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dynamic measurements

Richard Jardine

Dynamic soil properties seminar

17th March 2010

© Imperial College London



Scope for comparisons• -, ,

Needs big shaking tests or seismic arrays, plus powerful lab!

• Lab versus field at smaller strains: body wave velocities, and

•

static versus dynamic lab

• Key points:

Sampling disturbance and in-situ macro-structure

Imposed stress & strain paths



u non- near response rom ana ys s o

Example: Lotung Taiwan - operating since 1985

Figures from Elgamel et al (1995)




Seismic array analysis




Interpretion: Vs velocities, G values & damping curves

Experience: “Lab Vs and G values typically well below field values,

although decay curves may match better”

RC Lab trends

RC Lab trend




•

sand structure? Usual to rely on in-situ testing..

• Clays and mudrocks also give problems, how should they

be sampled?

• Consider historical progression of Imperial College work

• See that im rovements in sam lin and testin allow us

to be happier about comparisons between lab and field


C l ti l b d ( tl BRE) fi ld



Correlating lab and (mostly BRE) field

At ICP pile research sites:

• anons ar , on on c ay

• Pentre, deep, low OCR, glacio-lacustrine clay-silt,

rops re

• Dunkerque, medium dense marine sand, Northern

- , ,

• London clay: Terminal 5 Heathrow

Also Crag and London Tertiaries at Sizewell – Hight et al (1997)

ry ng o n a an e on on c ay e av our



ry ng o n a an e on on c ay e av our Conventional tests can’t match geophysics

(expressed as Eu equivalent to 3G)

ardine et al (1985)

BRE reflective field geophysics

Plate, SB Pressuremeter &Back Analysis profiles

And conventional laborator

triaxial tests


R i i th i t f li it



Recognising the importance of non-linearity

‘ ’

New insights offered by locally instrumented triaxial tests

Canons Park & Bell Common

Reference ‘small strain’

Thin walled samples, UU tests

Electrolevel axial strain sensors

Stiffnesses @ 0.01% strainStiffer response when:

Ko reconsolidated

Conventional

testing

High quality rotary core samples

0.001 0.01 0.1 1 1

Behaviour over non-linear range


,u , no c ear near e as c reg on..

i t li k l b d fi ld L d l b h i



rying to link lab and field London clay behaviour

ardine et al (1985)

UU Eu(0.01) profile

Static ‘back-analysis’ < Eu(0.01) < Dynamic 3Ghh

From Canons Park

CUKo triaxial tests on rotary samples

Any elastic range?

Geophysics

Insitu Ghh AbbissWhat about anisotropy?




Si il li t d f L d l fi ld



Similar non-linear trends from London clay field

es s Jardine et al (1985)

Re-interpretation of Cooke Price and Tarr (1979)Stresses ad acent to ile from theor strains from in- lace inclinometers


Similar trends from non linear Self Boring



Similar trends from non-linear Self Boring

Pressuremeter & UU and CUKo

triaxial tests; Jardine (1992)

• Importance of strain level is clear

-

range from various experiments

• No reliable Gmax comparisons

• o ana ys s o an so ropy




Subsequent lab developments and new tools

• Better local strain sensors

• IIS Tokyo LDTs (Goto et al 1991), better electrolevel gauges; Hall effect

devices & LVDT systems

• Hollow Cylinder (HCA) Resonant Column Apparatus: more uniform

, u , -

• Bod waves: multi-directional S-wave bender element and P-wave

measurements

• Locally instrumented static Hollow Cylinder Apparatus (HCA)

•

IC Resonant Column HCA



IC Resonant Column HCA,

=

di = 38 mm

o

vh

External and semi-local

instrumentation (corrected

for apparatus compliance)

100 mm


ome checks made with local au es



, ,

glacial lacustrine clay-silt

BRE Seismic CPT tests’ Gvh

compared by Chow 1997 with:

n piston samples: Gvh mode

riaxial tests Connolly (1997)

Fair match, closer if thinner wall,

harp edged, stainless steelampling tubes used?

s in Bothkennar stud ….

P t d l OCR l ilt



Pentre: deep, low OCR clay-siltan ors ona ear es s s ow a r agreemen a

mall strains for silt (& sands) Porovic (1995)

Greatly different strain rates: RC > 104 faster

Resonant Column

TS Scatter

Torsional shear

easuring anisotropic elastic stiffness in triaxial tests



For cross-anisotropic materialeasuring anisotropic elastic stiffness in triaxial testsav

θaar vh

θ E E E

r h==

arahv θννν ==

θaar vhGGG ==

r r rr hh θθνννν === Shibuya (1992). See Kuwano & Jardine (1998) or Lings et al (2000)

σaResonant columnGvh

Vertically & horizontally

polarised BE tests:Hi h resolution τaθ giving Ghh and Ghvstress-strain

probing tests:σ

θ

σr

en er e ements ,hh hv

σ

changing σ΄v andσ΄r individually

a a(v)

σ

σr

© Imperial College London r

D k i t i l b tiff t d



Dunkerque: anisotropic lab stiffness sets and

BRE seismic CPT profiles:Chow (1997), Kuwano (1999), Jardine et al (2003)

0 100 200 300 400 500 600 700

Elastic stiffness, MPa

Dunkerque laboratory profiles for dense sand and field sesimic profile

Also, good agreement for

reconstituted sands’ Gvh0

between:

Eu from TXC tests'

• esonan co umn• Bender element

•

15 D e p

t h , m

E'h from TX testsGvh from TX BE testsGhh from TX BE tests

Gvh from field seismic CPT testsEu from TXC testsE'v from TXC testsPorovic (1995),

20

rom tests

Connolly & Kuwano (1999)


Gvh Gvh Ghh E’h E’v Eu

Seismic CPT -------------------- All laboratory------------------------

Dunkerque trends over non linear range;



Dunkerque trends over non-linear range;

m te scope o tr ax a testsDunkerque dense sand secant shear stiffness data OCR = 2

=

1400

1600

Stiffness characteristics

1000

1200

Undrained triaxial extension with stress state;

Kuwano and Jardine (200

800

G / p '

400

600 Torsional shear

0

200


0.001 0.01 0.1 1

Es, %

Measuring anisotropic stiffness in HCA tests



For cross-anisotropic materialMeasuring anisotropic stiffness in HCA testsav

= θ

νννaar vh

==

θ

E E E r h

==

arahv θ

ννν ==

GGG == νννν ===

Resonant column tests Can also apply

σaResonant columnGvh

- vh

Static uniaxial probes for

‘τaθ

a s ness o ssonratio’ components

σθ

σr

Bender elements G ,Ghh hv

Uniaxial tests to failure

a a(v)

a

σr

(1997)

© Imperial College London r

r

Application or London clay in Heathrow T5 project



pp y p j

PhDs: Gasparre, Nishimura, Minh – see Imperial College website

Papers: - Geotechnique February/March 2007; IS-Atlanta 2008

Block sampling

-


Two deep rotary-cored boreholes

down hole

eo h sics

London clay T5 lab testing in Gvh mode



London clay T5 – lab testing in Gvh modeesonan o umn an ors ona ear s mura ,

BE tests and static probing tests by Gasparre (2005) and Nishimura (2006)

Multiple tests on rotary

Resonant column

cores and block samples

Torsional shear Resonant Column

Gmax typically 20%

higher than Torsional

Shear Gvh at γ = 3x10-5

5 Field & laboratory



5 Field & laboratory

v pro s

fter Nishimura (2006)

ood agreement down to 20m

ab Bender Element < RC Gvh

ab RC < seismic Gvh in

eeper layers

Laboratory BE Gvh

Laboratory HCA RC Gvh

esult of macro-fabric? Seismic Gvh:

r imperfect sampling & testing?

Triaxial stress path testing



p g

,

PC

load

cellPC

load

cell

CRSP air-oil

interface

CRSP air-oil

interface

volumegaugevolumegauge

air-water

interfaceexternalLVDT

air-water

interfaceexternalLVDT

pore pressurepore pressure


trans ucercell pressure

transducer

trans ucercell pressure

transducer

Triaxial tests by Gasparre (2006)



437

Triaxial tests by Gasparre (2006)

436

k P a ]

Search for kinematic yield surfaces

Study of possible stress history effects

435

' a

Y1 0 300 400 500 600

p' [kPa]

]

434

0.0000 0.0005 0.0010 0.0015 0.0020 0.0025 0.0030

εa [%]-100

q [ k P

A3

C &

B2(c)

B2(a)

0.12

0.16

-

0.08

0.00

0.04

Y2

1 s en o e as c range

. .

εv [%]

2 characteristics & other features

More HCA tests



More HCA tests

niaxial probing tests inar y n - n

x o , n anceElectro-level & Proximitylocal strain measurements

for four strain components

amples - h = 200 mm- i = mm

- do= 100 mm


Stiffness anisotropy from HCA tests



Stiffness anisotropy from HCA testsn ax a pro ng es s o a ure: ree en ca samp es

300

Uniaxial tests

Stiffness [MPa]

E'h

200 [ M P a ]

∆σθ

∆σz

σ r = cons an

p' = 280kPa

E z a n d G

z ∆τ

zθ

.

E'v

100 e c a n t E

θ ,

Gvh

© Imperial College London10

-310

-210

-110

0

Absolutte strains εθ, εz and γzθ [%]

0

Anisotoropy from static and dynamic lab tests



py y

Lab data match general trends from in-situ geophysics

More divergence at depth: macro-fabric or sampling?

0 200 400

Young's Moduli [MPa]

0 100 200

Shear moduli [MPa]

0 100 200

Bulk modulus, K [MPa]

C

B2(c)

x x xx

10

[ m ]

B2(b)

x x x20

D e p t h

B2(a)

Bxx x x x

30

Ev' (TX)

Ev' (HCA)

Gvh

(BE)

Ghh (BE)

A3(2)


40Eh' (TX)

Eh' (HCA)

Gvh (RC)

Gvh (Static)

Continuing work:



Continuing work:Lab & geophysical testing of Cretaceous and Jurassic

Mudrocks

x or c ay - comp e e

Gault Clay – underway

Kimmeridge - underway

HCA & advanced triaxial testing by Amandine Brosse, Ramtin KamalHossieni, micro-fabric & geology by

Stephen Wilkinson

CONCLUSIONS:



Aim: synthesize lab & field dynamic properties over the full range

ee s power u a es s p us se sm c array a a, or o er nverse e

analysis. Can expect strong rate effects in non-linear range.

‘Reasonable’ matches possible between field and (possibly slightly softer)

lab stiffness, if advantage is taken of improvements in:

Sampling quality

Understanding anisotropy & strain level effects

Test interpretation

Note the great value of appropriate field geophysical testing


Acknowledgements



esearc sponsors an par ners: , an o ers

work has been referred to including:

John Burland

Fiona Chow

Apollonia Gasparre

David Hi ht

Nguyen Anh-Minh

Satoshi NishimuraEsad Porovic

Tim Connolly




TC-29

ISSMGE

-




,

successor to:

SIP-London (1997)

IS-Torino 1999

IS-Lyon (2003)IS-Atlanta (2008)


Professor Alan Bishop



-

“Bishop” Lecture for future TC-29 main

, -

and practical geotechnical engineeringcontributions, continuing spirit of Professor

Alan Bishop.


columna resonante 3

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