e interfacing  m a t e r i a l s u s i n g t h e p u l l o u t b o x a p p a r a t u s , w h i c h is c l o s e t o t h o s e a c h i e v e d i n this r i n g s h e a r  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 6—86  T a b l e 6.5. S u m m a r y o f interface friction angles f r o m r i n g shear tests o n s m o o t h H D P E - T r e v i r a 1120  Name of test  No  On  ^peak  ^residual  (kPa)  0  O 7.6  1  HDTR50  49  NP  2  HDTR50B  48  NP  7.2  3  HDTR50S  59  NP  7.7  111  NP  7.5  208  NP  7.4  299  NP  7.3  HDTR100  98  NP  7.7  5  HDTR200  204  NP  7.6  6  HDTR200B  202  NP  7.4  4  Note: NP=no peak  T a b l e 6.6. S u m m a r y o f interface friction angles f r o m r i n g shear tests o n s m o o t h H D P E - P o l y f e l t T S 5 5 0  Name of test  No  On  ^peak  <5 residual  (kPa)  O  O  1  HDPF50  51  NP  6.7  2  HDPF100  97  NP  6.1  3  HDPF200  196  NP  6.4  Note: NP=no peak  p r o g r a m . U s i n g t h e U B C r i n g s h e a r a p p a r a t u s N e g u s s e y ( 1 9 8 8 ) f o u n d a <5 tests o n H D P E - d r y  geotextile (Texel 7621) or o n H D P E - w e t Texel  In c o m p a r i s o n to the preceding data for VLDPE ^resiHiwi  r e s i d u a  i of 6.5° for  7621.  geomembranes, the very l o w values o f  attained in this series o f tests are attributed to the v e r y s m o o t h , h a r d g l o s s y  surface  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 6—87  35 30  A  Trevira 1120-Smooth HDPE  O  TS 550-Smooth HDPE  25 20 15 10 5  5  O  0 200  100  300  (kPa)  F i g u r e 6.5. R e s i d u a l interface friction angles f r o m r i n g tests o n smooth HDPE-geotextiles  of HDPE.  H o w e v e r , the  fibres  o f the geotextiles  shear  w e r e still slightly p u l l e d o u t , albeit n o t  as  m u c h as that f o u n d with the tests o n the V L D P E - g e o t e x t i l e combination. 6.4  PVC-Geotextiles N i n e ring shear tests w e r e p e r f o r m e d to investigate the nature o f interface friction be-  t w e e n aP V C g e o m e m b r a n e a n d these t w o geotextiles  (Trevira 1120 and Polyfelt T S  550).  S t r e s s l e v e l s w e r e a p p l i e d b e t w e e n 5 0 k P a a n d 1 5 0 k P a f o r five t e s t s o n P V C - T r e v i r a  1120,  a n d 50 k P a a n d 200 k P a for 4 tests o n P V C - P o l y f e l t .  Interface Strength of Various Geosynthetics and  Soils from Ring Shear Tests: CHAPTER 6—88  A typical profile o f the resulting d for b o t h series o f tests at n o r m a l stress o f a b o u t 5 0 k P a is s h o w n i n F i g u r e 6.6. T h e P o l y f e l t g e o t e x t i l e s e e m s t o g i v e a stiffer r e s p o n s e . is a t t r i b u t e d t o t h e a r r a n g e m e n t o f its  fibers:  they appear  firmer  than those composing  This the  Trevira, w h i c h in contrast are easier to pull out. F i g u r e 6.7 illustrates the resulting values of d listed i n T a b l e s 6.7 a n d 6.8. T h e v a l u e s o f <5  r e s i d u a  i  r e s i d u a l  from  from  b o t h series o f tests that are  the tests o n PVC-Trevira  vary from  31.5° to 33.8°, while those o f P V C - P o l y f e l tvary f r o m 23.5° to 25.8°. O n c e again the  angle  o f interface friction a p p e a r s to b e i n d e p e n d e n t o f n o r m a l stress, a n d h i g h e r f o r the T r e v i r a geotextile. T h e latter results for Polyfelt agree well w i t h d = 2 3 °  from  a test o n a so-called  F i g u r e 6.6. V a r i a t i o n o f interface friction angle d i s p l a c e m e n t from t e s t s o n P V C - g e o t e x t i l e s  with  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 6—89  Table 6.7. S u m r n a r y o f interface friction angles f r o m ring tests o n PVC-Trevira 1120  Name of test  No  1  PVTR50  2  PVTR50S  3 4  PVTR100 PVTR150  ,  ^residual  (5 peak  On  shear  o  (kPa)  0  45  33.4  32.3  48 103  34.3  33.8  NP  33.7  157  NP  32.6  95  32.0  31.5  148  33.4  32.5  Note: NP=no peak  Table 6.8. S u m m a r y o f interface friction angles tests o n PVC-geotextiles  Name of test  No  On  O peak  from  ring  <5residual  (kPa)  0  0  1  PVPF50  51  25.3  23.5  2  PVPF50B  52  25  24.3  3  PVPF50S  55  26  25.7  102  NP  25.4  153  NP  25.7  206  NP  25.8  4  PVPF100  102  25.3  25.0  5  PVPF150  154  25.5  25.4  Note: NP=no peak  shear  Interface Strength of Various Geosynthetics and  Soils from Ring Shear Tests: CHAPTER 6—90  OO  100  200  300  (kPa)  F i g u r e 6.7. R e s i d u a l interface friction angles f r o m r i n g shear tests o n PVC-geotextiles  r o u g h P V C - n o n w o v e n C Z 6 0 0 r e p o r t e d b y M a r t i n et al ( 1 9 8 4 ) . I n g o l d ( 1 9 9 1 ) listed values of d PVC  r e s i d u a  i  from  the  the observations o f Weiss and Batereau (1987) o n the interface o f a  film a n d n o n w o v e n geotextile as v a r y i n g  from  1 6 ° to 2 4 ° .  T h e v e r y h i g h f r i c t i o n g e n e r a t e d at t h e i n t e r f a c e o f t h e P V C w i t h b o t h g e o t e x t i l e s is attributed to the texture a n d relative stiffness o f the interfacing materials. O f a l lthe  geomem-  branes u s e d t h r o u g h o u t this research, the P V C w a s the softest material a n d the o n e w i t h the roughest surface (excluding the profiled surface o f the textured HDPE). PVC  T h e flexibility o f the  is b e l i e v e d t o b e i m p o r t a n t t o t h e m o b i l i z a t i o n o f a v e r y h i g h i n t e r f a c e f r i c t i o n : a p p l i c a -  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 6—91  tion o f load to the fibres o f the geotextile causes t h e m to press into the surface o f the P V C . C o n s e q u e n t l y m o r e contact o f the fibres c o m p o s i n g the geotextile likely t o o k place o n a softer  surface. T h e existence o f a h i g h friction at the interface w a s further p r o v e n f r o m tests at a  n o r m a l stress o f 50 k P a o n the interface o f O t t a w a sand-Trevira 1 1 2 0 - P V C , as s h o w n  in  F i g u r e 6.8. T h e P V C s p e c i m e n w a s g l u e d o n t o the steel b a s e a n d fixed in the b o t t o m h a l f o f the confining  rings,  t h e g e o t e x t i l e w a s t h e n p l a c e d o v e r it a n d t h e O t t a w a s a n d f i n a l l y p l a c e d  Top confining rings  Ottawa sand geotextile PVC  Bottom confining rings  fixed steel base  F i g u r e 6 . 8 . A r r a n g e m e n t o f t h e ring s h e a r t e s t o n O t t a w a sand-geotextile-PVC  o v e r the geotextile. Marks w e r e inscribed o n the outer sides o f the P V C a n d the geotextile to m o n i t o r w h e r e slip o c c u r r e d . N o d i s p l a c e m e n t w a s o b s e r v e d at the interface o f the P V C geotextile. T h i s d e m o n s t r a t e d that shearing w a s t a k i n g p l a c e at the interface o f the sand-geotextile  a n d the friction at the interface o f the P V C - T r e v i r a  Ottawa  was apparently higher  t h a n t h a t i n t e r f a c e . F i g u r e 6 . 9 s h o w s t h a t t h e r e s u l t i n g 6 o b t a i n e d f r o m this t e s t is e q u i v a l e n t to that f r o m the test o n the interface o f O t t a w a s a n d - T r e v i r a 1120.  Interface Strength of Various Geosynthetics and  40  i  i  1  1  Soils from Ring Shear Tests: CHAPTER 6—  i  r  r  1  30  OO  20  C  10  — Ottawa sand-Trevira 1120-PVC  -A—  0  0  Ottawa sand-Trevira 1120  O  —Ar T  I  I  10  20  30  I  I  I  40  50  60  Shear displacement  I  I  70  (TRSP50)  I  I  80  T  I  90  100  (mm)  F i g u r e 6.9. V a r i a t i o n o f interface friction angle w i t h d i s p l a c e m e n t from t e s t s o n O t t a w a s a n d - T r e v i r a 1 1 2 0 - P V C a n d Ottawa sand-Trevira 1120  6.5  Textured HDPE-Geotextiles  Previous tests reported for the textured H D P E  with Ottawa sand and with  compacted  clay suggest that w h e n a g o o d interface stability a n d l o w permeability are o f c o n c e r n , then textured HDPE HDPE  is t h e m a t e r i a l o f c h o i c e . R i n g s h e a r tests o n t h e i n t e r f a c e o f  textured  with t w o types geotextiles, Trevira and Polyfelt, were conducted to evaluate  c o m b i n a t i o n o f materials. T h r e e single stage tests a n d t w o multistage test w e r e o n the textured HDPE-Trevira;  and, three single stage a n d multistage tests o n the  H D P E - P o l y f e l t . Stress levels w e r e applied  from  values o f d are s u m m a r i z e d in Tables 6.9 a n d  this  performed textured  about 50 k P a to 150 k P a and the resulting 6.10.  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 6—93  Typical curves of 6 with shear displacement under normal stresses o f approximately 50 kPa for the two types of geotextile with the textured H D P E are illustrated in Figure 6.10. A l l tests exhibited a distinct peak strength and a gradual reduction to a constant, residual value at displacements between 60 mm and 80 mm. The response is somewhat different to that observed in the previous tests on the smooth geomembranes with the same types o f geotextile. The controlling mechanism on the peak strength at small displacement is that from a resistance derived from ripping o f fibres by the tips on the surface o f the textured H D P E . Once the normal stress was applied, the tips penetrated through the fibres and, with shear displacement, started tearing the geotextile. Duller and aligned tips of the texture were found during visual inspection of the specimens after each test. This also implies that the values o f <5  resid  i were mobilized by a combination o f tearing and friction.  Figure 6.11 illustrates the values of ( 5 ues o f ( 5  residual  residual  listed in the Tables 6.9 and 6.10. The val-  mobilized by the textured HDPE-Trevira 1120 and textured HDPE-Polyfelt  T S 550 were 15° to 16° and 1 7 . 9 ° to 1 8 . 4 ° respectively. The values of ^  r e s i d u a  , for these tests  seem to be independent o f the applied normal stresses.  Table 6.9. Summary of interface friction angles from ring shear tests on textured HDPE-Polyfelt T S 550  No  Name of test  (kPa)  Speak  ^res  (°)  n  1  HDTPF50  45  34.8  18.3  2  HDTPF50S  52  26.9  18.3  107  NP  17.9  154  NP  17.9  3  HDTPF100  100  26.5  18.4  4  HDTPF150  150  25.9  18.4  Note: NP=no peak  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 6—94  Table 6.10. S u m m a r y o f interface friction angles f r o m ring shear tests o n textured HDPE-Trevira 1120  No  Name of test  O  n  (kPa)  (5 peak  Oresidual  o  o  1  HDTTR50  48  22.9  16.2  2  HDTTR50S  49  20.9  15.5  109  NP  15.0  158  NP  15.0  3  HDT7R100  106  23.5  15.8  4  HDTTR100S  98  22.4  16.0  155  NP  16.0  5  HDTTR150  148  18.9  15.4  Note: NP=no peak  30 — \  tO  C  20 — ,  10 —  0  20  40 60 Shear displacement (mm)  80  100  Figure 6.10. Variation o f interface friction angle with displacement f r o m tests o n textured H D P E - g e o t e x t i l e s  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 6—95  35 30 —|  O  TS 550-Textured HDPE  A  Trevira 1120-Textured HDPE  25 20 15 -  00 4^  .  A  A  10 -  100  200  30  (kPa)  Figure 6.11. Residual interface friction angles f r o m ring shear tests o n textured FIDPE-geotextiles  In contrast to the results obtained for the geotextiles w i t h s m o o t h g e o m e m b r a n e s , v a l u e s o f <5 from  r e s i d u a l  from  the tests o n the textured HDPE-Trevira  the  are slightly l o w e r than those  the textured HDPE-Polyfelt. Visually, the diameter o f filaments c o m p o s i n g the Polyfelt  is g r e a t e r t h a n t h a t o f t h e T r e v i r a . I n a d d i t i o n , t h e m a s s p e r u n i t v o l u m e f o r t h e T r e v i r a  1120  is l e s s t h a n t h a t o f t h e P o l y f e l t T S 5 5 0 . A l t h o u g h s i m i l a r t e a r i n g a n d f r i c t i o n p h e n o m e n a a l s o exist w i t h the Polyfelt material, the p u l l e d fibres left o n the texture o f g e o m e m b r a n e testing w e r e not so p r o n o u n c e d as those for the tests using the Trevira. Interestingly, v a l u e s o f the <3  r e s i d u a l  are lower than those exhibited by the P V C - g e o t e x t i l e interface.  after the The  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: CHAPTER 6—96  explanation for this behaviour is that the action of tearing was no longer completely mobilized when most of the fibres at the very surface of the geotextile specimen were already pulled out and covering the tips of the texture of the geomembrane. Visual inspection after testing revealed that pulled fibres covering the tips of the texture.  6.6 Summary Results from ring shear tests on four geomembranes and two geotextiles lead to the following conclusions : •  ^residual  •  <5 iduai  1S  f°  res  dependent of stress level r m  e  smooth geomembranes with Trevira 1120 is higher than that  with Polyfelt TS 550, a behaviour which is attributed to the less glossy fibres composing the Trevira than those of the Polyfelt. •  f°  ^ id ai res  U  rm  e  textured geomembranes with Trevira 1120 is lower than that  with Polyfelt TS 550, a behaviour which is attributed to the smaller diameter offilamentscomposing the Trevira than those of the Polyfelt. •  Residual  i s  controlled by :  - texture and stiffness of the geomembranes - type offibrescomposing the geotextiles - arrangement of the fibres of geotextiles • the values of <5  a t residual  normal stresses from 45 to 301 kPa, are as follows:  - VLDPE-Trevira:  15.4° to 16.5°  - VLDPE-Polyfelt:  12.7° to 14.2°  - smooth HDPE-Trevira:  7.2° to 7.7°  - smooth HDPE-Polyfelt  6.1° to 6.7°  Interface Strength of Various Geosynthetics and  Soils from Ring Shear Tests: CHAPTER 6—97  PVC-Trevira:  3 1 . 5 °to 33.8°  PVC-Polyfelt:  23.5° to 25.8°  •textured HDPE-Trevira:  1 5 . 0 °to 1 6 . 2 °  •textured HDPE-Polyfelt:  1 7 . 9 °to 1 8 . 4 °  CHAPTER 7 C O N C L U S I O N S  The  ring  s h e a r d e v i c e is u s e d t o s i m u l a t e t h e c o n d i t i o n s o f s h e a r i n g w h i c h t a k e p l a c e at  t h e t i m e o f stability f a i l u r e i n g e o t e c h n i c a l c o n s t r u c t i o n s . T h e d e v i c e is c a p a b l e o f s h e a r i n g an annular sample to an unlimited magnitude o f displacement in one direction-a condition w h i c h d e s c r i b e s w e l l t h e f a i l u r e o f s l o p e s . I n t h i s p r o g r a m o f l a b o r a t o r y w o r k , it w a s extensively to investigate the behaviour and interface strength between various and  between  used  geosynthetics,  t h e s e g e o s y n t h e t i c a n d soils. T h e soils u s e d i n testing w e r e a  c o m p a c t e d clay, a n d a u n i f o r m l y g r a d e d O t t a w a sand; the geosynthetics w e r e a PVC, and smooth and textured HDPE  fine-grained, VLDPE,  geomembrane, and two n o n w o v e n geotextiles. T h e  applied stress levels w e r e generally between 50 a n d 300 k P a ; l o w e r a n d higher levels  were  occasionally used. U n l e s s otherwise stated, all tests w e r e p e r f o r m e d at a rate o f shear 0.04  of  mm/s. T h e r e s i d u a l s t r e n g t h o f t h e c o m p a c t e d c l a y is v e r y sensitive t o m o i s t u r e c o n t e n t ,  g i v e s v a l u e s o f c = 2 0 . 9 k P a a n d <p - 2 3 . 9 ° a t a m o i s t u r e c o n t e n t a p p r o x i m a t e l y 2 % o p t i m u m . T h i s has v e r y i m p o r t a n t implications for design c o n s i d e r i n g slope stability. residual interface strength o f the compacted clay with the s m o o t h g e o m e m b r a n e w a s  98  and above The found  Interface Strength of Various Geosynthetics and  Soils from Ring Shear Tests: CHAPTER 7—99  to be very l o w ( 1 3 % to 2 3 % ) c o m p a r e d with those obtained f r o m the t w o series of tests o n compacted clay with the textured HDPE  g e o m e m b r a n e ( 5 7 % to 90%) a n d with the n o n -  w o v e n P o l y f e l t T S 5 5 0 g e o t e x t i l e ( 7 8 % to 9 5 % ) . T h e v a r i a t i o n i n s t r e n g t h is a t t r i b u t e d i n part to small differences in water content o f the reconstituted clay samples. H o w e v e r  the  b e h a v i o u r of the textured g e o m e m b r a n e w a s also f o u n d to be v e r y d e p e n d e n t o n stress level. T h e friction m o b i l i z e d at the interface o f the O t t a w a s a n d w i t h the g e o m e m b r a n e s  is  apparently controlled b y the stiffness a n d the texture o f the g e o m e m b r a n e s . O f a l l g e o m e m b r a n e s u s e d in this research p r o g r a m , the v e r y stiff a n d s m o o t h surface o f the H D P E  tended  to exhibit the lowest interface friction varying f r o m 3 4 % to 4 5 % of the residual friction angle o f t h e O t t a w a s a n d (0  av  = 2 8 . 8 ° ). A h i g h e r r e s i d u a l f r i c t i o n b e t w e e n 4 4 % a n d 5 9 % o f t h a t o f  the O t t a w a sand w a s mobilized in tests with the VLDPE  g e o m e m b r a n e : it is a t t r i b u t e d t o t h e  r e l a t i v e l y s o f t e r s u r f a c e o f this g e o m e m b r a n e . T h e s a m e t y p e o f r e s p o n s e is e v e n m o r e a p parent in tests with the P V C , w h i c h w a s the softest material u s e d in the p r o g r a m of testing. At n o r m a l stresses f r o m 50 k P a to 223 k P a , the interface exhibited a residual friction resist a n c e o f 7 0 % to 97%) o f the O t t a w a sand. I n all c a s e s the interface strength o f t h e s e s m o o t h g e o m e m b r a n e s w a s f o u n d to be dependent o n stress level: the P V C w a s m o s t d e p e n d e n t a n d the smooth HDPE  least dependent. Tests c o n d u c t e d o n the O t t a w a sand w i t h a steel c o n -  f i r m e d t h a t t h e l e v e l o f s t r e s s d e p e n d e n c y is a l s o g o v e r n e d b y t h e h a r d n e s s o f a m a t e r i a l . H a r d e r materials tend to exhibit less d e p e n d e n c y o n stress level. T h e v e r y r o u g h surface o f the textured HDPE  m o b i l i z e d the highest friction o f all materials e x a m i n e d i n the tests. T h e  efficiency ratio of unity achieved b y the textured HDPE  implies that the shearing action  was  fully d e v e l o p e d w i t h i n t h e a d j a c e n t s a n d itself. Tests performed on two geotextiles—Trevira 1120 and Polyfelt T S 550—revealed f r i c t i o n a l b e h a v i o u r t h a t is i n f l u e n c e d t o s o m e e x t e n t b y t h e t y p e o f  fiber  composing  a the  Interface Strength of Various Geosynthetics and  Soils from Ring Shear Tests: CHAPTER 7—700  fabric. T h e glossier fibers o f the Polyfelt tend to mobilize a slightly l o w e r residual interface friction angle. Residual friction angles o f the O t t a w a sand with the Trevira a n d Polyfelt from  8 5 % to 9 6 % a n d 8 1 % to 8 8 % o f that for the O t t a w a sand respectively, a n d  were  essentially  i n d e p e n d e n t o f stress level. Results o f the ring shear tests o n t w o geotextiles, the Trevira 1120 a n d the T S 550, with the smooth H D P E , V L D P E , P V C , and textured H D P E  Polyfelt  geomembranes  t h a t t h e m o b i l i z e d i n t e r f a c e f r i c t i o n is g o v e r n e d b y t h e t e x t u r e a n d t h e stiffness o f  reveal  geomem-  brane, as well as the type a n d the arrangement o f fibers c o m p o s i n g the geotextile. Again, the lowest interface  friction  w a s observed in the tests with the s m o o t h H D P E ;  the highest  achieved with the P V C . Taking the residual interface friction resistance o f the vira 1120-the highest measured values (6  a v  was  PVC-Tre-  = 32.7°)-as a benchmark, then the VLDPE  in-  terface w i t h T r e v i r a 1120 a n d Polyfelt T S 550 exhibits 4 9 % a n d 4 1 % respectively o f this value. M u c h lower ratios o f only 2 3 % and 2 0 % were mobilized b y the s m o o t h H D P E  with  the Trevira 1120 and with the Polyfelt T S 550, and the PVC-Polyfelt T S 550 exhibits  75%.  Tests o n the textured HDPE  with Trevira1120 and Polyfelt T S 550 gave respectively  40%  a n d 5 6 % ) o f t h e b e n c h m a r k v a l u e . A n i n t e r p r e t a t i o n o f t h e results, t h a t is c o n f i r m e d b y v i s u a l inspection suggests there are t w o different m e c h a n i s m s controlling the residual friction o f the n o n w o v e n geotextiles w i t h all o f the s m o o t h g e o m e m b r a n e s textured HDPE  interface  and with  the  g e o m e m b r a n e . I n t h e c a s e o f t h e s m o o t h g e o m e m b r a n e s , f r i c t i o n is attrib-  uted to sliding between the geotextiles and the geomembranes. T h e textured  geomembrane  d e v e l o p s a r e s i s t a n c e t o s h e a r t h a t is a t t r i b u t e d t o a r i p p i n g o f t h e g e o t e x t i l e f a b r i c b y t h e t i p s o f texture o f the  geomembrane.  Generally, w h e n issues o f slope stability are a priority, the use o f s m o o t h , h a r d a n d stiff g e o m e m b r a n e s is o f t h e m o s t c o n c e r n s i n c e t h e i n t e r f a c e f r i c t i o n e x h i b i t e d b y this t y p e  of  Interface Strength of Various Geosynthetics and  SoilsfromRing Shear Tests: CHAPTER  g e o m e m b r a n e w i t h b o t h t h e c o m p a c t e d c l a y a n d t h e g r a n u l a r soil, is r e l a t i v e l y l o w . A  tex-  tured g e o m e m b r a n e , or a s m o o t h g e o m e m b r a n e with a soft surface s e e m to be the material o f c h o i c e . I f a n o n w o v e n g e o t e x t i l e is u s e d w i t h a s m o o t h g e o m e m b r a n e , a g e o t e x t i l e m a d e o f less glossy fibers with smaller filaments w o u l d appear m o r e desirable. O n the other hand, a  fibrous  n o n w o v e n geotextile with larger  filaments  that are well interwoven offers  resistance to shear displacements w h e n used with a textured  geomembrane.  more  7—101  REFERENCES Bishop, A . W., Green, G . E . , Garga, V. K . , Anderssen, A . , and Brown, J . D . (1971). A  N e w R i n g S h e a r A p p a r a t u s a n d its A p p l i c a t i o n t o t h e M e a s u r e m e n t o f R e s i d u a l Strength, Geotechnique 21, No.4, pp.273-328. Bosdet, B . W. (1980). T h e U B C R i n g S h e a r D e v i c e , M . A . S c . T h e s i s , U n i v e r s i t y o f B r i t i s h Columbia. Druschel, S. J . and O'Rourke, T. D. (1991). S h e a r S t r e n g t h o f S a n d - G e o m e m b r a n e I n t e r face for C o v e r System and Lining Design, Proceedings of Geosynthetics'91 Conference, Atlanta, Georgia, U S A . pp. 159-173. Geotechnical Fabric Report (1993). S p e c i f i e r ' s G u i d e , V o l u m e 1 0 N u m b e r 9 . Ingold, T. S. (1991). F r i c t i o n T e s t i n g , G e o m e m b r a n e s I d e n t i f i c a t i o n a n d P e r f o r m a n c e T e s t ing, R e p o r t o f Technical C o m m i t t e e 103-MGH M e c h a n i c a l and H y d r a u l i c Testing o f G e o m e m b r a n e s , A . Rollin a n d J. M . R i g o , editors, R I L E M , G r e a t Britain, C a m bridge. Kharchafl, M . and Dysli, M . (1993). S t u d y o f S o i l - G e o t e x t i l e I n t e r a c t i o n b y a n X - R a y M e t h o d , G e o t e x t i l e s a n d G e o m e m b r a n e s , 9, p p . 3 0 7 - 3 2 5 . Lahlaf, A . M . and Yegian, M . K . (1993). S h a k i n g T a b l e T e s t s f o r G e o s y n t h e t i c I n t e r f a c e , Proceedings of Geosynthetic'93 Conference, Vancouver, British Columbia, Canada. V o l u m e 2, p p . 6 5 9 - 6 6 9 . Martin, J . P., Koerner, R. M . , and Whitty, J . E . (1984). E x p e r i m e n t a l F r i c t i o n E v a l u a t i o n  o f Slippage B e t w e e n G e o m e m b r a n e s , Geotextiles a n d Soils, Proceedings o f the International Conference on Geomembranes, Denver, U.S.A., pp. 191-196. Mitchell, J . K . , Hooper, D. R., and Campanella, R. G . ( 1 9 6 5 ) . P e r m e a b i l i t y o f  102  C o m -  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: BIBLIOGRAPHY—103  pacted Clay, Journal o f the Soil M e c h a n i c s and Foundations Division, ASCE, N o 4, p p . 4 1 - 6 5  V o l 91  Mitchell, J. K , Seed, R. B., and Seed, H. B. (1990). K e t t l e m a n H i l l s W a s t e L a n d f i l l S l o p e F a i l u r e . I: L i n e r - S y s t e m P r o p e r t i e s , J o u r n a l o f G e o t e c h n i c a l E n g i n e e r i n g , ASCE, 116(4), pp.647-668. Negussey, D., Wijewickreme, W. K . D., and Vaid, Y.P. (1988). O n G e o m e m b r a n e  Inter-  face Friction, Soil M e c h a n i c s Series N o . 119, D e p a r t m e n t o f Civil Engineering, versity o f British Columbia.  Uni-  O'Rourke, T. D. and Druschel, S. J. (1990). S h e a r S t r e n g t h C h a r a c t e r i s t i c s o f S a n d - P o l y m e r Interfaces, Journal o f Geotechnical Engineering, A S C E , 116(5), p p . 4 5 1 - 4 6 9 . Rinne, N . F. (1989). E v a l u a t i o n o f I n t e r f a c e F r i c t i o n b e t w e e n C o h e s i o n l e s s S o i l s a n d C o m m o n Construction Materials, University of British Columbia. Seed, R. B., Mitchell, J . K., and Seed, H. B. (1988). S l o p e S t a b i l i t y F a i l u r e I n v e s t i g a t i o n : Kettleman Hills Repository Landfill Unit B-19, Phase I-A. Geotechnical Research Report N o . U C B / G T / 8 8 - 0 1 ,Univ. of California, Berkeley, California. Skempton, A . W. (1985). R e s i d u a l S t r e n g t h o f C l a y s i n L a n d s l i d e , F o l d e d S t r a t a a n d Laboratory, Geotechnique 35, N o . l . pp.3-18..  the  USEPA (1989). T e c h n i c a l G u i d a n c e D o c u m e n t : F i n a l C o v e r s o n H a z a r d o u s W a s t e L a n d fil s a n d S u r f a c e I m p o u n d m e n t s , U . S . D e p a r t m e n t o f C o m m e r c e , N a t i o n a l T e c h n i c a l Information Service, Springfield, V A , U S A . Waste Management Act (1988). S p e c i a l W a s t e R e g u l a t i o n : D e s i g n G u i d a n c e , B r i t i s h C o lumbia, Canada Wiess, W. and Batereau, C . (1987). A N o t e o n P l a n a r S h e a r B e t w e e n G e o s y n t h e t i c s C o n s t r u c t i o n M a t e r i a l s , G e o t e x t i l e s a n d G e o m e m b r a n e s , 5, p p . 6 3 - 6 7 .  and  Wijewickreme, W. K . D . (1986). C o n s t a n t V o l u m e F r i c t i o n A n g l e o f G r a n u l a r M a t e r i a l s , M.A.Sc Thesis, University of British Columbia. Williams, N . D. and Houlihan, M . (1986). E v a l u a t i o n o f F r i c t i o n C o e f f i c i e n t s b e t w e e n G e o m e m b r a n e s , Geotextiles and Related Products, Proceedings o f the Third Intern a t i o n a l C o n f e r e n c e o n G e o t e x t i l e , V i e n n a , A u s t r i a . V o l u m e III, p p . 8 9 1 - 8 9 6 . Yegian, M. K . and Lahlaf, A . M. (1992). D y n a m i c I n t e r f a c e S h e a r S t r e n g t h P r o p e r t i e s o f G e o m e m b r a n e s and Geotextiles, Journal o f Geotechnical Engineering, ASCE, 118(5), pp.760-779.  APPENDIX A TEST DATA ON COMPACTED CLAY-GEOSYNTHETIC INTERFACES  I. COMPACTED CLAY 100 — i 80 — i? a  60  -^  —  „  40 — , 20 — n U  300  —  200  —  )  50  100  150  200  250  & §. 100 —  U  l  ()  l  |  50  |  i  100  i  150  Shear displacement (mm)  F i g u r e A . 1. 104  CLAY50S  i  200  |  250  Interface Strength of Various Geosynthetics and  100 v H  —| 80  —  60  -  ^  40-^ 20  — n  r — "  U  to %  Soils from Ring Shear Tests: APPENDIXA—  i  i  300  —  200  —  )  i  i  20  40  i  i  i  60  i  i  80  100  80  100  80  100  I 100  — n U  ()  20  40  60  Shear displacement  Figure A.2.  to 3  100  —|  200  —  100  —  0  20  C L A Y 1 0 0 C  40  60  Shear displacement  Figure A 3 .  (mm)  C L A Y 1 0 0 D  (mm)  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIX B—106  II. COMPACTED CLAY-SMOOTH HDPE  30  — i  20 — 10 — -—— r\ U  i  300 — _  _r  )  |  20  "  i  | 40  i  ^  | 60  i  ~'  "  | 80  i  "  |  i  |  i  |  100  120  140  40 60 80 100 Shear displacement (mm)  120  140  200 — 100 —  I  n U  ()  20  Figure A.4.  C H D S 2 5 S B  Interface Strength of Various Geosynthetics and SoilsfromRing Shear Tests: APPENDIXA—107  50  —i  40 — ?  30  -  s  20 —  r  10 — u 300 —  )  i  |  200  300  i  i  100  ^ I  I  400  |  500  200 —  1,  b  100 — n u —  l  (3  I  l  100  200  l  300  | 400  I  |  500  Shear displacement (mm)  Figure A.5.  30  |  C H D S 1 0 S  -—i  20 —  c b  g  100  -  0  50  100  150  200  Shear displacement (mm)  Figure A.6.  C H D S 2 5 S  250  300  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIXA—108  30  —i  20 10 0 200  fl cd  I c)  I 20  I  I  I  I  I  I  | 100  I  40  60  80  I 40  I 60  80  | 100  80  100  100  0  I 0  I 20  Shear displacement (mm)  Figure A.7.  CHDS50S  30 —, 20 -\  0  20  40  60  Shear displacement (mm)  ' FigureA.8. CHDS50SB  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIX A—109  30 —I 20  r  10  f.  0 200  I  _c  I 20  )  1  .  1  40  |  1  |  1  80  60  | 100  100  b£  0  1  0  1  20  1  |  I  60 40 Shear displacement (mm)  Figure A.9.  30  I  I  I  80  100  80  100  CHDS50SC  —i  20 —\  ~ b  200 — • £  100  —  0  20  40 60 Shear displacement (mm)  F i g u r e A . 10.  C H D S 1 0 0 S  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIX A—110  30 — i 20  —  10  —  n U  200 —  fl  b  CO  a  l  I  )  |  i  40  20  i  l  |  80  60  100  100 —  n U  l 20  0  |  i l l  100  80  40 60 Shear displacement (mm)  F i g u r e A . 11.  I  I  C H D S 1 0 0  30 —| 20  —  10  —  ,  n U  i  J  I  I  i  10  i  20  I  i  30  I  i  40  I  i  50  I 60  200 —  u  l  J n  |  10  l  |  I  |  I  20 30 40 Shear displacement (mm)  F i g u r e A . 12.  C H D S 1 0 0 B  l  i  50  60  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIX B—111  III. COMPACTED CLAY-TEXTURED HDPE  100 -  e S3  80 —| 60 40 20 -  1 | 300  0  1  50  |  |  1  1  |  |  1  1  |  1  |  1  |  100 150 200 250 300 350 400  200  bW  100 "i  0  50  I  r  1  i i i r  100 150 200 250 300 350 400 Shear displacement (mm)  Figure A . 13.  CHDT25S  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIX A—112  100 —| 80 — ?  60  a  -  40 — 20 — n U  )  300 —  100  50  150  200  250  300  350  400  200 —  fl  OS  r•  100 — u n  c)  i  50  i  i  100  150  i I  200  l  i  i  250  i  300  i 350  i I  400  Shear displacement (mm)  F i g u r e A . 14. C H D T 2 5 S B  120 —|  0  100 200 300 400 500 600 700 800 Shear displacement (mm)  F i g u r e A . 15.  C H D T 5 0 S  900  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIX A—113  120 100 80 60 40 20 0 300  - ° i  100  200  300  400  300  400  200 -  b &  100 —| 0  T  100  200  Shear displacement (mm)  F i g u r e A . 16. C H D T 5 0 S B  e  2a  120 100 80 60 40 20 —| 0 300  100  200  300  100  200  300  200 —\  b a.  100  Shear displacement (mm)  F i g u r e A . 17.  C H D T 1 0 0 S  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIXB—114  IV. COMPACTED CLAY-GEOTEXTILE (POLYFELT TS 550)  H  140 120 — 100 — 80 — 40 — . 20 — n u  ^  6  0  I I  300 — ) _ C  —  ' I  100  I  I  200  I 300  200 —  CO  & a 100 — u n c)  I  |  I  100 200 Shear displacement (mm)  F i g u r e A . 18.  CPF50S  i  300  Interface Strength of Various Geosynthetics and  F i g u r e A . 19.  Figure A.20.  Soils from Ring Shear Tests: APPENDIX  CPF100S  CPF200  A—115  APPENDIX B T E S T  D A T A  O N  O T T A W A  S A N D - G E O S Y N T H E T I C F A C E S  I N T E R -  I. OTTAWA SAND 40 —| 30 — A -  -e-C  20 — 10 — n u  i  i  400 —  )  20  I  i  I  i  i  I  40  60  80  100  40  60  80  100  300 —  b a  2 0 0  -  \  100 — n u  c)  20  Shear displacement (mm)  Figure B.l. 116  S A N D 2 0 0 S  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIX B—117  40 30 -e-C  20 — 10 0  I  c)  400 300  b §.  I  I  I  20  I  I  40  60  |  I  100  80  —  /  . 200 100 0  .I  0  .1  |  20  . |  I  . I  40  I  80  60  I 100  Shear displacement (mm)  40  S A N D 2 5 0  I  I  —I  30 -e-C  Figure B.2.  20 —  I  10 0 400  c)  I  20  !  40  I  60  80  I  100  300  b&  200 100 0  I  0  |  I  20  |  40  l  |  l  60  Shear displacement (mm)  Figure B.3.  S A N D 2 5 0 S  |  80  I  I  100  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIX B—118  40 30 -e-C  P  20 10 0  i  C)  400 300 to a  |  20  40  60  i  80  |  100  —  200  —  100 0  I  0  |  i  20  i  40  |  i  60  |  I  I  80  100  80  100  80  100  Shear displacement (mm)  Figure B.4.  S A N D 2 0 0  40 30 20 —| 10 0 400  °  20  40  60  300  to a  200 100 0  T  20  40  T  60  Shear displacement (mm)  Figure B.5.  S A N D 2 0 0 S B  Interface Strength of  -e-C  40  —|  30  —  20  —  10  — n u  b  Various Geosynthetics and  -  i  500  —)  400  —  « ^  300  -  -  200  —  |  i  20  |  Soils from Ring Shear Tests: APPENDIX  l  40  |  I  60  |  I  80  100  /  —  100  n u  i  C)  l  20  Figure B.6.  I  |  40 60 Shear displacement  S A N D 2 0 0 S C  l  (mm)  |  80  l  |  100  B—119  Interface Strength of Various Geosynthetics and  I.  Soils from Ring Shear Tests: APPENDIX B—120  OTTAWA SAND-SMOOTH HDPE 40 30  to  C  20 10 0  I  I  )  400  i  20  |  l  40  l  |  60  I  80  |  100  300 200  -  100 0  i  0  I  |  I  '  Shear displacement  (mm)  20  '  40  Figure B.7.  60  H D S P 5 0  I  I  80  100  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIX B—121  40 30 20 —|  to  10 0 400  °  20  40  60  80  100  80  100  300 fl  cd  b §.  200 100 0  T  20  40  60  Shear displacement (mm)  Figure B.8.  H D S P 5 0 B  40  60  Shear displacement (mm)  Figure B.9.  H D S P 5 0 S  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIX B—122  40 30 co  C  20 — 10 0  I  c)  400  i  20  |  40  I  |  i  60  |  I  80  100  300  b  a  200  —  100 0  l  0  i  20  |  |  I  40  l  60  |  l  80  |  100  Shear displacement (mm)  F i g u r e B . 10.  H D S P 1 0 0  40 30 20  CO  10 0 400  i  0  |  20  i  |  i  |  i  |  i  |  40  60  80  100  40  60  80  100  300  b  §.  200 100 0  20  Shear displacement (mm)  Figure  B . 1 1 . H D S P 2 0 0  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIX B—123  40 —I 30 — to  C  20 10  A,  0 400  I  c)  i  20  l  I  l  40  60  |  100  80  300 200 100 0  l  0  l  20  |  40  l  i  60  Shear displacement (mm)  F i g u r e B . 12.  H D S P 3 0 0  |  80  I  |  100  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIX B—124  III. OTTAWA SAND-VLDPE  to C  40  —  30  —  20  —  10  —  p  —  ,  n u  -  i  100 —)  i  20  40  i 60  i 100  80  b&  I  U  ()  |  I  20  | 40  I  I 60  Shear displacement (mm)  Figure B . 13.  VLSP50  I 80  | 100  Interface Strength of Various Geosynthetics and Soils from Ring'Shear Tests: APPENDIX B—125  20  40  60  Shear displacement (mm)  F i g u r e B . 14.  80  100  VLSP50B  40 30 to  20 10 0 400  |  °  I  20  ]  I  40  |  1  1  1  1  60  80  100  60  80  100  300 -  b £  200 —| 100 0 -  T  20  40  Shear displacement (mm)  F i g u r e B . 15.  VLSP50C  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIXB—126  F i g u r e B . 16.  V L S P 1 0 0  40  60  Shear displacement (mm)  F i g u r e B . 17.  V L S P 1 0 0 B  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIX B—727  40  —i  30 — to  C  20 — 10 — 0  I  c)  400  |  i  20  |  l  40  l  60  I  80  |  100  300  b &  200  —  100 0  l  0  i  i  20  40  |  i  60  Shear displacement (mm)  F i g u r e B . 18.  V L S P 1 0 0 C  40  60  Shear displacement (mm)  F i g u r e B . 19.  V L S P 1 0 0 D  |  80  1  1 100  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIX B—128  40 —| 30 — co €  20 —  —I  10  0  400  20  40  60  80  100  300 —  I  b  —  200 100  —  0  20  40  60  80  100  Shear displacement (mm)  F i g u r e B.20.  V L S P 1 0 0 E  40 30 C  co  20 10 0  ' C)  400 300 fl  ca  I  '  I  20  '  40  I  '  60  I  1  80  100  —  200 100  —  0  I  0  I  I  20  !  40  I  60  Shear displacement (mm)  F i g u r e B.21.  V L S P 2 0 0  80  |  100  Interface Strength of Various Geosynthetics and  IV.  Soils from Ring Shear Tests: APPENDIX B—129  OTTAWA SAND-PVC  40  —  30 CO  C  20  —  10 0  l  c)  100  0  20  I  ()  40  |  20  l  I  |  I  40  I  60  Shear displacement  Figure B.22.  80  60  |  P V S P 5 0  i  l  100  I  I  80 (mm)  |  100  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIX B—130  40 — i  co  C  30  —  20  —  10  —  .  — .  —  n u 100  —  )  20  40  60  80  100  80  100  b §.  n u  I c)  20  I  I  I  40 60 Shear displacement (mm)  Figure B.23.  P V S P 5 0 B  40 30 to  C  20 — 10 0  ' c)  300  I 20  40  I  0  |  I  I  | 100  80  /  /  0  '  60  200 100  I  '  ' I  I  20  |  40  I  |  I  60  Shear displacement (mm)  Figure B.24.  P V S P 5 0 S  |  80  I 100  Interface Strength of Various Geosynthetics and  Soils from Ring Shear Tests: APPENDIX  40 30 to  20  ^  10 0  n  20  200  20  40  60  40  60  Shear displacement  Figure B.25.  100  80  80  (mm)  100  P V S P 1 0 0  40 30 to  C  20 10 0  I  C)  200  I  20  l  |  40  I  60  |  1  80  100  /  100  0  I  l  0  20  I  40  |  60  Shear displacement  Figure B.26.  |  I  P V S P 1 0 0 B  (mm)  80  I  I  100  B—131  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIX B—132  40 —, 30 —  oo €  20 — 10 — n u 300 —  )  20  J  C  b  40  60  80  100  40  60  80  100  '  eg  §.  100 — n U  ()  20  Shear displacement (mm)  Figure B.27.  P V S P 2 0 0 B  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIX B—133  V. OTTAWA SAND-STEEL 40  —i  30 — to C  20 10 0 400  I  J. )  l 20  | l | l | l | 40  60  80  100  j  I  120  140  300  b £  200 100 0  1  0  | 20  l  | l 40  | 60  l  | 80  l | 100  Shear displacement (mm)  Figure B.28.  STEEL  |  |  120  140  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIX B—134  40 — 30 — to  20 —  C  10 — n  u  b  i  )  20  C)  20  300  —  200  —  /  |  I  40  60  80  40  60  80  a 100  — U  n  Shear displacement (mm)  Figure B.29.  STEELS  40 30 to  C  20 — 10 — 0  ' c)  400  I • ' 20  I  '  40  60  | 80  60  80  I  300 200 100 0  i  0  i  20  |  I  40 Shear displacement (mm)  Figure B.30.  STEELSB  Interface Strength of Various Geosynthetics and SoilsfromRing Shear Tests: APPENDIX B—755  VI. OTTAWA SAND-TEXTURED HDPE  r—  40 —| 30 — to  C  20 — 10 — n u  i  400 — )  I  i  20  I  I  i  40  i  60  I  i  80  100  300 —  b |  '200100 — n U  i  C)  | 20  i  |  i  |  1  40 60 Shear displacement (mm)  Figure B.34.  H D T S P 5 0  |  80  I  |  100  Interface Strength of  Various Geosynthetics and  Soils from Ring Shear Tests: APPENDIX B—136  Figure B.35.  H D T S P 5 0 B  Figure B.36.  H D T S P 1 0 0  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIXB—137  40  —I  30 — CO  C  20 — 10 0 400  I c)  20  0  | 20  i  |  i  40  |  i  60  | 80  l  | 100  300 c T&  b %  200 100 0  l  | 40  l  |  l  60  Shear displacement (mm)  Figure B.37.  H D T S P 1 5 0  | 80  I  I 100  Interface Strength of Various Geosynthetics and SoilsfromRing Shear Tests: APPENDIX B—138  VII. OTTAWA SAND-TREVIRA 1120 40 — 30 — to  C  —  20 — 10 — n u 400 — )  20  40  60  80  100  300 —  fcf  200  -  100 — n u  i  C)  |  20  i  |  i  I  40 60 Shear displacement ( m m )  Figure B.38.  T R S P 5 0  |  80  I  100  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIXB—139  vo €  20 — 10 — °  :  0  400  ' I ' I ' I ' I '—I—'—I—'—I—'—I—'—I—'—I 20 40 60 80 1 00 1 20 1 40 1 60 1 80 200  300 —  b I  2 0 0  —  /  100 —  0  I  '  20 40 60 80 100 120 140 160 180 200 Shear displacement (mm)  FigureB.39.  TRSP50S  300 —  b |  2 0 0  —  100 —  0  20  40  60  Shear displacement (mm)  FigureB.40.  TRSP100  80  100  Interface Strength of Various Geosynthetics and  Soils from Ring Shear Tests: APPENDIX B—140  Figure B.41.  TRSP150  Figure B.40.  PFSP100  Interface Strength of Various Geosynthetics and  Soils from Ring Shear Tests: APPENDIX  VIII. OTTAWA SAND-POLYFELT TS  to  C  40  —i  30  —  20  —  10  — n u  tog  i  400  —)  300  —  200  -  100  —  n U  |  20  i  C)  l  l  40  |  20  |  i  |  60  i  PFSP50  |  I  80  |  40 60 Shear displacement  Figure B.42.  l  (mm)  80  |  100  |  I  550  I 100  B—141  Interface Strength of  Various Geosynthetics and  Soils from Ring Shear Tests: APPENDIX B—142  40 30 to  20  —  10  —I "i—I—i—I—i  ,  0  nn  400 300  20  40  60  I  80  i  I  i  I  100  120  i  I  140  r  160  —i  200 100 0 1—|—I—|—I—|—I—|—I—|—I—|—I  0  20  40  60  80  100  Shear displacement  Figure  B.43.PFSP50S  Figure B.44.  PFSP100  120 (mm)  140  160  |  I  |  Interface Strength of Various Geosynthetics and  /  2-  CO  40  —I  30  —  20  —  Soils from Ring Shear Tests: APPENDIX B—143  10 0  I  c)  400  |  20  I  |  I  40  |  l  60  |  l  100  80  300 ti  c' T  200 100 0  0  |  I I I  1  20  40  60  Shear displacement  Figure B.45.PFSP  150  80 (mm)  I  I  100  APPENDIX C T E S T  D A T A  O N  G E O M E M B R A N E - G E O T E X T I L E F A C E S  I N T E R -  I. VLDPE-TREVIRA 1120 40 —I 30 CO  —  20 10 0 400  I  I  l  20  ()  |  l  |  40  l  60  | 80  l  | 100  300 n.  a. bc  200 100 0  1  0  | 20  I  I  40  |  I  60  Shear displacement (mm)  F i g u r e d . 144  V L T R 5 0  80  1  1 100  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIX C—145  40 30 20  to  10 0 20  0  400  40  60  80  100  80  100  300 — -  200 —  c  -  b  100 — T  T  20  40  60  Shear displacement (mm)  Figure C.2.  VLTR50B  40 30 o  20  to  /  10 0  r—  I  i  ()  400  I  I  40  20  I  60  |  100  80  300 — ll b  c  200 100  —  -  0  l  0  |  20  i  i  40  |  60  i  Shear displacement (mm)  Figure C.3.  VLTR100  | 80  I  100  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIX C—146  40  —I  30 — o  20  to  10 0 400  r  i  i  (  i  20  |  40  i  I  60  80  100  300 e bc  200 100 0  l  |  0  20  l  |  |  l  40  I  l  60  80  Shear displacement (mm)  Figure C.4.  |  100  VLTR100B  40 30 20  to  10 0 400  f  «•  i  ()  X  o,  X i  20  |  x  i  40  i  60  i  I  80  |  100  300 f*l.  §2  b  ci  200 100 0  I  0  I  20  |  40  I  |  60  I  Shear displacement (mm)  Figure C.5.  VLTR200  |  80  I  I 100  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIX C—147  40 30 to  20 10 0 400  1  0  |  20  1  |  40  |  1  |  1  60  1  80  |  1  |  1  |  1  |  100 120 140 160  300 200 100 "i—I  20  40  60  i  I i  80  I r  100 120 140 160  Shear displacement (mm)  Figure C.6.  VLTR200S  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIX C—148  II. VLDPE-POLYFELT TS 550 40 30 — to  20 — 10 0 400  I  l  20  ()  l  |  40  60  i  80  | 100  300 CL.  a b  200 100 0  I  0  |  20  i  i  40  |  60  i  Shear displacement (mm)  Figure C.7.  VLPF50  1  80  1 100  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIXC—149  40 30 to  20 — 10 —  0  400  20  40  60  80  100  80  100  300 200 100  T 20  40 60 Shear displacement (mm)  Figure C.8. V L P F 5 0 S  40 — 30 — o  ,Z  20  to  p_  — _  10 — i  n 400  —  )  i  20  i  40  |  I  60  l  80  100  300 — * b  200 — 100 — i  u n C)  |  20  i  |  i  |  I  40 60 Shear displacement (mm)  Figure C.9. V L P F 1 0 0  |  80  I  100  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIX C—150  Figure CIO.  VLPF150  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIX C—151  III. SMOOTH HDPE-TREVIRA 1120 40 30 o  to  20 10 —  0  r i  |  20  400  l  i  40  |  l  60  |  80  I  |  100  300  a b  200 100 0  I  0  |  20  '  I 40  '  I  '  60  Shear displacement (mm)  Figure C l l .  H D T R 5 0  I 80  100  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIXC—152  co  40  —  30  —  20  —  10  —  n u  I )  400  c  b  300  —  200  —  100  —  n u  20  i  0  l 20  I  |  !  40  60  80  I  l40  60  i  80  Shear displacement (mm)  100  100  F i g u r e C.12.HDTR50B  40 30 CO  20 -  -  10 n \j  —  400 -  I ()  |  ' ' |  20  40  ' 60  i  |  80  r I  300 b  c  l 100|  200 100 -  I  n u  I 0  I 20  I 40  I  60  l  Shear displacement (mm)  F i g u r e d 3.HDTR50S  80  i 100|  Interface Strength of Various Geosynthetics and  o  to  40  —i  30  —  20  —  Soils from Ring Shear Tests: APPENDIXC—  10 0  I  I J. )  400  |  -i  |  i  40  20  I 100  80  60  300  Kb  200 100  0  I  I  i  —|  30  —  10  —  i  60  Shear displacement  F i g u r e C . 14.  40  |  40  20  0  |  |  I  I  100  80 (mm)  H D T R 1 0 0  to n  U  ^ b  B  I  |  )  400  —  300  —  200  —  100  — n  U  20  I (3  I  |  I  40  |  20  Figure  I  |  I  60  |  I  80  |  i  Shear displacement  (mm)  40  i  |  60  C . 1 5 . H D T R 2 0 0  100  |  80  i  |  100  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests:  APPENDIXC—154  40 30 to  20 10 0 400  —|  1  20  1 40  1  1  1  60  1  I  |  80  100  80  100  300 b  200 100 0  T  T  20  40  60  Shear displacement (mm)  F i g u r e C . 16.  HDTR200B  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIX  IV. SMOOTH HDPE-POLYFELT TS 550 40 —| 30 — 20 —  to  10 — l  u 4  0  0  0  300  —  200  —  100  —  | 20  l  | 40  I  I 60  I 80  100  80  100  a %  b  0  20  40 60 Shear displacement (mm)  F i g u r e C . 17.  HDPF50  C—155  Interface Strength of Various Geosynthetics and  £  40  —|  30  —  SoilsfromRing Shear Tests: APPENDIX C—1  -  2 0  10  — nU  i  I  }  400  —  300  —  200  —  i  I  20  I  i  40  60  40  60  i  i  I  80  100  80  100  §2  ~ b  c  —  100 U  n  ()  20  Shear displacement  F i g u r e C . 18.  ,StO  40  —|  30  —  20  -  10  — n u  K  I  400  —  300  —  200  —  100  —  )  H D P F 1 0 0  I  I  20  (mm)  I  40  !  60  80  100  b  n  U  l  ()  l  20  |  40  |  I  Shear displacement  Figure C.19.  i  60  H D P F 2 0 0  | 80  (mm)  i  | 100  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIXC—157  V. PVC-TRIVERA 1120 40 —I  to  30  —  20  —  10 0 400  I  ()  I  i  40  20  |  i  |  i  100  80  60  300  % b  200 100 0  I  0  |  20  I  |  40  l  |  l  60  Shear displacement (mm)  Figure C.20.  PVTR50  I  80  I 100  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIX C—l 58  Figure  C . 2 1 . P V T R 5 0 S  40 — i 30 to  20 10 -  400 -  20  40  60  80  100  80  100  300 b  200  —I  100 T  20  40  T  60  Shear displacement (mm)  Figure C.22.  P V T R 1 0 0  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIX  o  CO  40  —I  30  — —  20  >  10 0 ()  400 P3  I  l  l  40  20  |  |  l  60  l  100  80  300  K  200  b  100 0  l 0  | 20  l  | 40  l 60  Shear displacement (mm)  Figure  |  I  C . 2 3 . P V T R 1 5 0  80  I  I 100  C—159  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIX C—160  VI. PVC-POLYFELT TS 550 40 —I 30 — <o  20 10 0 400  I  ()  I  I  |  i  40  20  i  60  | 80  | 100  300 —  a  200 100 0  I  0  |  20  I  |  40  |  l  60  l  Shear displacement (mm)  Figure C.24.  PVPF50  | 80  I  I 100  Interface Strength of Various Geosynthetics  and Soils from Ring Shear Tests: APPENDIX  40 — 1  to  30  —  20  —  10  —  n  i l l  u  20  400  a ""is  300  -  200  —  100  —  n  i  u  |  c  20  40  i  60  |  i  i  40 60 Shear displacement (mm)  Figure C.25.  |  |  80  100  |  I  80  100  P V P F 5 0 B  40 —  0  to  30  -  20  -  10  -  i  n  i  u 400  |  0 -  300  —  200  —  100  —  I  20  I  40  |  I  60  |  I  80  100  /  b  _  n  j  '  i  u  D  I  20  I  |  40 60 Shear displacement (mm)  80  Figure C.26.  I  |  P V P F 5 0 S  I  100  C—l 61  Interface Strength of Various Geosynthetics and  40  —I  30  —  o  (  20  to  10 0  I  b  20  c)  400 "at  SoilsfromRing Shear Tests: APPENDIX C—162  I  I  |  I  I  |  40  60  | 100  300 200 100 0  I  l  l  20  0  |  40  I  Figure C.27.  40  -n  30  —  10  —  |  80  60  Shear displacement  I  I  100  (mm)  P V P F 1 0 0  f  n U  % b  l 80  I  400  —)  300  —  200  —  100  —  I  20  l  nU  ()  I  40  l  20  i  P V P F 1 5 0  80  100  80  100  i  60  Shear displacement  Figure C.28.  I  60  l  40  I  (mm)  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIX C—163  VII. TEXTURED HDPE-TREVIRA 1120  20  40  60  Shear displacement (mm)  Figure C.29.  HDTTR50  80  100  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIX C—164  40  —I  30 o  20  to  10 0 400  I  1  1  _i )  |  20  I  |  40  l  I  |  |  80  60  100  300  03 .  200  b  100  /  1  0  I  1  0  20  I  I  40  60  I  I  |  80  Shear displacement (mm)  100  Figure C.30. H D T T R 5 0 S  40 30 o  to  20 10 0 400  i  )  |  i  20  40  60  | 80  l  |  I  |  100  300 b  200 100 0  '  I  0  20  I 40  '  I  '  60  Shear displacement (mm)  Figure C.31. H D T T R 1 0 0  80  100  Interface Strength of Various Geosynthetics and  40  Soils from Ring Shear Tests: APPENDIX C—165  —i  30 20  to  10  HI  '  I  0  400  '  I  20  1  '  40  60  40  60  '  1  '  1  80  100  80  100  300 200 100  20  Shear displacement  Figure C.32.  (mm)  H D T T R 1 0 0 S  40 30 o  CO  20  -  10 0  |  i  20  ()  400  I  I  l  40  |  |  I  60  I  80  |  100  300  X  200  D  100 0  I  0  |  20  i  |  40  i  |  i  60  Shear displacement  Figure C.33. H D T T R 1 5 0  (mm)  80  I  I  100  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIX C—166  VIII. TEXTURED HDPE-POLYFELT TS 550 40 30 0 CO  20 10 0 400  I  c)  i  20  l  40  |  l  60  |  80  100  300 — b  200 100 0  I  0  |  20  l  I  40  |  I  60  Shear displacement (mm)  Figure C.35.  HDPF50  |  80  I  I 100  Interface Strength of Various Geosynthetics and  Soils from Ring Shear Tests: APPENDIX C—167  40 30 o  20  CO  10 0  I  «  2a b  20  ()  400  I I I  1  40  60  80  |  100  300 200 100  —  -  I  0  |  1  0  20  i  |  40  i  |  i  60  Shear displacement  Figure C.36.  H D T P F 5 0 S  Figure C.37.  H D T P F 1 0 0  (mm)  |  80  I  I  100  Interface Strength of Various Geosynthetics and Soils from Ring Shear Tests: APPENDIX C—168  Figure C.38.  HDTF150  

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