Transcript Diapositiva 1 - dmt flat dilatometer papers

The Flat Dilatometer Test (DMT):
Design Applications
and Recent Developments
P. Monaco, S. Marchetti & G. Totani
University of L'Aquila, Italy
KEY DMT REFERENCES
ORIGINAL PAPER
MARCHETTI S. (1980). In Situ Tests by Flat Dilatometer.
J. Geotech. Engrg. Div. ASCE, 106(GT3), 299-321
STANDARDS
ASTM D6635-01 (2001). Standard Test Method for
Performing the Flat Plate Dilatometer.
EUROCODE 7 – Geotechnical Design – Part 2: Ground
Investigation and Testing. EN 1997-2:2007
SOA REPORT
TC16 (2001). The Flat Dilatometer Test (DMT) in Soil
Investigations. May 2001, 41 pp. Reprint in Proc. 2nd Int.
Conf. on Flat Dilatometer, Washington D.C., 7-48
INTERNET
www.marchetti-dmt.it biblio site (download papers)
FLAT DILATOMETER (DMT)
BLADE
FLEXIBLE
MEMBRANE
GENERAL LAYOUT of DMT
Push force provided by
penetrometer or drill rig
 DMT blade
 Push rods (e.g. CPT)
 Pneumatic-electrical cable
 Control unit
 Pneumatic cable
 Gas tank
 MEMBRANE EXPANSION
p0 & p1 readings at 20 cm
depth intervals
SOILS that can be TESTED by DMT
 CLAY, SILT, SAND – But can cross through
GRAVEL layers  0.5 m
 Soils from VERY SOFT to VERY STIFF
(upper limit is push capacity of rig)
Clays: Cu = 2-4 to 1000 kPa (marls)
Moduli: up to 400 MPa
Basic DMT reduction formulae (TC16 2001)
p0
p1
ID
KD
ED
K0
OCR
cu

ch
kh

M
u0
Corrected First Reading
Corrected Second Reading
Material Index
Horizontal Stress Index
Dilatometer Modulus
Coeff. Earth Pressure in Situ
Overconsolidation Ratio
Undrained Shear Strength
Friction Angle
Coefficient of Consolidation
Coefficient of Permeability
Unit Weight and Description
Vertical Drained Constrained
Modulus
Equilibrium Pore Pressure
p0 = 1.05 (A - ZM + A) - 0.05 (B - ZM - B)
p1 = B - ZM - B
ID = (p1 - p0) / (p0 - u0)
KD = (p0 - u0) / 'v0
ED = 34.7 (p1 - p0)
K0,DMT = (KD / 1.5)0.47 - 0.6
OCRDMT = (0.5 KD)1.56
cu,DMT = 0.22 'v0 (0.5 KD)1.25
safe,DMT = 28° + 14.6° log KD - 2.1° log2 KD
ch,DMTA  7 cm2 / tflex
kh = ch w / Mh (Mh  K0 MDMT)
(see chart in TC16 2001)
MDMT = RM ED
RM = 0.14 + 2.36 log KD
if ID  0.6
RM = 0.5 + 2 log KD
if ID  3
if 0.6 < ID < 3 RM = RM,0 + (2.5 - RM,0) log KD
with RM,0 = 0.14 + 0.15 (ID - 0.6)
if KD > 10
RM = 0.32 + 2.18 log KD
if RM < 0.85 set RM = 0.85
u0 = p2 = C - ZM + A
DMT results
KD = 2  NC clay
ID

soil type
(clay, silt, sand)
M
Cu


common use
KD

shape similar to OCR
helps understand
history of deposit
Design using soil parameters
 In most cases DMT used to determine
common geotechnical design parameters
 Experience has shown undrained shear
strength Cu and constrained modulus M by
DMT generally accurate and dependable for
design
 Comparisons at several research sites indicate
quite good agreement between profiles of Cu
and M by DMT and reference values by other
tests ( see TC16 2001)
Comparisons Cu DMT vs. Cu reference
Nash et al.
(1992)
AGI (1991)
Research Site
Bothkennar (UK)
Research Site
Fucino (Italy)
Comparisons MDMT vs. Mreference
M (MPa)
z (m)
0
20
40
60
80
0
MDMT
10
20
M back-calculated
Marchetti et al.
(2006)
Lacasse
(1986)
30
M by DMT vs. M by high
quality oedometers
Onsøy (Norway)
M by DMT vs. M backcalculated from local
vertical strains measured
under Treporti full-scale
test embankment (Italy)
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)
Summary of comparisons
DMT-predicted 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
Compaction control
 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 vs. CPT before/after compaction
BEFORE
qc
MDMT
AFTER
MDMT
qc
Ratio MDMT /qc before/after compaction of a loose sand fill
(Jendeby 1992)
Detecting slip surfaces in clay slopes
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)
DMT for LIQUEFACTION
 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 …
– Correlation KD – Relative Density
– Correlation KD – In situ State Parameter
 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
DMT for 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
DMT for 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
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)
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)
Validation of Vs by SDMT
SDMT
(2004)
SCPT
Cross Hole
SASW
AGI (1991)
Comparison of Vs
profiles by SDMT
and by other tests
Fucino research site
(Italy)
SDMT results
SHEAR WAVE
VELOCITY
Vs (m/s)
SDMT profiles at the site of Fiumicino (Italy)
SDMT  accurate and highly repeatable Vs
(in addition to usual DMT results)
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
0.05to
– 0.1
0.1%
%
Mayne (2001)
Ishihara (2001)
SDMT  small strain modulus G0 from Vs
working strain modulus MDMT (settlements)
 Tentative methods to derive in situ G- curves by SDMT
 Two points help in selecting the G- curve
SDMT for LIQUEFACTION
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
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
Special thanks to Allan McConnell (IGS)