Transcript Document

SDMT Workshop and Field Demonstration
Cesano 18 novembre 2011
Applicazioni alla progettazione geotecnica
Frontespizio
Università degli Studi dell’Aquila
Ing. Sara Amoroso
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.
Coop M.R.
Springman S.M.
Uang A.B.
Zornberg J.G.
Georgia Institute of Technology, Atlanta, USA
Imperial College, London, UK
Swiss Federal Institute of Technology, Zurich, CH
National Chiao Tung University, Taiwan, China
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)
DMT TEST
BLADE
FLEXIBLE
MEMBRANE
1. BLADE
INSERTION (20 cm)
2. HORIZONTAL
LOAD TEST
EXECUTION
Design via DMT parameters
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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
1 - Settlement prediction
No. 1 DMT application
by Boussinesq
S1 DMT 

 v
z
M DMT
 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
Baligh & Scott (1975)
Jamiolkowski (1988)
“Without Stress History, impossible to
select reliable E (or M) from Qc”
 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)
Stiffnes

Strenght
Strength
Observed and DMT predicted modulus
M (MPa)
z (m)
0
0
20
40
60
MDMT
10
M back-calculated
20
M by DMT vs. M back-calculated
from local vertical strains
measured under Treporti full-scale
test embankment (Italy)
30
Marchetti et al. (2006)
80
Summary of comparisons DMTpredicted vs. observed settlements
400
DMT/measured=0.5
Measured settlement (mm)
350
ALL SOILS
300
Monaco et al.
(2006)
250
DMT/measured=1
200
DMT/measured=2
150
100
Hayes 1990
Skiles & Townsend 1994
Marchetti 1997
Didaskalou 1999
Marchetti et al. 2004
Mayne 2005
50
0
0
50
100
150
200
250
300
350
DMT-calculated settlement (mm)
400
 Large No. of case
histories  good
agreement for wide range
of soil types, settlements,
footing sizes
 Average ratio DMTcalculated/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
Mortaiolo (Italy)
NC soft clay
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)
 Independent validations  2 methods provide
similar predictions, in very good agreement with
observed full-scale pile behaviour
3 - Design of diaphragm walls
Monaco & Marchetti (2004 – ISC'2 Porto)
g.l.
s
H
L
 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
4 - Detecting slip surfaces in OC clay
1. SLIDING
3. RECONSOLIDATION
(NC STATE)
2. REMOULDING
4. INSPECT KD PROFILE
02
10
20
KD (DMT) 2
30
DMT-KD method  Verify if an OC clay slope contains
ACTIVE (or old QUIESCENT) SLIP SURFACES
(Totani et al. 1997)
Validation of DMT-KD method
LANDSLIDE "FILIPPONE" (Chieti)
DOCUMENTED
SLIP SURFACE
LANDSLIDE "CAVE VECCHIE" (S. Barbara)
DOCUMENTED
SLIP SURFACE
(inclinometers)
Totani et al. 1997
5 - Monitoring densification /
stress increase
 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
compaction
Schmertmann 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 CPT
Ghent group (1993)  DMTs before-after installation
demonstrate more clearly [than CPT] beneficial effects of
Atlas installation
DMT vs. CPT before/after compaction
BEFORE
qc
MDMT
AFTER
MDMT
qc
Ratio MDMT /qc before/after compaction of a loose sand fill
(Jendeby 1992)
6 - Liquefability evaluation
 Correlations for evaluating Cyclic Resistance Ratio
CRR from KD developed in past 2 decades,
stimulated by:
– 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)
 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
Curves for evaluating CRR from KD
(Seed & Idriss 1971 simplified procedure)
0.5
0.5
Reyna & Chameau 1991
M = 7.5
CSR
LIQUEFACTION
0.4
or 0.4
Marchetti 1982
CRR
0.3
0.3
Range of curves
derived from CPT
New tentative
CRR-KD curve
Monaco et al. 2005
0.2
0.2
Range of curves
derived from SPT
0.1
0.1
Robertson & Campanella 1986
NO LIQUEFACTION
0
0
00
2
2
4
4
66
88
KD
10
10
 Summary + latest version CRR-KD correlation
see Monaco et al. (2005 ICSMGE Osaka)
 Magnitude M = 7.5 – Clean sand
Curves for evaluating CRR from KD
(Seed & Idriss 1971 simplified procedure)
Tsai et al. (2009)
 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.
7 - Subgrade compaction control
Bangladesh Subgrade Compaction Case History
90 km Road Rehabilitation Project
MDMT acceptance profile
(max always found at 25-26 cm)
 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)
8 - FEM input parameters
 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)
Monaco & Marchetti (2004)
Seismic Dilatometer (SDMT)
Combination S + DMT
• 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
Hepton 1988
Martin & Mayne 1997, 1998 ... (Georgia Tech, USA)
Correlation to estimate Vs (G0) from
mechanical DMT data (ID, KD, ED)
From large amount SDMTs at 34 sites various soils & geography 
• No point today. Vs direct
(but might provide rough Vs in
previous sites DMT).
Marchetti et al. (2008)
• 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).
Decay decreases with KD (stress history)
Earthquake in L’Aquila, 6 April 2009
Vs profiles
measured by SDMT
estimated from "mechanical" DMT data
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)
10 - In situ G- decay curves by SDMT
Maugeri (1995)
HARA (1973)
YOKOTA et al. (1981)
TATSUOKA (1977)
SEED & IDRISS (1970)
ATHANASOPOULOS (1995)
CARRUBBA & MAUGERI (1988)
0.05 –0.05
0.1 %
0.05
to
– Mayne
0.1%
0.1
% (2001)
0.01 – 1 % Ishihara (2001)
SDMT  small strain modulus G0 from Vs
working 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
Earthquake in L’Aquila, 6 April 2009
1.1
1.0
normalised shear modulus, G/G0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0.0001
GDMT/G0 from SDMT
γDMT = 0.1 – 0.5 %
RC - cese di preturo S3-C1
RC - cese di preturo S3-C3
DSDSS - roio piano S3-C3
DSDSS - pianola S1-C1
G-DMT/Go cese di preturo S3-C1
G-DMT/Go cese di preturo S3-C3
G-DMT/Go roio piano S3-C2
G-DMT/Go pianola S1-C1
0.001
0.01
0.1
1
shear strain,  (%)
Test site
Amoroso (2011)
Sample
Vs
G0
MDMT
(m/s)
(MPa)
(MPa)

GDMT/G0
γ
(%)
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
11 - Liquefability evaluation
SDMT  2 parallel independent evaluations of CRR
from VS e KD
(Seed & Idriss 1971 simplified procedure)
CRR from Vs
Andrus & Stokoe (2000)
Andrus et al. (2004)
CRR from KD
Monaco et al. (2005)
ICSMGE Osaka
Earthquake in L’Aquila, 6 April 2009
Vs
Kd
Vittorito – L’Aquila (April 2009)
Moment magnitude MW: 6.3
Distance from the epicentre: 45 km
Peak ground acceleration PGA: 0.065 g
Earthquake in L’Aquila, 6 April 2009
Satellite Conference 2-3 October 2009
0.6
0.5
LIQUEFACTION
Fc <=5%
Fc= 15%
Fc >= 35%
0.4
Cyclic Stress Ratio CSR or
Cyclic Resistance Ratio CRR
Cyclic Stress Ratio, CSR or
Cyclic Resistance Ratio, CRR
0.5
0.3
0.2
NO
LIQUEFACTION
0.1
0
0.4
LIQUEFACTION
0.3
Proposed CRR-KD curve
(Monaco et al. 2005)
0.2
NO LIQUEFACTION
0.1
0
0
50
100
150
200
250
0
Normalized shear wave velocity, vs1(m/s)
Liquefaction depth from Vs: 1-2.5 m
2
4
6
8
KD
10
Liquefaction depth from KD: 2-6 m
Monaco et al. (2009, 2010)
FINAL REMARKS
 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