UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

An evaluation of the full displacement pressuremeter O’Neill, Bruce Ernest 1985

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-UBC_1985_A7 O54.pdf [ 3.95MB ]
Metadata
JSON: 831-1.0062643.json
JSON-LD: 831-1.0062643-ld.json
RDF/XML (Pretty): 831-1.0062643-rdf.xml
RDF/JSON: 831-1.0062643-rdf.json
Turtle: 831-1.0062643-turtle.txt
N-Triples: 831-1.0062643-rdf-ntriples.txt
Original Record: 831-1.0062643-source.json
Full Text
831-1.0062643-fulltext.txt
Citation
831-1.0062643.ris

Full Text

AN EVALUATION OF THE FULL DISPLACEMENT PRESSUREMETER  by  BRUCE O'NEILL BASC, The U n i v e r s i t y o f B r i t i s h C o l u m b i a , 1982  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE  in  THE FACULTY OF GRADUATE STUDIES DEPARTMENT OF CIVIL ENGINEERING  We a c c e p t t h i s t h e s i s as conforming t o the r e q u i r e d s t a n d a r d  THE UNIVERSITY OF BRITISH COLUMBIA July,  ©  1985  Bruce O ' N e i l l ,  1985  In  p r e s e n t i n g  r e q u i r e m e n t s o f  B r i t i s h  i t  f r e e l y  a g r e e f o r  t h i s f o r  a n  I  a v a i l a b l e  t h a t  u n d e r s t o o d  t h a t  f i n a n c i a l  b y  h i s  t h a t  e x t e n s i v e  may  o r  c o p y i n g  g a i n  d e g r e e  r e f e r e n c e  f o r  p u r p o s e s  o r  p a r t i a l  a g r e e  f o r  p e r m i s s i o n  d e p a r t m e n t  i n  a d v a n c e d  C o l u m b i a ,  s c h o l a r l y  f o r  t h e s i s  b e  h e r o r  s h a l l  The  U n i v e r s i t y  1956  Main  b e  Canada  1Y3  Date  C3/81-)  B r i t i s h  JUNE 20,  1985  t h e  U n i v e r s i t y  L i b r a r y  s h a l l  a n d  s t u d y .  I  c o p y i n g by  a l l o w e d  C o l u m b i a  o f  t h e  p u b l i c a t i o n  CIVIL ENGINEERING o f  t h e  t h e  o f  o f  make  f u r t h e r t h i s  h e a d  r e p r e s e n t a t i v e s .  n o t  Mall  V a n c o u v e r , V6T  DE-6  o f  a t  g r a n t e d  p e r m i s s i o n .  Department  f u l f i l m e n t  I t  t h i s  w i t h o u t  t h e s i s  o f  my  i s t h e s i s my  w r i t t e n  ABSTRACT  The s e l f - b o r i n g pressuremeter which i s i n s e r t e d i n t o the ground without  d i s t u r b i n g the surrounding s o i l  operators  are  needed t o i n s e r t the probe i n t o the  d i s t u r b i n g the s o i l , action  or  a  simplifying  has two drawbacks. ground  Skilled without  and the s e l f - b o r i n g p r o c e s s r e q u i r e s a j e t t i n g  rotating  c u t t e r and  drilling  mud.  One  method  the pressuremeter i n s t a l l a t i o n procedure i s t o displacement manner.  A solid tip  of  install  the  probe i n a f u l l  i s placed  the  end o f the probe and then the pressuremeter i s pushed i n t o  oh the  ground i n t h e same manner as a cone penetrometer.  This of  research p r o j e c t was performed to examine the  u s i n g the f u l l  modulus,  suitability  displacement p r e s s u r e m e t e r f o r d e t e r m i n i n g  i n s i t u horizontal  stresses,  The v a r i a b l e s examined were;  shear  and undrained shear s t r e n g t h .  the type o f p r e s s u r e m e t e r , whether the  pressuremeter was run i n a s t r e s s or a s t r a i n c o n t r o l l e d manner, size  of the t i p pushed i n f r o n t o f t h e p r e s s u r e m e t e r ,  and  whether  time was allowed f o r the dynamic pore p r e s s u r e s to d i s s i p a t e . were conducted i n sand, s i l t ,  When  the  shear  Tests  and c l a y .  moduli measured w i t h  the  full  displacement  pressuremeter were a d j u s t e d t o account f o r the d i f f e r e n c e s i n level,  and  mean e f f e c t i v e  the  strain  s t r e s s they compared very well w i t h  the  dynamic shear moduli measured with t h e s e i s m i c c o n e . The attempts determine pressure determined  the  insitu  horizontal  were u n s u c c e s s f u l . using  s t r e s s by examining  the  liftoff  The u n d r a i n e d shear s t r e n g t h s of  c a v i t y expansion t h e o r y compared very  u n d r a i n e d shear s t r e n g t h s determined u s i n g the f i e l d vane.  ii  to  well  clay with  TABLE OF CONTENTS  Page Abstract  H  L i s t of F i g u r e s  v  Acknowledgement  viii  C h a p t e r 1.  Introduction  1.1  History  1.2  Thesis Outline  C h a p t e r 2.  1  o f the P r e s s u r e m e t e r  1 3  Parameter I n t e r p r e t a t i o n  4  2.1  Parameters determined w i t h the p r e s s u r e m e t e r  4  2.2  Shear Modulus  5  2.3 Undrained Shear S t r e n g t h 2.4 I n s i t u H o r i z o n t a l S t r e s s Chapter 3. Equipment and T e s t P r o c e d u r e s 3.1 3.2  Introduction R o c t e s t Pencel 3 . 2 . 1 D e s c r i p t i o n of the Pencel Probe 3 . 2 . 2 T e s t Procedure and D a t a A c q u i s t i o n 3.2.2.1 Stress Controlled Test 3 . 2 . 2 . 2 C a l i b r a t i o n s f o r the S t r e s s Controlled Test 3.2.2.3 Strain Controlled Test 3 . 2 . 2 . 4 C a l i b r a t i o n s f o r the S t r a i n Controlled Test 3.3 Hughes P r e s s u r e m e t e r 3 . 3 . 1 D e s c r i p t i o n of the Hughes P r e s s u r e m e t e r 3 . 3 . 2 T e s t Procedure and D a t a A c q u i s i t i o n 3.3.2.1 Stress Controlled Test 3 . 3 . 2 . 2 C a l i b r a t i o n s f o r the S t r e s s Controlled Test 3.3.2.3 Strain Controlled Test 3 . 3 . 2 . 4 C a l i b r a t i o n s f o r the S t r a i n Controlled Test  ill  9 15 17 17 17 18 22 22 28 35 38 40 40 42 43 43 47 54  Page Chapter 4. 4.1  F i e l d Program  55  Introduction  55  4.2  Langley 4.2.1 Site Description 4.2.2 Results 4 . 2 . 2 . 1 Shear Modulus 4.2.2.2 Horizontal Stress 4 . 2 . 2 . 3 Undrained Shear S t r e n g t h 4 . 3 Boundary Road 4.3.1 Site Description 4.3.2 Results 4 . 3 . 2 . 1 Shear Modulus 4.3.2.2 Horizontal Stress 4 . 4 McDonalds Farm 4.4.1 Site Description 4.4.2 Results 4 . 4 . 2 . 1 Shear Modulus 4.4.2.2 Horizontal Stress  C h a p t e r 5.  Conclusions  57 57 57 60 67 71 76 78 78 82 86 89 89 92 95 99 106  5.1 Summary 5.2 Shear Modulus 5.3 I n s i t u H o r i z o n t a l S t r e s s 5.4 Undrained Shear S t r e n g t h 5.5 Recommendations f o r F u r t h e r Research References  106 106 107 108 108 109  iv  LIST OF FIGURES  F i g u r e No. 2.1  Ti t i e  Page  Summary o f S t r e s s Paths And P r e s s u r e Expansion Curves as a F u n c t i o n o f P r e s s u r e m e t e r I n s t a l l a t i o n  7  2.2  Shear Modulus A t t e n u a t i o n Curves  10  2.3  Determining Undrained Shear S t r e n g t h from the P r e s s u r e m e t e r Curve  12  2.4  Determining Undrained Shear S t r e n g t h  from the  P r e s s u r e vs Log V o l u m e t r i c S t r a i n P l o t  14  3.1  Pencel Probe  19  3.2  M o d i f i e d Menard G-Am C o n t r o l  3.3  P e n c e l : Curves determined w i t h v a r i o u s  Box  23 initial  volumes  26  P e n c e l : Type o f c u r v e g e n e r a t e d by a s t r e s s controlled test  27  3.5  Pencel Membrane C a l i b r a t i o n :  30  3.6  Pencel Membrane C a l i b r a t i o n : E f f e c t the time increment  of  Pencel Membrane C a l i b r a t i o n : E f f e c t  of  3.4  3.7  Effect  of c y c l i n g varying  31 varying  the s i z e o f the p r e s s u r e increment  33  3.8  S t r a i n Control  37  3.9  Pencel Membrane C a l i b r a t i o n : E f f e c t  Device of  varying  the s t r a i n r a t e  39  3.10  Hughes P r e s s u r e m e t e r ( HPM )  41  3.11  HPM C o n t r o l  44  3.12  HPM Membrane C a l i b r a t i o n Curve  3.13  HPM: Comparison o f p r e s s u r e r e a d i n g a t  3.14  s u r f a c e and a t the probe HPM: Comparison of v o l u m e t r i c s t r a i n c i r c u m f e r e n t i a l s t r a i n measurements  Box  v  46 the 49 and 51  F i g u r e No. 3.15  Ti t i e  Page  HPM: Comparison of c u r v e s g e n e r a t e d w i t h v o l u m e t r i c s t r a i n and those g e n e r a t e d w i t h circumferential strain  53  4.1  S i t e L o c a t i o n Map  56  4.2  Langley cone p r o f i l e  58  4.3  I n s i t u t e s t s conducted a t Langley  59  4.4  Pencel: Typical  61  4.5  Comparison of Pencel  Curves a t Langley c u r v e s w i t h HPM c u r v e s :  Langley  62  4.6  Profile  of Shear Modulus a t L a n g l e y : Pencel  63  4.7  Profile  of Shear Modulus a t L a n g l e y :  65  4.8  Profile  of Measured H o r i z o n t a l  4.9  A t L a n g l e y : Pencel P r o f i l e of Measured H o r i z o n t a l A t L a n g l e y : HPM  4.10  4.11  4.12  4.13  HPM  Effective  Stress 68  Effective  Stress 70  P r o f i l e of Undrained Shear S t r e n g t h from the Pencel Curves  Determined  P r o f i l e of Undrained Shear S t r e n g t h from the HPM Curves  Determined  72  74  P r o f i l e of Undrained Shear S t r e n g t h Determined from the P - Log S t r a i n P l o t : Pencel Profile  of Undrained Shear S t r e n g t h  from the P - Log S t r a i n P l o t :  75  Determined  HPM  77  4.14  Boundary Road Cone P r o f i l e  79  4.15  I n s i t u T e s t s conducted a t Boundary Road  80  4.16  Pencel: Typical  81  4.17  Comparison o f Pencel C u r v e s w i t h HPM C u r v e s :  Curves a t Boundary Road  Boundary Road  83  vi  F i g u r e No. 4.18  4.19  4.20  Ti t i e  Page  P r o f i l e of Shear Modulus a t Boundary Pencel and HPM  Road  P r o f i l e of Measured H o r i z o n t a l A t Boundary Road: Pencel  Effective  Profile  Effective  of Measured H o r i z o n t a l  85 Stress 87 Stress  A t Boundary Road: HPM  88  4.21  McDonalds Farm cone p r o f i l e  90  4.22  I n s i t u t e s t conducted a t McDonalds Farm  91  4.23  Pencel: Typical  93  4.24  Comparison o f Pencel c u r v e s and HPM c u r v e s :  4.25  McDonal ds Farm P r o f i l e o f N o r m a l i z e d Shear Modulus a t McDonalds Farm: Pencel  4.26  4.27  4.28  4.29  4.30  4.31  Curves a t McDonalds Farm  94 96  P r o f i l e of N o r m a l i z e d Shear Modulus a t McDonalds Farm: S t r e s s C o n t r o l l e d HPM  97  P r o f i l e of N o r m a l i z e d Shear Modulus a t McDonalds Farm: S t r a i n C o n t r o l l e d HPM  98  P r o f i l e of Measured H o r i z o n t a l E f f e c t i v e S t r e s s A t McDonalds Farm: S t r a i n C o n t r o l l e d P e n c e l  101  P r o f i l e of Measured H o r i z o n t a l E f f e c t i v e S t r e s s A t McDonalds Farm: S t r e s s C o n t r o l l e d P e n c e l  102  P r o f i l e of Measured H o r i z o n t a l E f f e c t i v e S t r e s s A t McDonalds Farm: S t r e s s C o n t r o l l e d HPM  103  P r o f i l e of Measured H o r i z o n t a l E f f e c t i v e S t r e s s A t McDonalds Farm: S t r a i n C o n t r o l l e d HPM  104  vii  ACKNOWLEDGEMENT  I  would  and D r . technical  R.G.  l i k e t o thank  P.K.  Robertson,  C a m p a n e l l a , my c o l l e a g u e s and the C i v i l  Engineering  staff  for their  The f i n a n c i a l Research C o u n c i l  my  advisors,  research  project.  S c i e n c e s and E n g i n e e r i n g  o f Canada i s a l s o g r a t e f u l l y  is  Dr.  assistance with t h i s  support o f the N a t u r a l  This presentation all  my  acknowledged.  d e d i c a t e d t o my w i f e Sue, my f a m i l y ,  and  f r i e n d s who p r o v i d e d u n s t i n t i n g s u p p o r t when I needed  it  most.  viii  Chapter  1.  Introduction  1.1  The  H i s t o r y o f the Pressuremeter  self-boring  pressuremeter  was developed i n  the  early  1970's as a method of i n s e r t i n g t h e pressuremeter i n t o the w i t h o u t d i s t u r b i n g the s u r r o u n d i n g s o i l . advantages  over  the t r a d i t i o n a l  ground  T h i s p r e s e n t e d two major  Menard-type  pressuremeter;  t e s t s were conducted on u n d i s t u r b e d s o i l s ,  and the a n a l y s i s  be c a r r i e d out u s i n g fundamental  developed w i t h  principles  the could  cavity  expansion t h e o r y .  The  self-boring  pressuremeter has  two  drawbacks;  skilled  are needed t o i n s e r t t h e probe i n t o the ground  without  • operators disturbing jetting  the  action  complicated if  soil,  and  or  rotating  a  the s e l f - b o r i n g cutter  process  and  drilling  i n s t a l l a t i o n procedure i s o f p a r t i c u l a r  t h e t e s t i s t o be conducted a t c o n s i d e r a b l e depth  Reid  et  pressuremeter  al, (  PIP  1982  developed  )  one  as  an  to  The PIP was designed to be pushed a s h o r t  into  the h o l l o w core of t h e i n s t r u m e n t .  push-in  overcome  pressuremeter.  ground with s o i l  The  offshore.  problems  the  a  significance  installation  into  with  mud.  open-ended  alternative  associated  requires  the  the  self-boring  p a s s i n g through the c u t t i n g The d i s t u r b a n c e  distance shoe can  and be  minimized somewhat with an a p p r o p r i a t e c u t t i n g shoe d e s i g n but the instrument  is  a  thick  walled  tube  1  and  some  disturbance  is  inevitable. withdrawn  One  advantage  of t h i s  probe  is  a f t e r each t e s t and the sample o b t a i n e d i n the c o r e  of  the i n s t r u m e n t can be examined.  design i s  t h a t the  The c o r r e s p o n d i n g d i s a d v a n t a g e  t h a t the i n s t r u m e n t must be withdrawn a f t e r each t e s t to a l l o w soil  the  i n the c o r e to be removed.  The step  Full  Displacement P r e s s u r e m e t e r ( FDPM ) i s  a  further  i n the p r o c e s s o f s i m p l i f y i n g the i n s t a l l a t i o n p r o c e d u r e .  solid  tip  pushed  i s p l a c e d on the end o f the probe and the FDPM i s  A  then  i n t o the ground i n the same manner as a cone p e n e t r o m e t e r .  The s o i l  around the probe i s  Robertson,  to s o i l  fully  disturbed.  However r e s e a r c h by  1982 w i t h the s e l f - b o r i n g p r e s s u r e m e t e r ( SBPM ) showed  t h a t the moduli  d e r i v e d from u n l o a d - r e l o a d c y c l e s were  disturbance.  T h i s has i m p o r t a n t  implications  insensitive  if  the major  parameter t h a t i s  to be d e r i v e d from the p r e s s u r e m e t e r t e s t i s  soil  The  stiffness.  piezometer-friction  FDPM c o u l d be combined w i t h  be stopped a t r e g u l a r i n t e r v a l s  cone  The p e n e t r a t i o n  could  interest  The a d d i t i o n of good  to be developed f o r o b t a i n i n g s o i l  the cone p e n e t r a t i o n  This  The  measurements from the p r e s s u r e m e t e r would a l l o w  correlations  the  electronic  or i n layers of s p e c i f i c  p r e s s u r e m e t e r t e s t s c o u l d be c o n d u c t e d .  stiffness  an  cone to form a cone p r e s s u r e m e t e r .  c o u l d p r o v i d e a c o n t i n u o u s l o g o f the s o i l .  and  is  parameters  better from  test.  research p r o j e c t continues  p r e v i o u s work conducted w i t h  the FDPM i n sand by Hughes and R o b e r t s o n ,  2  1984.  1.2  Chapter  2  lists  the s o i l  w i t h the p r e s s u r e m e t e r . are discussed i n  Chapter project.  describes  the equipment used i n  attention  4  this  i s g i v e n to the  p r e s e n t s the r e s u l t s o f the t e s t s  research acquistion  calibrations  undrained  at  the  The p r e s s u r e m e t e r c u r v e s are examined,  are compared w i t h r e s u l t s  from the UBC s e i s m i c  three  the cone,  shear s t r e n g t h i s compared w i t h r e s u l t s from the  and  vertical  estimated parameters  t e s t procedures and the methods o f data  research s i t e s .  vane,  be  required.  Chapter  moduli  parameters t h a t can  The methods o f d e r i v i n g these  are e x p l a i n e d . C o n s i d e r a b l e t h a t are  Outline  detail.  3  The  Thesis  the  measured  effective  Chapter  horizontal  stress is  compared  shear the field  to  the  stress.  5 p r e s e n t s the c o n c l u s i o n s  r e s e a r c h and p r e s e n t s recommendations  3  t h a t were drawn from t h i s  for further  research.  Chapter 2 Parameter  2.1  Interpretation  Parameters determined with the pressuremeter  There i s a long l i s t  of s o i l  parameters t h a t can be  measured  with the pressuremeter. They i n c l u d e the undrained shear s t r e n g t h , the  angle  of i n t e r n a l  horizontal  stress,  consolidation. attempts  friction, and  The  the shear modulus,  the  horizontal  the  insitu  coefficient  of  s t r e s s s t r a i n curve can a l s o be d e r i v e d ,  have been made to use pressuremeter data t o  the s u s c e p t i b i l i t y o f a s o i l  investigate  t o l i q u e f a c t i o n . Pressuremeter c u r v e s  can a l s o be m o d i f i e d to g i v e p r e s s u r e - d i s p l a c e m e n t c u r v e s f o r i n a beam s p r i n g a n a l y s i s of l a t e r a l l y  This modulus  paper (G),  horizontal  use  loaded p i l e s .  be c o n f i n e d t o d e t e r m i n a t i o n o f  the u n d r a i n e d shear s t r e n g t h ( S u ) ,  the  and the  shear insitu  stress.  Research been  will  and  directed  with  the f u l l  at  the design  displacement pressuremeter has of  laterally  loaded  piles.  also The  development o f p r e s s u r e - d i s p l a c e m e n t c u r v e s from the pressuremeter curves  and  the comparison o f p r e d i c t i o n s with a c t u a l  r e s u l t s i s presented i n Robertson e t a l ,  Hughes and Robertson friction  could  pressuremeter  not using  pile  1985a.  , 1984 showed t h a t the a n g l e o f  be determined analysis  from  developed  4  test  the for  internal  full  displacement  the  self—boring  pressuremeter. an  empirical  full  T h i s does not however p r e c l u d e the development correlation.  displacement  good c o r r e l a t i o n s been  S i n c e the eventual  p r e s s u r e m e t e r w i t h a cone f o r the a n g l e of i n t e r n a l  developed i t  the  secant  moduli  positions stress.  already that  have  been  determined.  variety  When  the  of  Menard  i s b e i n g i n t e r p r e t e d a modulus c o r r e s p o n d i n g l i n e a r p o r t i o n of the  to  pressuremeter  With the s e l f - b o r i n g p r e s s u r e m e t e r a range  of  are sometimes measured a t s t r a i n s c o r r e s p o n d i n g  to  such  as 0.5 o f the l i m i t  F o r t h e s e moduli  determine  f r i c t i o n have  of the p r e s s u r e m e t e r a  the s l o p e o f the a p p r o x i m a t e l y c u r v e i s measured.  where  Shear Modulus  history  moduli  pressuremeter t e s t  penetrometer  the  time.  2.2  deformation  i s to p a i r  does not appear to be necessary t o f o l l o w  l i n e of research at t h i s  Throughout  goal  of  whether  p r e s s u r e o r 0.5 o f  t o be used i n d e s i g n , i t  they a r e a p p r o p r i a t e  is  to the s o i l  the  peak  necessary model  to  being  used.  Small  s t r a i n c a v i t y expansion theory  unloaded  and then r e l o a d e d ,  pressure  versus  elastic  t h a t has been well  ie.  2G.  s t r a i n p l o t would be The shear modulus i s  r e s e a r c h e d and can be used d i r e c t l y  In t h e i r 1984 p a p e r ,  the s o i l  is  the s l o p e o f the r e s u l t i n g l i n e on a  circumferential  s h e a r modulus,  says t h a t i f  Full  twice  the  a parameter in  design.  Displacement Pressuremeter T e s t i n g  5  i n Sand, Hughes and Robertson showed t h a t the method o f  installing  the  pressuremeter i n t o the ground s h o u l d not s i g n i f i c a n t l y  the  slope  of the u n i o a d - r e l o a d c y c l e  (see F i g u r e 2 . 1 ) .  alter  This  is  based on the assumption t h a t s o i l  t h a t i s unloaded beneath a y i e l d  surface w i l l  Wroth, 1982 shows t h a t t h e r e are  behave e l a s t i c a l l y .  l i m i t s on the s i z e of the uni o a d - r e l o a d loop w i t h i n which the can  be  expected  allowable  size  to be remain e l a s t i c . of the s t r e s s c y c l e  cohesionless s o i l ,  For a c l a y ,  i s 2 Su and,  the  maximum  a  drained  for  the maximum s i z e o f t h e s t r e s s c y c l e 2 s i n J2f  soil  is:  ,  1 + sin/5  the  0  i s t h e angle of i n t e r n a l  o  i s the e f f e c t i v e  radial  friction stress  J a n b u , 1963 e s t a b l i s h e d t h a t shear modulus i s p r o p o r t i o n a l  to  mean  is  effective  s t r e s s r a i s e d to the nth power,  t y p i c a l l y 0.5 f o r c o h e s i o n l e s s s o i l s . effective  where  n  T h i s means t h a t as the mean  s t r e s s i n c r e a s e s so does the measured shear modulus. G = Kg * Pa * (  <r£  / Pa  f  where: Kg = shear modulus number 67K = mean e f f e c t i v e Pa = r e f e r e n c e  stress  stress  A pressuremeter t e s t run i n a c l a y i s g e n e r a l l y c o n s i d e r e d to be u n d r a i n e d .  I f t h a t i s the c a s e , the t o t a l  6  stress i s  increasing  (a) Pre-Bored Pressuremeter Test (Me'nard)  Strain, €  6  (b) Self-Boring Pressuremeter Test  Strain, €g ( c) Full - displacement Pressuremeter Test  Strain, €  Q  Stress Path during Installation Stress Path during Pressure-Expansion Test Summary of S t r e s s Paths and P r e s s u r e Expansion Curves as a F u n c t i o n of P r e s s u r e m e t e r I n s t a l l a t i o n ( A f t e r Hughes and R o b e r t s o n , 1984 )  during  the  test,  approximately during  a  equal.  In  constant.  reality  occurs.  s t a g e s of the t e s t  a  ( PMT ) i n c l a y  measurements compared.  various  times  pressure  i n c l a y and  T h i s r e s u l t s i n the  be  gradients  some  drainage  effective  stress  c a u s i n g the shear moduli measured a t  later  initial  4.2.2.1).  constantly of  remaining  should t h e r e f o r e  PMT i n f r e e d r a i n i n g m a t e r i a l  rises  is  to be h i g h e r than those measured a t the  (see s e c t i o n  During  stress  Shear moduli measured a t  during a pressuremeter t e s t  certainly  stress  effective  t h e r e a r e very h i g h pore  r i s i n g d u r i n g the t e s t ,  stages  the  pressuremeter t e s t  generated almost  but  G  and  this  must  the  be  a t v a r i o u s times d u r i n g the  Robertson,  1982  mean  effective  accounted PMT  are  showed t h a t the mean e f f e c t i v e  for  if  to  be  stress  around a s e l f b o r i n g p r e s s u r e m e t e r i n sand c o u l d be e s t i m a t e d as a function full  around  a  d i s p l a c e m e n t p r e s s u r e m e t e r i n sand a r e much more d i f f i c u l t  to  estimate the  o f the e f f e c t i v e  probe.  the  As  s t r e s s e s caused by i n s e r t i o n  a comprehensive u n d e r s t a n d i n g o f  d i s p l a c e m e n t probe was l a c k i n g ,  where the mean e f f e c t i v e  times the e f f e c t i v e  base  The s t r e s s e s  it  the  order  radial  of  stresses  was d e c i d e d  same approximate approach developed f o r the  pressuremeter  In  stress.  because of the r e s i d u a l  around the f u l l use  radial  to  self-boring  s t r e s s i s taken to be  0.5  stress.  to compare the shear moduli  o r s t a n d a r d mean e f f e c t i v e  from PMT's i n  s t r e s s must be  established.  v a l u e s o f shear modulus are a l s o t o be compared t o those  8  sand  a The  obtained  from  the UBC s e i s m i c cone so 1t was d e c i d e d to n o r m a l i z e a l l  moduli the  to the i n s i t u mean e f f e c t i v e  stress  s t r e s s which  a t which s e i s m i c cone t e s t s  description  are  range d e s c r i b e d by Wroth, shear  modulus  F i g u r e 2.2 and  order  1982.  attenuates  presents typical for clay.  shear s t r a i n o r , Therefore  conducted.  p r e s e n t e d i n Robertson e t a l , A p r i l  The u n l o a d - r e l o a d l o o p s are not t r u l y  sand  approximately A  of the UBC s e i s m i c cone and the t e c h n i q u e of  seismic testing i s  the  1s  elastic  They e x h i b i t with  full  downhole  85.  even w i t h i n  the  some h y s t e r e s i s  and  increasing  shear  strain.  shear modulus a t t e n u a t i o n c u r v e s  The shear modulus d e c r e a s e s w i t h  for  increasing  i n the case of PMT, the u n l o a d - r e l o a d l o o p  the l o o p  the  size.  s i z e was s t a n d a r d i z e d as much as p o s s i b l e  to decrease the number of v a r i a b l e s .  2cm  and  5cnr  in  loops  3 predominated  the  tests  with  the  Pencel  predominated the t e s t s with the Hughes 2.3  There strength  are from  interpreted employed this  i n an e m p i r i c a l  { Su )  determining  pressuremeter t e s t s .  Undrained  manner o r by c a v i t y  in c o n j u n c t i o n with a s o i l model.  research p r o j e c t  cavity  approaches to  loops  pressuremeter.  Undrained Shear S t r e n g t h  two  p r o b e . /.5"cm  undrained strength expansion  shear can  theory  I t was the o b j e c t  to examine the p o s s i b i l i t y  of using  expansion t h e o r y methods to determine the u n d r a i n e d  be  of  present shear  strength.  Gibson  and  Anderson,  1961  modeled c l a y  9  as  an  elastic  /  c o CO  o  OJ  x:  ca> I .0 u \_ Q. I  co  _3  • D X)  o  o  0.8  g II  to  "5  Static Strains  Dynamic Strains  a V)  _3  0.6  Range of va lues for Sand — (After Seeci and Idris, I 9 7 C  0.4  3  TJ O  0.2  v_ O  0)  to  x: to  10- 4  >-2 10"'  I0""  3  10 - i  Shear Strain, y % ( a )  OI  6.2  CX3 04 (X5 (X6 SHEAR STRAIN T ,% ( b )  F i g u r e 2.2  Shear Modulus A t t e n u a t i o n Curves  10  07  0.8  perfectly Su.  p l a s t i c material  Several  which  other  1982 s t a t e s  pressuremeter  for  determining  more r e c e n t a n a l y s e s were p u b l i s h e d  a r e not r e s t r i c t e d t o t h i s  Wroth,  not  and d e r i v e d a method  that  in  1972  s t r e s s s t r a i n model o f the  soil.  from e x p e r i e n c e  gained w i t h the  the e x t r a s o p h i s t i c a t i o n o f the 1972  Cambridge  analyses  are  r e q u i r e d and t h a t f o r d e s i g n purposes the G i b s o n and Anderson  analysis  is  adequate f o r most c l a y s .  approach was used i n t h i s  research  The  Gibson  and  Anderson  project.  There are two methods o f d e t e r m i n i n g the Su t h a t come out the  Gibson  during full  and  Anderson a n a l y s i s .  this project  displacement  to see i f  Both methods  were  employed  e i t h e r o r both would work w i t h  the  the  pressuremeter.  The f i r s t method o f d e t e r m i n i n g the u n d r a i n e d shear uses  of  p r e s s u r e m e t e r curve d i r e c t l y .  a n a l y s i s l e a d s to the  The G i b s o n and  Anderson  equation: ( PI -  Su=  strength  Po )  — 1 + In ( G / Su )  As i s  demonstrated i n F i g u r e 2 . 3 ,  liftoff  pressure,  Po,  are  the l i m i t determined  p r e s s u r e , P I , and the directly  from  p r e s s u r e m e t e r c u r v e . Su can be determined from an i n i t i a l o f the s t i f f n e s s r a t i o ,  G / Su,  followed.  is  modulus  The  problem  ( Gmax ) ,  the  estimate  and t h e n an i t e r a t i v e p r o c e s s  then whether to use the dynamic  shear  a v a l u e o f G c o r r e s p o n d i n g t o the s t r a i n  level  at f a i l u r e ,  o r some o t h e r v a l u e f o r G. D u r i n g the a n a l y s i s i n  paper,  was d e c i d e d t o use a v a l u e of In ( G / Su ) = 6 . 5 .  it  is  11  this If  F i g u r e 2.3  D e t e r m i n i n g Undrained Shear S t r e n g t h from the P r e s s u r e E x p a n s i o n Curve  12  f o r example,  Gmax was used t o c a l c u l a t e the s t i f f n e s s r a t i o a t  depth of 8m a t L a n g l e y ,  the s t i f f n e s s  a  r a t i o would be:  In (Gmax / Su) = In (150 / 0.25)  = 6.4~6.5  Gmax i n the above example was determined w i t h the s e i s m i c cone and Su  was determined w i t h the f i e l d vane.  method PI.  I t can be seen t h a t  o f c a l c u l a t i n g Su depends h e a v i l y on the v a l u e of P o ,  Because of the l o g a r i t h m f u n c t i o n the v a l u e of the  ratio  is less  The using  and  Applied  volumetric failure  method o f d e t e r m i n i n g u n d r a i n e d  Gibson  Figure 2.4.  strain.  Anderson  the l i n e  approach  stiffness  analysis  is  shear  strength  demonstrated  in  p r e s s u r e i s p l o t t e d v e r s u s the l o g a r i t h m This  s h o u l d be a  has been reached and i f of  and  important.  second  the  slope  this  i s equal  linear  natural  to S u .  relationship  once  logarithms are used,  The prime advantage  i s t h a t no e s t i m a t e of the s t i f f n e s s  ratio  is  of  the  of  this  required,  nor do Po or PI need t o be measured. PI can sometimes be a problem to  measure  if  the t e s t  i s not c a r r i e d to a  high  enough  strain  level.  These  a n a l y s e s a r e based on the assumption t h a t the c l a y  u n d r a i n e d d u r i n g the p r e s s u r e m e t e r t e s t . i n s e c t i o n 2.2 test  and  As was a l r e a d y  mentioned  h i g h pore p r e s s u r e g r a d i e n t s a r e c r e a t e d d u r i n g the  some d r a i n a g e does o c c u r .  This w i l l  cause the c l a y  c o n s o l i d a t e and t h u s the u n d r a i n e d shear s t r e n g t h i n c r e a s e s . is from  one  o f the reasons why undrained shear  the PMT a r e g e n e r a l l y  conventional  is  tests  h i g h e r than those  ( see Wroth,  1984).  13  strengths  to This  determined  determined by  Some o f the o t h e r  other reasons  1  1  1—I—1—I s lope  3-  W < 03  UJ  or in  ui cc a.  1Converting  to n a t u r a l  Su = S l o p e  T  10  LANGLEY*  F i g u r e 2.4  T  T  logarithms  / 2.303  T  T  VOLUMETRIC STRAIN <X ) 3BMM TIP STRAIN CONTROLLED  T—i—r DEPTH 6M  D e t e r m i n i n g Undrained Shear S t r e n g t h from the P r e s s u r e vs Log V o l u m e t r i c . S t r a i n P l o t  14  100  are;  s t r a i n rate e f f e c t s  other conventional  ( PMT's a r e u s u a l l y  run much f a s t e r  than  t e s t s and many c o h e s i v e s o i l s have s t r a i n  rate  dependent  shear  strengths),  expansion  is  spherical  cavity expansion,  actually  assumed i n the  and the f a c t t h a t  somewhere between  a  a  pressuremeter  cylindrical  not a t r u l y c y l i n d r i c a l  analysis.  compared  Nilcon  to  field  u n d r a i n e d shear s t r e n g t h s  vane.  given in Greig,  A  insitu  pressuremeter  obtained  d e s c r i p t i o n of the N i l c o n  with  field  the  vane  is  1985.  2.4  The  a  e x p a n s i o n as  The undrained shear s t r e n g t h s d e r i v e d from the were  and  Insitu Horizontal  Stress  p r e s s u r e m e t e r p r e s e n t s the p o s s i b i l i t y horizontal  stress,  a  parameter  of measuring  required  for  the  detailed  computer a n a l y s i s . The s e l f - b o r i n g p r e s s u r e m e t e r which i s  supposed  to  tool  be i n s t a l l e d w i t h o u t  measuring the i n s i t u self-bored  into  disturbance. significant the  errors  probe i s  horizontal  the  In  d i s t u r b i n g the s o i l  this  disturbed,  path  followed  the  still  small can  horizontal  near a f u l l  ,  lead  to  s t r e s s . When  probe.  i s s u b j e c t e d t o very h i g h  i n s e r t a t i o n o f the p r o b e ,  15  of  1984 examined the displacement  the l a t e r a l  is  amount  d i s p l a c e m e n t manner the s o i l  Hughes and Robertson by the s o i l  a  disturbance  i n measuring the i n s i t u  s u g g e s t t h a t although the s o i l during  small  installed in a full  fully  for  s t r e s s . However, when the probe  ground t h e r e i s  sand  i s the i d e a l  is  stress They  stresses  stresses  then  relax  and r e t u r n to somewhere near the i n i t i a l  L a c a s s e and Lunne, determining tests. on  the l i f t o f f  pressure  membrane f i r s t the  system  judgment. yields than  p r e s s u r e from  self-boring  versus c i r c u m f e r e n t i a l  b e g i n s to move.  must  be  Lacasse  slightly the  best  sufficiently  strain  is  in  pressuremeter  determine the  An allowance  made and t h e r e  plot  point where  the  f o r the compliance  considerable  room  of for  and Lunne have shown t h a t t h i s method u s u a l l y  lower e s t i m a t e s of the i n s i t u estimates  pressuremeter.  stress.  1982 p o i n t out some o f the d i f f i c u l t i e s  The s i m p l e s t method i s to v i s u a l l y  the  lateral  Visual  horizontal  p r e d i c t e d by methods inspection  was  other  considered  a c c u r a t e e s t i m a t e of the l i f t o f f  stress  than to  be  pressure during  the a this  project.  One of.  o f the problems encountered when examining  insitu  horizontal  The l i f t o f f  p r e s s u r e r e p r e s e n t s the t o t a l  around the p r o b e . pressure the  The l i f t o f f  horizontal  effective  w i t h the v e r t i c a l  horizontal  effective  compared stress  pressure i s  pressure.  plotted  to.  acting  p r e s s u r e minus the e q u i l i b r i u m  ( Uo ) r e p r e s e n t s the e f f e c t i v e h o r i z o n t a l  measured  observed  s t r e s s i s what s h o u l d they be  measurements  pore If  together  s t r e s s the measured v a l u e o f Ko can be  directly.  16  Chapter 3 Equipment & T e s t Procedures  3.1  The into  two  the  Introduction  most common methods o f i n s e r t i n g the  ground a r e to s e l f - b o r e  pre-bored hole.  There i s ,  is  the probe i n  to  install  pressuremeter i s  it  however, a  pressuremeter  or to p l a c e the probe  the  full  displacement  f i t t e d w i t h a s o l i d cone t i p  equipment  used  in  displacement pressuremeter t e s t s , the  equipment,  this  manner.  Two types of t h i s  UBC  r e s e a r c h program.  during  is  and how d i f f e r e n t  chapter  the  prepare  obtained. procedures  They were: a) the R o c t e s t Pencel The p r e s s u r e m e t e r s were i n s t a l l e d described i n  Roctest  required to i n s t a l l  and b) using  detail  in  Pencel  probe has a d e f l a t e d diameter o f 32mm.  advantages o f t h i s  course  1981.  3.2  Pencel  full  be examined and d i s c u s s e d .  I n s i t u T e s t i n g v e h i c l e which i s  Campanella and R o b e r t s o n ,  The  This  of p r e s s u r e m e t e r probes were used d u r i n g the  the Hughes P r e s s u r e m e t e r . the  study  the type o f d a t a o b t a i n e d and how i t  The procedures used to run the t e s t s  The  and then pushed i n t o  the p r o c e d u r e s needed t o  and equipment a f f e c t the d a t a w i l l  a  an a l t e r n a t i v e method and t h a t  the ground i n the same manner as a cone p e n e t r o m e t e r . examines  in  The  small p r e s s u r e m e t e r are t h a t the p u s h i n g the probe i s  17  main force  reduced and t h a t the probe can be  p l a c e d behind an e l e c t r o n i c 10 sq.cm.  cone penetrometer.  e l e c t r o n i c cone has a diameter o f 36mm. Thus the Pencel  probe i s s m a l l e r than a s t a n d a r d e l e c t r o n i c  An the  However a standard  10 s q . cm. cone.  important a s p e c t o f t h i s r e s e a r c h p r o j e c t was t o  e f f e c t o f v a r y i n g the diameter o f the s o l i d t i p  the p r o b e . tip,  The a l t e r n a t i v e t o a 10 s q . cm. t i p  which  tip is  is  i s the same diameter as the p r o b e .  in  evaluate front  of  a 32mm diameter  The use of a 36mm  s i m i l a r to the s i t u a t i o n where t h e probe i s p l a c e i n a p r e -  bored hole and the s o i l  i s allowed t o  3 . 2 . 1 D e s c r i p t i o n of the Pencel  The  Pencel  probe  relax.  Probe  differs  from  previous  Roctest  p r e s s u r e m e t e r s , such as t h e Menard G-Am p r o b e , i n t h a t i t has only one c e l l  r a t h e r than t h r e e . The mono c e l l  approach i s the one t h a t  has been adopted with s e l f - b o r i n g p r e s s u r e m e t e r s .  The of  four  flexible 22mm  Pencel  pressuremeter u n i t shown i n F i g u r e 3.1  components;  the probe and  t u b i n g and a c o n t r o l  diameter  hollow s t e e l  unit.  fittings,  a  consisted  membrane,  The c o r e o f the probe was  c y l i n d e r with t h r e a d s on e i t h e r  Extending from e i t h e r end o f the probe was a s h o r t p i e c e of tubing.  The  piece of  steel  is  normally  process.  Each  flexible  piece  passageway i n the wall  a  end. steel  t u b i n g from the c o n t r o l box a t t a c h e s t o one  t u b i n g and the o t h e r p i e c e o f s t e e l sealed,  the  can of  be opened t o steel  in  the  t u b i n g was connected to  of t h e probe t h a t  18  aid  tubing,  which  saturation a  ran t o a p o i n t j u s t  small past  TO CONTROL UNIT  LOCK NUT  FLUID INLET  TAPERED METAL RING  RUBBER MEMBRANE COVERED BY STAINLESS STEEL STRIPS CORE  F i g u r e 3.1  P e n c e l Probe  19  the  retaining l i p .  The two r e t a i n i n g l i p s were c e n t e r e d  probe and were 390mm a p a r t . retaining lock  on  the  The membrane was s e a l e d a g a i n s t these  l i p s by t a p e r e d metal  r i n g s which were h e l d i n p l a c e by  nuts.  The  membrane  was a 2.5mm t h i c k  13mm wide s t a i n l e s s s t e e l strips  extended  membrane  to  rubber sheath  with  s t r i p s glued to the o u t s i d e .  within  25mm o f the end o f  the  sixteen  The  metal  410mm  long  and were only g l u e d along one edge so t h a t they d i d  not  p r o h i b i t the membrane from e x p a n d i n g . The ends of the metal  strips  were  caused  held  underneath  the  i n c r e a s e d end c o n s t r a i n t s . the  ability  assumption  of made  the  metal  rings  which  I n c r e a s i n g the end c o n s t r a i n t  probe t o expand as  in  d i s c u s s e d more f u l l y  tapered  the i n t e r p r e t a t i o n in section  The 20m l e n g t h o f f l e x i b l e  a of  right the  decreased  cylinder, data.  This  an is  3.3.2.3.  t u b i n g used d u r i n g t h i s study  had  an o u t s i d e diameter o f 6.35mm and an i n s i d e diameter o f 2.0mm. The tubing  was found to have a very small compliance f o r the range of  p r e s s u r e s used i n t h i s study  ( 0 t o 20kpa).  F o r the purposes of t h i s r e s e a r c h p r o j e c t i t was decided to  purchase  develop  the c o n t r o l  control  u n i t s u p p l i e d by R o c t e s t but  u n i t s t h a t would be v e r s a t i l e enough  f u t u r e r e s e a r c h needs. The c o n t r o l following  subsections.  20  rather to  not to  handle  u n i t s used are d i s c u s s e d i n the  There was a problem encountered assembling the Pencel When  the  against  the  inlet. the  tapered  To  r i n g s were put i n p l a c e t o seal  retaining l i p ,  the  the membrane a l s o s e a l e d  probe. membrane  the  fluid  overcome t h i s problem a groove was c u t i n the c o r e  probe t h a t allowed the f l u i d to flow f a r t h e r along the  before  it  supplied  entered  t h e area  the  manufacturer  by  behind have  the this  membrane.  of  probe  New  probes  modification  already  incorporated.  The  Pencel  has been designed so t h a t i t can be combined w i t h  an e l e c t r o n i c cone penetrometer. The i n s i d e diameter o f t h e Pencel probe i s such t h a t a s h i e l d e d 14 c o n d u c t o r c a b l e such as used with the  UBC e l e c t r o n i c cones can be passed through the probe but  probe i s not l a r g e enough to allow the s l i g h t l y at  the  cone  end of t h e c a b l e t o pass t h r o u g h .  cable  strung  being  onto t h e c a b l e .  insufficient  overcome Instead  however, does not have  seal  the  i n s i d e t h i s a d a p t e r and when i t  room t o t h r e a d t h e cone method o f  cable.  s e a l i n g the passageway  This was  and then s e a l i n g the p i e c e o f t u b i n g w i t h a n u t , could  is  to  be threaded d i r e c t l y  be the  sufficient  t u b i n g used d u r i n g  of s e a l i n g the passageway by a t t a c h i n g a p i e c e  tubing screw  if  probe  the  The a d a p t e r t h a t i s r e q u i r e d between  c l e a r a n c e i n s i d e t o accept t h e c a b l e . The s t e e l the s a t u r a t i o n must f i t  connectors  This necessitates  rewired each time the Pencel  probe and the cone penetrometer,  is  larger  the  i n t o the c o r e o f the  does  there  could  be  altered. of  steel  a  small  probe  to  the passageway.  The  method o f a t t a c h i n g the membrane to the probe appears  21  to  limit  the type o f s o i l  found  i n which the t e s t can be p e r f o r m e d .  I t was  t h a t whenever the CPT qc v a l u e exceeded about 150 b a r ,  membrane was t o r n o f f limited  the  failure  of  friction  depth to which the the  force  tapered  the probe d u r i n g p e n e t r a t i o n .  membrane  appears to  problem  membrane  as  originate  slightly tightly,  severely  installed. from  The  the  high  the  lower a  self  s i n c e once a membrane had been p u l l e d  from  between the r e t a i n i n g l i p become  be  p u l l i n g the membrane out from between  r i n g and the r e t a i n i n g l i p .  perpetuating  would  probe c o u l d  This  the  T h i s appeared t o be  and the t a p e r e d r i n g , enlarged  and would  therefore  not  the next  the t a p e r e d hold  membrane  ring  the  next  pulled  out  more e a s i l y .  3.2.2  T e s t P r o c e d u r e and Data  3.2.2.1  Acquisition  Stress Controlled  Test  The p r e s s u r e m e t e r t e s t has t r a d i t i o n a l l y a  stress  applied strain  controlled and,  is  recorded.  pressuremeter, controlled the  G-Am  after  manner.  That i s ,  probe  The  The Pencel so  control  inserted  sectional  into  unit  from  the a  pressure  is  Menard  G-Am  was used t o perform the  stress  i t was n e c e s s a r y t o  read  the  volume  Therefore a s o l i d brass  the water r e s e r v o i r  to  decrease  than more  cylinder  the  a r e a . The s c a l e was then r e c a l i b r a t e d t o r e f l e c t  22  in  corresponding  probe has a much s m a l l e r volume  a c c u r a t e l y over a smaller range. was  certain  a s p e c i f i e d time i n t e r v a l ,  shown i n F i g u r e 3 . 2 ,  test.  a  been c a r r i e d out  cross the new  ^ ®  ©  graduated c y l i n d e r  L_  f=\  U  F i g u r e 3.2  Modified  from gas b o t t l e to orobe to probe  Menard G-Am  1  Control  23  fROCTESTl  Box  SS  volume  /  length  determination  relationship.  This  allowed  o f the volume and s t i l l  a  more  accurate  m a i n t a i n e d adequate  volume  range f o r the P e n c e l .  The  pressure  and  strain  during t h i s  test.  volume  the f l u i d r e s e r v o i r .  with  in those  volume  done  the  section  The  r e a d i n g s were r e c o r d e d as changes  that  validity  In o r d e r to compare t h e s e  of  this  the  strain.  the membrane  of  This  expands  assumption  is  in  tests  changes  in  was  done  a  right  as  discussed  the prime problems w i t h a n a l y z i n g s t r e s s  in  controlled  i s a t t e m p t i n g t o understand the d r a i n a g e c o n d i t i o n s . initial  p o r t i o n of the t e s t the s o i l  s t r a i n e d s l o w l y enough t h a t the s o i l approaches f a i l u r e , become  conditions  One  the s t r a i n  undrained.  is  around the probe may  fully  rate greatly  In the middle  During be  d r a i n e d . As the  soil  i n c r e a s e s and the  soil  of the  test  the  drainage  a r e even more complex.  o f the problems w i t h u s i n g the Pencel  controlled the  manually  3.3.2.3.  One  may  recorded  w i t h the Hughes p r e s s u r e m e t e r  asssumption  cylinder.  the  were  were c o n v e r t e d t o c i r c u m f e r e n t i a l  using  tests  The s t r a i n  readings  manner i s  initial  volume  probe  in a  d e t e r m i n i n g which v a l u e s h o u l d be 1n  the  calculations.  After  stress  used  for  performing  a  pressure expansion t e s t ,  the membrane 1s a l l o w e d t o c o l l a p s e  to  The membrane cannot be drawn back t o any  the c l o s e d p o s i t i o n .  specific control  position box.  This  unless  a vacuum source  1s  attached  l e a d s to the q u e s t i o n of whether the  24  to  back  the  Initial  volume s h o u l d be taken as the volume a t the s t a r t o f each t e s t should be  it  be taken as the t o t a l l y  c o l l a p s e d volume so t h a t  c o n s i s t e n t from t e s t to t e s t .  most  of  the t e s t s w i l l  strain,  I f the l a t t e r  s t a r t w i t h some  it  initial  is  shown  in Figure 3.3.  situation the  inflated  An a d d i t i o n a l  where the i n i t i a l  tests  test  as  strain  it  was  volume,  shown  for  F o r ease i n comparing  thus  the  initial  of  as i t was  with  would  be  delineated.  a curve such as shown  in  As shown i n  time  r e q u i r e d f o r the f l u i d t o flow i n t o the t e s t there i s  i n the t u b i n g t h e r e f o r e  Figure  3.4  the  immediately  but  probe.  the head  time must be a l l o w e d  the p r e s s u r e i n the probe and a t the s u r f a c e to e q u a l i z e .  25  In  no c o r r e c t i o n made f o r the  sufficient  d i s c u s s e d f u r t h e r i n the f o l l o w i n g  after the  r e a d i n g t a k e n a t the s u r f a c e i n c r e a s e s  controlled  it  If  pressure  stress  the  described  the volume r e a d i n g was r e c o r d e d .  volume r e a d i n g was r e c o r d e d c o n t i n u o u s l y  is  each  circumferential  the s t r e s s c o n t r o l l e d t e s t was i n i t i a l l y  3.4  of with  s t a t e d t h a t the p r e s s u r e increment was a p p l i e d and then  Figure  the  tests.  a s p e c i f i e d time i n t e r v a l  loss  effect  volume was choosen to be the s i z e  z e r o a t the s t a r t o f each t e s t ,  o t h e r types of  When  curve i s  was decided t o use the volume a t the s t a r t  the i n i t i a l  even  volumes on the p r e s s u r e m e t e r c u r v e s  opening c r e a t e d by the 36mm t i p .  other  was  initial  then  circumferential  a f t e r the probe has been pushed t o the next t e s t d e p t h . The choosing d i f f e r e n t  can  i s the c a s e  s i n c e the membrane tends to remain s l i g h t l y  of  or  section.  This  for is  -15  0 15 CIRCUMFERENTIAL STRAIN C X ) LANGLEY. 3BMM T I P STRESS CDNTROLLED  30 DEPTH 8M  LEGEND Ro - 32MM Ro - I N I T I A L R Ro - 36MM  F i g u r e 3.3  Pencel:  Curves determined w i t h v a r i o u s 26  initial  volumes  CIRCUMFERENTIAL STRAIN  < X>  LEGEND CONTINUOUS READINGS 30 SECOND READINGS  F i g u r e 3.4  P e n c e l : Type o f curve g e n e r a t e d by a s t r e s s controlled test 27  3.2.2.2  Data  Calibrations  readings  from  f o r the S t r e s s C o n t r o l l e d  the Pencel  account f o r the system c o m p l i a n c e ,  probe must  p r e s s u r e caused by the f l u i d  Before  adjustments  performed;  a  system  can  i n the f l e x i b l e  be made two  compliance  adjusted  to  the membrane s t i f f n e s s and the  hydrostatic the  be  Test  tubing.  calibrations  calibration  and  must  a  be  membrane  cal i b r a t i o n .  The unit of  system  compliance  i s a measure of how much the  and the t u b i n g expand under p r e s s u r e . the  Pencel  constant. test  The  probe was r e l a t i v e l y system  low  The system and  is  compliance  approximately  c o m p l i a n c e does not depend on whether  was run i n a s t r e s s or s t r a i n c o n t r o l l e d  system compliance  was  control  manner.  When  known, the volume i n j e c t e d i n t o the probe  the the can  be c a l c u l a t e d . Vpr = Vsur - Vcom where: Vpr  = actual  Vsur  = volume change r e c o r d e d a t the  Vcom  = volume a t t r i b u t e d t o system c o m p l i a n c e  Vcom  = P * System Compliance  P  = P r e s s u r e a p p l i e d to the  The  hydrostatic be  probe  surface  system  p r e s s u r e measured a t the s u r f a c e must be a d j u s t e d i n two  ways to r e f l e c t  must  volume i n j e c t e d i n t o the  the p r e s s u r e e x e r t e d by the probe on the s o i l .  head o f water above the probe i n the f l e x i b l e  added  to the p r e s s u r e measured a t the s u r f a c e  28  The  tubing and  the  resistance  o f the membrane to e x p a n s i o n must be  subtracted  from  the measured p r e s s u r e .  The  adjustment  and  is  type  pressuremeter.  f o r the h y d r o s t a t i c  head i s  straight  a p r o c e d u r e t h a t has always been r e q u i r e d w i t h the  The depended  membrane on  stiffness  several  was d i f f i c u l t  factors.  The f i r s t  to  was  T h i s was e s p e c i a l l y  noticeable  Menard  determine  factor  c o n s i d e r e d b e f o r e c a l i b r a t i n g the membrane i s t h a t use.  forward  that it  as  it  must  be  softens  when the membrane was new.  recommended by the m a n u f a c t u r e r t h a t the membrane be  inflation  /  s h o u l d be c o n s i d e r e d a minimum whereas  deflation  recommendation. calibration  This  is  The  cycles  effect  would  that  shown i n F i g u r e 3 . 5 .  appear  to  be  s o f t e n i n g has on After inflating  a  twenty  the  membrane  and  deflating to  volume a t z e r o p r e s s u r e . The membrane can however,  deflated  back  external  pressure  to  the i n i t i a l is  volume but f o r t h i s  required.  i m p o r t a n t when t r y i n g t o c a l c u l a t e t o measure t h i s  This pressure i s the l i f t o f f  to  an  but  is  pressure.  creeps.  In o r d e r a  vacuum  Therefore,  the membrane c a l i b r a t i o n curve  on the time between p r e s s u r e i n c r e m e n t s . F i g u r e 3 . 7  29  be  box.  Under c o n s t a n t p r e s s u r e the membrane in Figure 3 . 6 ,  the  occur  small  p a r t of the membrane c a l i b r a t i o n c u r v e ,  s o u r c e was a p p l i e d t o the c o n t r o l  shown  total  better  the membrane a number of times the probe no l o n g e r r e t u r n s same i n i t i a l  It  inflated  i n a i r to maximum volume and then d e f l a t e d to z e r o volume a of f i v e times.  with  is  as  dependent  shows t h a t  the  cn cc < CO  UJ CC D  cn cn  LU CC Q.  1 1 r 40 60 80 CHANGE IN VOLUME C CC ) PENCEL MEMBRANE  100  120  LEGEND • NO PRE-CYCLING • AFTER 10 CYCLES - AFTER 20 CYCLES  F i g u r e 3.5  P e n c e l Membrane C a l i b r a t i o n : E f f e c t of c y c l i n g 30  LEGEND  • 30S 60S 180S BOOS  F i g u r e 3.6  INTERVAL INTERVAL INTERVAL INTERVAL  P e n c e l Membrane C a l i b r a t i o n : E f f e c t o f v a r y i n g the time increment  31  size  of  the  pressure  c a l i b r a t i o n curve. and  time  possible  Increment  also  affects  intervals  should would  be used  for  the  be to use the same  i n t e r v a l s t h a t are used d u r i n g the t e s t s . test  membrane  The q u e s t i o n then a r i s e s as to which  approach  typical  the  calibration. pressure  Take,  performed i n medium dense s a n d .  i n c r e m e n t s were a p p l i e d e v e r y 30 seconds u n t i l  pressure  for One  One  and  time  example, bar  a limit  a  pressure  pressure  of  11 b a r s was r e a c h e d . An u n l o a d - r e l o a d loop was a l s o p e r f o r m e d . The total the  time o f the e x p a n s i o n p a r t of the t e s t was 10  minutes.  If  c a l i b r a t i o n curve was generated i n the same way o n l y two data  points  would be o b t a i n e d s i n c e t h r e e bars would g e n e r a l l y  the l i m i t p r e s s u r e f o r a membrane expanded i n a i r . r e q u i r e d to i n f l a t e half  minutes.  exhibits  it  has been e s t a b l i s h e d t h a t  time dependent c r e e p , by  the  Another  approach  above approach does not appear  time  to  generated  be  correct.  Alternatively,  the t o t a l  between  so t h a t the t o t a l  the t o t a l  time  time t o run the  time f o r e x p a n s i o n  A  test  during  t e s t c o u l d be d u p l i c a t e d by u s i n g the same time i n t e r v a l s  s m a l l e r p r e s s u r e i n c r e m e n t s d u r i n g the c a l i b r a t i o n .  a  membrane  would be to i n c r e a s e the time i n t e r v a l  t o run the c a l i b r a t i o n approximates  the  the  u s i n g a c u r v e t h a t was  p r e s s u r e increments d u r i n g the c a l i b r a t i o n  i n the f i e l d .  The t o t a l  the probe would have been l e s s than one and  Since  quickly  exceed  but  close  look  applied to  the  a t what i s happening when a p r e s s u r e increment  is  probe  increment  is  portion  that  1s  increment  1s  during  a  carried  entirely  carried  by  carried  mostly  PMT by  shows t h a t the p r e s s u r e the membrane nor i s  the membrane c o n s i s t e n t . by  the  soil  w i t h the  32  the  The p r e s s u r e portion  carried  by  not  the  LEGEND 1 BAR INCREM 0. 5 BAR INCREM  Figure  3.7  P e n c e l Membrane C a l i b r a t i o n : E f f e c t o f v a r y i n g the s i z e of the p r e s s u r e increment 33  membrane  dependent  on the amount of s t r a i n c o r r e s p o n d i n g t o  the  increment.  The  question  increment program  still  should it  be  was  remains as to  used.  desired  what  F o r the purposes  not  t o have  to  pressure  increment  of  calibration. the  30  seconds  This  sand.  curve  increment  was  manner,  curve. the  the  separate Therefore,  and  a  test  and  and  corresponded  in clay,  silt,  time the allow  to  and  the loose  recommendation f o r the Menard G-Am p r o b e , stress  controlled  to use s t a n d a r d i z e d 0.25 b a r increments a p p l i e d a t  was  stiffness  to be d e f i n e d  used d u r i n g t e s t s  second time i n t e r v a l s  It  was used f o r both  a l s o d e s i g n e d to be performed i n a  is  a  duration.  time  research  was a small enough p r e s s u r e increment to  The m a n u f a c t u r e r ' s  which  and  this  increment was s t a n d a r d i z e d a t 0 . 5 b a r  calibration  pressure  of  generate  c a l i b r a t i o n curve f o r each t e s t of d i f f e r e n t the  pressure  very  f o r both the t e s t and the  difficult  correction  to determine  calibration.  the  correct  f o r the u n l o a d i n g p a r t o f the  membrane  pressuremeter  The membrane s t i f f n e s s d u r i n g u n l o a d i n g was a f u n c t i o n  maximum  initial  volume to which the probe  portion  differences differences  in in  had  been  expanded.  o f the u n l o a d i n g c u r v e was very steep and the the  volume pressure  reading  corresponded  correction.  60  This  to  was  of The  small large  especially  i m p o r t a n t when u n l o a d - r e l o a d l o o p s were b e i n g a n a l y z e d . A membrane calibration  i n c l u d e d a u n l o a d - r e l o a d loop s t a r t i n g  at  the same volume as the loop b e i n g a n a l y z e d was r e q u i r e d . S i n c e  the  test  was  curve that  performed  i n a s t r e s s c o n t r o l l e d manner  34  it  was  very  difficult  to match the volumes a t the s t a r t o f the  l o o p s . A f a m i l y o f c a l i b r a t i o n c u r v e s was t h e r e f o r e  unload-reload required.  was l e s s of a problem w i t h the s t r a i n c o n t r o l l e d t e s t . controlled test, the  test  and  specified  The  In a s t r a i n  the volume was c o n t r o l l e d so the u n l o a d i n g during  the c a l i b r a t i o n c o u l d be  carried  cylinder  and the p r e s s u r e  using standard laboratory  guages.  The  cylinder  techniques  and the  gauge was c a l i b r a t e d w i t h a dead w e i g h t p r e s s u r e  tester.  3.2.2.3  The  Strain Controlled  strain  controlled  test  controlled  test  There  the  injected  was  pressure  be h e l d c o n s t a n t  stress into  the the  r a t e of s t r a i n r a t h e r than  at  increments.  a r e many reasons f o r wanting t o run the  can  a  the  T h i s allowed  r a t e s c a u s e d by p r e s s u r e  i n a s t r a i n c o n t r o l l e d manner.  rate  from  r a t h e r than the p r e s s u r e .  test  t e s t to t e s t  differed  i n t h a t the volume o f f l u i d  was c o n t r o l l e d  the v a r i a b l e  Pencel  at  Test  to be performed a t a c o n s t a n t  have  out  o t h e r two components t h a t r e q u i r e d c a l i b r a t i n g were  calibrated  test  during  volumes.  graduated  tubing  This  pressuremeter  The f a c t t h a t the s t r a i n  rate  f o r the d u r a t i o n of the t e s t and v a r i e d  from  i s important  1n d e a l i n g w i t h s o i l s t h a t are known  dependent p r o p e r t i e s .  probe was the f a c t  Equally  as important  t h a t membrane c a l i b r a t i o n s  s t r a i n c o n t r o l l e d manner are dependent on fewer  35  with  performed  variables  to the in and  are  more r e p e a t a b l e .  T h i s 1s d i s c u s s e d i n d e t a i l  In the  following  section.  The  strain  accommodate expected Figure  the  needs 3.8  components  is  control needs of  u n i t was developed and b u i l t  programs.  versatile,  are a screw j a c k which i s  of a brass c y l i n d e r .  is  The u n i t which i s and easy  to  use.  is a f i l l e r  motor  pressure  transducer  volumes  more  allowed  accurately  c o n t r o l l e d t e s t equipment.  the measurement  than  was  of  possible  be was  advantage  reduced  a  The screw for  the  an the and  stress the  recorder.  d e v i c e was t h a t i t  was  to apply a vacuum to the probe so t h a t the membrane c o u l d  drawn back to the same s t a r t i n g volume a f t e r each a  cylinder,  The data was r e c o r d e d by c o n n e c t i n g  of the s t r a i n c o n t r o l  in  inside  pressures  with  the  main  The use of the LVDT and  LVDT and the p r e s s u r e t r a n s d u c e r to an XYY c h a r t  possible  The  and a p r e s s u r e t r a n s d u c e r .  to be used i n s t e a d .  to  shown  turned by a hand crank but t h e r e are f a c i l i t i e s  electric  One  as  attached to a p i s t o n  A t t a c h e d t o the u n i t  LVDT to measure d i s p l a c e m e n t , jack  UBC  o f t h i s r e s e a r c h program as w e l l  future  simple,  at  great  a i d i n s t a n d a r d i z i n g the t e s t  and  may  test.  This  have  also  membrane damage because the probe was not b e i n g pushed t o  the next depth i n a p a r t i a l l y d u r i n g the s t r e s s c o n t r o l l e d  expanded s t a t e , test.  36  a common o c c u r r e n c e  I I  i the pressure transducer i s Located behind  •filler  cylinder  LVDT.  screw j a c k b r a s s pressure c y l i n d e r '  F i g u r e 3.8  the p i s t o n i s a t t a c h e d to the screw j a c k and i s l o c a t e d within the p r e s s u r e c y l i n d e r  S t r a i n C o n t r o l Device  3.2.2.4  When  Calibrations  the  f o r the S t r a i n C o n t r o l l e d  pressuremeter  controlled  manner  calibration  pressure  strain rate,  as shown i n F i g u r e  The strain  a  controlled  performed  relationship  in  a  between  and volume was e s t a b l i s h e d  any  different  curves  (  F i g u r e 3.9  r a t e of f l o w o f f l u i d the  rates  thoroughly.  have  adequate  produced  stress  included tubing.  different  i n the t u b i n g .  due to s t r a i n  r a t e but  The  this  the  difference was  not  The s t r e s s c o n t r o l l e d c a l i b r a t i o n c u r v e was  a  calibration  There may be some  a head l o s s component because t h e r e time  the  ) was because the head l o s s v a r i e d w i t h  membrane s t i f f n e s s  examined  for  t e s t and the c a l i b r a t i o n curve f o r the  strain  given  3.9.  t h a t c o r r e s p o n d e d t o the head l o s s i n the  reason  strain membrane  for  t e s t was t h a t the s t r a i n c o n t r o l l e d c u r v e  component  not  unique  was  major d i f f e r e n c e between the c a l i b r a t i o n c u r v e  controlled  in  test  Test  did  generally  an  l a p s e between the time the p r e s s u r e increment  was  a p p l i e d and the time t h a t the volume was recorded d u r i n g which  the  p r e s s u r e s throughout the system e q u a l i z e d .  Figure  3.9 a l s o shows t h a t o b s e r v a t i o n o f the p r e s s u r e  drop  when the i n f l a t i o n was stopped a l l o w e d the head l o s s component  of  the c a l i b r a t i o n to be i d e n t i f i e d .  to  identify the  same  However,  i t was not n e c e s s a r y  t h i s component because the head l o s s d u r i n g the t e s t was as the head l o s s d u r i n g the  s t r a i n r a t e s were the same.  38  calibration  provided  the  LEGEND • 5 SEC / REV — 2 . 5 S E C / REV  F i g u r e 3.9  Pence! Membrane C a l i b r a t i o n : E f f e c t of the s t r a i n r a t e  39  varying  Calibrating  the  volume  of  voltage  increment.  same  LVDT was s i m p l y a m a t t e r of  l i q u i d e x p e l l e d from the c y l i n d e r c o r r e s p o n d i n g  dead  weight p r e s s u r e t e s t e r used t o c a l i b r a t e  3.3  Hughes  the to  The p r e s s u r e t r a n s d u c e r was c a l i b r a t e d w i t h  gauge i n the Menard G-Am c o n t r o l  The  recording  the  box.  Hughes P r e s s u r e m e t e r  p r e s s u r e m e t e r i s of i n t e r e s t because  it  allows  full  d i s p l a c e m e n t manner. The o n l y d i f f e r e n c e s between s e l f - b o r e d  tests  this  a s e l f - b o r i n g a c t i o n w i t h those i n s e r t e d i n  was  a  with  by  the  pressure  d i r e c t comparison between p r e s s u r e m e t e r t e s t s where the probe inserted  a  i n s t r u m e n t and f u l l  installation. and  method  With the Pencel of  data  all  different  from  those  pressuremeter.  Hughes p r e s s u r e m e t e r ( HPM ) i s p a t t e r n e d a f t e r the  developed  by Hughes and Wroth a t Cambridge i n the  p a r t i c u l a r model  casing,  The probe which i s  one  1970's. smaller  i t can be lowered through a s m a l l e r  a concern on commercial  pressurized  early  has been c o n s t r u c t e d w i t h a s l i g h t l y  d i a m e t e r of 76mm so t h a t  with  are  membrane t y p e ,  D e s c r i p t i o n of Hughes P r e s s u r e m e t e r  The  This  probe the d i a m e t e r ,  collection  employed u s i n g the s e l f - b o r i n g  3.3.1  d i s p l a c e m e n t t e s t s i s the manner of  drill  projects.  shown i n F i g u r e 3.10 i s  generally  n i t r o g e n gas which i s c o n t r o l l e d by a  40  inflated pressure  Signal Wires to S u r f a c e  N  Pressure Hose• C a s i n g Support'  Air  (Pressurized)  E l e c t r i c a l Signal Conditioners Pressure  Transducer-  Pore P r e s s u r e Displacement  Cell-  Transducers-  Flexible Membrane  —  ( A f t e r Hughes and R o b e r t s o n , 1984 )  Solid Cone Tip  F i g u r e 3.10  Hughes Pressuremeter  ( HPM )  41  regulator measured the  at  the  surface.  The e x p a n s i o n  membrane.  Pencel  converted strain than  These  arms measure r a d i a l  1s  to  volumetric  pressure c e l l  strain.  The  One  important  directly  to  is  and  electronically  to  then  monitored  smaller  movements a  The membrane on the HPM i s  than the membrane used on  i n f l u e n c e o f the f l e x i b l e  s m a l l e r membrane s t i f f n e s s c o r r e c t i o n s . sheath  1s  The p r e s s u r e 1s measured by  i n s i d e the p r o b e .  more f l e x i b l e  of  which  probe where changes i n volume a r e measured  considerably  steel  displacement  arms are more s e n s i t i v e and can d e t e c t  probe.  membrane  s t r a i n . T h i s 1s 1n c o n t r a s t  the Pencel measuring s y s t e m .  total  the  by s t r a i n gauges a t t a c h e d to t h r e e arms a t the c e n t e r  e a s i l y c o n v e r t e d to c i r c u m f e r e n t i a l the  of  the  membrane i s  The p r o t e c t i v e  not a t t a c h e d t o the membrane  the probe i n such a way t h a t  it  is  Pencel  but  is  the  stainless attached  free to s l i d e  at  one e n d .  The  expandable p o r t i o n of the membrane i s 456mm l o n g w i t h  resulting ratio  3.3.2  1/d r a t i o o f 6 .  o f 7.5 f o r the Pencel  This  slightly  s m a l l e r than the  Acquistlon  ( HPMT ) was performed i n two d i f f e r e n t  formats.  T e s t s were performed i n the s t r e s s c o n t r o l l e d format because was how the l o c a l l y the  object  displacement  was  1/d  probe.  T e s t Procedures and Data  The HPM t e s t  is  a  available  that  s e l f - b o r i n g t e s t s were performed and  t o compare the s e l f b o r i n g r e s u l t s to  r e s u l t s as d i r e c t l y  as p o s s i b l e .  the  full  The HPMT was  also  performed  i n a s t r a i n c o n t r o l l e d format f o r the same  were l i s t e d i n s e c t i o n  3.3.2.1  The performing  as  3.2.2.3.  Stress Controlled  control  reasons  Test  box shown i n F i g u r e 3.11 was n o r m a l l y  used  the HPMT when s e l f - b o r e d i n t o the ground and was  for also  used when the HPM was i n s t a l l e d i n a f u l l - d i s p l a c e m e n t manner.  No  modifications  an  electrical  were  necessary.  The  power supply because i t  control  box  required  was used to power the  strain  gauges and t r a n s d u c e r s i n the p r o b e . A p r e s s u r i z e d n i t r o g e n was  attached  pressure supply  to  the c o n t r o l  box.  The c o n t r o l  r e g u l a t o r and a flow c o n t r o l of  gas  to the p r o b e .  a digital  voltmeter.  v a l v e which  The s i g n a l s from  r e c e i v e d and a m p l i f i e d i n the c o n t r o l  box  box,  bottle  included  regulated the  probe  a the  were  and c o u l d be read w i t h  The s i g n a l s c o u l d a l s o be r e c o r d e d on a c h a r t  r e c o r d e r . The f a c t t h a t gas r a t h e r than a l i q u i d was b e i n g used to inflate was  this  probe meant t h a t the p r e s s u r e a p p l i e d a t the  approximately  probe.  the  same p r e s s u r e t h a t was  There was no h y d r o s t a t i c  p r e s s u r e head.  head l o s s i n the t u b i n g b u t i t was n e g l i g i b l e , s h a l l o w t e s t depths s t u d i e d i n t h i s  3.3.2.2  There test; the  Calibrations  measured  especially  research project  system c o m p l i a n c e .  43  the  at  the  ( i e . < 20m).  Test  are f o u r components t h a t must be c a l i b r a t e d pressure c e l l ,  in  There was a small  f o r the S t r e s s C o n t r o l l e d  the membrane, the t o t a l  surface  for  the s t r a i n arms,  this and  REGULATOR  Figure  3.11  HPM  Control  Box  The The  HPM  membrane  membrane was much s o f t e r than the Pencel  membrane.  calibration  3.12  which  c o n s i d e r e d t o be a c o n s t a n t .  is  shown  An i n i t i a l  in  Figure  p r e s s u r e of  0.35 b a r was r e q u i r e d to cause the membrane to s t a r t it  continued  to i n f l a t e  was  approximately inflating  to the maximum a l l o w a b l e volume a t  and this  pressure.  The s t r a i n arms were d i f f i c u l t the  membrane  individually  once  membrane  being  r e a d i n g was r e c o r d e d when the arms were  fully  had been  i n s t a l l e d a voltage  installed.  to c a l i b r a t e P r i o r to the  compressed and the amount o f e x p a n s i o n c o r r e s p o n d i n g t o voltage  readings  calibration been  was measured d i r e c t l y .  factors  installed  f o r each s t r a i n  it  was  had  difficult  expanded.  subsequent  This yielded  arm.  Once the  to  determine  However,  the  different  membrane how  much  individual  arm  electrical  connecting  the probe to the s u r f a c e was s u b j e c t to a l o t  and o f t e n needed to be r e p a i r e d . Whenever the e l e c t r i c a l repaired expensive  the ($66  calibration each)  it  changed. was d e s i r a b l e  Since  the  had  of  an  cable abuse  c a b l e was  membranes  are  not to have t o remove  and  r e p l a c e them every time a s t r a i n arm c a l i b r a t i o n was r e q u i r e d . s t r a i n arms c o u l d be c a l i b r a t e d w i t h the membrane on by the probe i n s i d e a s t e e l assumption t h a t a l l  The  total  The  inflating  c y l i n d e r of known d i a m e t e r and making the  t h r e e arms expanded the same amount.  pressure c e l l  was e a s i l y c a l i b r a t e d i n  manner as the p r e s s u r e t r a n s d u c e r i n the s t r a i n c o n t r o l  45  the  same  device.  LEGEND STRAIN CONTROLLED STRESS CONTROLLED  F i g u r e 3.12  HPM Membrane C a l i b r a t i o n Curve  The and  system c o m p l i a n c e was measured and found  was g e n e r a l l y  taken to be i n s i g n i f i c a n t w i t h i n  range used d u r i n g t h i s  3.3.2.3  The controlled tubing.  problem  manner  Due  study  ( ie.  Strain Controlled  main  t o be very  pressure  ).  Test  encountered  was  to i t s  < 20 b a r  the  u s i n g the HPM  the s i z e o f the  larger size,  head  in  loss  a  the volume o f f l u i d  than t h a t r e q u i r e d f o r the Pencel  Therefore,  if  r a t e was to be the same as was used d u r i n g the Pencel  As  it  the  tests,  the  probe,  a  more  The presence o f e l e c t r o n i c s  i n the  that  Pencel  probe where water was u s e d . The f l u i d o r i g i n a l l y  a l i g h t hydraulic  f l u i d used must be  oil.  However,  this  non-conducting,  unlike  the  chosen was  the  fluid  was i n j e c t e d i n t o the probe c o u l d not be drawn back i n t o  reservoir proved  instrument  proved to be too v i s c o u s and  head l o s s e s w i t h the 20m o f t u b i n g were such t h a t  that  to oil  even  under a f u l l  work was WD-40, and s o l v e n t .  vacuum.  The f l u i d  that  a commercially a v a i l a b l e  WD-40 was l e f t  stretch  s i t t i n g i n the p r o b e .  47  the  eventually mixture  The o n l y major drawback to the use of  was the tendency f o r the membrane to the  the  non-compressible  meant  when  strain  probe.  u n i t used w i t h the Pencel  f l u i d was r e q u i r e d .  fluid  greater  was d e s i r e d to run the s t r a i n c o n t r o l l e d t e s t w i t h  same c o n t r o l  light  to  must flow through the t u b i n g r e s u l t i n g i n even g r e a t e r head  l o s s e s than w i t h the Pencel  the  the  required  s t r a i n was much  probe.  strain  through  expand the HPM to a g i v e n c i r c u m f e r e n t i a l  fluid  low  of this  considerably  T h i s problem  was  easy to c o n t r o l and the f l u i d ends  of  s i n c e the ends o f the membrane c o u l d be  d r a i n e d from the  the  membrane  were  undamped  probe when i t was not i n u s e .  The  reclamped  the  without  damaging  membrane.  The used  strain  control  d e v i c e used w i t h the Pencel  f o r the HPM s t r a i n c o n t r o l l e d t e s t  control  box n o r m a l l y used w i t h the HPM.  allowed  probe  was  with  the  in conjunction  The s t r a i n c o n t r o l  device  the r a t e a t which f l u i d was i n j e c t e d i n t o the probe to be  control l e d .  There  were two b i g advantages  o p e r a t i n g on one p r o b e . the  total  surface. loss  to having both c o n t r o l  The f i r s t was the o p p o r t u n i t y  t o d i r e c t l y measure the  i n the t u b i n g and to observe t h a t p r e s s u r e  the s u r f a c e were not p r e s e n t i n the probe  the  compare  p r e s s u r e i n the probe to the p r e s s u r e measured a t T h i s a l l o w e d an o p p o r t u n i t y  The  to  systems  second  opportunity  fluctuations  ( see F i g u r e 3.13  advantage to h a v i n g the two c o n t r o l to examine the d i f f e r e n c e  probe w i t h the c i r c u m f e r e n t i a l  arms a t the c e n t e r of the membrane. a r e shown i n F i g u r e 3 . 1 4 . volume  divided  calculated  using  circumferential  by the o r i g i n a l the strain  s t r a i n measured by the The r e s u l t s of the  The v o l u m e t r i c  original is  volume. diameter  of  the  into  comparison  volume probe.  the change i n r a d i u s measured  48  was  strain  s t r a i n i s the change The o r i g i n a l  at  volumetric  s t r a i n c a l c u l a t e d from measuring the amount of f l u i d i n j e c t e d the  head  ).  systems  between the  the  by  in was The the  0  F i g u r e 3.13  2  HPM:  4 6 CIRCUMFERENTIAL STRAIN < X >  Comparison of p r e s s u r e r e a d i n g a t the s u r f a c e and a t the probe  49  8  10  strain  arms d i v i d e d by the o r i g i n a l  assumption cylinder radial  r a d i u s of the p r o b e .  the v o l u m e t r i c  s t r a i n s h o u l d be a p p r o x i m a t e l y  Suyama e t a l ,  expand  very  the  1983 used X - r a y r a d i o g r a p h y 1n model  c l o s e to a r i g h t c y l i n d e r when  mono-cell  expanded  in  The e x a c t formula r e l a t i n g the two t y p e s of s t r a i n 1s shown  on F i g u r e  3.14.  The that  fact  t h a t the membrane i s c o n s t r a i n e d a t each end  means  i t can never expand as a t r u e r i g h t c y l i n d e r but as the  ratio  i n c r e a s e s the e f f e c t  o f the end c o n s t r a i n t  HPM has a s o f t e r more f l e x i b l e membrane, because as i t 1/d is  right  twice  e x p e r i m e n t s and showed t h a t p r e s s u r e m e t e r s employing t h e  sand.  the  1s made t h a t the probes expand 1n the form o f a  strain.  design  If  the  protective  steel  i s w i t h the Pencel ratio  that  cylinder  ( 6.0 vs 7.5  diminishes.  and l e s s end  The  constraint  sheath i s not clamped a t both  probe.  However,  ) than the Pencel  the HPM has a probe.  ends  smaller  The f i n a l  result  the HPM p r o b a b l y expanded i n a shape c l o s e r t o  a  than  previous  did  the Pencel  pressuremeters having a t r i - c e l l d e s i g n was to reduce the e f f e c t  The  1/d  The  purpose  of  design r a t h e r than the  mono-cell  o f the end c o n s t r a i n t .  the  strain  measured by the arms a t the c e n t e r of the probe was always  greater  than  This  to show  results  probe.  right  shown i n F i g u r e 3.14 i n d i c a t e  that  the s t r a i n c a l c u l a t e d from the volume measurements. be e x p e c t e d because of the end c o n s t r a i n t . t h a t the v o l u m e t r i c  circumferential 1s h e l p f u l  The  results  also  s t r a i n agrees much more c l o s e l y w i t h  strain in s t i f f e r material.  50  the  To understand t h i s  t o c o n s i d e r the e x p a n s i o n of the probe i n a i r .  In  is  it  this  < or  i— in  u Ul  2: _i o >  CIRCUMFERENTIAL STRAIN  LEGEND •  F i g u r e 3.14  THEORETICAL SAND SILT SILT CLAY CLAY  HPM: Comparison o f v o l u m e t r i c s t r a i n and c i r c u m f e r e n t i a l s t r a i n measurements  51  case the expanded probe i s  shaped somewhat l i k e  the probe i s expanded i n a s t i f f m a t e r i a l in  the  c e n t e r o f the  probe i s  a  football.  the amount o f  When  constraint  going t o be p r o p o r t i o n a l  to  amount o f e x p a n s i o n . T h e r e f o r e when the c e n t e r o f the probe t o expand more than the ends o f the probe i t meets more and is  closer  to  the  ends.  The  stiffer  pressure  expansion  calculated strain  the  material  from  curves.  the  One  curve  is  shown  I f the Pencel  c e n t e r of the membrane to the average  expanding  question as  circumferential  a  that right  strain.  arises  is  cylinder  that i f  the  then  what  strain  measured  of  membrane  is  is  correct  the  not  center  volumetric  which r e p r e s e n t s some s o r t o f an average o v e r the  52  strain  calculated  Should the measured s t r a i n a t the  l e n g t h o f the membrane.  expands  i s w i t h the HPM.  the membrane be used o r the one c a l c u l a t e d from the  increase  the  strain  probe  l i k e a r i g h t c y l i n d e r than the HPM than the r a t i o  The  less  various  with  i n j e c t e d volume and the o t h e r from  a t the c e n t e r of the p r o b e .  the  the  i n d i f f e r e n t ways on the  from the volume i n c r e a s e would be h i g h e r than i t  of  resistance  the end r e s t r a i n t s become. F i g u r e 3.15 i l l u s t r a t e s  e f f e c t o f c a l c u l a t i n g the s t r a i n  at  begins  the membrane expands along the path of l e a s t r e s i s t a n c e which  significant  less  the  entire  CIRCUMFERENTIAL  STRAIN  C X )  0  2  4  6  8  10  12  0  4  8  12  16  20  24  <  VOLUMETRIC STRAIN  < X>  LEGEND —  F i g u r e 3.15  VOLUMETRIC STRAIN CIRCUMFERENTIAL  STRAIN  HPM: Comparison o f c u r v e s generated w i t h v o l u m e t r i c s t r a i n and those g e n e r a t e d w i t h c i r c u m f e r e n t i a l s t r a i n 53  3.3.2.4  The stress  C a l i b r a t i o n s f o r the S t r a i n C o n t r o l l e d Test  calibrations controlled  were b a s i c a l l y the same as those  test.  The major e x c e p t i o n  was  for  the  the  membrane  calibration.  When  the  test is strain controlled i t  became apparent  the membrane c a l i b r a t i o n shown i n F i g u r e 3.12 was a n e a r l y relation  linear  between p r e s s u r e and s t r a i n as was t o be expected from a  l i n e a r e l a s t i c m a t e r i a l . Note t h i s i s i n c o n t r a s t t o t h e observed i n the s t r e s s c o n t r o l l e d t e s t .  In the s t r e s s  t e s t the membrane behaved l i k e a b a l l o o n i n t h a t i t initial  that  pressure  to  begin the i n f l a t i o n and very  pressure to continue the  inflation.  54  behaviour controlled  took a c e r t a i n little  extra  Chapter 4 F i e l d Program  4.1  Field  tests  conducted Valley.  at  Introduction  w i t h the f u l l  three  displacement  research s i t e s  One s i t e c o n s i s t e d p r i m a r i l y  organic  silt,  in  the  other  lower  and the t h i r d p r i m a r i l y o f c l a y .  insitu  were  Fraser  River  o f sand, another p r i m a r i l y  chosen because they r e f l e c t e d the t h r e e s o i l the  pressuremeter  These s i t e s were  t y p e s and because  t e s t s which had been or were  of  being  of  conducted  there.  The Highway. layer  first The  of  s i t e was i n L a n g l e y , soil  just off  the  Trans  Canada  c o n s i s t s of normally c o n s o l i d a t e d c l a y with  over c o n s o l i d a t e d material  a t the s u r f a c e .  The  second  s i t e was a t Boundary Road on L u l u I s l a n d i n the F r a s e r R i v e r . soil  profile  c o n s i s t s of o r g a n i c s i l t  o f p e a t near the s u r f a c e .  profile  The t h i r d s i t e was a t McDonalds Farm on  documented i n many UBC r e s e a r c h p u b l i c a t i o n s . at  McDonalds  density overlying s i l t  The  o v e r dense sand w i t h a l a y e r  Sea I s l a n d i n the F r a s e r R i v e r d e l t a . The McDonalds Farm s i t e been w e l l  a  Farm c o n s i s t s o f 13m of and c l a y .  55  sand  The of  has soil  varying  1. Langley 2. Boundary Road 3. McDonalds Farm  F i g u r e 4.1  Site Location  Map  4.2  Langley profile  chosen  contains  accessible a  was  a  depth.  as a r e s e a r c h  fairly  This  Langley  uniform  site  clay  because  layer  at  the a  soil  readily  s i t e was a l s o one of the l o c a t i o n s  used  r e s e a r c h program i n v o l v i n g d e t e r m i n a t i o n of the u n d r a i n e d  strength  from  result  cone  of the o t h e r r e s e a r c h program,  already vane  the f i e l d vane and t h e  available  at this  penetrometer.  As  as s e v e r a l  Nilcon  a  were field  profiles.  4.2.1  Site  The  Description  site  overpass,  is  just off  l o c a t e d on the approach to  i n d i c a t i o n o f the s o i l  at  2.75m.  consolidated continue  clay.  below  stratigraphy.  Below  6m  is  Interbedded  that depth.  meters below the  232nd  Street B.C.  shown i n F i g u r e 4.2 g i v e s a  a  The good  The upper 6m c o n s i s t s of two  d i s t i n c t l a y e r s of o v e r c o n s o l i d a t e d c l a y , located  the  the Trans-Canada Highway i n L a n g l e y ,  p i e z o m e t e r - f r i c t i o n cone p r o f i l e  4.2.2  shear  s e v e r a l cone p r o f i l e s  s i t e as w e l l  in  w i t h a very s t i f f  uniform  silt  layer  layer  of  normally  layers begin  at  14m  The water t a b l e  i s between 3  and  and  4  surface.  Results  The t a b l e  shown i n F i g u r e 4 . 3 l i s t s  all  were conducted a t L a n g l e y and used i n t h i s  57  the i n s i t u  tests  r e s e a r c h program.  that  UBC Sita On  I M  Location! Slta  Loci  S I T U  T E ST I N G  LANGLEY  CPT D a t a • 0CT02 1884  UPPER S I T E  Cona Uaadi  CB€ 8EARJNC  Oapth I n e r m n t  F i g u r e 4.2  CB FPSG 6UBC  FRICTION RATIO  i  . 025 m  L a n g l e y cone p r o f i l e  58  P o g a Not  1 / 1  Comantfi  PORE PRESSURE  M O M Oapth .  INTERPRETED  I S . 82 m  TESTS CONDUCTED AT THE LANGLEY TEST SITE  Test Designator  Instrument  T e s t Date  Comments  Depths a t which PMTs were conducted  Lanrl  P e n c e l Probe  06/09/84  Stress controlled  32mm t i p  2.75,6,8,10,11.5,15  Lanr2  P e n c e l Probe  06/09/84  S t r e s s c o n t r o l l e d 36mm t i p  2.75,6,8,10,11.5,15  Lanr3  Pencel Probe  16/11/84  S t r a i n c o n t r o l l e d 36mm t i p  3,6,7,8,9,10,11  Lanr4  P e n c e l Probe  16/11/84  S t r a i n c o n t r o l l e d 32mm t i p  3,6,8,9,10  LI  HPM  18/07/84  Stress c o n t r o l l e d  3,6,8,10,12  L2  HPM  19/07/84  Stress controlled  3,6,8,10,12  L3  HPM  20/01/85  Strain controlled  CPT #1  Seismic  cone  02/10/84  N i l c o n F i e l d Vane P r o f i l e  F i g u r e 4.3  I n s i t u t e s t s conducted a t Langley  0.5,1,1.5,2.75,5,6  Typical obtained Figure  curves  using 4.4.  from  the  each o f the  Pencel'probe  various  pressure,  pressure  four  varied  section 4.2.2.2.  considerably  strain  section  diameter  tip  4.2.2.1  Figure  to  is  closing  The  be  liftoff  discussed  discussed  in  erratic  further  of in  to  t e s t s conducted w i t h the 32mm  controlled  corrections  Again  the  pressure.  t h r e e of the t e s t s had the same c l o s i n g p r e s s u r e .  Shear Moduli  a profile  of the  s i t e w i t h the Pencel  shear modulus  probe.  determined  The r e s u l t s  d u r i n g the s t r a i n c o n t r o l l e d t e s t s .  determine  shear  moduli  from  w i t h the s t r e s s c o n t r o l l e d Pencel  very  HPMT.  tended towards the same l i m i t  were two reasons f o r t h i s . a  this will  This  stress  curves a l l  obtained  performed  the  4.6 i s  Langley  possible  were  device.  4.5 compares the Pencel  Note t h a t a l l  There  tests.  seen;  which was a f u n c t i o n of the hand c r a n k i n g  control  pressuremeter  those  and the  in  4.3.2.  Figure  the  and  are  The s t r a i n c o n t r o l l e d t e s t y i e l d e d a very  pressuremeter curve, the  with a l l  tests  shown  similarities  the c u r v e s tended toward the same l i m i t  pressures  of  a t a depth of 6m a r e  Examining F i g u r e 4 . 4 s e v e r a l  was almost i d e n t i c a l  types  significant were  a  factor  function  of  in  the  so  many  a p p r o p r i a t e c o r r e c t i o n s were very d i f f i c u l t  60  shown  are  was  not  It  unload-reload a t any o f the  1) The c a l i b r a t i o n  at  loops sites.  corrections  calculation variables to determine.  and  the  that  the  2)  The  i  0  5  1  10 15 CIRCUMFERENTIAL STRAIN LANGLEY DEPTH 6M  LEGEND •  F i g u r e 4.4  32MM 36MM 3BMM 32MM  r  1  TIP TIP TIP TIP  STRESS STRESS STRAIN STRAIN  P e n c e l : T y p i c a l Curves a t Langley  61  20 C X>  25  or < C O  CO  or  cuio tn  or  a.  32mm t i p s t r a i n  ~1  5  1  1  10  15  —V  20  CIRCUMFERENTIAL STRAIN C X > LANGLEY DEPTH 6M LEGEND  32MM TIP STRESS 32MM TIP STRAIN HPM STRESS CONT  F i g u r e 4.5  Comparison o f P e n c e l c u r v e s w i t h HPM  62  curves: Langley  25  2Gmax 457 bar  • 4-  6a.  ui Q  •  8-  4Hd  10-  12-  4*  • •  •  1 r— 100 200 SHEAR MODULUS C BARS ) LANGLEY  300  LEGEND 32MM T I P STRAIN 36MM T I P STRAIN GMAX C SEISMIC >  F i g u r e 4.6  P r o f i l e o f Shear Modulus a t L a n g l e y :  63  Pencel  control of  u n i t used f o r the s t r e s s c o n t r o l l e d t e s t s was not  accurately  unload-reload  Figure  r e g i s t e r i n g the small  volume changes i n v o l v e d  4.6  a l s o shows the dynamic shear modulus  with  technique.  The s e i s m i c cone o b t a i n s Gmax v a l u e s  by  (  Gmax  the UBC s e i s m i c cone u s i n g the downhole  wave v e l o c i t y o v e r a lm depth i n t e r v a l .  measured  with  loops.  determined  shear  capable  the  Pencel  probe i s a t a  shear  seismic  from the  average  The shear  modulus  strain  level  a p p r o x i m a t e l y 1%.  The shear modulus measured w i t h the s e i s m i c  is  strain levels.  a t very small  )  Shear modulus a t t e n u a t i o n  of cone  curves  for clay  such as those shown i n F i g u r e 2.2  modulus  a t 1% s t r a i n s h o u l d be 10 t o 40% o f Gmax depending on the  plasticity measured  index by  the  of the c l a y . Pencel  between  probe  inserted  was  The u n l o a d - r e l o a d  the  There seems t o be no  the 32mm t i p  i n s e r t e d w i t h the 36mm o v e r s i z e d t i p . the  measured  unload-reload  moduli  c o n s t a n t even i n the very s t i f f discontinuous profiles.  The  sand  layers  and when  Gmax  discernible  the  when  the  probe  was  Note t h a t the r a t i o and Gmax  values  of  50%  u n l o a d - r e l o a d moduli measured  with  shear  moduli  probe a r e between 25 and  measured w i t h the s e i s m i c c o n e . difference  s u g g e s t t h a t the  appears  between  to  remain  l a y e r where Gmax was 467 b a r .  were apparent on  some  of  Thin  the  cone  o c c u r r e n c e o f such a l a y e r would e x p l a i n the  high  u n l o a d - r e l o a d G v a l u e s r e c o r d e d w i t h the Pencel probe a t 11.5m.  The Langley  unload-reload  shear  moduli measured w i t h  are presented i n Figure 4 . 7 .  With the HPM,  the  HPM  at  the  unload-  r e l o a d shear moduli were between 15 and 50% o f those measured w i t h  64  2-  6OL HI  a  8-  10-  • mn  dBfl)  (BDIZD an DO 12-  1 1— 100 200 SHEAR MODULUS < BARS ) LANGLEY  LEGEND  •  o  F i g u r e 4.7  STRESS CONTROLLED TEST STRESS CONTROLLED TEST STRAIN CONTROLLED TEST  P r o f i l e of Shear Modulus a t L a n g l e y : HPM  65  — i  300  the s e i s m i c  The loop the  cone.  soil  is  assumed to be u n d r a i n e d d u r i n g an  performed w h i l e mean  effective  therefore during  test  will  1s the  the  unload-reload  remain  constant  loops  test  and  of drainage,  some d r a i n a g e w i l l  the mean e f f e c t i v e  be  will  somewhat h i g h e r than those i n the  modulus number,  calculated effective  The  Kg,  will  occurring.  stages  initial  As  a  test The  cannot  a r e known and the  a  the  stages.  be mean  s t r e s s can be e s t i m a t e d .  unload-reload 65%  shear  modulus measured w i t h the  o f t h a t measured w i t h the  Pencel  HPM  probe.  has a much s m a l l e r d i a m e t e r and the e x c e s s pore  would tend t o d i s s i p a t e much f a s t e r than w i t h the HPM. the  In  i n the  be c o n s t a n t but t h i s  u n l e s s the d r a i n a g e c o n d i t i o n s  approximately Pencel  conducted.  s t r e s s i n c r e a s e s and  u n l o a d - r e l o a d shear modulus a t l a t e r  shear  and  r e g a r d l e s s of when  are  measured be  case,  very h i g h pore p r e s s u r e g r a d i e n t s a r e c r e a t e d d u r i n g  pressuremeter result  s t r e s s i n the s o i l  If t h i s  the shear modulus s h o u l d be c o n s t a n t  the  practice,  the probe 1s 1n c l a y .  unload-reload  The  pressures If t h i s  c a s e then the s h e a r moduli measured w i t h the P e n c e l would  e x p e c t e d t o be h i g h e r because o f the h i g h e r mean e f f e c t i v e The shear moduli measured w i t h the HPM were however,  is  1s be  stress.  subjected  to  l e s s a t t e n u a t i o n because the u n l o a d r e l o a d l o o p s were s m a l l e r than those performed w i t h the P e n c e l  There 1s i n s u f f i c i e n t  probe.  d a t a to draw any c o n c l u s i o n s  66  about  the  differences  between  unload-reload  shear  moduli  measured  with  s t r e s s and s t r a i n c o n t r o l l e d t e s t s w i t h the HPM.  4.2.2.2  The  Horizontal  liftoff  pressuremeter total  pore  pressure  )  pressure between  Stress  pressure  pressure  measured  expansion  by  a  ful1-displacement  i n s e r t e d i n c l a y can be expected t o be between (  the  and the i n s i t u  the  measured  will  hydrostatic  horizontal  +  total  the  stress.  depend on the time a l l o w e d  stop i n p e n e t r a t i o n and the s t a r t  drainage  the  pressure  and  the l i f t o f f  by the t o t a l soil layer  is  horizontal  above  dissipated,  a  pressures.  total  Therefore, stresses  horizontal  stresses.  Figure effective  4.8  stress.  This  after  dominated  i s c o m p l i c a t e d somewhat when the  After all  stress.  it  will  shows  Immediately  the  overconsolidated  the pore  pressures  have  p r e s s u r e c o u l d be expected t o be a measure  during  horizontal  stress.  p r e s s u r e c o u l d be expected t o be  depth of 3m.  consolidation  effective  as i s the c a s e w i t h  the l i f t o f f  o f the h o r i z o n t a l some  effective  pore p r e s s u r e .  unsaturated,  horizontal  for  t h e r e f o r e be e x p e c t e d t o be between the dynamic pore p r e s s u r e  insertion,  measured  liftoff  can  insitu  The  of  The  pore  stress  the  test.  dynamic  the  a  The s o i l ,  however,  the d i s s i p a t i o n o f can  be  expected higher  profile  the  of  the that  be somewhat  has undergone excess the  than  measured  the  measured  Most of t h e s e t e s t s were quick t e s t s ;  pore  insitu  horizontal ie.  a p r e s s u r e expansion t e s t was performed immediately a f t e r the  67  where stop  1 0  1  1  1  1 2 3 L I F T O F F PRESSURE MINUS Uo LANGLEY  1  1  4  5 < BARS 5  LEGEND X • A O  Figure  4.8  32MM 36MM 36MM 32MM - VERT  TIP TIP TIP TIP EFF  STRESS STRESS STRAIN STRAIN STRESS  P r o f i l e o f Measured H o r i z o n t a l E f f e c t i v e At L a n g l e y : P e n c e l  68  Stress  1 6  in  penetration  opportunity  and  pore  were  given  shown shaded i n F i g u r e 4 . 8 where the pore p r e s s u r e s  were  allowed  to d i s s i p a t e up to an e s t i m a t e d 90%.  opportunity  for  controlled the  pore  tests  t e s t w i t h the 32mm t i p pore  pressure  effective sounding  but  than  shows  the  horizontal expected probe  performed  presented  the  why  soil  note  using  performed  effective  the  little  controlled  36mm  tests  effective  than the v e r t i c a l  during  stress  to the v e r t i c a l  still  tip  recorded  lower  T h i s i s to be  larger  recorded  higher  horizontal  effective  stresses  l a y e r above a depth o f 6m.  69  the  is  not  consistently tests.  HPM  to  I t 1s  measured  and  recorded  s t r e s s e s are  s t r e s s and seem stress.  than It  same p a t t e r n as those  effective  that  1s  s t r e s s e s r e c o r d e d by the  effective  90%  horizontal  can r e l a x i n towards the p r o b e .  The measured h o r i z o n t a l  overconsolidated  had  stress.  produces a c a v i t y  i n F i g u r e 4 . 9 f o l l o w the  the  that  lower  s t r e s s e s than the s t r a i n c o n t r o l l e d  horizontal  proportionally to  show  The s t r a i n  effective  the s t r e s s c o n t r o l l e d  by the P e n c e l . greater  the  slightly  other t e s t s  because the 36mm t i p  lower h o r i z o n t a l  The  to  s t r e s s e s than t e s t s u s i n g the 32mm t i p .  and  obvious  a  the measured h o r i z o n t a l  tests  the  dissipate  pressure.  v e r y much h i g h e r than the v e r t i c a l  The  to  The r e s u l t s o f  t h a t was a l l o w e d time f o r an e s t i m a t e d  dissipation  stress  appear  pressures  i n f l u e n c e on the measured l i f t o f f  to t h i s are  an  results  strain  The e x c e p t i o n s  not  test  tip  dissipate.  pressures  the  36mm  to  the  all  increase  Interesting in  the  The r e s u l t s from the  LEGEND • A O  F i g u r e 4.9  STRESS CONTROL STRESS CONTROL STRAIN CONTROL VERT EFF STRESS  P r o f i l e o f Measured H o r i z o n t a l E f f e c t i v e At L a n g l e y : HPM 70  Stress  dissipation dissipated tests of  tests  show  results  are  no  particular  the arms were i n good agreement. data p o i n t i s  4.2.2.3  4.10  circumferential  presents  strain  values  than the 36mm t i p  limit  The few depths where  only  the  values of  pressures  the  measured  undrained  between the l i m i t  apparent:  p l o t s of the Pencel  are  lower  show  pressure  probe  1) the 32mm t i p y i e l d s and 2) the  results.  slightly  strain controlled tests  r e s u l t s than the s t r e s s  controlled  the  controlled  same  but  the 32mm  tip  tests consistently y i e l d e d higher  difference  therefore  pressure  between  the  limit  s m a l l e r d u r i n g those t e s t s .  shear strength i s consequently  and The  The tended  the  liftoff  strain  pressures.  pressures  calculated  smaller.  t h a n the r e s u l t s o b t a i n e d from the f i e l d vane. T h i s 1s i n results  undrained  is  undrained  The c a l c u l a t e d u n d r a i n e d shear s t r e n g t h s are almost a l l  to  Su  yield  tests.  and  liftoff  Two  lower  p r e s s u r e s r e c o r d e d by the v a r i o u s types of t e s t s a l l  towards  shear  p r e s s u r e which were taken from the p r e s s u r e v e r s u s  trends  slightly  They  Strength  s t r e n g t h determined from the d i f f e r e n c e and the l i f t o f f  quick  identical.  Undrained Shear  Figure  the  the  HPMT's.  shown a r e where the l i f t o f f  from the two arms were  of  The r e s u l t s from two  the s t r a i n arms a r e shown f o r each o f the  one  Some  h i g h e r than the r e s u l t s from  and o t h e r s l o w e r as would be e x p e c t e d .  that  The  trends.  r e p o r t e d by Wroth,  1984 where the  contrast  determination  shear s t r e n g t h u s i n g the s e l f - b o r i n g p r e s s u r e m e t e r  71  lower  of was  CL UJ  a  i  r  .75 1 UNDRAINED SHEAR STRENGTH LANGLEY  LEGEND X • A 0  F i g u r e 4.10  32MM T I P STRESS 36MM T I P STRESS 36MM T I P STRAIN 32MM T I P STRAIN F I E L D VANE  P r o f i l e of Undrained Shear S t r e n g t h Determined from the P e n c e l Curves 72  1.25 < BARS >  1.5  1.75  a p p r o x i m a t e l y 50%  generally  h i g h e r than those measured  with  f i e l d vane. H o w e v e r , t h i s would depend somewhat on the v a l u e f o r the s t i f f n e s s chosen  for this  excellent  chosen  G / S u . A v a l u e o f In (G / Su) = 6.5  ratio,  I f a v a l u e o f In (G / Su) = 5.0  study.  agreement  the  was  was  used  would have been o b t a i n e d between the  Pencel  d e r i v e d Su and the f i e l d vane v a l u e s .  Figure curves. the  4.11  shows  the v a l u e s  results  but  in  the n o r m a l l y c o n s o l i d a t e d  a p p r o x i m a t e l y 10 t o 20%  are  results.  Thus  the  HPM  s t r e n g t h s than the P e n c e l  The where  the  HPM  They f o l l o w the same t r e n d as the f i e l d vane p r o f i l e .  results  the  method  is  soil  h i g h e r than the  indicating  higher  pressure strain,  is  perfectly  The  In  field  the  HPMT  field  vane  undrained  shear  probe.  plotted against  eliminates  the  strength,  logarithm  the need t o e s t i m a t e G /  i s based on the assumption t h a t the m a t e r i a l  second  the  second method o f d e r i v i n g the u n d r a i n e d shear  volumetric  of Su.  the This  1s e l a s t i c  /  plastic.  values  o f Su d e r i v e d from the Pencel  method a r e shown 1n F i g u r e 4.12.  probe  using  They a r e very s i m i l a r  the to  r e s u l t s o b t a i n e d u s i n g the p r e v i o u s method. T h i s would tend t o  confirm  the e s t i m a t e of the s t i f f n e s s r a t i o used i n the  calculation. 1n  from  o v e r c o n s o l i d a t e d l a y e r the r e s u l t s a r e lower than  vane  the  of Su d e r i v e d  this  There 1 s ,  however,  second s e t o f r e s u l t s .  73  previous  a much g r e a t e r degree of The r e s u l t s from  the  scatter  36mm  tip  Q. LU  a  T .5 .75 1 UNDRAINED SHEAR STRENGTH LANGLEY  LEGEND D A O  F i g u r e 4.11  STRESS CONTROL STRESS CONTROL STRAIN CONTROL FIELD VANE  P r o f i l e of Undrained Shear S t r e n g t h Determined from the HPM Curves  74  1.25 BARS >  1.5  1.75  LEGEND X D  A O —  F i g u r e 4.12  32MM T I P STRESS 36MM T I P STRESS 36MM T I P STRAIN 32MM T I P STRAIN FIELD VANE  P r o f i l e of Undrained Shear S t r e n g t h Determined from the P r e s s u r e vs Log V o l u m e t r i c S t r a i n P l o t : P e n c e l 75  strain any  controlled  of  this.  t e s t s are c o n s i s t e n t l y  about twice as h i g h  the o t h e r r e s u l t s and no e x p l a n a t i o n has been  The  a t ten m e t e r s .  strength at t h i s a discontinuous  They a r e very  The h i g h e r v a l u e o f measured  p a r t i c u l a r depth i s l i k e l y  test  Ministry  l o a d e d both a x i a l l y and the i n s i t u  the  At  B.C.  shear of  load t e s t .  Details  prediction  of axial  1985a.  The  o f the p i l e  Their  load capacity  and the p r e d i c t i o n of l a t e r a l  corner  using  the  test.  this  site,  a r e the shear moduli  the s o i l  76  test pile's also  the  cone  d i s p l a c e m e n t u s i n g the  parameters d e a l t w i t h i n t h i s  and the h o r i z o n t a l  pile  paper  p r e s s u r e m e t e r data t o the measured r e s u l t s  load  of  T h i s l o c a t i o n was  t e s t i n g program used t o p r e d i c t  compares  ful1-displacement  i  and l a t e r a l l y .  i s g i v e n by Robertson e t a l ,  the p i l e  undrained  Site  of Highways p i l e  reaction  penetrometer,  One e x c e p t i o n  program was conducted a t a s i t e on the  s i t e of a B.C.  program  similar  due to the presence  Boundary Road T e s t P i l e  Boundary and D i k e Road i n New W e s t m i n i s t e r ,  was  using  sand l e n s e .  4.3  the  results  undrained s h e a r s t r e n g t h s c a l c u l a t e d from the HPM  t o the Su v a l u e s c a l c u l a t e d u s i n g the f i r s t method.  The  for  test.  the second method a r e shown i n F i g u r e 4 . 1 3 .  is  found  There does not seem to be a c o n s i s t e n t t r e n d 1n the  o f the s t r e s s o r s t r a i n c o n t r o l l e d  as  stresses.  from  paper  3E  0.  LU Q  i  r 1.25 BARS > .5 .75 1 UNDRAINED SHEAR STRENGTH C LANGLEY 1  1.5  LEGEND •  A O •  Figure  4.13  STRESS CONTROL STRESS CONTROL STRAIN CONTROL FIELD VANE  P r o f i l e of Undrained Shear S t r e n g t h Determined from the P r e s s u r e vs Log V o l u m e t r i c S t r a i n P l o t : HPM  77  1.75  4.3.1  Site  Description  The s i t e  1s covered w i t h a p p r o x i m a t e l y 3m o f r u b b l e  o r d e r t o p r e v e n t damage to the p r o b e s , and  backfilled  tests,  with l o o s e  cone of  a 3m deep t r e n c h was  sand a t the l o c a t i o n s  and a t the l o c a t i o n o f the t e s t p i l e .  p i e z o m e t e r - f r i c t i o n cone p r o f i l e profile organic  shows 3m o f l o o s e  silt.  fill.  of  the  In dug,  insitu  F i g u r e 4.14 shows a  of the s i t e a t Boundary Road. The sand o v e r l y i n g 2m o f p e a t and  U n d e r l y i n g the o r g a n i c  silt  10m  i s a dense l a y e r  of  sand e x t e n d i n g t o a depth of about 30m.  A  list  Boundary  of  Road  all Pile  the v a r i o u s i n s i t u Load  T e s t s i t e and used  r e s e a r c h program a r e l i s t e d i n the t a b l e  4.3.2  4.16 shows t y p i c a l  s t r a i n control  as  part  in Figure  4.15.  c u r v e s from the Pencel  t e s t data appears very e r r a t i c .  o f the method used t o run the t e s t s . run w i t h a hand c r a n k . variations loss  at of  the this  Variations  bar,  The s t r a i n c o n t r o l  d e v i c e was  i n the speed o f c r a n k i n g caused tubing.  can  only  be  based  inflation.  78  i s not r e c o r d e d , on  the  The head  approximately  i s g r e a t e r than any o f the f l u c t u a t i o n s  As the e x a c t r a t e o f i n f l a t i o n correction  The  a function  i n the head l o s s through the f l e x i b l e  which  tests.  This i s  i n the t u b i n g a t the normal e x p a n s i o n r a t e i s  curve. loss  conducted  Results  Figure  0.4  tests  average  In the rate  the head of  UBC Site On  I  Locotloni Si to  Loci  rsi  ITU  s  BOUNDARY ROAD  CPT Data t JUNE 06  PILE  Cona Ucadi  LOAD TEST  CONE BEARING Ot (bar)  19B4  UBC6 STD TIP  FRJCTJON RATIO Rf (X) 0 10  S T I N G P090 Noi  Commentti  PORE PRESSURE U (a. of l a t e r ] -P SO  1/4  3m Pra-bor«c INTERPRETED PROFILE  loose sand backfill  peat  soft organic silty c lay  in  L 0) -P Ql E  10  0.  LU Q  15-  medium dense sand  ZD  Dapth Increment i  F i g u r e 4.14  Boundary Road  . OZS m  cone  Max D e p t h i  profile  78.B25 m  TESTS CONDUCTED AT THE BOUNDARY ROAD TEST SITE  Test Designator  Instrument  T e s t Date  Comments  Depths a t which PMTs were conducted  UBC #1  Seismic cone  05/07/84  UBC #2  Seismic cone  12/07/84  UBC #3  HPM  10/08/84  Stress  UBC #4  P e n c e l Probe  06/08/84  Stress controlled  36mm t i p  5,7,9,11,13,15  UBC #5  Pencel Probe  05/08/84  Stress controlled  32mm t i p  5,7,8,9,10,11,12,13,14,  UBC #6  HPM  18/08/84  Stress  UBC #7  Pencel Probe  30/10/84  Strain controlled  UBC #8  HPM  22/01/85  Strain  controlled  5,7,9,11,13,3  controlled  3,5,7,9,11,13 32mm t i p  controlled  A x i a l P i l e Load T e s t  P i l e D r i v e n to 67m  A x i a l P i l e Load T e s t  P i l e D r i v e n to 78m  A x i a l P i l e Load T e s t  P i l e D r i v e n to 94m  Lateral  P i l e D r i v e n to 94m  P i l e Load T e s t  F i g u r e 4.15  I n s i t u T e s t s conducted a t Boundary Road  3.5,5,7,9,11,13,15 1,2,3,5.5,7,9,10,11  3-  36mm t i p s t r e s s  cn or <  controlled  CD  2OH LO CO Ul  a: a.  132mm t i p s t r a i n  ~1  5  controlled  1  1  10  15  20  CIRCUMFERENTIAL STRAIN C X> BOUNDARY ROAD DEPTH 7M  LEGEND 32MM T I P 36MM T I P 32MM T I P  F i g u r e 4.16  STRESS STRESS STRAIN  P e n c e l : T y p i c a l Curves a t Boundary Road  81  r-  25  Four 1) The  important limit  approximately liftoff not  pressure equal;  pressure  seem  using  of  the  various  from  Figure  tests  seem  4.16: to  2) The s t r a i n c o n t r o l l e d t e s t has a  than the s t r e s s c o n t r o l l e d t e s t s ;  36mm t i p  3) There does curves  t e s t s and curves u s i n g the 32mm t i p .  p r e s s u r e from a l l  t h r e e t e s t s was the  be  higher  to be a s i g n i f i c a n t d i f f e r e n c e i n shape between  the  closing  f a c t o r s can be observed  same.  4)  No  The  strain  c o n t r o l l e d t e s t s were performed w i t h the 36mm t i p .  Figure  4.17  compares  c o n t r o l l e d HPMT with t y p i c a l 32mm as  tip.  typical  The HPM i n d i c a t e s a l i f t o f f  higher.  shown  curve  from  curves from the Pencel  the s t r e s s c o n t r o l l e d Pencel  much  the  stress  t e s t s w i t h the  p r e s s u r e i n t h e same range  t e s t but the l i m i t  pressure  4.3.2.1  The  site  s e i s m i c cone. cone was the  velocity  Shear Modulus  investigation  i n c l u d e d a sounding  stress  was  with  the  UBC  The dynamic shear modulus measured from the s e i s m i c standard t o which the shear moduli measurements from  and  effective stress. soil  were  representative.  pressuremeter were compared.  wave  was  The r e s u l t s from t h e s t r a i n c o n t r o l l e d HPMT are not  because t h e r e were equipment problems and the r e s u l t s  not c o n s i d e r e d  the  a  The s e i s m i c cone measures shear  thus the shear modulus In t h e c l a y a t L a n g l e y ,  undrained  at  In the peat and  82  insitu  mean  i t was assumed t h a t the  d u r i n g the PMT so t h a t  stayed c o n s t a n t .  the  the  mean  effective  LEGEND 32MM TIP STRESS 32MM TIP STRAIN HPM STRESS CONT  F i g u r e 4.17  Comparison o f P e n c e l Curves w i t h HPM Curves: At Boundary Road  83  organic less  silt  d e p o s i t a t Boundary Road the d r a i n a g e c o n d i t i o n s  certain.  the  mean  Some d r a i n a g e may be o c c u r r i n g d u r i n g the t e s t  effective  s t r e s s may be r i s i n g .  p r e s s u r e s a r e not known d u r i n g the t e s t , to  estimate  variations  the  the  This  the  the fall  HPM,  or  and the UBC s e i s m i c  what  cone.  The  Pencel  w i t h i n a range of 20 t o 50% o f the measurements  seismic cone.  unload-reload is  The  measurements  are  relatively  range.  At a given  l o o p s performed a t l a t e r  stages  i n the  test.  to be expected from the above d i s c u s s i o n on d r a i n a g e . .  HPM r e s u l t s g e n e r a l l y a t any i n d i v i d u a l  a t 10m.  show l e s s  s c a t t e r than those  d e p t h . The e x c e p t i o n to t h i s  from  i s a t lm  Near the s u r f a c e the sand was f r e e d r a i n i n g and  effective  increases 11m  stress,  and do not seem t o vary o v e r a l a r g e  the Pencel  mean  no attempt has been made  the l a r g e r v a l u e s of shear modulus were g e n e r a l l y measured  The  and  pore  4.18 compares the shear moduli measurements from  UBC  consistent  from  the  the  probe,  depth,  effective  as  effect  measurements from  mean  However  and  have on the shear modulus measurements.  Figure Pencel  are  stress  increased  dramatically  with  consequent  i n the s h e a r modulus as the t e s t p r o g r e s s e s .  adjacent  cone p e n e t r a t i o n s o u n d i n g s . Wherever one of t h e s e l a y e r s  occurred,  soil  sandy s i l t  l a y e r s were i d e n t i f i e d  From 9 t o  i n the  the  occasional  the  was a l l o w e d to d r a i n w i t h a r e s u l t i n g i n c r e a s e i n  shear  modulus as the t e s t p r o g r e s s e d . These l a y e r s were s t i f f e r than surrounding modulus did  not  soil,  a  r e s u l t which was r e f l e c t e d i n h i g h e r  v a l u e s measured by the p r e s s u r e m e t e r . show  up i n the s e i s m i c cone p r o f i l e  84  Thin s t i f f of  shear  the  shear layers modulus  n i  II II  i  4DO  •  Q_  •  •***• u r n  Ul  a  • rrrw» 12'  •  16-  -T50  •  •  100  150  200  SHEAR MODULUS C BARS BOUNDARY ROAD  LEGEND HPM STRAIN CONT PENCEL 32MM T I P GMAX C SEISMIC >  F i g u r e 4.18  P r o f i l e o f Shear Modulus a t Boundary P e n c e l and HPM 85  Road;  250  because  the  shear  wave v e l o c i t y  used  to  calculate  the  shear  modulus was averaged o v e r a 2m i n t e r v a l .  4.3.2.2  The  Horizontal  horizontal  Stresses  effective  are presented i n Figure 4 . 1 9 . First,  the v a l u e s a l l  depth.  This  vertical test  rate  effective  recorded  expected forms  to  an  probe. tests  is  trends.  s i m i l a r to the r a t e  stress.  of  increase  Second, the 36mm t i p stresses.  the l o w e s t h o r i z o n t a l  oversized hole,  of  controlled  The 36mm  stresses  the  tip  is  because  it the  The t h i r d t r e n d i s c o n s i s t e n t w i t h t h a t observed from  the  namely t h a t the s t r a i n c o n t r o l l e d t e s t s t r e s s e s than the s t r e s s c o n t r o l l e d  4.20 shows the h o r i z o n t a l  c o n t r o l l e d HPMT's.  readings  and the s o i l  stress  with  can r e l a x up a g a i n s t  Figure  The data i s  indicates  indicates  test.  s t r e s s e s measured from shown i n p a i r s  taken from two s e p a r a t e s t r a i n arms.  two arms responded s i m i l a r l y  was  They show t h r e e s i g n i f i c a n t  i n c r e a s e a t a p p r o x i m a t e l y the same r a t e  indicate  higher horizontal  test  Pencel  the l o w e s t h o r i z o n t a l  at Langley,  stress  s t r e s s e s measured w i t h the  indicating  The f a c t t h a t  a good t e s t .  The one s e t  r e s u l t s a t 9m t h a t i n d i c a t e d a much h i g h e r h o r i z o n t a l in  strengths  a  thin  discontinuous  were a l s o  sand  noted.  86  layer,  where  the  much  the of  stress higher  1 0  1  1  —1  1  1 2 3 L I F T O F F PRESSURE MINUS Uo BOUNDARY ROAD  4  1  1 6  5 C BARS 5 (  LEGEND • A O  F i g u r e 4.19  3BMM T I P 32MM T I P 32MM T I P • VERT E F F  STRESS STRESS STRAIN STRESS  P r o f i l e o f Measured H o r i z o n t a l E f f e c t i v e At Boundary Road: P e n c e l  87  Stress  x  1  D  1  1  1  1 2 3 LIFTOFF PRESSURE MINUS Uo BOUNDARY ROAD  1  1  1  4  5  6  < BARS >  LEGEND • A  F i g u r e 4.20  STRESS CONT #1 STRESS CONT #2 - VERT EFF STRESS  P r o f i l e of Measured H o r i z o n t a l E f f e c t i v e At Boundary Road: HPM  88  Stress  4.4  McDonalds  Farm  McDonalds Farm  has been a r e s e a r c h s i t e f o r the UBC  t e s t i n g group s i n c e 1979. performed well  at t h i s  known.  documented  T h i s was the s i t e  and  are  from t h i s  and the s o i l  in Robertson,  self-boring results  site,  Many d i f f e r e n t  full  types of t e s t s have been  profile  displacement  comparing the  pressuremeter  p r e s e n t e d f o r comparison with the  research  and p r o p e r t i e s  o f some o f the d o c t o r a l  1982 d i r e c t l y  insitu  are  research, results  tests.  results  These  obtained  project.  The main d i f f e r e n c e between McDonalds Farm and the o t h e r research s i t e s at  is  the d r a i n a g e c o n d i t i o n s .  The p r e s s u r e m e t e r  McDonalds Farm were performed i n the l a y e r of c l e a n  two tests  sand where  the p e r m e a b i l i t y was high enough t h a t the sand remained d r a i n e d all  times  4.4.1  The silt  d u r i n g the  Site  at  tests.  Description  research  site  a t McDonalds Farm i s c o m p r i s e d o f  o v e r l y i n g 11m o f c l e a n s a n d .  t r a n s i t i o n zone of s i l t y a s o f t clayey s i l t .  The  of  table  Between 13 and 15m t h e r e i s  s a n d , and below 15m, the s o i l  F i g u r e 4 . 2 1 shows a t y p i c a l  CPT  consists  of a of  profile.  p r e s e n t e d i n F i g u r e 4.22 shows the  t h a t were performed a t McDonalds Farm and a n a l y z e d i n  89  2m  insitu  tests  this  study.  UBC  IM  S i t e Locotloni  MCDONALDS FARM  On  CENTER OF PMTS  Slto  Loci  SITU CPT O o t o i  Conn Uaadi  CONE BEARING  FRICTION  Ot (bar)  Rf  200  T  0CT23 18B4 15 SO. CM. S E I S  RATIO  CO  S  0  TING P o g a Not  1 / 2  Comnantti  PORE PRESSURE  INTERPRETED  U (a. o f aotar)  0  PROFILE  100  soft clay and s i l t  coarse sand l o o s e to dense with layers of f i n e sand  10-  10-  10-  Qt max = 400 b a r  IS-  f i n e sand some s i l t  soft clayey silt  ECDapth Incramant i  F i g u r e 4.21  McDonalds  . 025 n  Farm cone p r o f i l e  90  Max D a p t h i  31. 973 m  TESTS CONDUCTED AT MCDONALDS FARM H"  TO C H  rt)  Test Designator  Instrument  Comments  T e s t Date  D e p t h s a t w h i c h PMTs were c o n d u c t e d  SBPM #1  HPM  03/12/80  Stress  controlled  *  3,3.8,4.6,5.3,6.3  SBPM #2  HPM  11/02/81  Stress  controlled  *  A.9,6.2,7,8.5,9.3,11,11.7,12.8  PPMT #1  HPM  OA/12/81  Stress  controlled  2.7,3.8,4.6  PPMT #2  HPM  20/01/82  Stress  controlled  2.75,3.8,4.6,5.5,6.7,7.6  PPMT #3  Pencel Probe  05/06/8A  Stress  controlled  36mm t i p  0.5,1.5,3.5,7.5,11.5, 13.5,16.5,18.5  PPMT #4  Pencel  06/06/8A  Stress  controlled  32mm t i p  3.5,5.5,7.5,13.5,14.5  PPMT #5  HPM  ^18/06/84  Stress  controlled  PPMT #6  Pencel Probe  09/10/8A  Strain controlled  32mm t i p  3,5,7,9  PPMT #7  Pencel  Probe  16/10/84  Strain controlled  36mm t i p  3,5,7,9,11  PPMT #8  Pencel  Probe  23/10/84  Pushed w h i l e p a r t i a l l y  PPMT #9  P e n c e l Probe  23/10/84  Strain controlled  36mm t i p  **1  PPMT #10  Pencel  23/10/84  Strain controlled  32mm t i p  3  M2  HPM  14/01/85  Strain controlled  0.5,1,1.5,3,7  M3  HPM  25/01/85  Strain controlled  0.5,1,3,5,7  MA  HPM  25/01/85  Strain controlled  CPT  S e i s m i c cone  31/01/85  3  co Hrr C rf  (D [A rr cn  O O 3  a.  c  o  rf (B  a. 3 o O o 3  IB f— CL cn  D> >i  Probe  Probe  * The p r e s s u r e m e t e r was s e l f - b o r e d  i n t o t h e ground  4,5,6,7,8  inflated  3,5  3,5,7,9  1,3,5,7  4.4.2  Results  Typical at  p r e s s u r e m e t e r c u r v e s o b t a i n e d w i t h the Pencel  McDonalds  pressure  Farm a r e shown i n F i g u r e 4 . 2 3 .  from  the  32mm  tip  strain  probe  The h i g h e r  controlled  liftoff  results  was  c o n s i s t e n t w i t h the r e s u l t s from L a n g l e y and Boundary Road. interesting  to  note t h a t the o t h e r t h r e e t e s t s a l l  liftoff  pressures,  and t h a t a l l  closing  pressures.  The  equilibrium  f o u r t y p e s of t e s t s  closing  pressure i s a  traditional  i s not  visible  w i t h the Pencel  F i g u r e 4.23 were t y p i c a l  tip from  similar of  the  sand.  Note fact  suprising.  placed in  an S shape curve upon i n f l a t i o n .  i n a very few o f the t e s t s with the o v e r s i z e d t i p ever  had  measure  Menard type o f p r e s s u r e m e t e r i s  p r e - b o r e d h o l e and e x h i b i t s  this  similar  l i m i t p r e s s u r e so the  t h a t the c u r v e s d i d not appear to converge  The  had  pore p r e s s u r e f o r p r e s s u r e m e t e r t e s t s i n  t h a t with sands t h e r e i s no t h e o r e t i c a l  I t was  probe.  of the c u r v e s  Only  ( 36mm t i p  The c u r v e s  a  ) was  shown  in  obtained.  F i g u r e 4 . 2 4 compares the P e n c e l  t e s t s conducted w i t h the 32mm  t o the s t r e s s c o n t r o l l e d HPMT.  The l i f t o f f  the s t r e s s c o n t r o l l e d HPMT was  pressure closing  obtained  pressure  obtained  comparable w i t h the  liftoff  from the s t r e s s c o n t r o l l e d  Pencel  p r e s s u r e s were s i m i l a r f o r the two types of  c l o s i n g p r e s s u r e was measured.  92  test. tests  The where  I  0  I  5  I 1 10 15 CIRCUMFERENTIAL STRAIN C X> DEPTH MCDONALDS FARM  1 20  LEGEND •  F i g u r e 4.23  3BMM 32MM 36MM 32MM  TIP TIP TIP TIP  STRESS STRESS STRAIN STRAIN  P e n c e l : T y p i c a l Curves a t McDonalds Farm  93  1 25  LEGEND •  F i g u r e 4.24  32MM T I P STRESS 32MM T I P STRAIN HPM STRESS CONT  Comparison o f P e n c e l c u r v e s and HPM c u r v e s : At McDonalds Farm  94  4.4.2.1  Shear Modulus  Shear modulus i s clean  sand  excess  pore  effective the the  at  dependent on the mean e f f e c t i v e  McDonalds Farm i s  pressure  fully  d r a i n e d so  g e n e r a t e d d u r i n g the t e s t s  s t r e s s increases with r a d i a l  measured shear modulus w i t h  stress.  stress. there  and  The  is  the  no mean  In o r d e r to compare  the shear modulus o b t a i n e d  from  s e i s m i c cone, o r to compare v a l u e s o b t a i n e d a t d i f f e r e n t  times  during  the PMT the shear modulus must f i r s t be n o r m a l i z e d to  i n s i t u mean e f f e c t i v e  A  s t r e s s as was d i s c u s s e d i n s e c t i o n  shear modulus p r o f i l e probe i s  Pencel  were a p p r o x i m a t e l y 10 t o 20%  seismic  cone.  shown i n F i g u r e 4 . 2 5 .  The  The moduli measured w i t h  seem t o d i f f e r  unload r e l o a d l o o p s . T h i s  the UBC  significantly  o r the o v e r s i z e d t i p was u s e d .  were o b t a i n e d from 5cm  controlled  o f Gmax measured w i t h the  r e s u l t s d i d not  whether the 32mm t i p  2.2.  o b t a i n e d w i t h the s t r a i n  Pencel  the  These  moduli  represents  about  2-2.5% s t r a i n . T h i s was w i t h i n the bounds s e t by Wroth, 1984 where the  sand w i l l  behave e l a s t i c a l l y .  Although Seed and I d r i s s '  modulus  a t t e n u a t i o n c u r v e s p r e s e n t e d i n F i g u r e 2.2  to  shear s t r a i n l e v e l  this  shear  modulus a t 2%  they would i n d i c a t e  do not  t h a t the  shear extend  measured  s t r a i n would be e x p e c t e d t o be l e s s than  10%  o f Gmax.  The  Pencel  shear moduli  r e s u l t s obtained with 5cm  3  loops  McDonalds Farm appear to be more c o n s i s t e n t than the shear  at  moduli  a results  obtained  corrections  are  with  2cm  loops at  Langley.  The  q u i t e l a r g e compared t o the s c a l e 95  of  calibration an  unload  0. LU  a  T  200  :-  400  600  eoo  1000  SHEAR MODULUS NORMALIZED TO INSITU STRESS MCDONALDS FARM  LEGEND D  F i g u r e 4.25  32MM T I P 36MM T I P - GMAX < SEISMIC >  P r o f i l e o f N o r m a l i z e d Shear Modulus A t McDonalds Farm: P e n c e l  96  1200  noo  C BARS )  0.  LU Q  200  400 600 600 1000 1200 1400 SHEAR MODULUS NORMALIZED TO INSITU STRESS C BARS > MCDONALDS FARM  LEGEND * D  F i g u r e 4.26  SBPMT FDPMT - GMAX C SEISMIC 5  P r o f i l e o f N o r m a l i z e d Shear Modulus At McDonalds Farm: S t r e s s C o n t r o l l e d HPM  97  OD  EE  2X LTJDD  4xaon • • 60.  xx»x  Ul a  Txsaaaa  8-  10-  12-  —I 200  T  T  T  400 600 800 1000 1200 1400 SHEAR MODULUS NORMALIZED TO INSITU STRESS ( BARS ) MCDONALDS FARM LEGEND D X  F i g u r e 4.27  STRAIN CONT #1 STRAIN CONT #2 GMAX C SEISMIC >  P r o f i l e of N o r m a l i z e d Shear Modulus At McDonalds Farm: S t r a i n C o n t r o l l e d  98  HPM  reload  loop,  and d i d not i n c r e a s e l i n e a r l y w i t h the s i z e of  l o o p . The l a r g e r u n l o a d - r e l o a d l o o p s have a p r o p o r t i o n a l l y calibration  correction  and  appear to  yielded  more  the  smaller  consistent  results.  Two  Shear  moduli measured w i t h the HPM a r e shown i n F i g u r e 4 . 2 6 .  types  of t e s t s  pressuremeter three  are shown on  results  Figure  4.26.  The  self-boring  are p l o t t e d a g a i n s t the r e s u l t s  stress controlled f u l l  from  the  displacement pressuremeter t e s t s .  The  s e l f - b o r i n g t e s t s were a l s o run i n a s t r e s s c o n t r o l l e d manner. The moduli  measured  w i t h the s t r e s s c o n t r o l l e d HPM f a l l  within  the  range o f 2 0 t o 50% o f Gmax measured w i t h the UBC s e i s m i c c o n e . was  expected  t h a t the r e s u l t s would be h i g h e r than  from the Pencel  less  results  probe because the u n l o a d - r e l o a d l o o p s r e p r e s e n t  s m a l l e r s t r a i n w i t h the HPM than w i t h the P e n c e l . is  the  It  Therefore  a  there  shear modulus a t t e n u a t i o n w i t h the HPM.  The  normalized  shear  modulus  measured  with  c o n t r o l l e d HPM i s p r e s e n t e d i n F i g u r e 4 . 2 7 . There i s  the  strain  a little  more  s c a t t e r than with the s t r e s s c o n t r o l l e d t e s t but the t r e n d o f  the  results  is  almost the same.  4.4.2.2  The  horizontal  controlled recorded  Horizontal  Pencel by  Stresses  effective probe  are  s t r e s s e s r e c o r d e d by shown i n  the s t r e s s c o n t r o l l e d Pencel  99  Figure  the  4.28  probe i n  strain  and  those  Figure  4.29.  With  both types of t e s t s ,  those r e c o r d e d w i t h the 32mm t i p  higher  liftoff  p r e s s u r e s than those w i t h the 36mm t i p .  strain  c o n t r o l l e d t e s t s the l i f t o f f  a r e much h i g h e r . the  liftoff  Comparison between the two f i g u r e s  from the s t r e s s c o n t r o l l e d t e s t .  readily  apparent  for this  The  horizontal  however  stress is generally  less  disturbances horizontal measured  applicable  can  lead  stresses.  full  to  in  the f u l l  than  The full  displacement  significant tests  is  line.  Even  liftoff  errors  in  There i s a c t u a l l y  tests  are  controlled scatter self-  pressures  therefore  recorded  stresses.  shown  in  Figure  when compared t o  o f t e n than w i t h the were  the  Figure  less  recorded l i f t o f f  This  pressures  A l s o shown i n  p r e s s u r e s r e c o r d e d w i t h the HPM  much  initial  determining  the  the l a c k o f p o i n t s above the v e r t i c a l  pressures  small  r e s u l t s than t h e r e i s w i t h the  effective  difference  more  measuring.  where  the e q u i l i b r i u m pore p r e s s u r e and  liftoff  that  No e x p l a n a t i o n  p r e s s u r e s measured w i t h the s t r e s s  displacement  negative horizontal  tip  are  F i g u r e 4 . 3 0 p r e s e n t s the l i f t o f f  b o r i n g r e s u l t s . Note t h a t s e v e r a l less  sands  large  displacement pressuremeter.  among  32mm  assumed to be a parameter  by the s e l f - b o r i n g p r e s s u r e m e t e r .  4 . 3 0 are the l i f t o f f  the  observation.  t h a t the s e l f - b o r i n g p r e s s u r e m e t e r i s capable of is  With  indicate  p r e s s u r e s from the s t r a i n c o n t r o l l e d t e s t  h i g h e r than those is  p r e s s u r e s w i t h the  have  recorded  e q u i l i b r i u m pore p r e s s u r e .  100  stress that  were  strain 4.31. stress  controlled The  most  controlled  effective  stress  controlled  tests,  less  than  the  X  r-  0LU Q  i  1 2 3 L I F T O F F PRESSURE MINUS Uo MCDONALDS FARM  C BARS >  LEGEND D X  F i g u r e A.28  32MM T I P STRAIN 36MM T I P STRAIN - VERT E F F STRESS  P r o f i l e of Measured H o r i z o n t a l E f f e c t i v e S t r e s s At McDonalds Farm: S t r a i n C o n t r o l l e d P e n c e l  101  Figure  4.29  P r o f i l e of Measured H o r i z o n t a l E f f e c t i v e S t r e s s At McDonalds Farm: S t r e s s C o n t r o l l e d P e n c e l 102  3:  I  . L I F T O F F PRESSURE MINUS Uo MCDONALDS FARM  C BARS )  LEGEND • X  F i g u r e 4.30  FDPMT SBPMT - VERT E F F STRESS  P r o f i l e o f Measured H o r i z o n t a l E f f e c t i v e S t r e s s At McDonalds Farm: S t r e s s C o n t r o l l e d HPM  103  0  1 2 3 L I F T O F F PRESSURE MINUS Uo MCDONALDS FARM  4  5 C BARS )  LEGEND D  F i g u r e 4.31  FDPMT STRAIN VERT E F F STRESS  P r o f i l e o f Measured H o r i z o n t a l E f f e c t i v e S t r e s s At McDonalds Farm: S t r a i n C o n t r o l l e d HPM  104  Note  that  horizontal the  stresses  stress  recorded recorded  the  Pencel that  controlled horizontal  by  the  stress  strain  were  test.  much  Whereas  stresses  that  controlled  105  controlled  higher the  strain  were  tests.  than  tests  those  recorded  recorded  controlled  lower  than  the  by  HPMT's ones  Chapter 5 Conclusions  5.1  This  research  examining  the  pressuremeter  study  horizontal  stresses,  examined  were;  pressuremeter the  size  whether  for  of  using  determining  the shear  the  type  of  was  pushed i n f r o n t of  allowed  f o r the  the  dynamic  variables  whether  the  manner,  pore  and  pressures  were  made to account  and mean e f f e c t i v e  no  difference  and c l a y .  seismic  f o r the d i f f e r e n c e s  cone.  in  s t r e s s . The s i z e o f the t i p the r e s u l t s .  well  strain  in front  As was e x p e c t e d  between shear moduli c a l c u l a t e d  of  there  from  stress  c o n t r o l l e d t e s t s w i t h the HPM and s t r a i n c o n t r o l l e d t e s t s w i t h HPM.  to  Shear Modulus  the i n s t r u m e n t d i d not a f f e c t was  The  insitu  pressuremeter,  dynamic shear modulus measured w i t h the  Adjustments level,  modulus,  shear modulus measured w i t h the FDPM compared very  the  of  displacement  was run i n a s t r e s s o r a s t r a i n c o n t r o l l e d  5.2  with  intention  full  pressuremeter,  d i s s i p a t e . T e s t s were conducted i n s a n d , s i l t ,  The  the  and u n d r a i n e d shear s t r e n g t h .  o f the t i p time  was performed w i t h  suitability (FDPM)  Summary  the  The shear modulus measurements from t e s t s where the HPM were  installed  in  a  s e l f - b o r i n g manner were very  similar  measurements  from t e s t s where the probe was i n s t a l l e d i n  displacement  manner.  The  shear  106  modulus measurements  from a from  the full the  strain  controlled  measurements. associated soft  probe were very  However,  the  w i t h the Pencel  soils.  variables  Pencel  The  membrane  similar  to  stiffness  was  t e s t s was a very s i g n i f i c a n t  so  in  many  i n a s t r e s s c o n t r o l l e d t e s t t h a t i t was not p o s s i b l e  not p o s s i b l e  5.3  stress  factor  membrane c a l i b r a t i o n was dependent on  to determine  s t r e s s c o n t r o l l e d Pencel  In  HPM  correction  determine the c o r r e c t i o n w i t h any degree of c e r t a i n t y . it  the  general, by  improving method o f  shear modulus from any  Insitu Horizontal  of  the  Stress  the attempts to determine the i n s i t u  There  this  As a r e s u l t  tests.  examining  unsuccessful.  to  the  does  liftoff  pressure  not appear to be  any  horizontal  were  totally  possibility  t e c h n i q u e to the p o i n t where i t would be a  of  useful  analysis.  The  liftoff  pressure  was lower when an o v e r s i z e d  p l a c e d i n f r o n t o f the FDPM. was a l l o w e d to r e l a x the  liftoff  run  in  a  c o n t r o l l e d manner.  i n t o the c a v i t y  s u r r o u n d i n g the  soil  probe.  Also  h i g h e r when the t e s t s  were  controlled  manner  The l i f t o f f  p r e s s u r e s were so v a r i a b l e  t o determine i f  was  T h i s was t o be expected as the  p r e s s u r e was c o n s i d e r a b l y strain  tip  as  the l i f t o f f  opposed  to  a  stress that  was  difficult  p r e s s u r e showed any  the  e x p e c t e d d e c r e a s e when the dynamic pore p r e s s u r e s were  it of  given  an o p p o r t u n i t y t o d i s s i p a t e b e f o r e the p r e s s u r e e x p a n s i o n t e s t was run.  The  general  t r e n d o f the l i f t o f f  107  p r e s s u r e s was to  Increase  with  depth but they d i d not appear t o h o l d any o t h e r  w i t h the i n s i t u  horizontal  5.4  relationship  stresses.  Undrained Shear  Strength  The u n d r a i n e d shear s t r e n g t h s of c l a y  determined u s i n g  e x p a n s i o n t h e o r y compared very w e l l  w i t h undrained shear  determined  The undrained  using  calculation  is  the f i e l d vane.  made  liftoff  t h a t were  pressure.  The  tests  the h i g h e s t l i f t o f f  shear  where  ),  were a l s o the t e s t s where the  about 25% h i g h e r than those  5.5  those  goals  stresses  with  pressures  were  undrained  The HPM r e s u l t s were  generally  from the Pencel  Recommendations  o f many types of s o i l Further  the  lowest  for Further  The FDPM appears t o be a p r a c t i c a l  clay.  about  the s t r a i n c o n t r o l l e d t e s t s and the t e s t s w i t h the  s t r e n g t h s were c a l c u l a t e d .  moduli  strength results  observations  tip  shear  p r e s s u r e and the  the  smaller  strengths  dependent on the l i f t o f f  reflected  measured ( i e .  cavity  research in  mind.  probe.  Research  way of measuring the  shear  and the undrained shear s t r e n g t h  s h o u l d be conducted w i t h the The d e t e r m i n a t i o n  of  insitu  FDPM  of with  horizontal  the FDPM was not p o s s i b l e and the r e s u l t s  appear p r o m i s i n g enough t o warrant f u r t h e r r e s e a r c h . Some  do  not  specific  a r e a s of r e s e a r c h a r e suggested below:  1) F u r t h e r r e s e a r c h s h o u l d be conducted i n t o the  differences  between the c u r v e s t h a t are produced when the p r e s s u r e m e t e r i s  108  run  s t r e s s c o n t r o l l e d and when f t indicated  that  insufficient  2)  were  data a v a i l a b l e  Pressuremeters  measurement trying  there  run s t r a i n c o n t r o l l e d .  1s  some  but  study  there  was  to draw any c o n c l u s i o n s .  should  capability.  difference  This  This  be equipped would be  t o determine the mean e f f e c t i v e  with  pore  especially  pressure  useful  s t r e s s a t which the  when shear  modulus i s b e i n g measured.  3) drive.  The This  inconsistent completely cycle  strain control would hand  device  eliminate cranking.  s h o u l d be fitted w i t h  the head l o s s A  s t a n d a r d i z e the s t r a i n  motor  would  variations make  r a t e and the s i z e  used i n d e t e r m i n i n g shear m o d u l i .  109  a  it  motor due  to  easy  to  o f the  stress  REFERENCES Brown, P . T . , Masters o f A p p l i e d S c i e n c e T h e s i s , 1985, of B r i t i s h Columbia.  University  Campanella, R.G. and R o b e r t s o n , P.K., 1981, "Applied Cone Research", Symposium on Cone Penetration Testing and Experience, Geotechnical Engineering Division, ASCE, O c t . 1981, pg 343 - 3 6 2 . F a u g e r a s , J . C . , Gourves, R., Meunier P . , Nagura M . , M a t s u b a r a , L., Sugawara, N., 1983, " On the V a r i o u s F a c t o r s Affecting Pressuremeter Test Results", Proceedings of the International Symposium on Insitu Testing, Paris, Volume 2, pg 275 - 2 8 1 . Gibson, R.E., and A n d e r s o n , W . F . , 1961, " I n - s i t u Measurement of Soil with the P r e s s u r e m e t e r " . C i v i l Eng. and P u b l i c Works Review, V o l . 5 6 , No. 6 5 8 , May 1961, pg 615 - 618. Greig, Jim, Masters o f A p p l i e d S c i e n c e T h e s i s , 1985, o f B r i t i s h Columbia.  University  Hughes, J . M . O . and R o b e r t s o n , P.K., 1984, "Full-Displacement Pressuremeter T e s t i n g i n Sand", U n i v e r s i t y of B.C., Civil E n g i n e e r i n g D e p t . , S o i l Mechanics S e r i e s No. 78 J a n b u , N . , 1963, " S o i l C o m p r e s s i b i l i t y as Determined by Oedometer and T r i a x i a l T e s t " , P r o c e e d i n g s o f the European Conference on S o i l Mechanics and F o u n d a t i o n Engineering, Wiesbadden, V o l . 1, pg 1 9 - 2 5 . Lacasse, S. and Lunne, T . , 1982, " I n s i t u H o r i z o n t a l S t r e s s from Pressuremeter Test", Proceedings of the International Symposium on the P r e s s u r e m e t e r and I t s Marine A p p l i c a t i o n s , P a r i s , pg 187 - 208. M a s s a r s c h , K.R. and D r n e v i c h , V.P., normally consolidated clays", Geotechnical Engineering, BGS, pg 251 - 255. Reid,  "Deformation p r o p e r t i e s Design Parameters London, 1979, Vol.  of in 2,  W.M., St. John, H . D . , F y f f e , S. and R i g d e n , W . J . , 1982, "The P u s h - i n P r e s s u r e m e t e r " , P r o c e e d i n g s o f the Symposium;; on the P r e s s u r e m e t e r and I t s Marine A p p l i c a t i o n s , P a r i s .  Robertson, P . K . , 1982, " I n - s i t u T e s t i n g o f S o i l With Emphasis on its Application to L i q u e f a c t i o n Assessment", Phd Thesis, U n i v e r s i t y of B r i t i s h Columbia. Robertson, P.K., Campanella, R.G., Brown, P.T., Groff, I., Hughes, J.M.O., 1985a, "Design of A x i a l l y and Laterally Loaded P i l e s U s i n g I n - S i t u T e s t s : A Case H i s t o r y " , Submitted t o the Canadian G e o t e c h n i c a l J o u r n a l , A p r i l 1985.  110  Robertson, P.K., Campanella, R.G., Gillespie, D . G . , R i c e , A, 1985, "Seismic CPT t o Measure I n s i t u Shear Wave V e l o c i t y " , ASCE S p r i n g C o n v e n t i o n , Denver, A p r i l 1985. Seed,  H.B. and I d r i s s , I.B., 1970. " S o i l Moduli and Damping Factors f o r Dynamics Response A n a l y s i s " , Report No. EERC 70-10, U n i v e r s i t y o f C a l i f o r n i a , B e r k e l e y , Dec.  Suyama, K . , Ohya, S . , Imai, T . , M a t s u b a r a , M., Nakayama, E, 1983, "Ground Behaviour During Pressuremeter Testing" Proceedings of the International Symposium on In Situ T e s t i n g , P a r i s , Volume 2, pg 397 - 402. Wroth, CP., 1982, "British E x p e r i e n c e wwith the Self-Boring Pressuremeter", Proceedings of the Symposium on The Pressuremeter and Its Marine Applications, Paris, pg 143 - 164. Wroth, CP., 1984, Rankine Lecture, Imperial London,. QUEL Report No. 1541/84, Sm 051/84.  Ill  College,  

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.831.1-0062643/manifest

Comment

Related Items