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Pressuremeters in Geotechnical Design B.G. CLARKE Department of Ci vii Engineering Univcrsity of Newcastle upon Tyne

m

BLACKIE ACADEMIC & PROFESSIONAL An lmprint of Chapman & Hai

London · Glasgow · Weinheim · New York · Tokyo · Melbourne · Madras

Contents

List of symbols Jntroduction l.l 1.2 1.3 1.4

1.5

Tntroduction Defìnition of a pressuremeter The dcvelopmcnt of the pressureme ter The pressuremctcr test 1.4. 1 Thc probc 1.4.2 The expa nsion curve Summary

2 Pressuremeter probes a nd testing equipment 2.1 2.2 2.3

2.4

2.5 2.6

Introduction Key featurcs of pressurcmetcrs 2.2.1 The probe 2.2.2 Thc contro! unit Preborcd pressurcmeters 2.3.1 The Ménard pressuremeter 2.3.2 The Oyomcter 2.3.3 The high-prcssurc di!atometer 2.3.4 Other prebored pressurcmcters Sclf-boring pressuremcters 2.4.1 The pressiomètre autoforeur 2.4.2 Tbc Cambridge self-boring pressuremeter 2.4.3 T hc wcak rock self-boring pressuremeter 2.4.4 Other self-boring pressuremeters Pushed-in pressuremeters 2.5.1 Full displacement or eone pressuremeter 2.5.2 The Stressprobe Summary

3 Site operations 3.1 3.2

3.3

lntroduction Tnstallation techniques 3.2.1 lntroduc tion 3.2.2 Prebored pressuremeters 3.2.3 Thc self-bori ng pressuremeter 3.2.4 The pushed-in pressuremetcr Calibrations 3.3. 1 ln troduction 3.3.2 Pressure gauges 3.3.3 Displacement transducers 3.3.4 Total prcssure transducers 3.3.5 Effcctivc prcssure and porc pressure transducers 3.3.6 Membrane stiffness 3.3.7 Membrane thinning 3.3.8 Membrane compression

xi

l

7 8 Il Il 15

16

19 19

19 19

23 24 25

32 34

36 39 41 45

51 53 58 58

60 62

63 63 63

63 64 73

84 86 86 86 87 88 89 90 92 95

CO!':TENTS

VIli

3.4 3.5

3.6

3.7

3.8

4

Analysis of expanding cavities 4.1 4.2 4.3 4.4

4.5

4.6 4.7

4.8

5

3.3.9 Sy~ tem cornprcssio n 3.3.10 The initial dimcnsion of the probe and rcadings of the transduccrs 3.3. l l Frcqucncy an d rclevancc of calibrations On-si te systcm chccb Thc test 3.5. 1 Introduction The Ménard rncthod 3.5.2 3.5.3 Stress-controlled tests 3.5.4 Strain-controlled tests 3.5.5 Additional test procedures 3.5.6 Testi ng in ice 3.5.7 Summary of tes t procedures Termination of a test 3.6.1 Introduction :1.1l.2 Maximum pressure capacity Maximum oil ca pacity 3.6.3 3.6.4 Burst memb rancs Maximum displacement 3.6.5 Reduction of data and initial plots 3.7. 1 lnt roduction 3.7.2 Tbe Ménard pressuremetcr test and other volume type pressuremeter tests 3.7.3 Rad iai displacement type PBP tests Radiai displacemcnt type S BP and PIP pressuremeter tests 3.7.4 Summary

Introduction Distribution of stress and strain Elastic ground Undrained expansion of cylindrical cavity (quick tests in clay) Generai analysis 4.4.1 4.4.2 Linear elastic perfectly plastic soil 4.4.3 Non-linear materia! D rained expansion of a cylindrical cavity (tests in sand) Volu me changes 4.5.1 4.5.2 Generai analysis 4.5.3 Very dense sands Tests in rock Specific analyses 4. 7. 1 Non-linear stiffness 4.7.2 Undrained analysis assuming entire expansion at the limit press ure Coellìcient of consolidation 4.7.3 Summary

Factors affecting the interpretation of pressuremeter tests 5. 1 5.2

5.3

Introduction Reasons for the use of semi-empirica! methods 5.2.1 Introduction 5.2.2 Effects of installation 5.2.3 Etrects of the in-situ stress 5.2.4 Effects of discontinuities and bands of hard and sofi layers Effects of test procedure 5.2.5 5.2.6 Effects of test cavity shape Effects of pro be type 5.2.7 Summary

97 98 99 102 103 103 105 108 IlO Ili

115 117 l 17 117

11 9 119 121 121

121 121 122 125

126 128

130 130 131

133 135 135 136 139 142

142 144

147 148 153 153 156 158

160 161 161 161 161 162 164 167 168 171 172 174

C'OI'TF.NTS

6

7

Jnterpretation of pressuremeter tests 6.1 6. 2

Introd uction Daw quality and _ground typc 6.2. 1 Jntroducuon Qua lity of installation 6.2.2 G ro und type 6.2.3 63 lntcrpre tation o f a n MP M test: Thc prcssurcmete r modu1us and modificd limi! pressure Estimating horizonta1 stress from a pressuremeter test 6.4 Tntroduction 6.4.1 Lift-off method 6.4.2 Mcthods bascd on shear strength 6.4.3 Methods bascd on test procedure 6.4.4 Curve fitting methods 6.4.5 Correlations 6.4.6 6.4.7 The subjcctivi ty of the selectio n of horizontal stress Modulus 6.5 6.5. 1 Initial modulus Un1oadf re1oad modulus 6.5.2 Non-1inear stiA'ness profìle 6.5.3 Undrained shear strength 6.6 Generai analysis 6.6.1 Elastic perfectly plastic soil 6.6.2 6.7 Angles of shearing resistancc and dilation Limit pre.ssure 6.8 6.9 Consolidation and creep 6.10 Overconsolidation ratio 6.11 Summary

Design ruJes and applications 7.1 7.2

7.3 7.4

7.5 7.6

Tntroduction The d irect method: the Ménard mcthod 7.2. 1 Shallow foundations 7.2.2 Thc Ménard method based on results of SBP tests 7.2.3 Axially loaded piles Horizontally loaded pilcs 7.2.4 7.2.5 Ground anchors Other direct design methods for horizontally loaded piles Comparisons between results of p rcssuremeter and other tcsts 7.4.1 Total horizontal stress 7.4.2 Modulus 7.4.3 Undrained shear st rength 7.4.4 Angle of shearing resistance 7.4.5 Limil pressure Applicatio ns Summary

8 Choice of pressuremeter, specifications and developments 8.1

8.2 8.3 8.4

8.5 8.6

lntroduction Current s tate of pressuremeter testing Choosing a pressuremet.er A typica1 specifìcation Costs Future developments

Appendix

A. l

Specifications and quantities

Tntroduction

ix 175 175 175

l i5 175

177 179 182 182 183 190 195 196 201 202 202 203 203 207 211 213 217 222 229 232 234 236

238 238 239 240 247 247 254 256 258 264 264 270 278 284 288 289 295

297 297 297 301 304 311 311

314 314

x A.2

COKTENTS

Generai A.2. 1 Thc cquipmcnt A.2.2 Thc operator AJ Probcs A.3. 1 Gcncml A..l2 Volume displaccment type probes A.3.3 Radiai displacement type p robe.'> A.4 Calibrations A.4. 1 Typcs A.4.2 Total pressurc transducer A.4.3 D isplaccment transduccr A.4.4 Pore p rcssurc tra nsdueers (if fìtted) A.4.5 Systcm eomprcssion A.4.6 Memb ra ne stiffness A.4.7 Membra ne co mpressio n A.4.8 Frequency A.5 lnstallatio n A.5. 1 Prebo red prcssuremeters A.5.2 Self-borcd prcssuremeter A.5.3 Pushed-in pressuremeters A.6 Tcsting procedure A.6.1 Strain-controlled tests A.6.2 Stress-co ntro ll.ed tcsts A.6.3 Stress-controlled tests: Ménard mcthod A.7 On-site da ta proccssing A.7. 1 Volume displa ccment type probes A.7.2 Radi ai di splace ment type probes A.S Jnterpreta ti on A.9 Jnformation to be s ubmitted A.9. 1 Prior to commenci ng wo rk o n site A.9.2 Preliminary rcsults for each test A.9.3 Report data processing and analysis A.9.4 lnforma tion to be submil!ed in the report A. IO Bill o f quan tities

314 .ì l4 315 315

315 315 316 317

317 317 318 318

318 319 319

320 320 320 32 1 322 322 323 323 324 324 324

324 324

325 325 325 326

326 327

References and bibliography

330

lodex

357