Università degli Studi dell’Aquila Ing. Sara Amoroso SDMT Workshop and Field Demonstration Cesano...

Università degli Studi dell’Aquila

Ing. Sara Amoroso

SDMT Workshop and Field DemonstrationSDMT Workshop and Field Demonstration

Cesano 18 novembre 2011Cesano 18 novembre 2011

Applicazioni alla progettazione geotecnicaFrontespizio

REFERENCE: State-of-the-art Lecture No. 1 (Alessandria Egitto Oct 2009)

17th Int. Conf. on Soil Mechanics and Geotechnical Engng, 2009

Mayne P.W. Georgia Institute of Technology, Atlanta, USACoop M.R. Imperial College, London, UKSpringman S.M. Swiss Federal Institute of Technology, Zurich, CHUang A.B. National Chiao Tung University, Taiwan, ChinaZornberg J.G. University of Texas, Austin, USA

“Soil borings … laboratory testing … SPT … pressuremeter (PMT) … vane (VST) … crosshole (CHT) … Taken together, all of these are suitable … yet at considerable cost in time and money …”

“... In this fast-paced world, a more efficient approach … In particular, the Seismic Piezocone (SCPT) and the Seismic Dilatometer (SDMT) ... offer clear opportunities in the economical and optimal collection of data.

... SCPT and SDMT direct-push tests should serve as the basis … in routine daily site investigation practices …”

FLAT DILATOMETER (DMT)

BLADE

FLEXIBLE MEMBRAN

E

1. BLADE INSERTION (20 cm)

DMT TEST

2. HORIZONTAL LOAD TEST EXECUTION

Design via DMT parameters ID = material index KD = horizontal stress index ED = dilatometer modulus K0 = coeff. earth pressure in situ OCR = overconsolidation ratio cu = undrained shear strengh Φ = friction angle ch = consolidation coefficient kh = permeability coefficient g = unit weight and description M = vertical drained constrained modulus u0 = equilibrium pore pressure

Main DMT applications

Settlements of shallow foundations

Laterally loaded piles

Diaphragm walls

Detecting slip surfaces in OC clay

Monitoring densification/stress increase

Liquefability evaluation

Subgrade compaction control

FEM input parameters

by Boussinesq

1 - Settlement predictionNo. 1 DMT application

Classic linear elastic 1-D approach – or 3-D with E 0.8 MDMT (similar predictions)

Settlement under working loads (Fs 2.5-3.5)

Possible reasons DMT good settlement predictions

Jamiolkowski (1988)

“Without Stress History, impossible to select reliable E (or M) from Qc”

Stiffnes

Strenght

Wedges deform soil << than cones

Modulus by mini load test relates better to modulus than penetr. resistance

Availability of Stress History parameter Kd.(DMT is a 2-parameter test. Fundamental to have both: Ed and Kd)

Baligh & Scott (1975)

Strength

Observed and DMT predicted modulus

M by DMT vs. M back-calculated

from local vertical strains measured under Treporti full-scale test embankment (Italy)

M (MPa)

0

10

20

30

0 20 40 60 80

z (m

)

MDMT

M back-calculated

Marchetti et al. (2006)

0

50

100

150

200

250

300

350

400

0 50 100 150 200 250 300 350 400

DMT-calculated settlement (mm)

Me

as

ure

d s

ett

lem

en

t (m

m)

Hayes 1990 Skiles & Townsend 1994 Marchetti 1997 Didaskalou 1999 Marchetti et al. 2004 Mayne 2005

DMT/measured=0.5

DMT/measured=2

DMT/measured=1ALL SOILS

0

50

100

150

200

250

300

350

400

0 50 100 150 200 250 300 350 400

DMT-calculated settlement (mm)

Me

as

ure

d s

ett

lem

en

t (m

m)

Hayes 1990 Skiles & Townsend 1994 Marchetti 1997 Didaskalou 1999 Marchetti et al. 2004 Mayne 2005

DMT/measured=0.5

DMT/measured=2

DMT/measured=1ALL SOILS

Summary of comparisons DMT-predicted vs. observed

settlements

Monaco et al. (2006)

Large No. of case histories good agreement for wide range of soil types, settlements, footing sizes

Average ratio DMT-calculated/observed settlement 1.3

Band amplitude (ratio max/min) < 2 i.e. observed settlement within ± 50

% from DMT-predicted

2 - Design of laterally loaded piles

Robertson et al. (1987)Marchetti et al. (1991)

2 methods recommended for deriving P-y curves for laterally loaded piles from DMT (single pile, 1st time monotonic loading)

Mortaiolo (Italy)

NC soft clay

Mortaiolo (Italy)

NC soft clay

Independent validations 2 methods provide similar predictions, in very good agreement with observed full-scale pile behaviour

3 - Design of diaphragm walls

Tentative correlation for deriving the coefficient of subgrade reaction Kh for design of multi-propped diaphragm walls from MDMT

Indications on how to select input moduli for FEM analyses (PLAXIS Hardening Soil model) based on MDMT

g.l.

sH

L

g.l.g.l.

ssHH

LL

Monaco & Marchetti (2004 – ISC'2 Porto)

DMT-KD method Verify if an OC clay slope contains ACTIVE (or old QUIESCENT) SLIP SURFACES(Totani et al. 1997)

0 2

10

20

30

D

1. SLIDING

K (DMT) 2

3. RECONSOLIDATION(NC STATE)

4. INSPECT D PROFILEK

2. REMOULDING

4 - Detecting slip surfaces in OC clay

Validation of DMT-KD methodLANDSLIDE "FILIPPONE" (Chieti)

LANDSLIDE "CAVE VECCHIE" (S. Barbara)

DOCUMENTED SLIP SURFACE

DOCUMENTED SLIP SURFACE(inclinometers)

Totani et al. 1997

Experience suggests DMT well suited to detect BENEFITS of SOIL IMPROVEMENT due to its high sensitivity to changes of stresses/density in soil

Several comparisons of CPT and DMT before/after compactionSchmertmann et al. (1986), Jendeby (1992) Increase in MDMT after compaction of sand 2 increase in qc (CPT)Pasqualini & Rosi (1993) DMT clearly detected improvement even in layers where benefits were undetected by CPTGhent group (1993) DMTs before-after installation demonstrate more clearly [than CPT] beneficial effects of Atlas installation

5 - Monitoring densification /stress increase

Ratio MDMT /qc before/after compaction of a loose sand fill (Jendeby 1992)

DMT vs. CPT before/after compaction BEFORE AFTERBEFORE AFTERBEFORE AFTER MDMT

MDMTqcqc

6 - Liquefability evaluation Correlations for evaluating Cyclic

Resistance Ratio CRR from KD developed in past 2 decades, stimulated by:

Key element supporting well-based CRR-KD correlation: ability of KD to reflect aging in sands (1st order of magnitude influence on liquefaction) + sensitivity of KD to non-textbook OCR crusts in sands

– Sensitivity of KD to factors known to increase liquefaction resistance: Stress History, prestraining/aging, cementation, structure … (Marchetti, 2010)

– Correlation KD – Relative Density (Reyna & Chameau, 1991)

– Correlation KD – In situ State Parameter (Yu, 2004)

Summary + latest version CRR-KD correlation see Monaco et al. (2005 ICSMGE Osaka)

Magnitude M = 7.5 – Clean sand

0

0.1

0.2

0.3

0.4

0.5

0 2 4 6 8 10

0.5

0.4

0.3

0.2

0.1

0 0 2 4 6 8 10

KD

CSRor

CRR

Robertson & Campanella 1986

Marchetti 1982

M = 7.5

NO LIQUEFACTION

LIQUEFACTION

Reyna & Chameau 1991

Range of curves derived from CPT

Range of curves derived from SPT

New tentativeCRR-KD curveMonaco et al. 2005

0

0.1

0.2

0.3

0.4

0.5

0 2 4 6 8 10

0.5

0.4

0.3

0.2

0.1

0 0 2 4 6 8 10

0

0.1

0.2

0.3

0.4

0.5

0 2 4 6 8 10

0.5

0.4

0.3

0.2

0.1

0 0 2 4 6 8 10

KD

CSRor

CRR

Robertson & Campanella 1986

Marchetti 1982

M = 7.5

NO LIQUEFACTION

LIQUEFACTION

Reyna & Chameau 1991

Range of curves derived from CPTRange of curves derived from CPT

Range of curves derived from SPTRange of curves derived from SPT



Curves for evaluating CRR from KD

(Seed & Idriss 1971 simplified procedure)

All past CRR-KD curves were based on correlations Qc-Dr-KD or NSPT-Dr-KD. Tsai et al (2009) translated CPT-SPT using correlations Qc-KD or NSPT-KD and cutting out Dr.

Curves for evaluating CRR from KD


Tsai et al. (2009)

7 - Subgrade compaction control

MDMT acceptance profile(max always found at 25-26

cm)

Bangladesh Subgrade Compaction Case History90 km Road Rehabilitation Project

Acceptance MDMT profile fixed and used as alternative/fast acceptance tool for quality control of subgrade compaction, with only occasional verifications by originally specified methods (Proctor, CBR, plate), (Marchetti, 1994)

Linear elastic model: E 0.8 MDMT (Hamza & Richards, 1995)

DMT aims to calibrate FEM parameters PLAXIS hardening soil model:

E50,ref is correlated to MDMT (Schanz, 1997)

8 - FEM input parameters

Monaco & Marchetti (2004)

Seismic Dilatometer (SDMT)

• 2 receivers spaced 0.5 m

• Vs determined from delay arrival of impulse from 1st to 2nd receiver (same hammer blow)

• Signal amplified + digitized at depth

• Vs measured every 0.5 m

Combination S +

DMT

Hepton 1988Martin & Mayne 1997, 1998 ... (Georgia Tech, USA)

•No point today. Vs direct(but might provide rough Vs in previous sites DMT).

• Important : w/o stress history (KD) hopeless estimate Vs.

•Difficulty: Qc-Vs NSPT-Vs ???

•Use 1 parameter (NSpt, Su) as surrogate of Vs : questionable (as suggested by some codes).

Correlation to estimate Vs (G0) from

mechanical DMT data (ID, KD, ED)From large amount SDMTs at 34 sites various soils & geography

Decay decreases with KD (stress history)

Marchetti et al. (2008)

measured by SDMTestimated from "mechanical" DMT data

Vs profiles

Earthquake in L’Aquila, 6 April 2009

Monaco et al. (2009)

Main SDMT applications DMT applications

Seismic design (NTC08, Eurocode 8)

In situ G-g decay curves

Liquefability evaluation

9 - Vs for seismic design

Vs profile

Vs 30

Soil category(NTC08,

Eurocode 8)

SDMT small strain modulus G0 from Vsworking strain modulus GDMT from MDMT (Marchetti et al. 2008)

Tentative methods to derive in situ G- curves by SDMT

Two points help in selecting the G- curve

10 - In situ G- decay curves by SDMT

HARA (1973) YOKOTA et al. (1981) TATSUOKA (1977) SEED & IDRISS (1970) ATHANASOPOULOS (1995) CARRUBBA & MAUGERI (1988)

0.05 to 0.1%

HARA (1973) YOKOTA et al. (1981) TATSUOKA (1977) SEED & IDRISS (1970) ATHANASOPOULOS (1995) CARRUBBA & MAUGERI (1988)

0.05 – 0.1 %

Maugeri (1995)

0.05 – 0.1 % Mayne (2001)

0.01 – 1 % Ishihara (2001)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

0.0001 0.001 0.01 0.1 1

shear strain, (%)

no

rma

lise

d s

he

ar

mo

du

lus,

G/G

0

RC - cese di preturo S3-C1RC - cese di preturo S3-C3DSDSS - roio piano S3-C3DSDSS - pianola S1-C1G-DMT/Go cese di preturo S3-C1G-DMT/Go cese di preturo S3-C3G-DMT/Go roio piano S3-C2G-DMT/Go pianola S1-C1

Test site Sample Vs G0 MDMT GDMT/G0 γ

(m/s) (MPa) (MPa) (%)

Cese di Preturo C1 4.0-4.8 m 261 133 67 0.20 0.19 0.24

Cese di Preturo C3 17.5-18.0 m 274 149 39 0.20 0.10 0.48

Pianola C1 6.0-6.5 m 303 195 193 0.20 0.37 0.16

Roio Piano C2 7.0-7.5 m 233 105 64 0.20 0.23 0.46

Amoroso (2011)

GDMT/G0 from SDMTγDMT = 0.1 – 0.5 %


11 - Liquefability evaluationSDMT 2 parallel independent evaluations of

CRR from VS e KD


Andrus & Stokoe (2000)Andrus et al. (2004)

Monaco et al. (2005)ICSMGE Osaka

CRR from Vs CRR from KD


Vittorito – L’Aquila (April 2009)

Moment magnitude MW: 6.3Distance from the epicentre: 45 kmPeak ground acceleration PGA: 0.065 g

Kd

Vs


0

0.1

0.2

0.3

0.4

0.5

0.6

0 50 100 150 200 250

Normalized shear wave velocity, vs1(m/s)

Cyc

lic S

tre

ss R

atio

, C

SR

or

Cyc

lic R

esis

tanc

e R

atio

, CR

R

Fc <=5%Fc= 15%Fc >= 35%

LIQUEFACTION

NOLIQUEFACTION

Satellite Conference 2-3 October 2009

0

0.1

0.2

0.3

0.4

0.5

0 2 4 6 8 10

Cyc

lic S

tress

Rat

io C

SR

or

Cyc

lic R

esi

sta

nce

Ratio

CR

R

KD

Proposed CRR-KD curve (Monaco et al. 2005)

LIQUEFACTION

NO LIQUEFACTION

Monaco et al. (2009, 2010)

Liquefaction depth from Vs: 1-2.5 m Liquefaction depth from KD: 2-6 m

DMT quick, simple, economical, highly reproducible in situ test

Executable with a variety of field equipment

Dependable estimates of various design parameters/information

– soil type– stress state/history– constrained modulus M– undrained shear strength Cu in clay– consolidation/flow parameters– ...

FINAL REMARKS

Variety of design applications

Most effective vs. common penetration tests when settlements/deformations important for design (e.g. strict specs or need to decide: piles or shallow ?)

SDMT accurate measurements of Vs (and G0) + usual DMT results – greatly enhances DMT capability

FINAL REMARKS

Università degli Studi dell’Aquila Ing. Sara Amoroso SDMT Workshop and Field Demonstration Cesano...

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