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Stability of the Kamloops silt bluffs Lum, Ken King Yee 1979

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S T A B I L I T Y OF THE  KAMLOOPS S I L T BLUFFS by  KEN KING YEEjLUM,, BASc,  University of B r i t i s h  A T H E S I S SUBMITTED  Columbia,  IN P A R T I A L FULFILLMENT OF  THE REQUIREMENTS FOR THE DEGREE OF MASTER OF A P P L I E D SCIENCE  in  THE FACULTY OF GRADUATE STUDIES Department o f C i v i l E n g i n e e r i n g U n i v e r s i t y of B r i t i s h Columbia  We a c c e p t to  this  1975  t h e s i s as  the required  conforming  standard  THE UNIVERSITY O F ' B R I T I S H COLUMBIA March,  1979  c) Ken K i n g Yee Lum, 1979  In presenting this thesis in partial  fulfilment of the requirements for  an advanced degree at the University of B r i t i s h 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 representatives.  It  is understood that copying or publication  of this thesis for financial gain shall not be allowed without my written permission.  j  Department of  CIVIL ENGINEERING  The University of B r i t i s h Columbia 2075 Wesbrook P l a c e V a n c o u v e r , Canada V6T 1 W 5  Date  i i .  ABSTRACT  Stability  problems  are encountered w i t h i n the g I a c i o I a c u s t r i n e  o f t h e S o u t h Thompson V a l l e y n e a r K a m l o o p s , B r i t i s h i n v e s t i g a t i o n s have been c a r r i e d . o u t collapse  features  typical  Columbia.  examining slope  of the area.  The  strength  m e c h a n i s m and t h e n a t u r e o f t h e c o h e s i o n o f t h e s i l t  failures,  silts  Field piping  parameters,  and  collapse  were examined  in the  laboratory. The in  sensitivity  detail  from t h e s t r e n g t h  m e c h a n i s m has derived  been p r o p o s e d  from t h e  preliminary The  and given  considerations,  and  to slight structural  f o r the  lacustrine s i l t  laboratory  short  consideration  proposed.  of the s o i l  inputs  o f w a t e r has  stability  lacustrine s i l t .  aspects.  been A  collapse  Although the  t e s t s h a v e b e e n p e r f o r m e d on t h e c o l l u v i a l of the slopes  t o t h e e f f e c t s o f urban  a p o s s i b l e zoning  colluvium  i s known t o be h i g h l y c o l l a p s i b l e ,  long term s t a b i l i t y  only  material.  have b e e n . s t u d i e d w i t h  development.  scheme f o r u r b a n  examined  Based  development  on has  stability been  TABLE OF CONTENTS Page ABSTRACT  i i  L I S T OF FIGURES  vi-vi i i i x  L I S T OF TABLES  CHAPTER 1.  INTRODUCTION  1.1  Introduction  1.2  Geologic  1.3  Surficial  1.4  CI i m a t e  CHAPTER 2.  1  History  1-3  Geology  3-4 4  F I E L D RECONNAISSANCE  2.1  Problems Observed 2.1.1  Pipes  2.1 .2  Slope S t a b i I i t y  5  and S i n k h o l e s  5-7 8  2.2  S l o p e Geometry  2.3  Jointing  12-15  2.4  S o i I Sampl i n g  15-17  2.5  Field  17-18  CHAPTER 3.  8-12  Seepage S i m u l a t i o n  B A S I C S O I L PROPERTIES  3.1  Speci f i c G r a v i t y  3.2  Grain  3.3  Mineralogy  3.4  Atterberg Contents  19  Size Analysis  19-21 21-22  Limits & Field  Moisture 23  i  Page CHAPTER 4.  LABORATORY TESTS  4.1  Scanning  4.2  Unconfined  4.3  Triaxial  4.4  Electron Microscope  Studies  24-28  Compression Tests  29-30  Tests  30-31  4.3.1  Triaxial  4.3.2  S a t u r a t i o n Procedure  33-34  4.3.3  Experimental  34-35  Triaxial  Test Apparatus  31-32  Procedure  T e s t R e s u l t s and D i s c u s s i o n  4.4.1  Stress-Strain  4.4.2  Volume Changes D u r i n g  4.4.3  S t r e n g t h Envelope  35  Relationships Shearing  36-39 ....  40  (P-Q D i a g r a m ) ...  36-39  4.5  Unconventional  4.6  R e s u l t s and D i s c u s s i o n  45-50  4.7  Consolidation Tests  51-52  4.7.1  C o n s o l i d a t i o n Apparatus  52-53  4.7.2  S a t u r a t i o n Procedure  53-54  4.7.3  Experimental  4.8  CHAPTER 5. 5.1  'Dry' T r i a x i a l  Tests  45  Procedure  54  C o n s o l i d a t i o n R e s u l t s and D i s c u s s i o n  54-57  4.8.1  Incremental  57-65  4.8.2  Strain  4.8.3  D i s c u s s i o n o f C o m b i n e d R e s u l t s ....  Load T e s t  Controlled Test  66-70 70-72  STRUCTURAL S T A B I L I T Y OF KAMLOOPS S I L T L i t e r a t u r e R e v i e w on Co I I a p s i b I e S o i l s 5.1.1  Collapsible  S o i Is  ...  73 73  V.  Page 5.1.2  Collapse  Mechanisms  5.1.3  Engineering  Applications  5.2  Collapse  Phenomenon  5.3  Collapse  Mechanism o f Kamloops S i l t  CHAPTER 6.  73-76 76-77  o f Kamloops S i l t  78-80 80-83  SLOPE S T A B I L I T Y  6.1  F r e q u e n c y and E x t e n t  84  6.2  Jointing  84  6.3  Modes o f F a i l u r e  6.4  Influenze  o f Water  6.5  Stability  A n a l y s i s o f Deep F a i l u r e s  6.6  Long Term S t a b i l i t y  94-95  6.7  P o s s i b l e Zoning.Scheme  95-97  CHAPTER 7.  SUMMARY AND  93 ......  CONCLUSIONS  98-101  I.  APPENDIX  I I . SAMPLE TRIMMING PROCEDURES  108-110  APPENDIX  111. APPARATUS C O M P R E S S I B I L I T Y CORRECTIONS FOR THE CONSOLIDATION TEST  111-116  IV.  117-119  REFERENCES  S I T E S & SAMPLE DESCRIPTIONS  92-93  APPENDIX  APPENDIX  SAMPLING  84-90  .  CONSOLIDATION TESTS ON COLLUVIUM  ..  103-107  120-124  V  L I S T OF  FIGURES  FIGURES  Page  1.  Topographic  Map o f t h e S o u t h  2.  Horizontal  3.  Vertical  4.  S i n k h o l e s on t h e b e n c h s u r f a c e  7  5.  Isolated  7  6.  Slope  pipe  Thompson  Valley  ....  in Colluvium  2 6  pipe in c o l l u v i u m  6  sinkhole within the colluvium  f a i l u r e on t h e e a s t f a c e o f M a g a z i n e  Gul l y  9  7.  Bench s l o p e f a c i n g  South  Thompson  River  9  8.  Oblique aerial  9.  General  10.  Stereonet plot of j o i n t s  13  11.  Rose d i agram  14  12.  Sampling  13.  Grain size  14.  Microphotograph,  undisturbed s i l t ,  15.  Microphotograph,  remolded  16.  Microphotograph,  undisturbed s i l t ,  17.  Microphotograph,  remolded  18.  Microphotograph,  undisturbed s i l t ,  1000X  27  19.  Microphotograph,  undisturbed s i l t ,  2000X  27  20.  Unconfined  21.  Schematic  22.  Stress-strain  plot,  'overconsoIidated' state  23.  Stress-strain  plot,  'normally consolidated'  View o f s t u d y a r e a  10  s l o p e geometry  site  11  location  distribution  compression, diagram  16 curves  20  silt,  silt,  400X  400X  25  1000X  26  1000X  stress-strain  of t r i a x i a l  25  26  curves  ...  apparatus  29 32  ...  37  ....  38  i.  vii.  FIGURES  Page  24.  % .a-Volume v s . % s t r a i n ,  O.C. s t r e s s  region  41  25.  * ^Volume v s . % s t r a i n ,  N.C. s t r e s s  region  42  26.  P-Q D i a g r a m f o r K a m l o o p s S i l t  27.  P-Q D i a g r a m f o r t h e O.C. s t r e s s  28.  Mohr c i r c l e o f f a i l u r e  29.  Shear  30.  Incremental  31.  Structural  32.  A H v s Log t i m e p l o t  33.  P l o t o f p o r e p r e s s u r e d i s s i p a t i o n a n d amount o f c o n s o l i d a t i o n with time  63  34.  Strain controlled consolidation  67  35.  Swell  36.  Composite  37.  Percent collapse  38.  Slope  39.  Columnar j o i n t i n g  40.  Column t o p p l i n g  41.  Block or slab  42.  Rotated  43.  Approximate  44.  Consolidation Curve A  apparatus  Consolidation Curve B  apparatus  45.  strength  rate  saturations  curve  load  58  consolidation  curves  curves  vs P p l o t  near  Pritchard  in the lacustrine s i l t  mode o f f a i l u r e  failure  i n t a c t block  46 47  p r e s s u r e vs time graph  failures  ..  upon f l o o d i n g  f o r incr.  consolidation  44  graph  Consolidation  collapse  region  at various  vs. saturation  Load  43  60 62  69 71 79 85 87 88  mode  89  failure  90  s e t b a c k z o n i n g scheme  96  compressibility, 114 compressibility, 115  FIGURES 46.  47.  Page Consolidation Curve C  apparatus  Consolidation  curves  compressibility, 116  for colluvium  119  ix.  L I S T OF  TABLES  TABLE  Page  I.  Hydrometer A n a l y s i s R e s u l t s  20  II.  Composition  22  III.  Consolidated-drained Triaxial  IV.  'Dry' T r i a x i a l  V.  ' C o n s o l i d a t i o n ' T e s t s o f Kami o o p s S i l t  55  VI.  Results of the C o n s o l i d a t i o n Tests  56  VII.  O b s e r v e d and C a l c u l a t e d S l o p e H e i g h t s Taylor's Charts  o f Kami o o p s S i l t Tests  39  Test Results  50  Using 92  X.  ACKNOWLEDGEMENTS  I am i n d e b t e d t o my t h e s i s a d v i s o r , of C i v i l also nical  Engineering, for his helpful  Iike t o thank t h e B r i t i s h and M a t e r i a l s T e s t i n g  s u g g e s t i o n s and g u i d a n c e .  Columbia  Branch)  D r . R.G. C a m p a n e l l a ,  Department  for their  encouragement throughout t h e c o u r s e o f t h i s  o f Highways  financial  thesis.  Department I would (Geotech-  a s s i s t a n c e and  1.  CHAPTER 1  I NTRODUCTI ON  1 .1  I n t r o d u c t i on Geotechnical  of the  problems a s s o c i a t e d w i t h the  S o u t h Thompson V a l l e y h a v e been e x a m i n e d .  encompasses t h e j u s t east of H a r p e r Road  silt  ( f i g . 1).  excessive moisture This naturally  The  d r y s t a t e and  samples.  s i d e of the  of  study  S o u t h Thompson R i v e r ,  C o l u m b i a b e t w e e n H i g h w a y number 5  semi-arid environment  and  p i p i n g and  invariably  in behaviour  reconnaissance  and  extensive  soil  relate  History  The  of the  t o as  Receding  i c e from t h e  to  S o u t h Thompson was  of  undisturbed  Basic  with a proposed  in the  deposited  ( M a t h e w s , 1944)  uplands  lobe r e t r e a t i n g toward  Investigations  i s proposed.  along  in i t s  slope zoning  developments.  L a k e Thompson  tongue separated  silt  laboratory testing  A p o s s i b l e c o l l a p s e mechanism  Geologic  of the  in i t s saturated c o n d i t i o n .  c a l c u l a t i o n s are a l s o presented  silt  area  inputs.  referred  The  north  The  problems of s l o p e s t a b i l i t y ,  in the  scheme f o r u r b a n i z a t i o n a I  1.2  the  r e p o r t examines the c o n t r a s t  involve f i e l d  stability  b l u f f s on  Kamloops, B r i t i s h  c o l i a p s e encountered  silt  gIacioIacustrine s i l t s  l e f t an  vicinity  During  during the  i c e tongue  lake  l a s t deg I a c i a t i o n .  i n t h e main  valley.  o f Monte C r e e k ( f i g . 1 ) , t h e  K a m l o o p s L a k e and  Shuswap Lake ( F u l t o n , 1 9 6 5 ) .  in a g l a c i a l  the  t h e e a s t e r n one initial  receding  toward stage  western Little  from  the  FIG  1  .  TOPOGRAPHIC  MAP  OF  THE  SOUTH  THOMPSON  VALLEY  3.  adjacent  u p l a n d s , maximum  (up t o 20 f e e t / y e a r ) the  erosion  the  Thompson V a l l e y  till  was  e r o s i o n , t r a n s p o r t a t i o n , and d e p o s i t i o n  ( F u l t o n , 1965).  of the t i l l  Much o f t h e s i l t  on t h e u p l a n d s a d j a c e n t  in the v i c i n i t y  l e f t on t h e u p l a n d w h i l e t h e s i l t  was d e r i v e d  t o t h e v a l l e y and  o f Kamloops.  occurred  The c o a r s e  from entered  portion of the  was c a r r i e d i n t o t h e  valley.  W i t h t h e d r y i n g o u t o f Lake Thompson, d e s s i c a t i o n o f t h e s i l t s resulted, resulted  followed  in the formation  360 f e e t b e l o w (Ryder,  1971).  with  erosion  o f a s i n g l e broad  the bench-like Gullys  r i v e r channel. filled  by t h e i n c i s i o n o f t h e S o u t h Thompson R i v e r  Further  remnants  formed  a considerable  r i v e r t e r r a c e b e t w e e n 270 and  of the original  within the s i l t  erosion  bench,  of colluvium.  i s r e s u l t i n g in the formation  lake  floor  draining  of the lacustrine s i l t  thickness  which  i n t o t h e main  left the gullies  Today,  continuing  of secondary g u l l i e s w i t h i n . t h e v a l l e y  fill.  1.3  Surficial  Geology  The m a i n d e p o s i t  w i t h i n t h e S o u t h Thompson R i v e r V a l l e y h a s been  r e f e r r e d t o a s t h e S o u t h Thompson S i l t s lacustrine s i l t s Thompson R i v e r laminations. thin  form w e l l - d e f i n e d  near Kamloops. Each  c l a y band.  rhythmite  benches  The s i l t  The c l a y b a n d s v a r y  The s i l t  t o 250 i n c h e s parallel  bands g r a d e  t h i c k a t t h e base  These g l a c i o -  on e i t h e r s i d e o f t h e S o u t h  is characterized  f r o m one i n c h inch t o four  by v a r v i n g and  l a y e r on t o p o f a  o r less in thickness inches  near t h e lower  f r o m one i n c h a t t h e t o p o f t h e s e c t i o n ( F u l t o n , 1965).  t o t h e bedding are evident  Throughout  (1965).  consists of a thick s i l t  n e a r t h e t o p o f t h e s e c t i o n t o h a l f an section.  by F u l t o n  Horizontal  within the s i l t  much o f t h e v a l l e y , t h e s i l t  laminations  bands.  i s c o v e r e d by a brown  loess  4.  capping,on The  other  which  t h e bench s u r f a c e soil  derived  b e t w e e n 6 i n c h e s t o 10 f e e t  from t h e l a c u s t r i n e s i l t  covers the slopes  benches.  varying  below  t h e near v e r t i c a l  Gully floors are also f i l l e d  colluvium.  lack of varving  (although  laminations  of two w h i t e v o l c a n i c ash l a y e r s .  semi-arid  environment  by E v a n s a n d B u c h a n a n  The  d e p o s i t s may be i d e n t i f i e d  These t e p h r a  of the by i t s '  l a y e r s a r e t h o u g h t t o be  Y ( 3 2 0 0 y r s . B.P.) ( F u l t o n ,  below rapid  ground  mean a n n u a l  precipitation  260.6  mean a n n u a l  rainfall  186.9 mm  mean a n n u a l  snowfall  769.6  period.  I975).  has been  freezing.  Most o f t h e r a i n f a l l  In e a r l y M a r c h ,  mm  rise  temperatures sufficiently  D u r i n g t h i s month, t h e w e t t e s t  - e s p e c i a l l y when c o m b i n e d w i t h t h e o c c a s i o n a l  shower.  vegetative cover  bunchgrass.  with  o c c u r s a s summer s h o w e r s  temperatures  i c e and snowmelt c o n d i t i o n s .  intensity  summarized  mm  In D e c e m b e r , J a n u a r y a n d F e b r u a r y ,  conditions exist  The  o f t h e Kamloops r e g i o n  h o t summers r e a c h a mean t e m p e r a t u r e o f 20.8 °C i n J u l y  during t h i s  high  thicknesses  (1976):  d a i l y maximums o f 29 °C.  for  face of the  CIimate The  drop  bluff  material  may be p r e s e n t ) a n d by t h e p r e s e n c e  Mazama ( 6 6 0 0 y r s . B . P . ) a n d S t . H e l e n ' s  1.4  i s the colluvial  by c o n s i d e r a b l e  In t h e f i e l d , t h e c o l l u v i a l  thick.  i s sparse,  c o n s i s t i n g m a i n l y o f s a g e b r u s h and  5.  CHAPTER 2  FIELD  A low l e v e l  flight  RECONNAISSANCE  f r o m K a m l o o p s t o P r i t c h a r d a n d down t h e Okanagan  V a l l e y t o P e n t i c t o n was i n i t i a l l y  carried  out.-.  T h i s was f o l l o w e d by a  s e r i e s o f ground t r a v e r s e s , j o i n t mapping, a s o i l field  2.1  seepage  Observed  P i p e s and S i n k h o l e s  Many p i p e s w e r e f o u n d numerous, t h e y shaft-like inclined 12  d e p o s i t s and although  v o i d s w i t h t h e i r axes near h o r i z o n t a l ,  with the slopes,  attributed  in the colluvial  exist within the gIacioIacustrine s i l t .  feet i n diameter  silt  ( f i g 2'&  3).  h a v e been f o u n d .  t o ( I ) t h e p i p i n g process  (2) t h e c o l l a p s e o f t h e l o o s e s o i l A related  feature  pipes  has been  as a r e s u l t of water e r o s i o n away by f l o w i n g w a t e r  i n which  and/or  s t r u c t u r e as a r e s u l t o f w e t t i n g .  i s t h e presence o f l a r g e ground d e p r e s s i o n s They o c c u r  depressions  o r in alignment  (fig 4 & 5).  with g u l l i e s  e i t h e r as  (2) t o t h e c o l l a p s e o f s o i l o r a t depth  or  isolated  T h e s e h a v e been  t o (1) t h e c a v i n g o f t h e ground above a s u b t e r r a n e a n  (Hardy,  or  Pipe opennings as l a r g e as  f o u n d on t h e b e n c h s u r f a c e .  surface s i l t  less  e x i s t as  near v e r t i c a l  "sinkholes"  attributed  Pipes  The o r i g i n o f t h e s e  p a r t i c l e s a r e d i s l o d g e d and c a r r i e d  material  p r o g r a m and a  test.  Problems 2.1.1  sampling  pipe o r  s t r u c t u r e upon w e t t i n g , e i t h e r o f t h e n e a r  f o l l o w e d by s u c c e s s i v e c a v i n g o f t h e o v e r l y i n g  1950; E v a n s & B u c h a n a n ,  1976; N y l a n d & M i l l e r ,  1977).  Figure 2.  Horizontal pipe in colluvium is a p p r o x i m a t e l y 12 f e e t i n d i a m e t e r . Note t h e presence of t h e t e p h r a layer (white, horizontal band).  F i g u r e 3.  V e r t i c a l pipe in c o l l u v i u m near t h e base of a s t e e p b l u f f f a c e w i t h i n Magaz i ne GuI Iy.  Figure  5.  A  single  the  isolated  colluvium  M a g a z i ne  GuI  sinkhole  at the Iy.  bottom  within of  8.  2.1.2  Slope  StabiIity  Although instability failures the  no m a j o r s l o p e  d o e s e x i s t on  and  block  f a i l u r e s are evident w i t h i n the  a smaller scale.  f a i l u r e s can  S o u t h Thompson R i v e r and  deposit  ( f i g .6).  a l s o of small  s e e n on  in the  Colluvial  magnitude.  be  slope  steep  cutting  2.2  and  Slope  near v e r t i c a l  gully  However, o u t s i d e t h e  m a g n i t u d e due  of the toe of  the  slope  study  to  running bluff with to the  depths  the  1500  feet.  breaks  occurs  i n b e n c h e s on  The  bench t e r m i n a t e s  parallel  into c o l l u v i a l  One  study  t o the  of these  area  since  river  slopes  are  the  are of  facing  lacustrine  area  south  greater  s u c h as  ( f i g . 7).  under-  lacustrine s i l t  least stable slopes.  i n f i g u r e 9,  a t a 70°  into a very  slope, breaking slightly  chosen highest  From e i g h t  s l o p e geometry can  c o n s i s t i n g of  gullies  perpendicular  and  form g i v e n  of c o l l u v i u m t h a t grades  benches  line  irregular  sided  i t c o n t a i n s some o f t h e s t e e p e s t  s e c t i o n s w i t h i n Magazine G u l l y , the  100  Many s t e e p  was  surveyed  in the  i r r e g u l a r scarp  8)  faces, representing the  the  a t an e l e v a t i o n  (Magazine G u M y M f i g .  bluff  generalized  river  s i d e s of  below w h i c h a s t e e p  feet d i s s e c t the  gullies  both  a t an  standing  feet of  slopes  slopes.  i n t h e o r d e r o f 300  river.  detail  slab  Geometry  approximately  wall  a r e a , on  failures  S o u t h Thompson R i v e r , s l o p i n g g e n t l y t o w a r d s t h e 1600  area,  w a l l s w i t h i n the  to urbanizationaI disturbances  Near Kamloops, t h e s i l t  of  of shallow  f a i l u r e s w i t h i n the study  b l u f f s o f t h e Thompson V a l l e y , c o l l u v i a l frequency  Evidence  study  be  approximately  i n t o a 35°  concave-up s u r f a c e  slope which  as  F i g u r e 6.  E v i d e n c e o f a s l o p e f a i l u r e on e a s t face of Magazine G u l l y .  Figure  The b e n c h f a c i n g t h e S o u t h Thompson R i v e r c o n s i s t s of a steep i r r e g u l a r b l u f f w a l l which breaks i n t o c o l l u v i a l slopes.  7.  the  Figure  8.  O b l i q u e a e r i a l view of t h e d e t a i l study area (Magazine G u l l y ) l o o k i n g north.  7 70"  SCALE  L.ACUSTRIA/£' SilT  \  COLLUN/IUM \  N  \  FIG. 3 GENERAL SLOPE GEOMETRY WITHIN  MAGAZINE  GULLY  12.  could  be  approximated  Little  by  a uniform  i s known a b o u t t h e  a c r o s s - s e c t i o n given  by  dynamic cone penetrometer  the  gully  The  depth of the  that the  b o t t o m and  silt  than  1300  2.3  J o i nti  in depth  deposit  (Fulton,  the  joint steep  survey bluff  which trends poles  was  of  500  30  resistivity  t o 60  colluvial  f e e t and  unstable  feet  at  slopes. i t is believed  possibly  greater  radial  lengths representing stereonet.  nearly  a rose  the The  are  major s e t s e x i s t  at s t r i k e s  rose  at approximately  0°  and  columnar j o i n t i n g  90°. seen  of  The  kept  i n mind.  face of  stereonet  Magazine plot  steeply  dipping  since joints  dipping  east  diagram  30°  and  bluff  face.  is plotted  joints  diagram  t o the  The  east  the  in a l l j o i n t  mainly  number o f  perpendicular  As  along  ( f i g . 10)  in northern:hemisphere project.iorKof. a  is expected  a l l near v e r t i c a l ,  s e c t o r of the  from t h e  North-South.  plotted  traverses  compass.  c o n d i t i o n s on/the eastern  are  running  p r o b l e m s must be  l974).The j o i n t s  This  by  a Brunton  accessibility  joints  local  from  however,  1965).  face with  joints  western s e c t o r .  sets exist  deduced  slopes,  i s a l s o unknown b u t  c a r r i e d out  approximately  (Hoek & B r a y ,  represent  the  i n d i c a t e s depths of  J o i n t o r i e n t a t i o n s were measure, m a i n l y  WuIf n e t  on  f e e t midway down t h e  lacustrine s i l t  human b i a s and  shows t h e  colluvium  from the h o r i z o n t a l .  ng  base of t h e  Gully  28  ( I 9 7 6 ) w h i c h was data  15 t o 30  angle of  e x t e n d s t o a minimum d e p t h o f  feet  A small  surveys,  depth of  Evans  and  slope  falling  Since  the  ( f i g . 11)  indicated that  while  two  field  ( f i g . 39).  with  w i t h i n each four major  weaker s e t s  combination of t h e s e j o i n t  in the  would  almost h o r i z o n t a l beddding. 120°  towards  This  sets  type  of  10° joint Two  occur forms  the  13.  X  OF Jo»r*T$ Sites-  F\6.  /0  STEReoKET  P  L  O  T  O F  TOIKTS  14.  S  FIG. //•  RADIAL  S C A L E ;  I" = S  C1  FRoM. EASTEItK  6U>fF  C i  PRO»A  SVTCS  ROSE DIAGRAM  P O L E S  FA.CE.  columnar j o i n t i n g  i salso typical  Western United S t a t e s . is  of the s i l t y  I t s h o u l d be r e a l i z e d  l i m i t e d t o a very s p e c i f i c  loess deposits i n t h e that this  with j o i n t  is  spacings of about 4 t o 8 f e e t .  becoming d i s c o n t i n u o u s f i s s u r e s .  p r o b a b l y due t o s t r e s s Most j o i n t s  brown w e a t h e r e d the  2.4  fracture  SoiI  closely  of the jointing  r e l e a s e a n d s h r i n k a g e on d e s s i c a t i o n . b u t many a r e c o a t e d w i t h a  a n d a few show s i g n s o f s w e l l i n g  and s l a k i n g  along  Samp I i ng were e n c o u n t e r e d  Highways t o r e t r i e v e  intact  in attempts  undisturbed s i l t  by t h e D e p a r t m e n t o f  s a m p l e s by S h e l b y  s a m p l e s o b t a i n e d by t h i s m e t h o d w e r e h i g h l y  Sampling  a r e more  I i ne.  Difficulties  The  The o r i g i n  show no s i g n s o f w e a t h e r i n g , film  basis.  planar extending the f u l l  W i t h i n t h e t o p 20 t o 30 f e e t o f t h e s e c t i o n , t h e j o i n t s spaced,  survey  a r e a a n d may n o t a p p l y on a r e g i o n a l  Many o f t h e j o i n t s a r e c o n t i n u o u s a n d n e a r height o f t h e b l u f f exposure  joint  fractured.  Tubes.  Therefore,  by b a c k h o e o p e r a t i o n was e m p l o y e d .  B l o c k s a m p l e s were o b t a i n e d from two backhoe p i t s on t h e bench s u r f a c e adjacent t o Magazine g u l l y  (fig.  12) a t a d e p t h  b l o c k s w e r e hand c a r v e d w i t h a s h a r p fractures.  D u r i n g s a m p l i n g , t h e w e a t h e r was g e n e r a l l y c l o u d y w i t h The t e m p e r a t u r e s  15$  To p r e v e n t m o i s t u r e  (June 2 9 , 1976).  i m m e d i a t e l y wrapped w i t h " s a r a n wrap"  to  Kamloops  The  k n i f e , making use o f e x i s t i n g  periods of sunshine.  the  o f 4£ t o 51 f e e t .  l a b o r a t o r y f o r waxing.  the University of B r i t i s h  Columbia  reached  in-situ brief  31°C w i t h a h u m i d i t y o f  loss, the soil  in the field  s a m p l e s were  and t r a n s p o r t e d t o  The s a m p l e s w e r e t h e n t a k e n  by c a r  w h e r e t h e y w e r e r e - w a x e d w i t h a low  16.  p e r m e a b I i t y , p l i a b l e wax  and  stored  in a constant  temperature  laboratory  envi ronment. P r i o r t o the f r o m two gravity and  other  backhoe o p e r a t i o n ,  locations w i t h i n the  determinations  and  s p e c i a l equipment In mid-May o f  surface  block  lacustrine deposit  p r e l i m i n a r y t e s t s to acess  1977,  the  were s u p p l i e d  Branch) i n Kamloops. blocks  are  included  The  study  Field  Seepage  A small p i t #3  and  by t h e  was  f u r t h e r extended t o  was  f i I led w i t h  approximately  trench 27  a b o u t 0.9  observed at the trench  was  another hour. the  l o c a t i o n of  d e s c r i p t i o n of  the  the  was  continuously  and  fed  backhoe sample  s e e p a g e r a t e and  f a i l u r e t o o c c u r on  the  a small  head was  hour. 2  The  filled, water  backhoe t o determine the  attempt p i t face.  from a water t r u c k t o  1.0  trench  inch diameter  was  in the trench p o s i t i o n of the  maintain  trough.  ft.~Vmin.  The  dropping  then allowed  was  to  was  trench.  The  ft.^/min. after  then channelled  wetted  init  to  identation (pipe?)  g i v i n g a s e e p a g e r a t e o f 0.7 left  to  adjacent  of water at the m i d p o i n t of the  large c a p i l l a r y  The  samples  (GeotechnicaI  c e n t r a l b a s e - l i n e of the west s i d e of the  again  the  locations.  water t o observe the  f t . ^ / m i n . a f t e r one  drain completely  waxed b l o c k  e x c a v a t e d 4 f e e t west of the  inches  seepage under the  with the  include  Simulation  trench  small  Two  d e s c r i p t i o n s of the  I along  their site  t o cause p i p i n g and/or a slope The  specific  i t s trimmability  Department of Highways  enclosed  in Appendix  l a c u s t r i n e s a m p l e s and  2.5  for  obtained  requirements.  preliminary c o n s o l i d a t i o n t e s t i n g of colluvium. of c o l l u v i u m  samples were  front.  The  away front  with  extended 3 f e e t t o e i t h e r s i d e of the water trench f e e t and  6 f e e t below t h e t r e n c h  f l o o r on  e d g e s and  t h e e a s t and  extended  west s i d e s  4  respect-  ively. The  wetted  allotted on  f r o n t d i d not  as e x p e c t e d ,  t h u s no  enchroach onto the p i p i n g was  the west s i d e of the t r o u g h ,  i n s e r t an channel trench  arm  into.  extending  The  the  " p i p e " was  about 8  face, heading south  inches f o r an  evidenced  could easily  silt.  total  The  250  ft.~\  the  soiI.  go  a very  into the unknown  into the  low  this  f a c e and  in the  time  face.  However,  l a r g e enough  strength  to  'liquefied'  curving to parallel  distance.  partial  160  f t . " ^ o f w a t e r pumped  filling  v o i d space w i t h i n t h e wetted zone  t h e r e f o r e the water  on  " p i p e " f o r m e d was  C a l c u l a t i o n s show t h a t t h e e s t i m a t e d the trench  p i t face  input represents  of the is  o n l y 64$  voids  into  in the  approximately s a t u r a t i o n of  the  CHAPTER 3  B A S I C S O I L PROPERTIES  3. 1  Specific  Gravity  Specific gravity temprature  laboratory  according t o the  A total  resulted  i n s p e c i f i c g r a v i t i e s b e t w e e n 2.749 and  2.77  f o r the  attributed  seven t e s t s with  lacustrine s i l t .  t o the  presence of  S p e c i f i c g r a v i t i e s were a l s o The  sample from the  and  the  and  3.2  wall  I t w o u l d seem t h a t will  be  highly  Grain Size  the  of  the  student supervision.  a small  for  10  f o r two  its  p i p e had of  average  is probably  colluvial  the  samples.  of  2.60  a specific gravity  of  colluvium  i s not  uniform  from s i t e  #3  performed  location.  of  the  The  lacustrine s i l t  U.B.C. u n d e r p r o f e s s o r and  p r o c e d u r e as  described  u s i n g s o d i u m h e x a m e t a p h o s p h a t e as  Sample p r e p a r a t i o n a blender  an  Analysis  undergraduate students at  followed  2.796 w i t h  locations  silt.  determined  properties  d e p e n d e n t on  Hydrometer a n a l y s i s by  different  high s p e c i f i c g r a v i t y  in the  constant  i n Lambe  i n c i s e d c r e e k showed a s p e c i f i c g r a v i t y  sample from the  2.78.  in the  samples from f o u r  The  mica  out  procedure o u t l i n e d  (1951).  of  of  d e t e r m i n a t i o n s were c a r r i e d  included minutes.  mixing the  the  graduate  i n Lambe ( 1 9 5 1 )  deflocuI ating  s a m p l e and  was  was  agent.  defIocuI ating  agent  in  21 .  The  TABLE  data  I.  is plotted  in f i g u r e  Average r e s u l t s of the s i l t (lacustrine s i l t )  13.  Table  I summarizes the  hydrometer a n a l y s i s from s i t e #3.  % sand  of  the  results.  Kamloops  A%  % s i It % clay D  1%  1Q  D,  n  0.0027  mm  0.0092  mm  50 C  3.4 u  MIT  classification:  D a t a f r o m E v a n s and though a defIocuI a t i n g Their  grain  in the silts.  Buchanan  a g e n t was  size analysis  on  not  the  This s i m i l a r i t y  redeposition  the as  silt  suggests was  uniform clayey  silt.  (1976) a g r e e s w i t h added  colluvium  p a r t i c l e s i z e d i s t r i b u t i o n as  confirms that  3.3  'fairly'  13  even  in t h e i r t e s t i n g  procedure.  indicates  difference  little  compared t o t h a t  little  transported  figure  sorting  has  of  the  resulted  only a short distance  lacustrine and  consequently  prior  to  colluvium.  Mi n e r a l o g y MineralogicaI  Fulton  ( I 9 6 5 ) and  agreement  in the  analysed the  silt  analysis Quigley  and  sand on  the  (I976).  analysis.  X - r a y powder a n a l y s i s included).  on  lacustrine s i l t Tables  It s h o u l d  be  MA  and  has MB  been p r e s e n t e d shows a  r e a l i z e d however, t h a t  fractions o p t i c a l l y while Quigley  the  general  whole sample ( i e . with  the  clay  Fulton  used fraction  by  TABLE  MA.  COMPOSITION  OF KAMLOOPS S I L T  FULTON (optica My)  MINERAL  quartz  main  fe1dspar  major  constituent  moderate  mi c a  major  constituent  mi n o r  minor  constituent  mi n o r  ferromagnesian  TABLE  MB.  minerals  constituent  QUIGLEY ( X - r a y powder)  abundant  X-RAY DIFFRACTION OF CLAY FRACTION ONLY  M1NERAL  FULTON  QUIGLEY  montmor i 11 on i t e  35 - 40 %  abundant  i I I i te/mi ca  28 - 35 %  moderate  ch1 o r i t e  27 - 36 %  m i nor  - kaoLi nite  -  mi n o r  23.  3.4  Atterberq Data  and  L i m i t s and  for atterberg  Buchanan  (1976).  Mois+ure  Content  l i m i t s of the s i l t  Liquid  w i t h an a v e r a g e o f 31.1$ 11.7$  Field  limits  has  g i v e n ranged  and t h e p l a s t i c i t y  w i t h an a v e r a g e o f 8.4$.  been p r e s e n t e d by  f r o m 27$ t o 3 6 . 8 $  index ranged  On t h e p l a s t i c i t y  from  D u r i n g t h e summer, n a t u r a l Buchanan  (1976)  t h e backhoe  ranged  w a t e r c o n t e n t s m e a s u r e d by  Evans &  depth but  water t a b l e e x i s t s well  rapid  near the s u r f a c e .  i n June a t t h e t i m e o f s a m p l i n g . i t s actual  s u b j e c t e d t o s e a s o n a l and  the study area. during  (1960).  2.4$  However,  s n o w m e l t and  varved sequence  exists.  below  local  Samples  natural  variation The  i s not  regional  consideration  p o s s i b l e t h a t perched water  rainfall  from  A water gradient i s  fluctuations.  t h e s l o p e s under  i t is highly heavy  vertical  would  loess of  Holtz  from 0.2$.to  expected t o e x i s t with  ground  by G i b b s , Hi I f and  to  data  o p e r a t i o n a t a d e p t h o f a p p r o x i m a t e l y 5 f e e t had a  w a t e r c o n t e n t o f 7-8$  known and  1.9  chart, this  p l o t c l o s e t o t h e A - I i n e w i t h i n t h e same r e g i o n a s t h e s i l t y the western United states studied  Evans  above t h e c l a y  within tables  seams w i t h i n  the  24.  CHAPTER 4  LABORATORY TESTS  4.1  Scanning Electron Microscope Studies Three samples  were s t u d i e d  under t h e E t e c A u t o s c a n  E l e c t r o n M i c r o s c o p e on t h e U n i v e r s i t y o f B r i t i s h first and  two  undisturbed  samples  of the  C o l u m b i a campus.  lacustrine s i l t  p e r p e n d i c u l a r t o t h e b e d d i n g . . The  third  formed  conditions.  by a l l o w i n g The  initial  the  process (the u n d i s t u r b e d samples  and t h e r e m o l d e d  sample  remolded  sample laboratory  water c o n t e n t s a s s o c i a t e d w i t h t h e samples  low e n o u g h t h a t s t r u c t u r a l  1.6%  parallel  a remolded  The  The  a w e l l - m i x e d s l u r r y t o s l o w l y a i r dry under  considered drying  were scanned  s a m p l e was  viewed p e r p e n d i c u l a r t o the s e d i m e n t a t i o n d i r e c t i o n . was  Scanning  sample  was  alteration  a t 1.9%  was  negligible  were  during  had a w a t e r c o n t e n t o f  water content).  "Drying"  was  -4 achieved  by s l o w l y a p p l y i n g a vacuum o f  10  s a m p l e s w e r e t h e n c o a t e d w i t h a few h u n d r e d p a l l a d i u m c o a t i n g was des i  Angstroms  of carbon  advoided s i n c e X-ray micro-probe a n a l y s i s  The  (goldwas  red). Electron  photomicrographs of the s o i l  14 t o 19.  Stereopairs  preference  in orientation  remolded between void  t o r r t o the samples.  silt.  ( n o t shown) o f t h e s a m p l e s of the p l a t t y  Structurally,  t h e r e m o l d e d and  ratio  differences  are presented in figures  particles  t h e r e a p p e a r s t o be  undisturbed  ( I . I 4 and  1.28  showed a s t r o n g  horizontal  in the undisturbed little  lacustrine s i l t respectively).  difference  other than the  and  Figure  14.  P h o t o m i c r o g r a p h o f t h e Kamloops s i l t , u n d i s t u r b e d s a m p l e , s i d e v i e w , a t 400X magn i f i c a t i o n .  Figure  15.  Kamloops s i l t , remolded s a m p l e , v i e w , 400X m a g n i f i c a t i o n .  side  Figure  16.  Photomicrograph of undisturbed Kamloops S i l t a t 1000X m a g n i f i c a t i o n , v i e w e d parallel t o the bedding.  Figure  17.  Photomicrograph  of remolded  (Kamloops  a t 1000X  viewed to  silt)  from  the side,  the sedimentation  silt  magnification,  i e . perpendicular direction.  27.  Figure  Figure  18.  19.  P l a n e view o f t h e u n d i s t u r b e d Kamloops S i l t a t 1000X m a g n i f i c a t i o n . Particles 18A & 18B w e r e s t u d i e d u n d e r t h e Electron Microprobe.  Plane view of t h e u n d i s t u r b e d s i l t a t 1000X m a g n i f i c a t i o n . Peds 19A & 19B were s t u d i e d under t h e E l e c t r o n M i c r probe. Note t h e c l a y b r i d g i n g formed by 19A.  28.  A microprobe an  attempt to  is  always d i f f i c u l t  quantitative 19B  (Ortec Multichaniel  i d e n t i f y the  A n a l y s e r , Model  m i n e r a l o g y of  when o n l y  elemental  data being questionable.  in f i g u r e s  18 and  19  yield  the  the  particles.  d a t a can The  6 2 0 0 ) was  be  But  elements,  in  interpretation  o b t a i n e d and  p a r t i c l e s 18A,  following  used  18B,  the 19A  listed  in  and decreasing  peak i n t e n s i t y .  Particle  18A:  S i , A l , Fe,  K,  Particle  18B:  S i , A l , Ca,  Particle  19A:  Particle  19B:  The sheets The  Na,  Ti  Fe,  K,  Mg,  Na,  Ti  S i , A l , Mg,  Fe,  Ca,  Na,  Ti, S  S i , A l , Fe,  Ca,  S,  p l a t t y p a r t i c l e s in the  (eg.  p a r t i c l e 18A  c l u s t e r s of  Much o f  Mg,  the  19A  clay  and  present  the  same t i m e ,  The  photomicrographs are  clay  be  granuIata). therefore  generally  figure  Ti  may  are  montmori I l o n i t e .  possibly  19)  silt  small  be  mica  P a r t i c l e 18B  the  at too  probably  feldspar.  c l u s t e r s or  peds, but  particles it a scale  f o r small  C l o s e e x a m i n a t i o n of  c l e a r l y shows t h e  t y p e of  sample are  T h i s common s p e c i e s likely  s i l i c e o u s diatoms  is associated  dates back t o the  with  at  contacts.  the  bridging larger  bridging  grains.  throughout the  most  K,  s a m p l e e x i s t s as  clearly visible.  (eg.  between s i l t  Scattered  and  to  photographs  possible  19  i t provides bonding with  structures  scaled  18).  in f i g u r e  in the  Mg,  photomicrgraphs are  in f i g u r e 19B  K,  (me Ios i r a  freshwater  last degIaciat ion.  lakes  F I G .  20  UNC0NF\NEO  COMPfctSSloti  (  A N I ^ Y  OF  ( OF'K*«MU<>OPS  SC*«WT^ SOT'  APPROX.  —  ApPRox.  )  PERPENDICULAR  PARALLEL  TO  TO  tjEDOlUG  3-5:24.  JJO  3-5-25-  If  3-S.2C  V  3-  S.17  3-528  69°  3 - 5--2?  er  3 - -5\ZI  64°  3 - 5.23  8o°  STRAIN  BE.DD.MC  ,  C  VD  30.  4.2  Unconfined Compression To d e t e r m i n e w h e t h e r  silt,  e i g h t samples  Four samples  the  bedding  ( t 11°)  All  samples  were trimmed  and  The  i n t h e motor d r i v e n  were s u b j e c t e d t o a x i a l f o u r samples  parallel  b l o c k was  6.8$.  f o r the  lacustrine  unconfined compression  loads p e r p e n d i c u l a r t o  t o the bedding  f r o m t h e same i n t a c t  water content of the s i l t  minute.  strength anisotropy exists  were t e s t e d  apparatus.  a constant strain  Test  (+  b l o c k from s i t e  The  samples  #3.  data plotted  The  were f a i l e d  r a t e o f 0 . 1 " / m i n . o r a p p r o x i m a t e l y 3$ s t r a i n  stress-strain  10°).  at  per  i n f i g u r e 20 shows t h a t a  slight 2  (T)  a n i s o t r o p y e x i s t s w i t h maximum s t r e n g t h s for  samples  exhibited brittle 1969;  4.3  o f 1.93  loaded p e r p e n d i c u l a r t o t h e bedding.  axial  splitting  materials  which  - 2.36  Alt failed  in unconfined compression  (Townsend, Sangrey  &  Walker,  C o a t e s , , 1970).  Triaxial  Test  drained t r i a x i a l confining  t e s t s were performed  p r e s s u r e s used  s a t u r a t i o n a p p a r a t u s and Since undrained t e s t s  ranged  procedure  require  on s a t u r a t e d  f r o m 0.05  100$  saturation The  measured a t v a r i o u s s t a g e s of s a t u r a t i o n  g r e a t e r was  reached.  percolation  under a small  section  4.3.2).  The  a p p r o x i m a t e l y 24  effective  kg/cm^  in the following  until  a B-vaIue  required  sections.  o f 95$  f r o m 3-7  B, or  days  of  high backpressures (see  then subjected t o i s o t r o p i c  hours b e f o r e loading t o  The  pore p r e s s u r e parameter,  p r e s s u r e g r a d i e n t and was  samples.  f o r a c c u r a t e pore p r e s s u r e  This procedure g e n e r a l l y  sample  consolidated-  kg/cm^ t o 3.0  is described  measurements, d r a i n e d t e s t s were used.  for  samples  i s c h a r a c t e r i s t i c o f t h e f a i I ure mode o f  To d e t e r m i n e t h e s t r e n g t h e n v e l o p e o f t h e s i l t ,  was  kg/cm  failure.  consolidation  31 .  All  t e s t s were performed w i t h t h e d e v i a t o r s t r e s s a p p r o x i m a t e l y  perpendicular t o t h e bedding.  The b e d d i n g o r i e n t a t i o n  l a m i n a t i o n s on most o f t h e t r i m m e d briefly  outlined  i n Appendix  samples  (the trimming procedures a r e  I I ) . With t h e d e v i a t o r s t r e s s v e r t i c a l  t e s t i n g , t h e l a m i n a t i o n s were measured t o range w i t h most sample  4.3.1  Triaxial The  bedding o r i e n t a t i o n s  Test  triaxial  A thin  cell  was u s e d  from t h e c e l l  layer of s i l i c o n e  i s shown  bellofram cell  r e s e r v o i r a n d a T y c o Model  cell  unit.  connected t o t h e s a t u r a t i o n The  vertical  Machine  by a d i a l  matically carried to  signals  The t o p a n d b o t t o m  drainage  pipette, a The  reservoir attached t o and t o p d r a i n a g e l i n e s a r e  through a s e t of gears.  load c e l l  from t h e load c e l l  o u t by t r a n s f e r i n g  The d e f o r m a t i o n  p l a c e d above t h e l o a d i n g r o d . and p r e s s u r e t r a n s d u c e r were a u t o Data  t h e i n f o r m a t i o n onto computing  computer.  rate  The' Load was m e a s u r e d by a  r e c o r d e d by t h e V i d a r A u t o d a t a E i g h t u n i t .  t h e m a i n U.B.C.  A schematic  system.  gauge d u r i n g t h e t e s t .  b e r y l l i u m copper diaphragm Electrical  The b o t t o m  between  d e f o r m a t i o n r a t e was p r e - s e t on t h e 5 Ton Wykeham  Ferrance Compression checked  resistance.  a calibrated  lucite  samples  by d o u b l e  AB p o r e p r e s s u r e t r a n s d u c e r .  pressure i s applied through a c l e a r top of the t r i a x i a l  fluid  l u b r i c a n t was a p p l i e d  i n f i g u r e 21.  lines a r e connected t o a " t r e e " c o n t a i n i n g  was  i n which c y l i n d r i c a l  t w o r u b b e r membranes t o m i n i m i z e f r i c t i o n a l  diagram o f t h e apparatus  the  f r o m 5° t o 24° o f f h o r i z o n t a l  b e t w e e n 5° t o 12°.  3" h i g h by 1.4V i n d i a m e t e r a r e s e a l e d  the  during  Apparatus  conventional  r u b b e r membranes.  was e v i d e n c e d by  reduction  was  c a r d s and f e d  3L  CfLLL.  \ = T ^ AIR. P R E S S U R E  PORE.  PRESSURE.  \RW*SOUCER.  L~Z]  FIG.  2/  SCHEMATIC  O F  TRIAXIAL  APPARATUS  NJ  4.3.2  Saturation  Procedure  In s a t u r a t i n g drainage  line  up t h r o u g h  bottom d r a i n a g e bellofram.  rubber  which  in the reservoir  a i r from  i s drained.  to a clear  h a s been f l u s h e d t h r o u g h  also pressurized.  lucite  sample  a t o p p r e s s u r e o f 0.1  reservoir,  d r y , t h e sample kg/cm  gradient of approximately 2 0.5 kg/cm .  The  following  r e s e r v o i r which This  holds  reservoir i s  a small  p r e s s u r e g r a d i e n t c o u l d be backpressure.  s a t u r a t i n g g p r o c e d u r e c o n s i s t s o f two s t a g e s .  is essentially  at  entering the  The t o p d r a i n a g e  t h e sample.  a p p l i e d t o t h e s a m p l e and s t i I I m a i n t a i n a h i g h actual  dissolving  By c o n t r o l l i n g t h e p r e s s u r e s w i t h i n t h e b e l l o f r a m  r e s e r v o i r and t h e o u t f l o w  The  rubber  i n t o t h e sample.  p r e s s u r i z e d a i r from  i n t h e r e s e r v o i r and t o p r e v e n t  i s connected  The  i s a p p l i e d t o one s i d e o f t h e b e l l o f r a m  b e l l o f r a m serves t o prevent  l i n e o f t h e sample  line.  reservoir containing a  out the other side of the reservoir  s a m p l e when t h e w a t e r  the water  to a lucite  The d e s i r e d a i r p r e s s u r e  i n t o t h e water  i s f o r c e d from t h e bottom  t h e sample and o u t t h e t o p d r a i n a g e  i s connected  f o r c i n g t h e water The  a sample, d e - a i r e d water  2  is first  f l u s h e d with water  a n d a b a s e p r e s s u r e o f 0.2  13 cm/cm).  This procedure  The c e l l  Since the  pressure  kg/cm  2  applying  (pressure  i s maintained  forces a i r out of the top drainage. 2  in small  day, t h e c e l l  increments  pressure  i s s l o w l y i n c r e a s e d t o 4.00  simultaneously with the incremental  kg/cm  increase of the  2 t o p a n d b o t t o m p r e s s u r e s t o 3.60 and 3.80 kg/cm increment of The  i s checked  respectively.  s u c h fha't t h e e f f e c t i v e c o n f i n i n g  stress at the top  2 t h e s a m p l e i s n o t g r e a t e r t h a n 0.5 kg/cm and n o t l e s s t h a n t o p and bottom p r e s s u r e s a r e r a i s e d  i n increments  Each  which  2 0.2 kg/cm .  assures  2 a p r e s s u r e g r a d i e n t o f 0.2  kg/cm  a c r o s s t h e sample  i s not exceeded.  that  34.  Flushing  i s c o n t i n u e d a t t h e above p r e s s u r e s  or greater i s achieved. testing water  and  The  water  until  a B-vaIue of  c o n t e n t o f a l l samples were measured  c a l c u l a t i o n s show s a t u r a t i o n s o f e s s e n t i a l l y  c o n t e n t ) were a c h i e v e d .  saturations exceeding  100$  I n v a r i a b l y a few  due  95$  100$  (47 -  samples would  after  48$  show  t o e r r o r s i n t h e measurement o f  sample  voIume.  4.3.3  Experimental  Procedure  After saturation pore  i s complete,  pressure monitored.  and  then  The  t e s t then  outlined  t h e s a m p l e was  The  pore  by B i s h o p  & Henkel,  pore  A strain  i n pore  I974.  all  strain  r a t e was  pressures monitored  r a t e o f 0.15"/min.  to fail  in a t e s t i n g  procedures the  drainage conditions  no  the  significant  However s i n c e o v e r c o n s o I i d a t e d  l e s s t h a n 2$  a much s l o w e r  pressure.  a t t h e base of  strain,  Thus, t o a l l o w s u f f i c i e n t  of the s i l t ,  This resulted  at  equilibrium  s e l e c t e d on  (0.5$/min.) produced  p r e s s u r e w i t h i n the sample.  w o u l d o n l y be 4 m i n u t e s .  adopted.  The  p r e s s u r e measurements under s i n g l e  samples were e x p e c t e d  the behaviour  i s allowed t o reach  consolidated at the desired e f f e c t i v e  (drainage a t the top w i t h pore  rise  pressure  i s c l o s e d and i t s  follows the conventional consolidated-drained  basis of d i r e c t  sample).  the top drainage  the time to  time to  monitor  r a t e o f 0.0006"/min.  t i m e of/ a p p r o x i m a t e l y  failure  was  1 hour.  Thus,  o v e r c o n s o I i d a t e d samples were t e s t e d a t 0.0006"/min. W i t h i n t h e n o r m a l l y c o n s o l i d a t e d r e g i o n , s a m p l e #3.31  t o t h e same s l o w strains,  rate.  S i n c e f a i l u r e was  not  reached  subsequent normally c o n s o l i d a t e d samples  were t e s t e d a t 0.015"/min. t o d e c r e a s e f r o m t h e Mohr e n v e l o p e  plot that the  the t e s t i n g  was  until  very  (#3.34 and time.  increase in s t r a i n  subjected large  3.35)  I t was rate did  evident not  35.  a f f e c t the  soil  strength  (friction  angle). 2  Various e f f e c t i v e confining were used t o d e f i n e employed  i n an  the  Mohr e n v e l o p e .  lowest e f f e c t i v e c o n f i n i n g  in the  height  effective  of water  in the  shearing  would  stress  additional  12  (eg.  cm.  T h e r e f o r e , a much  sample a t such  could  not  swelling not  be  4.4  be  of  (as  greatly  stress.  can  few  in measurements of  re I i a b I e ( ( s e c t i o n  fluctuations  t o sample volume  was  in the  confining  r e s u l t in  an  backpressure).  e m p l o y e d as  the  accuracy to a t t a i n a  problem of  assume t h a t  possible  swelling  f l u s h i n g and  since the  s a m p l e #3.33) t h e  of  testing  magnitude strength  of may  DISCUSSIONS  that  1.30  listed  in t a b l e I I I . had  samples were e s s e n t i a l l y s a t u r a t e d . 100$  to  1.39.  oedometer mold 4.8).  t e s t s are  a I I samples a f t e r f a i l u r e  saturation  sample dimensions.  from  from the  The  eleven t r i a x i a l  s a m p l e s showed a b o v e  obtained  volumetric  in c o n s o l i d a t i o n  RESULTS &  confirm  samples ranged  kg/cm , s l i g h t  pressures during  only  W a t e r c o n t e n t s w e r e m e a s u r e d on  a  accurately.  in the  I.D.)  were  i n t e r c e p t more 2  water would 2  kg/cm  (1.0"  the  confining  r e s u l t s of the  Calculations  of  kg/cm  reduced.  T R I A X I A L TEST: The  1 cm^  l u c i t e tube  a d v o i d e d - we  i s small  too  low  0.05  t o 3.0  stresses  r e s u l t in s i g n i f i c a n t changes  drainage r e s e r v o i r , s a c r i f i c i n g  the  s t r e s s of  f r o m 0.05  confining  cohesion  head o f w a t e r o r 0.012  steady e f f e c t i v e c o n f i n i n g  low  d r a i n a g e p i p e t t e due  expulsion  larger  ranging  The  attempt t o determine the  At the  change d u r i n g  stresses  As  The  w h i c h was void  wi I I be  i s somewhat  the  l a t e r , the  l o w e r and  attained.  Invariably,  attributed to  r a t i o s of  seen  been  errors  triaxial void  deemed more  ratios  36.  4.4.1  Stress-strain Relationships A few s t r e s s - s t r a i n r e l a t i o n s h i p s a r e p l o t t e d  Figure  22 p r e s e n t s  consolidated within this  the s t r e s s - s t r a i n behaviour of t h e s i l t  stress field. region.  As e x p e c t e d , a p e a k  Being a drained  test,  s t r e s s c o r r e s p o n d s t o t h e maximum p r i n c i p a l overconsoIidated  or  less (seet a b l e  travel  cases, f a i l u r e III).  of the loading  platform  p r i o r t o load b u i l d - u p This the  seating loading The  ranged  be n o t e d  is realized  h a v e been  t h e maximum  deviator In  a t s t r a i n s o f 1.1$  however, t h a t  o f up t o 0.7$ s t r a i n  excessive  due t o i m p r o p e r  w i t h i n t h e s a m p l e was r e g a r d e d a s z e r o  problem r e s u l t s from t i l t e d  defined  stress ratio criteria.  had o c c u r r e d  I t should  in the over-  in strength  Thus t h e peak s t r e s s c o n d i t i o n s  as t h e f a i l u r e c r i t e r i a .  all  i n f i g u r e s 22 & 2 3 .  contact  seating  strain.  o f t h e sample ends  with  platforms.  orientation of the failure  planes of the s t r a i n e d  f r o m 2 8 ° t o 32° away f r o m t h e m a j o r p r i n c i p a l  samples  stress direction 2  with the  one e x c e p t i o n :  a t t h e lowest c o n f i n i n g  f a i l u r e mode r e s e m b l e d t h a t o f t h e u n c o n f i n e d  brittle  silt  Within  - ie. the failure the normally  curves e x h i b i t e d a rapid strength At  pressure  such  with  rising  p l a n e was n e a r l y  consolidated rise  strain  used  ( 0 . 0 5 kg/cm ) ,  compression t e s t of dry  vertical.  stress states, the stress-strain  in stress followed  up t o t h e t e s t e d  by s t e a d i l y  increasing  r a n g e o f 35$ s t r a i n  l a r g e s t r a i n s , t h e a r e a c o r r e c t i o n w h i c h assumes t h e sample  i n a r i g h t c y l i n d e r i s i n e r r o r a n d t h e s t r e s s e s on t h e f a i l u r e ill-defined. strains, soil  Since  the failure  a t 20$ s t r a i n .  likely  ( f i g . 23).  continue  t h e s t r e s s - s t r a i n c u r v e s do n o t l e v e l criteria  h a s been d e f i n e d  In t h e f i e l d ,  to failure.  plane i s  o f f at reasonable  as t h e s t r e n g t h  strains of this  deforms  of the  magnitude would  most  FIG. ZZ  L E G E N D  S T R E S S - S T R A I N PLOT  T/  I.8T  TlU/WlM_ TE.ST X  RESULTS  OVEikCo»4i<»V»DNT&o'  , KM*L0OPS  SiCT  STATE  X  ~*  3-1-3  -e  3-/4  \.oo  3-/.Z  0,20  *  (X<,./cj).  ui  39.  TABLE  Test  #  III.  CONSOLIDATED-DRAINED T R I A X I A L TESTS  Void Ratio  oc  3.1 1  1 .38  -  I . I00  2.429  1 .329  0.97$  3.12  1 .41  -  0.200  1.115  0.915  0.75$  3.13  1 .33  8°  0.493  1 .660  1 .167  1 .10$  3. 14  1 .30  11°  1 .000  2.223  1 .223  0.81$  3.21  1 .38  12°  0. 157  1 . 196  0.955  0.98$  3.22  1 .30  24°  0.500  1 .421  0.921  1 .05$  3.31  1 .33  15°  2.990  6.635  3.650  2 0 . 0 0 $ **  3.34  1 .34  17°  1 .440  3.324  1 .880  20.00?"-**  3.35  1 .34  11°  1 .90  4.313  2.409  2 0 . 0 0 $ **  4. 11  1 .39  5°  0.05 I  0.700  0.649  0.90$  4. 12  1 .36  6°  1 . 12  2.463  1 .343  3.17$  °3  <  +  °3 2  natural water contents: f i n a l water contents:  7-8$ 47-48$, e s s e n t i a l l y  or;  «<  +  2  Strain at Fa i I u r e  100$ s a t u r a t i o n  * i s t h e a n g l e b e t w e e n t h e b e d d i n g p l a n e and t h e & axis direction ** s a m p l e s 3 . 3 1 , 3.34 and 3.35 a r e n o r m a l l y c o n s o l i d a t e d and f a i l u r e i s d e f i n e d a t 20$ s t r a i n ; a l l o t h e r s a m p l e s a r e o v e r c o n s o I i d a t e d .  40.  4.4.2  Volume C h a n g e s D u r i n g Changes  the  i n sample volume were measured d u r i n g  amount o f w a t e r e x p e l l e d  Within  the overconsoIidated  occurred (fig.  24).  behaviour  4.4.3  in bulk observed  Strength  form o f a i ( c '  the  slope angle  a  i n sample volume  by s a m p l e d i l a t a n t c y consolidated  increasing strain  - cr^)  Similarly,  with  region  no  showed  dilatant  27 r e p r e s e n t s Thus  i s the e f f e c t i v e angle - cr^)  i f 'a' i s t h e  1969).  f a i l u r e envelope.  l i n e drawn t h r o u g h s u c h p o i n t s ,  where 0  consolidated  t h e data  o  silt  the  maximum o v e r b u r d e n s t r e s s w i l l  0  field.  kg/cm  .  region plotted  Conversion  to  2 a n d c ' = 0.609 kg/cm .  The e x i s t e n c e o f t h e o v e r c o n s o I i d a t e d the  frictional  i n t e r c e p t , t h e n c'=a/cos  stress  and a = 0.58 /  i t c a n be  of  of the overconsoIidated  oC = 17  I f oC i s  oC = 29° and t h e r e f o r e ,  From f i g u r e 2 6 ,  w i t h i n the normally  larger scale.  + o^)  versus  Mohr e n v e l o p e p a r a m e t e r s y i e l d s 0 = 17.8  region  i s noteworthy  since  i s a gIacioIacustrine deposit of the last degIaciation, therefore,  of o v e r l y i n g i c e . Since if  decrease  (P-Q D i a g r a m )  of the best  (Lambe & W h i t m a n ,  Figure  recording  ( f i g . 25).  shown t h a t s i n jd = t a n < *  33.7  by  s t r e s s c o n d i t i o n s a r e p l o t t e d i n f i g u r e s 26 & 27 i n  the  resistance.  followed  in the normally  volume w i t h  Envelope  The f a i l u r e  0=  region, a general  Samples sheared  shearing  from t h e sample i n t o t h e c a l i b r a t e d p i p e t t e .  up t o t h e p o i n t o f f a i l u r e  a decrease  to  Shearing  sampling  n o t c o n t a i n a c o m p o n e n t due t o w e i g h t d e p t h was b e t w e e n 41 t o 5{  we assume t h a t o n l y a few f e e t o f s i l t  w o u l d be i n s u f f i c i e n t o v e r l y i n g m a t e r i a l  f e e t and  had been e r o d e d away, t o produce t h e  there  overconsoIidated  STRAIN 02.  0-4-  o(>  1  1  £ i*  , o.e>  /-O  IZ  /.+  /•£>  0.7^  oa\  _J  F|<3.  2-4-  %  A\I0\-.  1 \1$  1 £ %  PoB.  OC  STttfcSS  R£GIOt4 .  4^  43.  effect exhibited behaviour  by t h e s i l t  of the s i l t  c o u l d be  (2) n e g a t i v e pore w a t e r chemical  c h a n g e s and  (4) a c o m b i n a t i o n a f t e r examining  4.5  silt,  due  to  (1) c h e m i c a l  'Dry'  Triaxial  physico-  to dessication  be  i n the next  (3)  further  or  discussed  chapter.  Tests  the e f f e c t of water  four t r i a x i a l  cementation  due  This point w i l l data  overconsoIidated  during dessication  bond f o r m a t i o n o f t h e c l a y  the consolidation  determine  Therefore, the  s t r e s s e s developed  of the above.  Unconventional To  samples.  c o n t e n t on t h e s t r e n g t h o f  t e s t s were performed  at d i f f e r e n t water  the  contents  2 with a consistent c e l l  p r e s s u r e o f 0.50  strained  r a t e o f 0.0006  at a constant  S a m p l e 3.22  was  s a t u r a t e d by  backpressures.  S a m p l e 3.71  and  was  s a m p l e 3.72  conditions  was  air-dried  f o r 30 d a y s .  constant temperature  of  placed  weight  was  105°C.  apparatus  4.6  D i s c u s s i o n s of the  test  c l o s e d and  t h e bottom  i n f i g u r e 28  The  after testing,  Triaxial  sample,  from t h e a i r .  dessicant pellets.  'Dry'  days under a  of the oven-dried  by t h e s a m p l e d u r i n g  results are plotted  From f i g u r e 2 9 ,  was  content  laboratory  f o r 30  a b s o r b t i o n of water  was  R e s u l t s and  oven-dried  During t e s t i n g  n e g l i g i b l e water  The  was  high  i t s n a t u r a l water  t o be t h e same b e f o r e and absorbed  and  under c o n s t a n t t e m p e r a t u r e  in a c o n t a i n e r of oven-dried determined  samples were  inches/min.  tested at  p r e c a u t i o n s were t a k e n t o m i n i m i z e  was  The  f l u s h i n g w i t h water  S a m p l e 3.73  top drainage of the t r i a x i a l  kg/cm .  The  drainage sample  indicating  testing.  Tests  a s Mohr c i r c l e s  i t i s evident that the strength i s s e n s i t i v e t o  of  failure.  the  0  l  2.  FIG.Z8  3  A  MOHR.  5"  CIRCLE  6  7  6  O F FAILURE  ?  A T  /0  VARIOUS  //  /2  /J  S A T U R A T I O N S  14-  IS  8 7  0  6  2 " , ^/fc/tt- 5- 4-1 1  1  10  1  1  3o  2.0  4c  S A T U R A T I O N  FIG.  ZS  So  70  Co  5  KM4U0OPS  %  Uo  /£  SHEAFk S T P . E N i 6 T H ( FOP*  So  S\l-T * )  VS- 5 A T U R A T \ 0 N f  48.  degree of  s a t u r a t i o n , e s p e c i a l l y towards the  found a s i m i l a r behaviour f o r V i c k s b u r g Also, for  Holtz  & Gibbs  various The  (1951) r e p o r t e d  saturations  of the  drier states.  loess  Lutton  under u n c o n f i n n e d  (1969)  compression.  a d i f f e r e n t Mohr e n v e l o p e e x i s t s  K a n s a s and  Nebraska  loess.  s t r e s s - s t r a i n d a t a shows a p e a k i n s t r e n g t h  in a l l four  samples  2 tested.  Thus under t h e  were c o n s i d e r e d The may of  be  t o be  increase  due  to  0.50  w i t h i n the  in strength  (1) t h e  combination of the  can  in terms of  -  (2) t h e  progressively  increase  be  total  t e n s i o n , the  are  C,  g r a i n s , or  (3)  in strength  Mohr f a i l u r e  -  to  a  criteria.  criteria  3 0  =  c'cos  0  p o s i t i v e for compression. stresses:  +  4  -  2u) sin  2 pore p r e s s u r e ,  0 =  2 being negative  in  tension.  be  negative  2  (cr  is the  d r i e r samples  s t r e s s as a r e s u l t  p r i n c i p a l e f f e c t i v e s t r e s s e s , the  cr.3  In t e r m s o f t o t a l  where u  range.  magnitude of the  c a l c u l a t e d from the  2 d'  samples  in i n t e r p a r t i c I e bonding  increase  sin  w h e r e C.' and  stress  p r e s e n t between s i l t  assume t h e  to water m e n i s c i i  pore water pressures Expressed  overconsoIidated  the  above.  i n t e r e s t , i f we  attributed  be  pressure,  in e f f e c t i v e confining  tension,  o f c l a y p a r t i c l e s w h i c h may  confining  e x h i b i t e d by  increase  pore water m e n i s c i i  For  kg/cm  c'cos.0  is:  Table  IV l i s t s  have t o d e v e l o p  the calculated  within  n e g a t i v e pore  pressures that  would  t h e samples t o e x h i b i t t h e s t r e n g t h s measured.  2 The p r e s s u r e d e f i c i e n c y an  apparent  o f 15 kg/cm  f o r the oven-dried  or " e f f e c t i v e " value since  there  sample  i s no f r e e w a t e r  i s only present  2 within at  an o v e n - d r i e d  4.9$ s a t u r a t i o n  Aitchison  and D o n a l d  sample.  The n e g a t i v e p o r e  p r e s s u r e o f 6.3  i s i n t h e o r d e r o f magnitude expected ( 1956) showed t h a t  for a  f o r ideal spherical  kg/cm silt.  particles,  2 n e g a t i v e pore silt-sized easily  pressures  i n t h e o r d e r o f 3.5 kg/cm  .can be a t t a i n e d f o r  p a r t i c l e s and p r e s s u r e d e f i c i e n c i e s o f 30 kg/cm  realized for clays.  c a n be  50.  TABLE  Test  IV.  #  'Dry' T r i a x i a l  Water content  Test  Data & R e s u l t s  s a t u r a t i on  Calc. U kg/cm 2  *3  °1  C  OC  m  3.22  47.8$  100$  0.5  2.341  1 .410  24°  0.921  3.71  7.71$  16.1$  0.5  6. 192  3.346  5°  2.846  -4.067  3.72  2.28$  4.9$  0.5  8.134  4.317  10°  3.817  -6.272  3.73  0.00$  0.0$  0.5  15.048  7.774  3°  All  stress values  i n kg/cm'  0  7.274 -15.048  51.  4.7  Consolidation  Tests  Consolidation  t e s t i n g of  silts  i s not  conventional.  Compared t o c l a y s and  concerning the  behaviour of s i l t s .  silts  generally  water content flooded  with  (usually water.  Although the are  not  sample  low  saturation)  (Gibbs & H o l t z ,  majority  and  therefore  air-water  term with  of the  1951;  consolidation  Lutton,  are  is expelled  the  at  i t s natural  oedometer mold  1969;  Dudley,  i s adopted  in i t s usual  expulsion  of  sample.  due  in t h i s  meaning.  non-saturated  from the  Kamloops s i l t ,  various  to air-dried  a simulated  were remolded assess the  e f f e c t of  The  allowed  r e m o l d i n g on  constant  by  strain  To  strain  samples a i r or  t o dry  out  contents  Also,  before  flooded samples  testing to  stability.  c a r r i e d out The  on  seven of  other  c o n t r o l l e d method  r a t e t e s t was  water  determine the s t r u c t u r a l  a c i d i c water.  lacustrine s i l t .  the  silts,  consolidation  i o n s , s a m p l e s were  structural  l o a d c o n s o l i d a t i o n was  samples were t e s t e d  1969).  free  s e p t i c t a n k e f f l u e n t and  c o n s o l i d a t i o n t e s t s of the  silt  states.  a d d i t i o n of  i n t o a s l u r r y and  Incremental 15  t o the  the  soil.  ranging  silt  Conventionally,  t o s t r u c t u r a l c h a n g e s as t h e  s t r u c t u r e of the  from s a t u r a t e d  report,  In t e s t s p e r f o r m e d on  Samp Ies w e r e c o n s o I 1 d a t e d a t v a r i o u s  with  1970;  pore water from  t e s t s were p e r f o r m e d .  response of the  is available  studying c o l l a p s i b l e  silt the  ' c o n s o l i d a t i o n ' t e s t s a r e on  settlements  In p r o b i n g  and' w i t h  'consolidation' test  i s r e f e r r e d t o as t h e  mixture  the  or  information  Many r e s e a r c h e r s  leading t o compression of the  the  little  standard  1975).  dealing  consolidation  sands,  perform oedometer t e s t s w i t h  Jennings & Knight,  we  considered  employed s i n c e  eight  the lacustrine  (Byrne & i t had  Oaki,  the  52.  advantage o f producing e-log (one  P data  i n a much s h o r t e r  hour as compared t o t h e 6 days r e q u i r e d  Also, there  i s t h e added a d v a n t a g e o f b e i n g  larger than those p o s s i b l e with colluvial  f o r incremental able  t o achieve  t h e incremental  samples from t h e Kamloops a r e a were a l s o t e s t e d  Consolidation  with  controlled test.  a 3 inch  fitted flushed  with  saturation the  i n t h e incremental Initially,  I. D. c o n s o l i d a t i o n  into a standard  triaxial  water while  process.  For s t r a i n  rigid  frame.  was a t t a c h e d  cell.  Since  This a high  t h e assembly  i n append i x  allowed  (appendix I V ) .  t o the rigid cell  r o d and load c e l l  base  backpressure t o a i d inthe  i s placed  within a triaxial  r o d , on t o p o f w h i c h s i t s  frame and i t s l o a d i n g loading  performed  t h e s a m p l e t o be  was s e a t e d  load t e s t s , a r o l l i n g  o f t h e a p p a r a t u s had t o be t a k e n deformation.  Four  t o determine t h e  r i n g and a s p e c i a l l y d e s i g n e d  maintaining  For incremental  of t h e loading  much  load t e s t and two i n t h e  c o n t r o l l e d t e s t s , t h e load c e l l  load t o t h e t r i a x i a l  loads  a l l c o n s o l i d a t i o n t e s t i n g was  l o a d was a p p l i e d t h r o u g h a l o a d i n g  cell.  water  tests).  Apparatus  Two s e t u p s w e r e u s e d strain  load  load a p p a r a t u s .  d e g r e e o f s t r u c t u r a l c o l l a p s e upon f l o o d i n g w i t h  4.7.1  t e s t i n g time  rod. At large  bellofram  a  become s i g n i f i c a n t .  load  against the a i r piston  ram t r a n s f e r s t h e loads,  cell,  constant  the.compression  Thus, t h e compression  i n t o a c c o u n t when c o m p u t i n g t h e s a m p l e  The s y s t e m c o m p r e s s i o n s  ( c o r r e c t i o n curves) are presented  I I I.  In s u b s e q u e n t t e s t s , s i n c e s a t u r a t i o n o f t h e s a m p l e was n o t n e c e s s a r y , a simple, tests,  more d i r e c t l o a d i n g  the loading  s e t u p was a d o p t e d .  r o d and t r i a x i a l  cell  For t h e s t r a i n  controlled  was o m m i t t e d a n d t h e c o n s o l i d a t i o n  r i n g and  p o r o u s s t o n e s w e r e p l a c e d i n an open c o n t a i n e r .  arrangement, load c e l l  the compression of the  deflection  was  still  loading  encountered.  c o r r e c t i o n s due t o s y s t e m c o m p r e s s i b i l i t y . load t e s t s , at  UBC  was  System  a small  was  o r d e r o f 0.003 i n c h e s a t  and  loading  4.7.2  samples  a strain  saturation  recently  diameter samples  n e g l i g i b l e and seating  l o a d s o f 450  III presents the  designed  were  the only  used.  extraneous  d e f l e c t i o n s which are in  kg.  Thus t h i s  f o r system c o m p r e s s i b i l i t y  s i m p l e system  c o r r e c t i o n s due t o  load  cell  rod d e f o r m a t i o n s .  Saturation Two  Appendix  but  For the subsequent incremental  system, 21"  essentially  this  eliminated,  s y s t e m w h i c h was  p r e s e n t a r e due t o i n i t i a l  e l i m i n a t e s t h e need  for  With t h i s  compressibility  deflections the  s i m p l e pneumatic  employed.  r o d was  With  Procedure were s a t u r a t e d  controlled  procedure  in the t r i a x i a l  t e s t and one  f o r an  is similar to that  cell  apparatus -  one  i n c r e m e n t a l load t e s t .  followed  in saturating  a  The  triaxial  2 sample.  Cell  p r e s s u r e s w e r e s e t a t 4.00  kg/cm  and  base d r a i n a g e p r e s s u r e s  2 w e r e h e l d a t 4.10 bellofram  reservoir  B-values could continued  the  up t h e s a m p l e  f o r an e x t e n d e d  into the c e l l  in t h i s  pushed  reservoir.  from  Since  apparatus, the percolation  p e r i o d o f 30 d a y s  the  i n an a t t e m p t t o  was  insure  sample.  Experimental Procedure In  24  T h u s , t h e d e - a i r e d w a t e r was  n o t be m e a s u r e d  s a t u r a t i o n of the  4.7.3  kg/cm .  hours  the  i n c r e m e n t a l load t e s t s ,  ( A P / P = 1) p r o d u c i n g 1-day  l o a d s w e r e a c h i e v e d by  the applied  loads were doubled  consolidation curves.  each  Increase of  increasing the a i r pressure applied  to the  54.  loading  pistons.  attached  to the  frame. bility  strain  is simply a  by  the  Byrne & Oaki  load c e l l .  For  by  sample  of the  The  t o the  can  pressures  be  the  load  achieved  i s being  a v a i l a b l e t o the  In t h e  case of the  strain  Consolidation Both  are  listed  Void average of  l o a d and  i n t a b l e V.  l a t e r date are  listed  The  measuring the  strain  water content of the  strain  load  rates  build-up highly  limited  is  within  the  permeable rise  r a t e was  silt,  in adopted  Discussion  strain  colluvial  controlled consolidation  tests  t e s t s which were p e r f o r m e d a t  ranged  from  1.26  to  1.30  with  r a t i o s were c a l c u l a t e d b e f o r e  testing  sample weight, dimensions w i t h i n the  m o l d and  s i d e trimmings of the  ratios  calculated  from t r i a x i a l  errors  in measuring the  be  sample.  Recall  samples were s l i g h t l y  sample dimensions.  dimensions could  a  IV.  lacustrine s i l t  A l l void  total  and  in appendix  r a t i o s of the 1.28.  This  not  controlled testing.  Test Results  incremental  sample.  monitored  incremental  of  pore pressure  following  oedometer mold  s i n c e we  the  saturated  compressi-  settlements.  samples',the c h o i c e  load.  gauge  fixed  f o r system  sample w i t h i n the  rate while  limiting  within the  most o f t h e  r i n g , the  true  a dial  r a t e o f 0.003 i n c h e s / m i n . p r o d u c e d an i n s i g n i f i c a n t  pore pressure  are  the  loads  saturated  determined  s a m p l e s t o 5-10$  4.8  referrenced  gauge were c o r r e c t e d  (1969).  Thus, high  maximum h o u s e - l i n e  a strain  rod as  m e a s u r e d by  c o n t r o l l e d c o n s o l i d a t i o n t e s t s were performed  t e s t apparatus.  for  dial  s t r a i n e d at a constant  generally  s a m p l e was  loading  when n e c e s s a r y t o o b t a i n  o u t l i n e by  by  a i r piston's  D e f l e c t i o n s of the  The the  Deformation of the  However, w i t h  measured a c c u r a t e l y  by  by the  t h a t the  higher  due  the  measuring  an  void  to  consolidation the  T A B L E V. 'CONSOLIDATION'  Test #  Descri ption  TESTS OF KAMLOOPS  SILT  Samp Ie Di am.  Stra i n Rate  e  w$  S$  o  3.32  saturated  3.0"  0.003"/min.  1 .260  43.1$  100.0$  3.33  saturated  3.0"  incr.  1 .279  36.0$  99.7$  3.41  dry, rebounded, flooded  3.0"  dry:0.015 flooded: .0.003"/min.  1 .273  40.0$  86.8$  3.42  flooded % 0.121 kg/cm  3.0"  0.003'/min.  -  -  3.43  flooded @ 0.329 kg/cm  3.0"  0.003"/min.  1 .283  46.2$  99.8$  3.44  dry  3.0"  0.003"/min.  1 .306  2.97$  6.3$  3.45  dry  3.0"  1 .281  2.44$  5.3$  3.51  moi s t  3.0"  0.0001 1 i n./mi n. 0.003"/min.  1 .301  22.8$  48.6$  3.62  dry  2.5"  incr.  load  1 .277  7.15$  15.3$  3.R1  remoIded,dry, flooded § ^ 6.786 kg/cm  2.5"  incr.  load  1.141  1 .70$  S.= 4.1$ SJ=87.8$  3.64  flooded @ „ 0.890 kg/cm  2.5"  incr.  load  1 .274  36.6$  92.3$  3.66  flooded % 0.845 kg/cm  2.5"  incr.  load  1 .269  36.1$  93.8$  3.67  dry  2.5"  0.003"/min.  1 .263  6.54$  14.3$  3.R2  flooded § „ 0.889 kg/cm  2.5"  incr.  load  1 . 137  32.9$  94.2$  3.71  flooded with 0.0 IM HCI  2.5"  incr.  load  1 .208  load  .1.291  56.  RESULTS OF THE CONSOLIDATION TESTS  Descri ption  "max. kg/cm  3.62  u n d i s t u r b e d , d r y , S=15.3$  3.R1  remolded, d r y  3.64  flooded  with  3.66  flooded with s o I u t i on  3.33  saturated with  3.R2  remolded,  3.71  P " P  C o m p r e s s i on Index, C c  ..14..  -  13  -  water  5.9  0.303  chemical  4.5  0.271  3.7  0.275  2.1  0.151  f l o o d e d w i t h 0.01M HCI  2.4  0.222  3.45  u n d i s t u r b e d , d r y , S=5.3$  26  -  3.44  u n d i s t u r b e d , d r y , S-6.3%  26  -  3.67  u n d i s t r u b e d , d r y , S=14.3$  13  0.240  3.41  dry,  12  0.240  3.51  m o i s t , S=48.6$  7.8  0.189  3.43  flooded,  6.2  0.215  water  flooded  S=14.4$  S=99.8$  ~U ro O  ncre menta I  Test #  TD  CD  controI  TABLE V I .  c ro L.  4-  3.33  s a t u r a t e d , S=100%  6.3  0.252  3.42  f l o o d e d , S=?  5.6  0.225  Ifl  57.  i n s i d e volume of the The  void  the  While the void  Initially, large  itself.  r a t i o of the  sample s i t e s . uniform,  mold  initial  c o l l u v i u m was  void  e-log  Since  p curve.  by t h e  the  l o s t of s o i l  l o s t was and  tests,  and  incremental  ]% of the  smaI I f o r  concern.  Incremental One-day  soil  incremental  with  location. due  to load  shape of  non-existent  the  in s t r a i n  may  be  of 3 of the  consolidation tests  less than  amount o f  affected  The  s a m p l e w e i g h t and  and  fairly  incremental  s e t s of data  different:  load t e s t .  l o s t was  Load R e s u l t s  is  squeezed out  of the  are  c o m p a r i s o n o f t h e two  in the  f o r t h e two  t h e r e f o r e would a l t e r the  large gradients  found t h a t the s o i l  less than  soil  at the top  measured a f t e r t h e c o m p l e t i o n  i t was  4.8.1  the  1.35  c o l l u v i u m appears t o vary  hydraulic gradients significant  and  lacustrine s i l t  concern t h a t the  s a m p l e w o u l d be  controlled  r a t i o of the  r a t i o of the  t h e r e was  1.07  1 gram,  t h e r e f o r e was  soil  representing considered  too  Discussions  load t e s t s of the  lacustrine s i l t  were  performed  under v a r i o u s c o n d i t i o n s :  curve  1.  at natural moisture  2.  flooded  3.  saturated  4.  flooded with  5.  flooded  6.  air-dried  7.  flooded  The  e-log  will  be  with  content  de-aired  sample  water  HCI  s e p t i c t a n k e f f l u e n t (#3.66) (#3.71)  remolded sample  remolded sample  p curves discussed  (#3.64)  (#3.33)  simulated  w i t h 0.01M  (#3.62)  (#3.R1)  (#3.R2)  of the t e s t s are separately.  presented  i n f i g u r e 30.  Each  58.  59.  1.  Sample a t n a t u r a l w a t e r c o n t e n t At t h e water c o n t e n t  (#3'..62)  o f 7.2$, t h e s i l t  behaves as a h i g h l y  incompressible  1 2 w i t h t h e ' e f f e c t i v e maximum p a s t p r e s s u r e ' o f 14 kg/cm . Upon 2 r e b o u n d t o 6.67 kg/cm , f l o o d i n g o f t h e s a m p l e w i t h d r i n k i n g w a t e r  soil  resulted  i n an a d d i t i o n a l 3.2$ ( A / e e  majority of the c o l l a p s e occurred  2.  ) d e c r e a s e i n b u l k volume. The o w i t h i n t h e f i r s t hour ( f i g . 3 1 ) .  F l o o d e d s a m p l e (#3.64) 2 S a m p l e 3.64 was c o n s o l i d a t e d t o 0.89 kg/cm  de-aired Further  d r i n k i n g water.  and t h e n f l o o d e d  with  Upon f l o o d i n g , no a d d i t i o n a l s e t t l e m e n t  consolidation in i t s flooded  s t a t e r e s u l t e d i n a much  occurred.  lower 2  maximum p a s t  p r e s s u r e t h a n t h a t f o r t h e d r y s a m p l e ( 4 . 5 kg/cm as 2 c o m p a r e d t o 14 kg/cm f o r t h e sample c o n s o l i d a t e d a t n a t u r a l water  3.  Saturated  Sample  content.  (3.33)  The s a t u r a t i o n p r o c e d u r e was d e s c r i b e d  i n s e c t i o n 4.7.2  The maximum  2 past  pressure  of t h e f l o o d e d Since  1.  i s 3.7 kg/cm  and t h e v i r g i n  slope  (C ) i s s t e e p e r  than  that  sample.  t h e s a m p l e was s a t u r a t e d , t h e p o r e p r e s s u r e  d i s s i p a t i o n could  A l t h o u g h t h e t e r m 'maximum p a s t p r e s s u r e ' o r maximum p r e c o n s o I i d a t i o n p r e s s u r e ' i s used i n t h e t e x t , t h e t e r m i s used o n l y t o d e n o t e t h e l i m i t i n g pressure, beyond' which deformations increase considerably ( i e . the t r a n s i t i o n t o ' v i r g i n ' compression). This p a r t i c u l a r p r e s s u r e v a l u e c a n n o t be c o n s i d e r e d t o be a t r u e p r e c o n s o I i d a t i o n p r e s s u r e b e c a u s e i t v a r i e s w i t h t h e d e g r e e o f s a t u r a t i o n and w i t h the type of l i q u i d s a t u r a t i n g the s o i l . Furthermore, the a b i l i t y of t h e s o i l t o s u p p o r t loads a t s t r e s s e s below t h i s l i m i t i n g v a l u e may n o t be due t o p a s t s t r e s s h i s t o r y , b u t i s m o s t l i k e l y due t o some t y p e o f i n t e r g r a n u l a r b o n d i n g s u c h as c e m e n t a t i o n , c l a y b r i d g i n g or c a p i l l a r y tension.  61 .  be m o n i t o r e d increment. occured curves  With  each  w i t h i n the ( f i g . 32)  to being a  along with.the settlement load  first  increment,  of each  large p o r t i o n of the settlement  a t t h e s t a r t and  pore p r e s s u r e s  the settlements continue Therefore,  at standard  a substantial  role  load  log-time  are very  implies that  a t t h e base of t h e sample for a given  a constant  increments  near  t o secondary c o n s o l i d a t i o n .  have e s s e n t i a l l y  at almost  This  load  settlement  settlement versus  a t t h e top o n l y ) t o t h e measured compression A f t e r 5 minutes,  of the  increment.  i s due  pore p r e s s u r e  l e a s t 50%  The  c o n c a v e up  l i n e a r t o w a r d s t h e end  F i g u r e 33 c o m p a r e s t h e  at  15 s e c o n d s .  are s l i g h t l y  upon a p p l i c a t i o n o f e a c h  fully  load  (drainage increment.  dissipated  r a t e (on a  (<^P/P=1), c r e e p  log-time  but plot).  behaviour c o n s t i t u t e s  in the c o n s o l i d a t i o n c h a r a c t e r i s t i c of the  wetted  silt.  4.  Flooded  with simulated s e p t i c tank  In some s o i l s , soil  the c o l l a p s e behaviour  is flooded with  d r i n k i n g water,  ( R e g i n a t t o & F e r r e r o , 1973). a concern,  Since  effluent.  Terrace,  i n 1972  i s d e p e n d e n t on w h e t h e r  s e w a g e w a t e r o r an leakages  V e r n o n , B.C.  were r e p r o d u c e d  • a n a l y s i s were r e a d i l y  available  from the  in the  Kamloops r e g i o n .  effluent  in a chemical S i n c e no  were  the  solution. could  i s determined from  by  be a  Kal  solution  s e p t i c tank  Kamloops a r e a ,  t h e c o n c e n t r a t i o n s o b t a i n e d "from K a l T e r r a c e  acidic  from s e p t i c t a n k s  Typical s e p t i c tank  i t s exchangeable c a t i o n concentrations.  expected  (#3.66)  the c o l l a p s e c h a r a c t e r i s t i c s of the s i l t  simulated s e p t i c tank  for  effluent  i t was  chemical  assumed  in the order of  that  magnitude  The  e x c h a n g e a b l e c a t i o n s and  Ion: Concentration The  pH  (ppm):  of the  Figure  34  Mg  K  Na  71  36  15  68  shows t h a t t h e  possiblity  also duplicated  of  decrease  r e a l i z e d in the  should  n o t e d t h a t e f f e c t s due  duplicated  5.  in the  F.looded w i t h I t was  the  silt  a strong exhibited  laboratory  chemical  0.01M  must be  I).  s o l u t i o n of  i s not  on  a much  borne  not  organic  from  i s noted.  longer  in mind.  time  Also,  matter  scale  it not  known.  (#3.71) HCI  produced a s t r o n g  T h u s , a c o n s o l i d a t i o n t e s t was  HCI  grossly  j u s t d r i n k i n g water  t o c h e m i c a l s and  s o l u t i o n are  HCI  7.8.  i n maximum p a s t p r e s s u r e  n o t e d t h a t a d r o p o f 0.5M  (appendix  with  further settlements  than that be  as  consolidation behaviour  samples flooded  Vancouver, although a s l i g h t However, t h e  are:  Ca  e f f l u e n t was  d i f f e r e n t t o t h a t of the  t h e i r concentrations  (0.01M).  The  reaction  c a r r i e d out  resultant consolidation  a more c o m p r e s s i b l e b e h a v i o u r t h a n t h e  on  with  curve  samples flooded  with  2 d r i n k i n g water.  The  maximum p a s t p r e s s u r e  was  2.4  kg/cm  as  compared  2 t o 4.5  6.  kg/cm  f o r the  silt  flooded  A i r - d r i e d Remolded sample The  water to  f o r m e d by  form a s l u r r y .  slurry  laboratory  c o n c e i v e d as  The  domestic  water.  mixing the  silt  (#3.R1)  r e m o l d e d s a m p l e was  temperature initially  with  was  then allowed  e n v i r o n m e n t f o r 30 an  attempt to  days.  The  r e - d u p l i c a t e the  with  t o dry  distilled i n "the  constant  remolded sample lacustrine  was  silt's  65  properties.  H o w e v e r , f r o m f i g u r e 30,  undisturbed  lacustrine s i l t  c o n t e n t does d i f f e r .  The  and  the  we  see  that  the  b e h a v i o u r of  remolded sample at the  remolded sample w i t h  the  same w a t e r  i t s s a t u r a t i o n of  4.1$  2 exhibits tested  a maximum p a s t p r e s s u r e o f  at a s i m i l a r s a t u r a t i o n  13  kg/cm  ( 5 . 3 $ ) has  while  a  lacustrine  a much h i g h e r  maximum  silt past  2 pressure of  a p p r o x i m a t e l y 26  Since the while  the  void  void  kg/cm .  r a t i o of the  r a t i o of  the  remolded sample  c u r v e s h a v e a l l been n o r m a l i z e d differences in  initial  7.  in the void  (e/e  shapes of the  ) i n an  Kamloops s i l t i s 1.14,  the  is  1.28  consolidation  attempt to account  consolidation  c u r v e s due  to  for  differences  ratios.  F l o o d e d Remolded Sample In t h e  undisturbed  flooded  (#3.R2)  s t a t e , the  maximum p a s t p r e s s u r e o f t h e  remolded  2 sample  i s 2.1  flooded  with  (eg. the  calcium silt  and  kg/cm HCI.  with This  C =0.151 w h i c h c  similarity  carbonate) destroyed that  this  b o n d i n g was  i s s i m i l a r t o t h a t of  suggests that the by  the  not  HCI  was  recovered  the  same t y p e o f  also  destroyed  upon  drying.  by  sample bonding remoldi  4.8.2  Strain Controlled Eight  various  Consolidation  constant s t r a i n  rate consolidation  &  Discussions  t e s t s were performed a t  degrees o f s a t u r a t i o n :  1.  laboratory  air-dried  2.  at natural  water content  3.  a t moist conditions,  4.  flooded  5.  saturated  Figure ( p g . 56  - Results  state  state  (#3.44 & #3.35)  (#3.41 & #3.67)  vi% = 23% (#3.51)  (#3.42 & #3.43)  state  (#3.32)  34 p r e s e n t s t h e d a t a  i n an e / e  Q  versus  ) s u m m a r i z e s t h e 'maximum p a s t p r e s s u r e s '  log p p l o t .  T a b l e VI  and 'C ' o f t h e  c o n s o I i d a t i on t e s t s .  1.  Air-dried  state  (#3.44, #3.45)  S a m p l e s #3.44 a n d #3.45 w e r e c o n s o l i d a t e d (0.003"/min. and 0.00011"/min. the  effect of strain  stresses,  in c o n s o l i d a t i o n  t h a t t h e two c o n s o l i d a t i o n  but i t i s b e l i e v e d characteristic  that  a large  At natural The s l i g h t  water content increase  rates  curves.  curves diverge  part  i s due t o t h e s l i g h t  c o n t e n t o f t h e s a m p l e s r a t h e r t h a n due t o s t r a i n  2.  strain  i n an a t t e m p t t o d e t e r m i n e  r a t e on t h e s h a p e o f t h e c o n s o l i d a t i o n  f i g u r e 34, i t i s e v i d e n t higher  respectively)  at different  rate  of t h i s  From at  difference  difference  i n water  effects.  ( # 3 . 4 1 , #3.67)  i n water c o n t e n t from t h e a i r - d r i e d  (water content of approximately  3%) t o t h e n a t u r a l  ( a p p r o x i m a t e l y 6.5$) p r o d u c e d a m a r k e d d e c r e a s e  water  state  content  i n t h e maximum  past  67.  pressure to  silt.  The  maximum p a s t p r e s s u r e  Moist  state  The  w a t e r c o n t e n t o f 23$  of the  t r i m m e d s a m p l e b e t w e e n two  the  porous s t o n e s were a b s o r b e d  throughout the triaxial  s a m p l e by  cell.  The  maximum p a s t p r e s s u r e of the  4.  f r o m 26  kg/cm'  (#3.51)  the  the  decreased  2 kg/cm .  13  3.  of the  m o i s t s a m p l e was  wetted by  allowing  porous stones.  the the  obtained  silt silt  and  The  water  distributed  t o stand  by  f o r two  placing  within  uniformly days  within  t e s t r e s u l t indicates a f u r t h e r decrease  as  a consequence of  increasing the  water  in  content  silt.  Flooded s t a t e s With a constant  n o t e d by  the  ( # 3 . 4 2 , #3.43) seating  load, the  soil  s w e l l i n g tendencies of the  r e s p o n s e on  sample a t  low  flooding  was  confining  stresses  2 (0.2  kg/cm ) and  With a s t r a i n s a m p l e and loading  s l i g h t c o l l a p s e at higher  controlled test,  swelling  platforms.  monitored  by  the  heave p r e s s u r e s  the  sample.  Initially,  rapid  stress  pressure  i s prevented  by  seating  there  soil  is a slight  increase.  The  initial  produced  a  d e s t r u c t i o n of c a p i l l a r y  the  upon f l o o d i n g .  montmori I l o n i t e w i t h i n t h e  silt.  soil  drop The  between  kg/cm' the  rigid  sample can  load c e l l .  be  Figure  time a f t e r f l o o d i n g of  r a p i d drop  inward g r a d i e n t r e s u l t of the  with  o f 0.8  is applied to  response of the  m e a s u r e d by t h e  response of the  pressures  load  c o n f i n i n g the  Upon f l o o d i n g , t h e  presents  a  a small  seating  in pressure  i s p o s s i b l e due build-up  tension  and  followed to the  in pressure the  swelling  may of  35 the by large be  •\8  -IT  R 6 . 35  % .14  SWELL PRESSURE A FLOOOED SAMPV-E. (*3A2.)  uJ " LpacL  >/3]  cell  o-cacracu '  - inrh'*t  £COTITM  - it . oz kq - £ .0044-  //>I/=  y»/c*r-  *UaiK«  /c~-•  llAVTlM. SEATING  SO  /OO  20O  70  The  c o n s o l i d a t i o n curves  controlled mental  5.  test closely  load t e s t s of  Saturated The  The  incremental  d i s t u r b a n c e due  4.8.3  incre-  to  s a m p l e has  shows  been d e s c r i b e d  in  l i t t l e d i f f e r e n c e in c o n s o l i d a t i o n  s a t u r a t e d sample.  Thus  i t is possible  load procedure initial  i s due  sample s w e l l  to a combination and  the  increases at the beginning  of  structural  shock d i s t u r b a n c e of each  load  by  increment  1964).  F i g u r e 36 consolidation  plots the  graph.  l o a d d a t a and The  void ratios  the e f f e c t s of v a r i a n c e s  a l l curves void ratio  Results  incremental  d a t a o n t o one  to minimize  Furthermore, normalized  from t h e  h i g h e r c o m p r e s s i b i l i t y of the s a t u r a t e d sample t e s t e d  D i s c u s s i o n o f Combined  normalized  of t h i s  r e s u l t a n t data  sudden pore p r e s s u r e (Crawford,  obtained  samples.  b e t w e e n a f l o o d e d and  that the s l i g h t l y the  flooded  the curves  strain  s t a t e (#3.32)  s e c t i o n 4.7.2.  in  f l o o d e d samples from the  approximates  s a t u r a t i o n procedure  behaviour  of the  are s h i f t e d  controlled  h a v e a l l been  in i n i t i a l  void  ratios.  t o t h e same r e f e r e n c e p o i n t w h e r e  i s unity at the  t h e samples were o b t a i n e d  strain  from a depth  field  overburden  pressure.  of approximately  5 feet,  the  Since the 2  normalized  v o i d r a t i o s of a l l samples should  of overburden errors  pressure.  in d e f i n i n g the  F i g u r e 36  clearly  This s h i f t i n g initial  be  u n i t y a t 0.2  of a l l the curves  seating position  of the  accounts  The  silt  for  samples.  r e v e a l s the e f f e c t of water content  c h a r a c t e r i s t i c s of the s i l t .  kg/cm  on t h e  compression  i s h i g h l y s e n s i t i v e t o changes in  72.  moisture content - e s p e c i a l l y dried  a t low d e g r e e s o f s a t u r a t i o n .  s t a t e o f 5.3$ s a t u r a t i o n , t h e maximum p a s t p r e s s u r e  In t h e a i r -  i s extremely  2 high  ( 2 6 kg/cm  p r e s s u r e drops altered  ).  In t h e f l o o d e d and s a t u r a t e d s t a t e s , t h e p r e c o n s o I i d a t i o n 2 t o a p p r o x i m a t e l y 6 kg/cm . S a m p l e s w h i c h a r e s t r u c t u r a l l y  by r e m o l d i n g o r by p o n d i n g  w i t h 0.01M HCI e x h i b i t s  maximum  2 p a s t p r e s s u r e s o f 2.1 a n d 2.4 kg/cm Upon w e t t i n g by p o n d i n g loads, a decrease  respectively.  of the relatively  i n b u l k volume r e s u l t s .  does n o t f o l l o w t h e c l a s s i c a l  time.  collapse,  The d e c r e a s e  can occur  The f o l l o w i n g t e r m s h a v e been a p p l i e d collapsing  compaction,  soil,  a t high s e a t i n g in bulk  volume  c o n s o l i d a t i o n t h e o r i e s but instead involves  a c o l l a p s e o f i n t e r g r a n u I a r s t r u c t u r e which of  dry s o i l ,  near  to this  surface subsidence,  and h y d r o c o n s o l i d a t i o n (Dudley,  in a brief  period  behaviour:  subsidence,  hydro-  1970).  F u r t h e r d i s c u s s i o n o f t h e c o l l a p s e b e h a v i o u r o f t h e Kamloops is  presented  r e v i ew.  in the following  chapter along with a b r i e f  silt  literature  73.  CHAPTER 5 STRUCTURAL  5.1  I N S T A B I L I T Y OF THE KAMLOOPS S I L T  LITERATURE REVIEW ON C O L L A P S I B L E SOILS  5.1.1  Co I I a p s i b I e Collapsible  world. the  Soi Is  soils  In g e n e r a l ,  increasing  h a v e been f o u n d  t h e y h a v e been  utilization  in various  located  of these areas  forms t h r o u g h o u t t h e  in arid  regions  in recent  and due t o  years there  has  been a g r o w i n g a w a r e n e s s o f t h e p r o b l e m . The dously.  types of s o i l s that  T h e y c a n be a i r d e p o s i t e d ,  made a n d g e n e r a l l y structure.  consist of s i l t  collapsible" collapse  by R e g i n a t t o  upon w e t t i n g  to the soil  This  and f i n e sand  only  structure.  deposit  condition  & Ferrero  will  (1973).  T h e s e h a v e been t e r m e d pressure  forming a loose collapse  level  open  under i t s "truly  Other s o i l s w i l l high  tremen-  r e s i d u a l o r man  h a s been t e r m e d  when s u f f i c i e n t l y  since the externally applied  stresses  exhibit  are applied  "conditionally collapsible"  governs whether  collapse  occur or not.  5.1.2  Collapse The  marized of  water deposited,  In many c a s e s , t h e s o i l  own w e i g h t when s a t u r a t e d .  will  d i s p l a y a c o l l a p s i n g behaviour vary  bulky  Mechanisms  mechanisms by D u d l e y  involved  (1970).  shaped g r a i n s  held  i n t h e c o l l a p s e phenomena h a v e been sum-  The b a s i c c o n c e p t together  i s t h a t o f open  by some b o n d i n g m a t e r i a l  structure or force.  This  b o n d i n g must be  duction  susceptible to  removal  of a d d i t i o n a l water, a l l o w i n g the  or  reduction  by t h e  grains to slide  intro-  i n t o the  vacant  spaces. The Dudley  1.  three  commonly p r o p o s e d m e c h a n i s m s w e r e s u m m a r i z e d  (1970):  Capi I l a r y  Tension  In many c a s e s , w i t h i n the until  t h i s temporary strength  partially  saturated  a certain saturation  optimal  value  sand, the  soil.  Generally,  i s r e a c h e d and  r e s u l t s in a decrease  i s due  in s o i l  peak e f f e c t i v e s t r e s s v a l u e  t o near s a t u r a t i o n , the  decreased or destroyed,  Clay  Coatings  With  the  Clay  large p a r t i c l e s ,  c o n s i s t of increases  and  capillary with  forces of  in the l e s s as  soil, the  the  the  the  silt  this and  capillary  fine  contents 1956).  tensions  e f f e c t i v e s t r e s s which  (Moore & M i l l a r ,  bulk of the The  grains to  are  reduces  collapse  1971).  der  more and  e f f e c t of c a p i l l a r y  forces  capillary  molecular  particles  a t t r a c t i o n become  more c l a y p a r t i c l e s  f o r c e s may  may  forces  However, f o r c l a y s i z e d  W a a l s and  Thus, w i t h  electro-chemical  intergranuIar  magnitude of the  particle size.  r e p u l s i o n , Van  much more s i g n i f i c a n t .  For  strength  Buttresses  forces.  decreasing  gains  ( A i t c h i s o n & Donald,  intergranuIar shear strength, thus a l l o w i n g the  i n t o a more s t a b l e a r r a n g e m e n t  2.  moisture  thus reducing  soil  tension  usually e x i s t s at moisture  When t h e  i s flooded  the  strength.  a b o v e 10$  soil  to capillary  saturations exceeding  l e s s t h a n s a t u r a t i o n and  the  by  present  become p r o p o r t i o n a l l y  f o r c e s become r e l a t i v e l y  more p r o m i n e n t .  A number o f d e p e n d i n g on clay  i s f o r m e d by  coating  may  addition  this  geologic  o r i g i n s and  weathering  structure  of water, the  t o some e x t e n t , An  s t r u c t u r a l a r r a n g e m e n t s become  e x i s t around the  conditions, the  the  possible  thereby  alternate  plates  grains. in the  The fluid  arrangement.  are  As forces  clay  grains.  have c o n s i d e r a b l e plates  may  into the  in water.  be  formed  As  the  i n t e r p a r t i c l e contact  Upon t h e an  grain  electro-chemical  in r e p u l s i v e  intergranuIar  s i z e s decrease a  forces  plates  increase  would s t i l l  of the  force  total  forces  (Dudley,  between t h e  portion  to capillary  due  i n t e r p a r t i c I e bonds:  to clay  strength  due  ions  buttress would  clay  plates  p r e s e n t as  However,  difficulty  the  the  larger  c l a y s i z e s , the  McGown & C o l l i n s ( 1 9 7 3 ) a l s o s t r e s s t h e of  the  dissolved  between t h e  smaller  important  :  dried,  ion c o n c e n t r a t i o n  in magnitude. be  clay  support.  into the  lesser portion  with  separate  i f the  flocculate into a  a d d i t i o n of water, the  increase  but  and  area of  clay  to  clay  dessicated  deposits  causing  plates  the  strength.  process would c o n c e n t r a t e the  the  a thin  stability;  tend to swell  loss of  When  Under  evaporation  contribute  between c l a y  could  soil.  authigenesis),  individual s i l t  suspended  in a decrease of  the  (by  s t r u c t u r a l arrangement could  drawn  decrease causing resulting  in place  producing a  p a r t i c l e s were o r i g i n a l l y clay  h i s t o r y of the  possible,  of  capillary the  capillarity  1970).  Barden,  distinguishing forces  and  " T h e r e a r e c l e a r l y many p o s s i b l e v a r i a t i o n s i n t h e s t r u c t u r a l arrangement of t h e c l a y p l a t e s between the quartz g r a i n s . The n a t u r e o f t h e c l a y b o n d i n g i s c o m p l i c a t e d , and i t i s n e v e r c l e a r how much i s due to electro-chemical e f f e c t s and how much t o c a p i l l a r y effects. The i m p o r t a n t p o i n t i s t h a t i n most c a s e s the lower the water c o n t e n t of the c l a y the greater t h e bond s t r e n g t h . " p. 5 1 .  that  3.  Chemical  Cementing  Structural  Agent  instability  a cementing agent.  natural  the  strength  water  r e s u l t from t h e l o s s  chemical  breakdown o f t h e c h e m i c a l  and t h e c o l l a p s e o f c l a y  years there  cementing agent.  c e m e n t i n g a g e n t due t o  i s a slower process than strength  In r e c e n t  of  o f ions w i t h i n t h e incoming water as well  dissolution rate of'the  dissipation  in strength  The r a t e o f s t r u c t u r a l w e a k e n i n g w o u l d depend on t h e  n a t u r e and c o n c e n t r a t i o n the  may  l o s s due t o c a p i l l a r y  In  as general  infiltratin tension  buttresses.  h a v e been a number o f e l e c t r o n  studies  p e r f o r m e d on v a r i o u s  Collins  ( 1 9 7 3 ) and C o l l i n s & McGown ( 1 9 7 4 ) h a v e shown m i c r o p h o t o g r a p h s  supporting  the existence  collapsible soils.  microscope  of t h e general  B a r d e n , McGown &  collapse  structures  mentioned  above. For the  some s o i l s , t h e c o l l a p s e  c h a r a c t e r i s t i c s of the liquid  loessial  soils  phenomena  i n t h e Cordoba r e g i o n f o r cases of ruptured  of  p l a i n water  with  5.1.3  Engineering The  task are void  of Argentina  (Reginatto  e x h i b i t e v e n more s u b s i d e n c e when  d e p e n d e n t on  saturating the s o i l .  more s e t t l e m e n t wetting  is strongly  For example,  frequently  sew.age p i p e s t h a n & Ferrero,  flooded  with  f o r cases  1973).  These  soils  a c i d i c water.  Applications  p r a c t i c a l problem f a c i n g t h e engineer  involves  the d i f f i c u l t  of p r e d i c t i n g t h e presence of these c o l l a p s i n g s o i l s . proposed  exhibited  f o r predicting the occurrence of collapse  ratios vs. void  ratios at their  liquid  limit  Many  b a s e d on  indexes natural  a n d on d r y d e n s i t i e s  77.  of t h e s o i l  (Markin,  1971; G i b b s & B a r a ,  1967; D e n i s o v ,  1 9 6 1 ; Dud I e y , 1 9 7 0 ) .  H o w e v e r , i t i s commonly a g r e e d t h a t t h e i n d i c e s a r e n o t reliable soils  fordifferentiating  (Dudley, To  between c o l l a p s i b l e and n o n - c o l l a p s i b l e  1970; E v a n s & B u c h a n a n ,  obtain  In t h i s t e s t ,  content, a certain void  The t o t a l  conditions,  in the field  the  durations  c o l l a p s e t o occur.  (Rabinovich  i n incremental  & Urinov,  will  be i m m e d i a t e ;  the  case of chemical  Col I i n s ,  1973).  inthe  f o rseveral  1974).  Usually  which  settle-  a f t e r several of  Furthermore, the type  w o u l d be e x p e c t e d t o g o v e r n  In t h e c a s e o f ' c a p i I I a r y  i n t h e case of t h e bridging cementing  required  than that  under f o u n d a t i o n s  months.  will  As a r u l e , h o w e v e r ,  load t e s t s s t a b i l i z e  of temporary bonding t h a t e x i s t s i n t h e s o i l rate of collapse.  t h e time  a r e much s h o r t e r  ( f i g . 31) w h e r e a s t h e c o l l a p s e o f s o i l s  b u i l d i n g s sometimes c o n t i n u e s  the  completely  1975).  i s a l s o concerned with  in the laboratory  in the field  m e n t s due t o c o l l a p s e  H o w e v e r , a s t h e t e s t s do n o t  1970; J e n n i n g s & K n i g h t ,  of the total  measured  is experienced  t h e change i n  t o t h e t e s t data t o p r e d i c t t h e c o l l a p s e t h a t  In some c a s e s , t h e e n g i n e e r certain portions  by c o n s i d e r i n g  under  c o r r e c t i o n f a c t o r s b a s e d on e x p e r i e n c e  (Dudley,  for  moisture  c o l l a p s e due t o s a t u r a t i o n  l o a d c a n be d e t e r m i n e d s i m p l y  a r e a m u s t be a p p l i e d  ( 1 9 5 7 ) i s commonly  two s i m i l a r s a m p l e s a r e t e s t e d ; one a t f i e l d  and one s a t u r a t e d .  reproduce f i e l d  hours  on t h e amount o f c o l l a p s e , t h e  by J e n n i n g s & K n i g h t  r a t i o between t h e two c u r v e s .  occur  1976).  quantitative information  double oedometer t e s t presented used.  completely  i t m i g h t be v e r y  s u c t i o n t h e drop clay, rather slow  in strength  slower;  ( B a r d e n McGown  and i n &  5.2  COLLAPSE PHENOMENON OF The  soil  THE  gIacioIacustrine s i l t  as d e f i n e d by  KAMLOOPS S I L T S under study  is a conditionally  Reginatto & F e r r e r o (1973).  Whether o r not t h e  structure will  u n d e r g o c o l l a p s e when f l o o d e d w i t h w a t e r  on  stress state.  i t s present  At very  exhibits  heaving  occurs.  This type of behaviour  &  Knight,  when f l o o d e d ; and  1975).  For  p r e s s u r e w h e r e no  0.2  kg/cm  possibly 3-4$  soil  i s dependent  low c o n f i n i n g p r e s s u r e s , t h e  soil  at higher s t r e s s levels, collapse  i s a l s o found  Kamloops s i l t ,  i n some d r y c l a y s  the actual c r i t i c a l  volume change r e s u l t s  2  collapsible  due  (Jennings  confining  to flooding lies  between  2 and  due  0.8  kg/cm .  The  to the swelling  of the s o l i d s ;  f o r c e s w h i c h may  lower s t r e s s e s i s  of t h e montmori I l o n i t e  Quigley,  be  heave e x h i b i t e d a t  1976)  (approximately  and/or the d i s s i p a t i o n  present w i t h i n the  of  capillary  soil.  2 'maximum p r e c o n s o I i d a t i o n p r e s s u r e ' i s a p p r o x i m a t e l y 26 kg/cm 2 f o r t h e a i r - d r i e d s t a t e and 6 kg/cm f o r the flooded s t a t e . Therefore, v e r y l i t t l e s u b s i d e n c e due t o w e t t i n g w o u l d be e x p e c t e d t o o c c u r a t The  2 stresses  less than  6 kg/cm  (see f i g . 37).  The  collapse is  approximately  2 2%  a t 6 kg/cm .  designs soil (fig.  and  F o r t h e s t r e s s l e v e l s commonly e n c o u n t e r e d  most e n g i n e e r i n g  problems, the  from t h e c o l l a p s e a s p e c t s 37).  additional  However, t h e subsidence.  i n s p i t e of  leaching of the The  'maximum p a s t  Kamloops s i l t i t s high  soil  in footing  i s not a  in-situ  void  problem  ratio  by a c i d i c w a t e r w i l l  pressure'  f o r the s i l t  cause flooded  2 w i t h 0.01M  HCI  i s 2.4  is approximately especially local  2%.  kg/cm .  At t h i s  s t r e s s , the  laboratory collapse  At h i g h e r s t r e s s e s , s e t t l e m e n t  when d i f f e r e n t i a l  settlements could easily  f l o o d i n g by a c i d i c s o l u t i o n s .  Although  p r o b l e m s may r e s u l t due  the a c i d i c  arise to  concentrations  19.  80.  encountered  in the f i e l d  decayed v e g e t a t i o n the  a r e much s m a l l e r  long t e r m e f f e c t o f r e d u c i n g  sti II  5.3  than the laboratory  the s i l t ' s  concentration,  structural stability is  present.  COLLAPSE MECHANISM In o r d e r  be  due t o w a t e r p e r c o l a t i n g t h r o u g h t o p s o i I and  t o understand t h e behaviour of the s i l t ,  made t o i s o l a t e t h e c o l l a p s e m e c h a n i s m  laboratory  t e s t r e s u l t s , a hypothesis  It appears t h a t t h e s t r e n g t h dry  state  complex and  involved.  an a t t e m p t must  B a s e d on t h e  i s proposed.  exhibited  by t h e s i l t  in i t s natural  i s n o t t h e r e s u l t o f any one s i n g l e f a c t o r , r a t h e r ,  interaction of c a p i l l a r y  chemical  to capillary unsaturated  cementation. stresses silts  extensive  tension,  Theoretical  i t is a  interparticIe clay attraction  computations presented with  by A i t c h i s o n & D o n a l d  regard  (1956) i n d i c a t e s t h a t f o r  (0.02mm t o 0.002mm), t h e e f f e c t i v e s t r e s s e s  may be i n  2 2 kg/cm t o 3.5 kg/cm . In c l a y s , c a p i l l a r y s t r e s s e s 2 as much a s 100 kg/cm may be r e a l i z e d . F o r t h e K a m l o o p s s i l t , t h e p o s s i b l e the  r a n g e o f 0.35  effective  s t r e s s due t o c a p i l l a r y  forces  as c a l c u l a t e d from t h e s t r e n g t h  2  data  (table  IV, p.50 ) j  s  6.3  kg/cm  f o r a w a t e r c o n t e n t o f 2.28$ and  2 15.0 kg/cm capillary  f o r an o v e n d r i e d s a m p l e ( m a k i n g t h e g r o s s a s s u m p t i o n forces  may e x i s t i n an o v e n - d r i e d  magnitude of these s t r e s s e s the of  idealized values,  sample (p.49 ).  are c e r t a i n l y within  s t r e s s due t o c a p i l l a r y  i s given  H o w e v e r , i t has been shown t h a t tension  c o n t e n t and 100$ s a t u r a t i o n  for silts  (Dudley,  The  r e a s o n as compared t o  e s p e c i a l l y when c o n s i d e r a t i o n  clay within the s o i l .  that  o c c u r between  t o the presence  peak e f f e c t i v e  10$ m o i s t u r e  1970; A i t c h i s o n & D o n a l d ,  1956).  81 .  Capillary As  tension  i s considered  t h e water content  increases  until  a maximum. capillary  non-existent  of the soil  increases,  a t a c e r t a i n water content,  R a i s i n g t h e water content f o r c e and c o n s e q u e n t l y  within the soil  which  Thus, f o r a s o i l  until  capillary  also  the meniscii  i s r e f l e c t e d by a d e c r e a s e whose b o n d i n g s t r e n g t h  would drop  A series of t r i a x i a l  tension  forces are at  f u r t h e r r e s u l t s i n a decrease i n in effective stress  in soil  i s solely  in strength  some o p t i m u m w a t e r c o n t e n t  level, the strength  state.  r e s u l t s i n a decrease  f o r c e s , we w o u l d e x p e c t an i n c r e a s e content  i n the oven-dried  with  strength.  due t o c a p i l l a r y  i n c r e a s i n g water  i s reached.  Beyond t h i s  moisture  again.  t e s t s were performed  ( s e c t i o n 4 . 5 , p. 45 )  a t t h e same c o n f i n i n g s t r e s s b u t a t v a r i o u s  water contents  t o determine  if  f o rthe s i l t ' s  strength.  capillary  The  resultant strength  increases strength this due  f o r c e s were s o l e l y  with  ( f i g . 2 9 , p. 47 ) shows t h a t t h e s o i l  c o n t i n u a l l y decreasing  i n the oven-dried  state.  water content;reaching  solely to capillary  indicates that  silt's  bonding s t r e n g t h  hypothesised interparticIe  ( B a r d e n , McGown  by D u d l e y  (1970)(section  grains. c o n t i n u a l l y decreasing  i s mainly  & Collins,  that the bulk of t h e s i l t ' s  under study.  responsible 1973).  dry strength  water  f o r the  Thus,  i t is  i s l a r g l e y due t o  i s , t h e second source o f temporary 5.1.2) i s e x p e c t e d t o a p p l y  The p r e s e n c e o f c l a y b e t w e e n s i l t  interparticle attractive forces.  with  interparticIe clay  (clay) forces; that  maximum  t h a t t h e bonding s t r e n g t h i s  between s i l t  results of increasing strength  content  presented  forces  strength  In l i g h t o f t h e a b o v e d i s c u s s i o n ,  behaviour rules out the p o s s i b i l i t y  The  soil  data  responsible  grains  bonding  t o the  produces  f o r c e s s u c h a s Van d e r W a a l s ' f o r c e s a n d London  Any w a t e r p r e s e n t  in the soil  will  migrate t o p a r t i c l e  contacts  upon b e i n g d r i e d At  and w i l l  lower w a t e r c o n t e n t s ,  forming stronger the  menisci.i  decrease. the clay  result in capillary the clay  plates  i n t e r p a r t i c I e bonds.  forces  come c l o s e r and c l o s e r  a t t r a c t i v e force  of ion concentration  between c l a y  forces  resulting shearing  plates  w i t h i n t h e pores  provides the bulk  with  t o an unknown f r a c t i o n o f t h e t o t a l Searching  capillary  soil  f o r more e v i d e n c e t h a t  to " v i s u a l l y "  Although electron  frequently  silt  occur  only  the  soil  which  contributing  i s t h e major  s c a n n i n g m i c r o s c o p e was  increased  loose  employed  m i c r o p h o t o g r a p h s do  strength  lower s h e a r s t r e n g t h  pressure"  some s o i l s ,  structure  effect of increasing  c h a r a c t e r i s t i c s ( f i g . 36).  exhibits  consolidation For  i n an o p e n  in the decrease of s o i l  consolidation  leading  clay  ( f i g . 19, p. 27 ) and may be s u f f i c i e n t t o h o l d  p a r t i c l e s together  The e l e c t r o - c h e m i c a l not  levels  show t h e p r e s e n c e o f c l a y c o n n e c t o r s b e t w e e n m o s t p a r t i c l e s ,  bridges the  forces  interparticIe clay  electron  not  stress  strength.  source o f bonding s t r e n g t h , t h e study the s i l t .  Micro-  i t i s the clay a t t r a c t i v e forces  of the strength  of  loss of e f f e c t i v e s t r e s s  can o c c u r under s u f f i c i e n t Thus,  decreases  The d e s t r u c t i o n o f  i n a f u r t h e r decrease of intergranular strength.  to structural collapse.  plates  resulting in separation  i s a l s o a c c o m p a n i e d by a  between g r a i n s  together,  between c l a y  p a r t i c l e s and l o s s o f i n t e r g r a n u l a r s t r e n g t h .  meniscii  also.  Upon f l o o d i n g o f a d r y s a m p l e ,  a r e b r o k e n and t h e i o n c o n c e n t r a t i o n  The r e d u c t i o n  t o be p r e s e n t  water content  but a l s o With  (sec.  4.1). is reflected  in the s i l t ' s  increasing  and d e c r e a s i n g  water  content,  "maximum p r e -  ( s e c . 4.8.3).  t h e magnitude of s t r u c t u r a l c o l l a p s e  by f l o o d i n g t h e s o i l  with  sewage w a t e r  (Reginatto  i s strongly &  Ferrero,  83.  1973).  In t h e c a s e o f K a m l o o p s s i l t ,  sewage w a t e r  exhibited  a sample f l o o d e d w i t h s i m u l a t e d  no a p p r e c i a b l e d i f f e r e n c e  in consolidation  as compared t o a sample f l o o d e d w i t h d i s t i l l e d  water  H o w e v e r , f l o o d i n g w i t h a HCI s o l u t i o n  a marked d e c r e a s e  strength.  The r e s u l t a n t a d d i t i o n a l  b r e a k d o w n o f some f o r m o f c e m e n t i n g (Quigley, Hardy,  agent  namely c a l c i u m c a r b o n a t e .  —  dry  slowly  exist, bonding  before testing  then  cementation.  between s i l t  grains.  forces should take e f f e c t t h e sample  into a slurry  ( s e c . 4.8.1).  remolding a sample  Upon s l o w  i t s cohesive strength. dried  the undisturbed s i l t  in the dry state.  consolidation  In  (fig.  30).  p a r t i c l e s t o g e t h e r and g i v e  However,  in i t s flooded state, the t h a t o f t h e sample  remolding of the s i l t  t e n s i o n and c h e m i c a l  the total  bonding  strength.  in  bonding  s t r e n g t h which  indicates that the bulk of the s i l t ' s  is  under a s u f f i c i e n t l y  cementation  large  in structural  load.  clay.  also contribute t o a portion of  Upon f l o o d i n g w i t h w a t e r ,  results  has  bonds.  cohesive s t r e n g t h i s a r e s u l t of t h e presence of i n t e r s t i t i a l Capillary  In t h e  i n a s i m i l a r manner t o  sample approximated  This suggests that  summary, a l l t h e e v i d e n c e  does  interparticIe  indeed t h e case.  destroyed the calcium carbonate  was  destroy t h e chemical  sample behaved  c u r v e o f t h e remolded  f l o o d e d w i t h HCI irreversibly  remolded  cementation  drying, the clay  T h i s was  does e x i s t  and a l l o w i n g t h e s a m p l e t o  will  the s i l t  consolidation test,a  cementation  If chemical  into a slurry  i n bonding  in the s i l t ;  Thus, a s m a l l p o r t i o n of  Further supporting evidence t h a t chemical .-.obtained by r e m o l d i n g t h e s i l t  in soil  i s p r o b a b l y due t o t h e  calcium carbonate).  s t r e n g t h i s due t o c h e m i c a l  4.8.1).  collapse  I 9 7 6 , r e p o r t s a p p r o x i m a t e Iy 5% c a I c i u m c a r b o n a t e  I 9 6 0 , r e p o r t s 5-6%  the s o i l  produced  (sec.  behaviour  i t i s the decrease  c o l l a p s e when t h e s o i l  84.  CHAPTER 6  SLOPE S T A B I L I T Y  6.1  Frequency & Field  evidence  Valley are very The  Extent  limited  two a d j a c e n t  slope  failures  of past  slope  f a i l u r e s along  slides  near P r i t c h a r d represent  ( f i g . 38).  bluffs  in their  o f t h e bench  of the slopes  i s a major  major by t h e  factor.  i s n o t d'irecif l y f e I t a t t h e t o e o f  local  silt  falls  stable  c o u l d cause slow  although  recession  edge.  J o i n t i ng As  described  with major j o i n t  i n s e c t i o n 2.3, t h e l a c u s t r i n e s i l t sets a t angles  the s t r i k e of the b l u f f parallel  to the bluff  face.  of approximately  face w i t h i n Magazine G u l l y .  Locally, these  joint  i s highly  jointed  60 a n d 30 d e g r e e s t o  f a c e and a f o u r t h s e t e x i s t s  p a t t e r n s commonly s e e n  6.3  recent,  n a t u r a l s t a t e appear c o n d i t i o n a l l y  a long t e r m b a s i s , s m a l l  bluff  deposit.  bIuffs.  The  6.2  the only  Here, t h e oversteepening  Generally, the e f f e c t of r i v e r erosion  on  Thompson  i n number and s i z e w i t h i n t h e l a c u s t r i n e  u n d e r c u t t i n g a c t i o n o f t h e S o u t h Thompson R i v e r  the s i l t  t h e South  A third  set strikes  perpendicular t o the  s e t s form t h e columnar t y p e  jointing  in the f i e l d .  Modes o f Fa i I u r e s In  highly jointed  evidenced  in the f i e l d .  slopes,  invariably  Two m a j o r t y p e s  jointing of s i l t  governs t h e f a i l u r e  falls  (shallow  modes  failures)  85.  Figure  38.  S l o p e f a i l u r e s c a u s e d by o v e r s t e e p e n i n g as a r e s u l t o f r i v e r e r o s i o n o f t h e t o e . ( N e a r P r i t c h a r d , on t h e S o u t h Thompson River, looking north).  86.  are  usually  1.  Co Iumn T o p p I i ng Local  observed:  columnar j o i n t i n g  the  setting  is  increased  is  reduced  such as those  f o r column t o p p l i n g f a i l u r e s . ( e g . by c l e f t  water pressures)  ( e g . by a d e c r e a s e o f s o i l  o r w e t t i n g ) , c o l u m n a r t o p p l i n g may  seen  i n f i g u r e 39  When t h e o v e r t u r n i n g moment o r when t h e s t a b i l i z i n g  s t r e n g t h as a r e s u l t o f  result.  The s i l t  b r e a k up on i m p a c t and " f l o w s " down t h e c o l l u v i a l debris 2.  failures.  The g e n e r a l  b o u n d e d by j o i n t  is  slope  instability  surfaces  usually  failing  ( f i g .41).  in this  result  e x i s t s as local  along  The l a t e r a l  strength.  a shear  end  surface  s t r e n g t h due t o w e a t h e r i n g  potential  f a i l u r e of the block.  The b a s e o f t h e b l o c k  o f t h e b l o c k moves downwards a l o n g similar to that  inclined  surfaces  out of provides  failure  surface.  o r i n t r o d u c t i o n of water The s i z e o f t h i s  l i m i t e d t o o n l y a few h u n d r e d c u b i c y a r d s  blocks.  field.  b l o c k o r wedge  The b u l k o f t h e r e s i s t a n c e t o f a i l u r e  r e s i s t a n c e on t h e i n c l i n e d  in a sliding  intact blocks the  loose  block or slab  and r e a r j o i n t  A s i m i l a r mechanism f r e q u e n t l y e n c o u n t e r e d intact  c o l u m n s commonly  s l o p e s as  geometry c o n s i s t s o f a s i l t  ( i f any) t e n s i l e  Decrease  is  face  due t o s h e a r  will  weathering  Fa i I u r e s  Most o f t h e f i e l d  little  moment  ( f i g . 40).  Block  the  provide  instability  of s o i l .  is failure  by r o t a t i o n o f  r o t a t e s o u t w h i l e t h e upper the rear j o i n t  surface.  Rotated  i n f i g u r e 42 a r e f r e q u e n t l y o b s e r v e d  in  87.  88.  F I G • 40  DI*\6RAMAPTIC T0PPLIH6  REPRESENTATIOK  MODE OP  FAILURE  OF T H E  COLUMN  89.  F I G . 4-1  DIA6RAMATIC 01 BLOCK  M o  12) B L O C K  RERESEKTTATIOK  OR. SLfcfc  FArfLUft£  OF MODS  ROTATIOKM- F A I L U R E  MODE  F i g u r e 42.  Rotated Gully.  intact block within  Magazine  6.4  InfIuence of Stability  infiltration during  Continued chemical be  soil  of the  as  suggested  long  the  by  the  stresses). envelope  rainwater  a slight  the  the  shear strength  to  low  water  known p a s t f a i l u r e s  remove t h e  Swelling  and  joints. dissolvable  Thus, t e n s i l e  confining  resistance  s l a k i n g of  stresses,  the  r e s u l t i n g in  slippage. soil  of the  will  loess.  in water content of loss  silt  (1960) a l s o  effective stresses)  w i t h i n the  Increasing  related to  h a v e an  immediate  by:  cause a dramatic  interaction  carbonate.  into the  Nebraska-Kansas  increase  conceivably  process.  o c c u r under  is susceptible  ( i n terms of of  can  calcium  G i b b s , Hi I f & H o l t z  saturation  c o r r e l a t i o n of the  weathering  j o i n t s may  stability  decreasing  strongly  conditions.  i n t r o d u c t i o n of water  e f f e c t on  2.  by  c e m e n t a t i o n s u c h as  near the  will  by  snowmelt  percolation  destroyed  The  a p p e a r s t o be  term c o n d i t i o n , water causes weathering along  a weak p l a n e w h i c h  1.  slopes  peak r a i n and In t h e  may  Water  in s o i l  ( i n terms of  found t h a t  e f f e c t i ve  a d i f f e r e n t Mohr  e x i s t s for varying At  a few  strength  low  degrees of  percent t o the as  a r e s u l t of  degrees  of  saturation, Kamloops  silt  clay-water  silt.  the  hydrostatic  forces  the  u n i t weight of the  on  the  cracks  and  joints within  the  s o i I. 3.  increasing  least s i g n i f i c a n t , f a c t o r of as  the  safety  increase  of the  internal friction  soil.  Although t h i s  in u n i t weight of the  slopes  when s t a b i l i t y  angle of  the  soil.  soil  can  d e p e n d s on  factor  is  decrease  c o h e s i o n as  the the well  92.  6.5  Stability Since  A n a l y s i s o f Deep F a i l u r e s  the strength of the s i l t  regime, t h e f i e l d increases with are  strength  depth.  not well defined.  i s h i g h l y d e p e n d e n t on t h e m o i s t u r e  p a r a m e t e r s may v a r y  Thus, t h e a c t u a l o p e r a t i v e A n a l y s i s must t h e n  possible strength of the undisturbed strength  data  Since  obtained  the soil  is not j u s t i f i e d . suffice bluff  soil  strength  i s not well  - that  along  i s , application of the  samples.  stability  charts  Table VII presents  with the c r i t i c a l  slope  analysis will  t h e observed  h e i g h t s as  calculated  from T a y l o r ' s  TABLE V I I  COMPARISON OF THE OBSERVED AND CALCULATED SLOPE HEIGHTS USING TAYLOR'S CHARTS.  Measured s l o p e angle ( i )  charts  parameters  known, d e t a i l e d s t a b i l i t y  Hence, t h e usage o f T a y l o r ' s  in the field  strength  content  p r o c e e d b a s e d on t h e w e a k e s t  from s a t u r a t e d t r i a x i a l  f o r t h e n e a r l y homogeneous s o i l .  heights  as t h e m o i s t u r e  ( T a y l o r , 1 9 4 8 , p. 4 5 9 ) .  Observed  Height  Calculated  Height  75°  122'  108'  66°  45'  126'  71.5°  70'.  114'  59.5°  38'  121 '  66°  70'  127'  79.3°  93'  99'  70.6°  139'  factor of safety  i s l e s s than one.  102'  **•*  ***  (H )  93.  It can  be  coupled with bluffs would  can  be  readily  seen  resuIt.  in-situ densities  s a t u r a t e d s t r e n g t h data, the f a c t o r of s a f e t y of the s i It less than  unity.  be e v e n more c r i t i c a l .  should  from t a b l e VII t h a t u s i n g  the s i l t  bluffs  If j o i n t i n g  is also considered,  Thus, t h i s s i m p l e  be s u f f i c i e n t l y  the  slopes  a n a l y s i s shows t h a t  w e t t e d , deep s l o p e  failures  may  94.  6.6  Long-Term S t a b i I i t y In t h e  will  long t e r m c o n d i t i o n ,  proceed u n t i l  data, t h i s  erosional  the angle of repose  is achieved.  i s d e t e r m i n e d t o be a p p r o x i m a t e l y 33°  on o u r c h o i c e o f t h e f a i l u r e  criteria).  e x i s t s a t an a v e r a g e a n g l e o f 35°. removal  p r o c e s s e s such as b l o c k f a l l s  o f t o e s u p p o r t and  added  From t h e  triaxial  ( b e i n g somewhat d e p e n d e n t  In t h e f i e l d , c o l l u v i a l  Without complicating  loads, e q u i l i b r i u m w i l l  slopes  f a c t o r s such exist at  as  this  angIe. In t h e e v e n t o f r e a c h i n g c o n d i t i o n s w h i c h a p p r o x i m a t e s t h e f l o w o f w a t e r down a s a t u r a t e d be a p p l i e d . be f o u n d  slope, the  In t h e c a s e o f t h e s i l t  infinite  bluffs,  slope analysis  1  t  the stable angle ( i ) could  0  )  =  16°  (Lambe & W h i t m a n , 1969,  Although the  infinite  n e v e r be f u l l y  represents the of  saturated  be met  realized  in the f i e l d  but  situation,  the seepage of water  i n t h e e v e n t o f heavy  33°  f o r the  the  frictional  resistance  and  o t h e r forms o f  364)  parallel  rain  long t e r m c o n d i t i o n .  and be  which  nevertheless, i t  In p r a c t i c e , t h e  From t h e p r e c e e d i n g r o u g h a n a l y s i s , t h e 16°-  p.  i s b a s e d on a s s u m p t i o n s  l o w e r bound f o r i n s t a b i l i t y .  s l o p e and  exactly  slope analysis  s e w e r m a i n r u p t u r e s , t h e a b o v e c o n d i t i o n s may  between  could  from  i = t a n " (( / / * ) t a n  may  parallel  assumptions  t o t h e s l o p e may  snownelt coupled locally  i s c o n s i d e r e d t o be m o b i l i z e d  with  approximated.  'safe' slope angle In t h i s  never  lies  long t e r m c a s e , o n l y and  cementation  . c o h e s i o n a r e c o n s i d e r e d t o be n o n - e x i s t e n t .  Thus,  even  95.  u n d e r t h e c o n d i t i o n s o f p e r c o l a t i o n o f a weak a c i d i c the s o i l , although  6.7  t h e above structural  limits s t i l l  apply  from t h e  c o l l a p s e may  occur  under  P o s s i b l e Zoning One  angle bility 100  repose  (16°).  vertical  33°,  an  (33°)  and  the  limiting  C o n s i d e r i n g an f e e t of b l u f f  f a c e a t 70°  of approximately  s t r u c t u r e s o f any 400',  a control  failure  aspect  and  repose 100'.  form s h o u l d  i s b a s e d on  s e c t i o n ( f i g . 43) and  200  the  for  insta-  consisting  f e e t of colluvi.al  t o the top of the Within this  be c o n s i d e r e d  100'  unsafe.  section  results  of the c l i f f Between  100'  and  be  s a f e f o r u r b a n i z a t i o n a I developments such  from t h e c l i f f 100'  h i g h and  edge.  The  maps o f t h e  area.  actual:  approach s i n c e s o i l  not  spread  over  a  in the  idealized  would r e q u i r e t h e  b a s e o f t h e s l o p e s may  be  Small  t o flow past large area  s i It f a l l s  w h i c h may  i t s present toe  before  impinging  zone  a bluff  face  of  s e c t i o n of topographic  delineated with a must a c c u m u l a t e  frequently occur  position  as  f u r t h e r removed  preparation of  removed a t t h e t o p o f t h e b l u f f  slopes.  be e x p e c t e d  h a v e t o be  d i s t a n c e s a r e b a s e d on  as g i v e n  zoning  foreset at the  the c o l l u v i a l  setback  slope geometries  f i g u r e 43.  The  The  u s e may  The  enforced.  b e y o n d 400'  industrial  be a l l o w e d .  edge,  as s t o r a g e s h e d s may  p r o j e c t s ; although  at  f o r e s e t c o u l d be d e l i n e a t e d .  o f t h e t y p e o f s t r u c t u r e s t o be e r e c t e d s h o u l d  is considered  of  slope  Temporary s t r u c t u r e s such  housing  -  foundations.  l o w e r bound s l o p e a n g l e  idealized  approximate safe setback  a setback  loaded  scheme f o r u r b a n d e v e l o p m e n t  Extension of the angle of in  sliding  through  Scheme  p o s s i b l e zoning  of  solution  similar on will  s i n c e t h e d e b r i s wi I I  on t h e t o e o f t h e  slope.  FIG. 4 3  APPROXIMATE SETBKCK ZONIMG SCUtrtE  97.  T h u s a f o r e s e t o f 100' may be s u f f i c i e n t when s a t u r a t e d applied  i f we c o n s i d e r  transferred foreset not  conditions  under d r y c o n d i t i o n s .  e x i s t s , t h e 400' f o r e s e t  that the soil  guideline  a s shown  i n f i g u r e 43.  n a t u r a l l y assumes t h e advance o f t h e t o e i n a g r a d u a l  momentum may  v e l o c i t y mass f a i l u r e ,  result in the debris  may  be  removed a t t h e t o p i s c o m p l e t e l y  t o t h e lower h a l f o f t h e s l o p e  a r e s u l t of a high  However,  This  p r o c e s s and  i n which case, t h e s i l t ' s  from s p r e a d i n g  f u r t h e r downs I o p e .  CHAPTER 7  SUMMARY AND  In t h e  attempt t o  CONCLUSIONS  understand the  silt,  extensive  t o be  extremely s e n s i t i v e to moisture  the  greater  failure  laboratory  behaviour of the  the  soil  strength.  ( i n terms of  saturation.  In t h e  t e s t i n g has  been e m p l o y e d . inputs.  The  The  silt  lower the  was  water  T h u s , a d i f f e r e n t Mohr e n v e l o p e  effective stresses) silt's  glaciolacustrine  fully  state, consolidated  content,  of  e x i s t s f o r each degree  saturated  found  of drained  2 triaxial angle  tests yield  (0)  of  17.8°  a cohesion  f o r the  normally consolidated The  above s t r e n g t h  i n t e r c e p t o f 0.609 kg/cm  overconsoIidated  stress  field,  The in t h e  i s a n i s o t r o p i c , the sensitivity  soil's  consolidation  of the  silt  apparatus.  In t h e  heave a t  c o l l a p s e o c c u r s under h i g h e r t o s w e l l i n g of the  3-4$  c o l l a p s e mechanism r e v o l v e s clay-water  and  silt's  low  levels.  around the  angle  is  33°.  (deviator soil  small.  is also  reflected  in i t s behaviour  in  the  s t a t e , ponding  pressures while The  the  Although the  n a t u r a l l y dry  confining  friction  Within  been shown t o be  hence,  a  loading  slight  montmori I I o n i t e w i t h i n t h e physico-chemical  structural  heave soil  by  i s probably  while  the  b e h a v i o u r of  the  soil.  b o n d i n g by  other a t t r a c t i v e forces  axial  to moisture content  stress  system w i t h i n the  IntergranuIar  by  bedding plane.  v a r i a t i o n has  structural stability,  water r e s u l t s in s o i l  due  t o the  range.  internal friction  p a r a m e t e r s were o b t a i n e d  stress direction) perpendicular strength  the  stress  and  of the  Van  der  clay  Waals'  plates  forces,  London f o r c e s  constitutes  the  bulk  of  and the  99.  bonding strength c l a y may grain of  exhibited  e x i s t as  contacts.  the  bridges  the  and  silt  in i t s n a t u r a l l y dry  c o n n e c t o r s o r as  Upon f l o o d i n g t h e  bounded w a t e r  slightly,  by  soil  with  l a y e r d e c r e a s e s and  r e s u l t i n g in a decrease of  thin coatings  water, the  the  state.  clay  at  ion  silt  concentration  p l a t e s tend t o  intergranular  bonding  The  separate  strength.  2 Under s u f f i c i e n t l y between g r a i n s network soil  (e =  and  occur,  1.28).  meniscii  substantial capillary  high  stress leading  forces  i s not  kg/cm ) ,  microshearing  t o s t r u c t u r a l c o l l a p s e of the  C a p i l l a r y forces  although the  forces  l e v e l s (above 6  must n e c e s s a r i l y  loose  e x i s t in a  b e t w e e n c l a y - c l a y and  clay-silt  actual  bonding strength  portion  known.  of the  open moist  contacts  Since structural collapse  may  due  be to  is i n s i g n i f i c a n t  2 below s t r e s s  l e v e l s of  6 kg/cm , c o l l a p s e a s  a problem under s t r e s s e s  a r e s u l t of  commonly e n c o u n t e r e d  flooding  in engineering  is  not  practice. 2  However, a d d i t i o n a l when t h e  soil  carbonate loss of  is flooded  (5-6%  by  as  with  w e i g h t ) by  small  shallow  correspond to conditions,  the  block  and  field.  corresponding  f a c t o r of  water  leads  of the  silt  snowmelt c o n d i t i o n s . not  as  to the  bluffs,  2.4  kg/cm  calcium further  limited  occur, they  are  The  Thus under  expected to occur.  i n t o the  failures.  safety  low  d i s s o l u t i o n of  Where t h e y do  o r a b n o r m a l l y wet  large scale slope  as  exist  T h e s e f a i l u r e s h a v e been o b s e r v e d  l a r g e mass f a i l u r e s a r e  disturbances,  The  acidic solution  conditions  failures.  excessive  stresses  strength.  in the  peak r a i n f a l l  i n t r o d u c t i o n of izational  evident  r e s u l t as  a c i d i c water.  present natural  f a i l u r e s are  lead t o  will  i n t e r g r a n u l a r bonding  Under t h e slope  collapse  slopes  as  a r e s u l t of  f a i l u r e m e c h a n i s m and the  usual  However,  climatic conditions,  d e p e n d e n t on  to  urbancan  possibly  its  j o i n t i n g system.  100.  Four, near v e r t i c a l  joint  sets w i t h i n the  columnar-type j o i n t i n g  pattern.  by  joint  combinations of the  90°,  and  a n a l y s i s has  under s a t u r a t e d  sets  states.  strength  long term z o n i n g the  f r o m an  angle of  infinite  e d g e and  considered  the  induce  laterally  0°,  33°  situation,  and  lower p a r t of t h e remains f i x e d ,  (16°).  soil  30°,  the  lower s e c t i o n , a m a r g i n a l l y  16°  slope  should The  the  33°  saturated  soil,  reduce the  soil  The  area  slope  form.  present  slopes  should  zone  includes  This  analysis.  In t h e  mid-height of the  projection.  be  beyond t h e  16°  However, c a u t i o n  must be  areas e x h i b i t i n g  e v i d e n c e o f s i n k h o l e s and  c o n t r o l s must be  enforced  considered  exercised  pipes.  w i t h i n a l l urbanized prevent the  be  the  profile in  between  the  within  area  term  deposited  delineated  t o t e m p o r a r y s t r u c t u r e s s u c h as  the  at  slope  Construction  p r o j e c t i o n may  be  long  u p p e r s e c t i o n and  zone c o u l d  be  angle c a l c u l a t e d  between t h e  colluvial  from the  safe  safe  d e v e l o p m e n t s may  restricted  must be o b s e r v e d t o  occur  ( a t 40-50$  be  housing developments.  drainages  of the  can  upper s e c t i o n must c o l l e c t  Assuming the  i s eroded  p r o j e c t i o n and  the  in Taylor's  removed f r o m t h e  slopes.  the  on  p r o j e c t i o n of the  p l a n e assumed  material  level  strength  for urbanizationaI  (33°)  analysis  soil  c o n d i t i o n s may  u n s a f e f o r s t r u c t u r e s o f any  probable f a i l u r e  sheds.  bonded  local  failure.  proposal  repose  slope  strength  u n u s a l l y wet  s u f f i c i e n t l y to  b a s e d on  region  be  forms a  large scale f a i l u r e s  However, s i n c e t h e  saturations during  cliff  may  area  (trending approximately  indicated that  s a t u r a t i o n ) drops t o n e a r l y the  A  Slope f a i l u r e s  study  120°).  A simple  field  detail  small safe  in the  this storage for surrounding  Naturally, certain  areas.  decrease of  Control soil  of  runoff  strength  and  w i t h w e t t i n g , as w e l l such  a s t h e one  s l o p e s by  roads  formed and  as t o p r e v e n t in the  extending  t h e b a s e o f t h e s l o p e s must be  field  the  formation of  seepage t e s t .  property  limits  prohibited  by  "liquified  pipes"  U n d e r c u t t i n g of removal  or s t r i c t l y  of s o i l  controlled.  the  from  APPENDICES  APPENDIX  1 :  SAMPLING S I T E S AND  SAMPLE  DESCRIPTIONS  APPENDIX 2 :  SAMPLE TRIMMING  PROCEDURES  APPENDIX 3 :  C O M P R E S S I B I L I T Y CORRECTIONS OF THE APPARATUS  APPENDIX 4 :  CONSOLIDATION  TESTING OF  COLLUVIUM  CONSOLIDATION  APPENDIX 1  SAMPLING S I T E S AND  SAMPLE  DESCRIPTIONS  APPENDIX 1  SAMPLING S I T E S AND  A.  G I a c i o - I a c u s t r i n e Samples  Site  #\: One  b l o c k s a m p l e was  running  parallel  t o the  Reserve boundary. was  consequently  silt  had  shinny  used  The  the  base of t h e  S o u t h Thompson R i v e r n e a r t h e n e a r s u r f a c e s a m p l e was  silt  bluff  Eastern  transported  of coarse  and lying  medium s i l t  sized particles  approximately  (0.1mm was  1mm)  placed  parallel reflected  by  and  The with lam-  the  sample.  in water, rapid s l a k i n g occured breakdown o f t h e  Indian  t o the  dark patches t h roughout the  by t h e  face  unwaxed  f o r s p e c i f i c g r a v i t y measurements o n l y .  laminations, followed  cohesionless  from the  s a m p l e showed s i g n s o f w e a t h e r i n g ,  small  When t h e  parallel  sample t o a  mass.  #2: A small  b l o c k s a m p l e was  Magazine G u l l y beside for  obtained  f l a k e s ( p o s s i b l y mica)  presence of  Site  This  laminations  inations.  to  SAMPLE DESCRIPTIONS  specific  testing The  a recent  obtained silt  gravity determinations  to acess the sample  from t h e  fall. and  The  Western b l u f f  unwaxed s a m p l e was  used  preliminary consolidation  a p p a r a t u s r e q u i r e m e n t s s u c h as  i s a medium f i n e s i l t  of  exhibiting  the  load c e l l same  capacity.  weathering  105.  patterns  as  submerged  S I T E #3  s a m p l e b l o c k #1,  in water, s l a k i n g  &  Magazine G u l l y \{  feet.  ( f i g . 12).  f e e t t h i c k and  fractures.  likely  #4,  both s i t e s ,  site  the  #3,  continuous  this  beside  loess  cover  from a depth of  A{  knife, following  consisted  f r e e of  was  lacustrine  also existed  of  was to  5{  existing  discontinuous  by  laboratory samples.  and by  bottom). the  the  distinct  #3,  the  backhoe.  As  a  At  field  10.  are  backhoe.  This  silt  consequence,  #3.  a 3/4"  This nearly  thick  s i t e #4,  silt. dessicated  horizontal  varved sequence which  sampled  The  figure  these  site  presence of  4 feet.  in the  of the  At  the  and  surface.  undisturbed gIacioIacustrine  deposits.  above the  existed  to obtain.  the  of  s t e r e o n e t of  action  from s i t e  are  part  s a m p l e s were marked (top  surfaces  d i s t u r b a n c e by  confirmed  represents  in the  scrapping  seam a t a d e p t h o f  layer  orientation  trimmed  the  samples were o b t a i n e d  of the  thickness  in the  fracture  b l o c k samples o b t a i n e d  teristic  plotted  i n t a c t samples d i f f i c u l t  dark grey c l a y  All  w e r e n o t e d and  i n t a c t and  The  bench s u r f a c e  brown  a sharp  Jointing generally  t o d i s t u r b a n c e s by  made l a r g e  much o f  the  the  samples were o b t a i n e d  many u n w e a t h e r e d  due  remained  When  Many o f t h e s e p l a n e s showed a r u s t y - b r o w n w e a t h e r i n g  Joint orientations  At  At  S a m p l e s w e r e hand c a r v e d w i t h  site  laminations.  resulted.  b a c k h o e s a m p l e s i t e s on  j o i n t s where p o s s i b l e .  At  lacking v i s i b l e  #4:  S i t e s 3 & 4 are  1 -  but  a clay  is charac-  seam o f  1"  horizon. as  t o the  o r i e n t a t i o n was presence of  thin  site  number  further  and  confirmed .  laminations  in  the  106.  The  l i g h t buff  as t h e s i l t silt  block  colored  samples e x h i b i t e d s i m i l a r weathering  from s i t e  was s u b m e r g e d  #1.  i n water.  R a p i d s l a k i n g was a l s o o b s e r v e d when t h e  When t h e s i l t  0.5M H C I , t h e s a m p l e e f f e r v e s c e d  was w e t t e d w i t h  and l e f t a c r a t e r l i k e  H o w e v e r , a d r o p o f 0.01M HCI p r o d u c e d no o b s e r v a b l e  B.  Colluvial  Samples  Two c o l l u v i a l  (sites  block  samples were s u p p l i e d  Branch o f t h e Department o f Highways  the  t o the preliminary  laboratory  characteristics of the colluvium. waxed b l o c k s .  a drop o f  pitted  surface.  reaction.  #5 & #6)  Materials study  patches  by t h e G e o t e c h n i c a l  and  i n Kamloops t o e x t e n d  investigation of the consolidation  B o t h s a m p l e s a r r i v e d a t U.B.C. a s  D e s c r i p t i o n s o f t h e sample  l o c a t i o n s were  included.  S I T E #5: Site  #5 was d e s c r i b e d  a s " t h e s i d e o f an i n c i s e d c r e e k a t t h e b o t t o m  of Magazine G u l l y , 5 f e e t south The  colluvial  r o o t s and r o o t intact The  The silt  holes  with  (light  buff  s a m p l e was d e f i n i t e l y  When p l a c e d  strength, although  3 & 4.  abundant  I r r e g u l a r fragments o f  from  1mm t o 2 cm a c r o s s  and f o r m e d  material. weaker  in strength  No l a m i n a t i o n s  than t h e l a c u s t r i n e  were v i s i b l e  i n w a t e r , t h e sample s l o w l y  the roots  with  color) are scattered within the block.  ranged  the matrix  samples o f s i t e s  sample.  with  t h r o u g h o u t t h e sample.  of lacustrine s i l t  sharp contacts  l i n e B".  s a m p l e was a medium b r o w n i s h - g r e y s i l t  lacustrine s i l t  pieces  of p r o f i l e  lost  its  h e l d t h e m a i n mass t o g e t h e r .  a d r o p o f 0.5M H C I , t h e s a m p l e e x h i b i t e d t h e same  in the cohesive When w e t t e d  effervescent  107.  c h a r a c t e r i s t i c s as t h e l a c u s t r i n e s i l t  SITE  slightly  more  vigor.  #6: This c o l l u v i a l  of  w i t h perhaps  a 1 f t . diameter  s a m p l e was d e s c r i b e d a s b e i n g t a k e n p i p e n e a r an a s h l a y e r by t h e f o r k  from t h e w a l l i n t h e road  within  Magaz i ne GuI I y . The  medium-fine s i l t  had a medium b r o w n i s h - g r e y  f l e c k s o f w h i t e powder ( a s h ? ) . the  lacustrine s i l t  previous c o l l u v i a l w i t h i n t h e sample.  The s t r e n g t h i s a l s o much w e a k e r t h a n  and c o n t a i n e d sample.  c o l o r and c o n t a i n e d  less  r o o t s and r o o t h o l e s t h a n t h e  No f r a g m e n t s  When s u b m e r g e d  of lacustrine s i l t  i n water o r wetted  was  w i t h 0.5M  t h e r e a c t i o n s were s i m i l a r t o t h a t o f t h e sample from s i t e  #5.  present HCI,  APPENDIX 2  SAMPLE TRIMMING  PROCEDURE  109.  APPENDIX 2  SAMPLE TRIMMING PROCEDURE  A.  Triaxial The  by  Sample Trimming  final  1.4'  cylindrical  in diameter.  Due  triaxial to the  time-consumming t r i m m i n g of the To  obtain  a triaxial  into smaller cut  at  l e a s t 2"  ensure minimal with The  frame  w i d e s e t 30"  The  procedure.  a sharp  laminations To  obtain  final  sample.  block  sample. blade  The  required  be  usually  in order  to  inch).  tends to is then  in the  visible  is slightly  saw  cause  further trimming  under more  a k n i f e tends t o cause chipping  obtained.  cut  teeth t o the  becomes d i s t i n c t l y  motions of a t h i n w i r e  s q u a r e edges can  are  sample diameter  c o r r e c t sample height  chipping.  is cut  block  the  p r o b l e m and  careful,  main b l o c k  rigidity  e n d s by  Slow s c r a p p i n g  blocks  (10  small  high  i s u n w r a p p e d and  The  s i n c e f i n e trimming of the edges.  silt,  sample dimensions  S w e d i s h saw  silt  of the  3'  i s mandatory t o prevent  i t s a d d e d w e i g h t and  of the  approximately  These s m a l l e r  final  k n i f e to the  the  nature  waxed s i l t  of the  f r a c t u r i n g of the  trimmed w i t h box.  disturbacnce  i s removed s i n c e  occassional  sample  sections.  larger than the  a flexible,  brittle  sample, the  rectangular  samples are  this  difficult at  does e l i m i n a t e  this  1 10.  B.  Sample Trimming P r o c e d u r e o f C o n s o l i d a t i o n The  to  silt  within  ring. silt  b l o c k i s trimmed  dimension, taking  had  ring  edge i s trimmed  The c o n s o l i d a t i o n  immediately beneath  t o be v e r y n e a r t h a t o f t h e c o n s o l i d a t i o n  the b r i t t l e  silt  which  when t r i a l  samples where  ring  would  result  Even when much c a r e  minimal  due t o b r i t t l e  fracturing.  sample volume.  ring's  ring  ring  i s then  the ring's The s a m p l e  size  inside diameter  before  i n v o i d s between t h e r i n g and i s taken t o ensure minimal c h i p p i n g ,  immediately extruded  from t h e r i n g  between t h e r i n g  The l o s t  and t h e volume o f t h e sample  the total  The  i n t o t h e sample t o prevent c h i p p i n g  i n s p e c t i o n , t h e r a r e v o i d may e x i s t  itself  apparatus  t o nearly the exact  t o almost t h e exact ring s i z e .  itself.  of  i s f u r t h e r shaven  1/8" a t a t i m e w h i l e t h e a r e a  t h e sample  for  in the trimming  p l a c e d on t o p o f t h e s a m p l e .  care not t o o v e r t r i m .  advancing t h e c o n s o l i d a t i o n of  i s then  o u t s i d e t h e contact area  cutting  knife  1/16 t o 1/8 i n c h e s o f t h e i n s i d e d i a m e t e r o f t h e c o n s o l i d a t i o n  The s h a r p e d g e d  pushed  with a sharp  Samples  lost  in soil  after  trimming  and t h e s a m p l e  was h o w e v e r v e r y  represented  less than  \%  APPENDIX 3  APPARATUS COMPRESS I B I L T Y CORRECTIONS FOR CONSOLIDATION TESTS  112.  APPENDIX 3  APPARATUS COMPRESS IBITY CORRECTIONS  The ficant  compression  of the c o n s o l i d a t i o n apparatus contributed  p e r c e n t a g e o f t h e measured c o m p r e s s i o n  a p p l i c a b l e , t h e apparatus compression loading warps  A.  FOR CONSOLIDATION TESTS  rod, loading  i n t h e porous  Correction  cell  or seating  problems  associated  Curve  the consolidation  compressibIity  r i n g mounted  slight  of the compression  correction  d e f o r m a t i o n o f t h e 1/8" d i a m e t e r by 8"  rod  and t h e d e f o r m a t i o n o f t h e b e r y l l i u m c o p p e r i s a t t r i b u t e d t o improper  l i n e a r through t h e o r i g i n .  seating  of the apparatus  inside the t r i a x i a l  the  B.  with  A ( f i g . 44)  majority  tests  Where  i s t h e r e s u l t o f d e f o r m a t i o n o f the.  The  strain  signi-  stones e t c .  T h i s curve a p p l i e s t o t h e system setup with  o f t h e sample.  a  cell.  i s due t o t h e c o m b i n a t i o n o f long, s t a i n l e s s s t e e l diaphragm  loading  load c e l l .  Little  since the c o r r e c t i o n curve i s  This c o r r e c t i o n curve applies t o c o n s o l i d a t i o n  3.22, 3 . 3 3 , 3 . 4 1 , 3.42, 3.43, 3.44, 3.45 and 3 . 5 1 .  Correction The  Curve  B ( f i g . 45)  c o r r e c t i o n c u r v e o f f i g u r e 48 a p p l i e s t o t e s t 3.67 o n l y  a more d i r e c t l o a d i n g and t r i a x i a l seating  cell.  problems.  w a r p was n o t i c e d  s e t u p was u s e d w h i c h  excluded t h e loading rod  The l a r g e s t r a i n s r e q u i r e d When t h e p o r o u s  i n t h e t o p porous  since  f o r load b u i l d u p  indicates  s t o n e s were examined c l o s e l y , a stone.  slight  113.  C.  C o r r e c t i o n Curve C The  extension  layout which correction  ( f i g . 46)  of t h i s  study  include colluvium  i s s i m i l a r t o t h a t of the  a p p a r a t u s used  curve B except that a d i f f e r e n t  t h i s s e t of equipment, a s l i g h t and  unloading.  was  applied.  correction  to  When a p p l y i n g The  curve.  data  of  load c e l l  h y s t e r e s i s was  the  required  and  5.11  third  in developing was  used.  m e a s u r e d when  c o r r e c t i o n s , only the  s a m p l e s 5.10  a  With  loading  loading  were a d j u s t e d  the  by  curve this  114.  1 15.  N  116.  »  APPENDIX 4  CONSOLIDATION TESTS ON COLLUVIUM  1 18.  APPENDIX 4  CONSOLIDATION TESTS ON COLLUVIUM  From t h e hand s p e c i m e n s , is not uniform  i t i s r e a d i l y evident  from one l o c a t i o n t o t h e next  L a b o r a t o r y t e s t s o f t h e two c o l l u v i a l differences  that the colluvium  (see appendix 1).  samples a l s o  results ins i g n i f i c a n t  of properties:  S i t e #5 specific  (G)  2.60  2.78  water content  (w$)  6.9$  9.2$  void  (e ) o  1.07  1.35  The It  gravity  S i t e #6  ratio  consolidation  curves  f o rthe colluvium  i s a p p a r e n t t h a t t h e "maximum  lower than t h a t  f o rthe intact  large settlements  past pressures"  lacustrine s i l t .  e v e n a t low l o a d s .  i t was n o t c o n f i r m e d w h e t h e r t h e s o i l  or  However, under even s m a l l  o c c u r and w i l l  present engineering  f o r colluvium Flooding  i n f i g u r e 47. a r e much  by w a t e r  causes  S i n c e t h e t e s t i n g p r o g r a m was  limited, not.  are presented  pressures,  was t r u l y c o l l a p s i b l e collapse  difficulties.  on w e t t i n g  does  REFERENCES  A b e l e v , Y.M., 1975. 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