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Slide 1
Reporter: S. Amoroso 6th February 2013 www.marchetti-dmt.it
Analysis of results and parameters derived from SDMT Banbury United
Kingdom
Slide 2
SDMT Test Layout Measurements performed after penetration
independant from insertion method DMT (static) SDMT (dynamic)
Slide 3
DMT test: P 0 & P 1 every 20cm Z (m) P 0 (kPa) P 1 (kPa)
0.20 0.40 0.60 0.80 1.00 1.20 220 210 305 310 285 290 300 310 420
450 380 390
Slide 4
DMT Intermediate parameters Intermediate Parameters Id:
Material Index DMT Readings P0P0 P1P1 Kd: Horizontal Stress Index
Ed: Dilatometer Modulus
Slide 5
DMT Formulae Interpreted parameters Intermediate Parameters Id
Kd Ed Interpreted Parameters Cu: Undrained Shear Strength Ko: Earth
Pressure Coeff (clay) OCR: Overconsolidation ratio (clay) : Safe
floor friction angle (sand) : Unit weight and description M:
Constrained Modulus
Slide 6
DMT Formulae (1980) Po and P1 Intermediate parameters
Interpreted parameters
Slide 7
I D contains information on soil type Performing DMT, immediate
notice that: p 1 CLAY p p 0 SAND p 0 p 1 p SILT falls in
between
Slide 8
I D contains information on soil type SAND CLAY
Slide 9
Obviously I D is not a sieve analysis. Eg. a mixture sand-clay
would probably be "wrongly" interpreted as silt. On the other hand
such mixture could perhaps behave mechanically as a silt. The
engineer is often interested to the grain size distribution not
"per se", but just to infer mechanical properties, PERHAPS, in SOME
cases, it could be better to have the I D interpretation than the
sieve analysis results and to infer from them the mechanical
behaviour. A mechanical information (a sort of Soil Type Behaviour
Index) that, in design, might be even more important than the
granulometric composition. Reliability of material index I D
Slide 10
K D contains information on stress history K D is an amplified
K 0, because p 0 is an amplified h due to penetration K D = vv (p 0
- u 0 ) K D well correlated to OCR and K 0 (clay) p0p0 DMTDMT
formula similar to Ko: (p 0 u 0 ) h
Slide 11
Depth Z Kd K D contains information on stress history 2 K D = 2
in NC clay (OCR = 1) NC OC K D > 2 in OC clay (OCR > 1)
Slide 12
K D contains information on stress history OC Kd > 2 NC Kd 2
Taranto 1987
Slide 13
Experimental Kamei & Iwasaki 1995 Theoretical Finno 1993
Theoretical Yu 2004 OCR=KdKd 1.56 Marchetti 1980 (experimental) 0.5
K D correlated to OCR (clay)
Slide 14
Theoretical 2004 Yu Experimental Marchetti (1980) K0K0 = KdKd
0.47 Marchetti 1980 (experimental) 1.5 0.6 K D well correlated to K
0 (clay)
Slide 15
E D contains information on deformation Theory of elasticity: E
D = elastic modulus of the horizontal load test performed by the
DMT membrane (D=60mm, 1.1 mm expansion) 1.1 mm DMTDMT ED =ED = 34.7
(P 1 - P 0 ) Gravesen S. "Elastic Semi-Infinite Medium bounded by a
Rigid Wall with a Circular Hole", Danmarks Tekniske Hjskole, No.
11, Copenhagen, 1960, p. 110. E D not directly usable corrections
(penetration,etc)
Slide 16
M obtained from Ed using information on stress history (Kd) and
soil type (Id) EdEd KdKd IdId M Constrained Modulus
Slide 17
How can be an undrained modulus Ed related to a drained modulus
M In the early days of DMT (1980) the initial idea was obviously to
correlate Ed-Eu, not Ed-M. But Ed-Eu impossible. Lab Eu values too
dispersed. M values from oedometers less dispersed. Though the link
Ed-M is presumably weaker, at least it can be tested. A correlation
Ed-M must be a complex function of many variables, among them the
Skempton pp parameters A & B and anisotropy (horiz. to vert.
modulus), which in turn depend on soil type (to some extent
represented by Id) and on OCR (to some extent represented by Kd).
These considerations encouraged investigating Ed-M using Id,Kd as
parameters. (Prof. Lambe of MIT (Jnl ASCE March 1977 Foundation
Performance of Tower of Pisa p.246) wrote: E typically 1/3-1/4 Eu.
Thus a connection E-Eu already invoked in the past). Final word
goes to real world. Several decades of observations appear to
confirm that Mdmt is a reasonable estimate of the operative M.
Slide 18
Ed must be corrected to obtain M M=Rm Ed with Rm=f(Kd,Id) Dont
use Ed as Youngs Rm has various correction tasks Distortion Horiz
to vertical Drained Undrained Once Ed is converted to M, Youngs E
0.8-0.9 M (elasticity)
Slide 19
Vertical drained confined tangent modulus (at ' vo ) Same as E
oed, traditionally measured by oedometer Usual range M 0.4 - 400
Mpa Except highly structured clays (sharp break), M variation
across pc is moderate Error in assuming M ~ constant : often
acceptable (other methods for M : not infrequent error factors 2-3)
May use M = constant if 'v large ? M = Eoed=1/mv= ' v / v (at ' vo
)
Slide 20
Ladd 1971 Terzaghi 1967 Compressibility of even good
samples
Slide 21
M Comparison from DMT and from Oedometer Norwegian Geotechnical
Institute (1986). "In Situ Site Investigation Techniques and
interpretation for offshore practice". Report 40019-28 by S.
Lacasse, Fig. 16a, 8 Sept 86 ONSOY Clay NORWAY Constrained Modulus
M (Mpa) Tokyo Bay Clay - JAPAN Iwasaki K, Tsuchiya H., Sakai Y.,
Yamamoto Y. (1991) "Applicability of the Marchetti Dilatometer Test
to Soft Ground in Japan", GEOCOAST '91, Sept. 1991, Yokohama 1/6
Virginia - U.S.A. Failmezger, 1999
Slide 22
Cu correlation from OCR Ladd SHANSEP 77 (SOA TOKYO) Ladd: best
Cu measurement not from TRX UU !! Using m 0.8 (Ladd 1977) and (Cu/
v ) NC 0.22 (Mesri 1975) Cu vv OC = Cu vv NC OCR m OCR=0.5KdKd 1.56
Cu = vv 0.5 KdKd 1.25 0.22 best Cu from oed OCR Shansep
Slide 23
Cu comparisons from DMT and from other tests Mekechuk J.
(1983). "DMT Use on C.N. Rail Line British Columbia", First
Int.Conf. on the Flat Dilatometer, Edmonton, Canada, Feb 83, 50
Skeena Ontario Canada Tokyo Bay Clay - JAPAN Iwasaki K, Tsuchiya
H., Sakai Y., Yamamoto Y. (1991) "Applicability of the Marchetti
Dilatometer Test to Soft Ground in Japan", GEOCOAST '91, Sept.
1991, Yokohama 1/6 Recife - Brazil Coutinho et al., Atlanta
ISC'98
Slide 24
Complaint : Cu field vane > Cu dmt (in very plastic clay)
From Book Soil Mechanics in Eng. Practice (by Terzaghi, Peck,
Mesri) Cu field vane needs a correction factor before it can be
used in stability analysys. The Bjerrum correction is eg 0.70 when
PI = 70. Cu field vane reduced by Bjerrums correction is often
considered the best available Cu for stability analysis. The DMT
1980 correlations for Cu were developed using for calibration such
operative Bjerrums-corrected Cu values. It is therefore Cu field
vane uncorrected which is too high - in plastic clays.
Slide 25
Summary of DMT 2 step data processing Id(soil type) Kd(stress
history) Ed(elastic modulus) M Cu Ko OCR DMT Readings Intermediate
Parameters Geotechnical Parameters P0P1P0P1
Slide 26
Main SDMT applications Settlements of shallow foundations
Compaction control Slip surface detection in OC clay Quantify ' h
relaxation behind a landslide Laterally loaded piles Diaphragm
walls FEM input parameters Liquefability evaluation Seismic design
(NTC08, Eurocode 8) In situ G- g decay curves
Slide 27
Main Application: Settlement prediction 1-D approach (classic
Terzaghi) Primary settlement at working loads (Fs 2.5-3 to b.c.) M
must be treated as if by oedometer LOADSOIL DMT Boussinesq S = z M
zz v M Z z
Slide 28
Circular area: Settlement Prediction from DMT M is evaluated
for each Dz (0.20 m) by DMT Ds is evaluated for each Dz (0.20 m) by
Poulus & Davis q = load Primary settlement is evaluated by
Poulus & Davis (1974)
Slide 29
Rectangular area: Settlement Prediction from DMT D Fadum Abacus
Rectangular area D M is evaluated for each Dz (0.20 m) by DMT Ds is
evaluated for each Dz (0.20 m) by Fadum Abacus q = load I =
influence value Primary settlement is evaluated by
Slide 30
Numerous case histories of favourable comparisons measured vs
DMT-predicted settlements (or moduli): Lacasse & Lunne (1986)
Dilatometer Tests in Sand. Proc. In Situ '86 ASCE Spec. Conf.
Virginia Tech, Blacksburg.Very good agreement between DMT-predicted
and measured settlements under a silos at a sandy site Steiner W.
(1994) Settlement Behaviour of an Avalanche Protection Gallery
Founded on Loose Sandy Silt. Settlement '94 ASCE Conf. at Texas
A&M.The DMT- predicted settlements agreed well with observed
settlements Mayne & Liao Tianfei (2004) CPT-DMT
interrelationship in Piedmont residuum. Proc. In ISC2 Porto. Over
two decades of calibration between the DMT and measured foundation
performance records have shown its value & reliability in
settlements computation Vargas (2009), Bullock (2008), Monaco
(2006), Lehane & Fahey (2004), Mayne (2001, 2004), Failmezger
(1999, 2000, 2001), Crapps & Law Engineering (2001), Tice &
Knott (2000), Woodward (1993), Iwasaki et al. (1991), Hayes (1990),
Mayne & Frost (1988), Schmertmann (1986,1988), Steiner (1994),
Leonards (1988), Lacasse (1986). Settlement Prediction from
DMT
Slide 31
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
Slide 32
M observed vs. predicted by DMT M by DMT vs. M back-calculated
from LOCAL vertical strains measured under Treporti full- scale
test embankment (Italy) Marchetti et al. (2006) Sliding Micrometers
installed every meter
Slide 33
Treporti Test Embankment (Venezia) Conclusion: OC increases
stiffness especially at operative modulus (working strain) Before
embankment constructionAfter embankment removal
Slide 34
Applicability of Oedometer, SPT, CPT, PMT, DMT, to predict
settlements of shallow foundations (GeoRisck ASCE Failmezger &
Bullock 2011) Oedometer:...Testing is time- consuming and is
typically performed at depth intervals exceeding 3 m...Sampling and
handling disturbance... SPT:...The hammer type is often omitted...
Extrapolation from a failure strain to an intermediate strain
CPT:...Extrapolation from a failure strain to an intermediate
strain PMT:... Static deformation to strain the soil to
intermediate strains... Relatively slow test... Drillers skill and
experience DMT:...Static deformation to strain the soil to
intermediate strains... The dilatometer test is therefore the best
choice of in-situ tests for settlement prediction of shallow
foundations... Mayne (2001)
Slide 35
Settlement Prediction DMT vs SPT
Slide 36
Possible reasons DMT good settlement predictions 1.Wedges
deform soil less than cones Baligh & Scott (1975) measure zone
2. Modulus by mini load test relates better to modulus than
penetration resistance Stiffness Strength 3.Availability of Stress
History parameter Kd Jamiolkowski (1988) Without Stress History,
impossible to select reliable E (or M) from Qc Robertson et al.
(1986) Prediction of soil stiffness from cone resistance can be
rather poor, especially for OC soils Leonards (Asce 88) Calculating
settlements on granular soils based on correlations [Penetr.
Resistance Soil Modulus] will seriously overestimate settlements if
deposit has been prestressed. Similar statements by Schmertmann 70,
Terzaghi 67
Slide 37
RATIO = E/Qc OCR??? CC Jamiolkowski: = 2.5 to 25. Factor 10 !
Depends on OCR(?) Jamiolkowski concludes (Isopt-1, '88, Vol. 1,
p.263) : "without Stress History it is impossible to select
reliable E (or M) from Qc"
Slide 38
Lee 2011, Eng. Geology CC in sand Effects of Stress History on
CPT and DMT Effect of stress history on norm. Qc (x 1.10-1.15)
Effect of stress history on Kd (x 1.30-2.50)
Slide 39
PRESTRAINING CYCLES simulated AGING (similar mechanism: grain
slippage) CC TEST N. 216 IN TICINO SAND Jamiolkowski (ISC'98
Atlanta) applied prestraining cycles in calibration chamber. Found
: K D (DMT) 3 to 7 times more sensitive to AGING than penetration
resistance K D + 20 % q D + 3 % K D ++ sensitive to Stress History
and aging than penetration resistance
Slide 40
Stress History also fundamental for liquefiability (e.g.
Jamiolkowski 1985) Lack of SH : probably reason high scatter in the
CPT- liquefaction correlations, possibly reduced with the SH info
from Kd or use directly Kd-CRR for liquefaction (eg Fig.14 Rob
2012). Kd : thanks for existing a formidable parameter for settlem.
& liquef. Appears the only parameter readily available today
reflecting clearly SH not many SH tools Yet for decades Terzaghi,
Skempton, Leonards, Schmertmann, Jam have been preaching (in
essence) : without SH go nowhere. Kd is a bargain.
Slide 41
Example: Settlement Prediction from DMT
Slide 42
Slide 43
Slide 44
Slide 45
DMT for Compaction Control The high sensitivity to changes of
stresses and density make the DMT particularly suitable for
detecting benefits of SOIL IMPROVEMENT Compaction of a loose
sandfill Resonant vibrocompaction technique Van Impe, De Cock,
Massarsch, Meng New Delhi (1994) Depth (m)
Slide 46
DMT vs CPT sensitivity to Compaction Schmertmann (1986) DYNAMIC
COMPACTION of sand site. M DMT % increase twice % increase in q c.
Jendeby (1992) monitored DEEP COMPACTION in a sand fill by
VIBROWING. M DMT increase twice increase in q c. Pasqualini &
Rosi (1993) VIBROFLOTATION job : "DMT clearly detected improvement
even in layers where benefits were undetected by CPT". Ghent group
(1993) before after CPTs DMTs to evaluate effects ( h, Dr) by PILE
(Atlas) INSTALLATION "DMTs before-after installation demonstrate
more clearly [than CPT] beneficial effects of Atlas
installation".
Slide 47
Compaction Control DMT vs CPT Jendeby (1992): Qc & Mdmt
before & after compaction of a loose sandfill Before compaction
After compaction
Slide 48
Subgrade Compaction Control M DMT acceptance profile (max
always found at 25-26 cm) Bangladesh Subgrade Compaction Case
History 90 km Road Rehabilitation Project Acceptance M DMT 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)
Slide 49
Slip surface detection in OC clay slopes DMT-K D method Verify
if an OC clay slope contains active (or old quiescent) slip
surfaces (Totani et al. 1997)
Slide 50
Slip surface detection in clay slopes SS. N. 83 Marsicana Gioia
dei Marsi (2006) blocked Mine of lignite S. Barbara (San Giovanni
Valdarno)
Slide 51
Validation of DMT-K D method LANDSLIDE "FILIPPONE" (Chieti)
LANDSLIDE "CAVE VECCHIE" (S. Barbara) DOCUMENTED SLIP SURFACE
(inclinometers)
Slide 52
healthy clay Reconstruction of multiple slip surfaces active:
Kd=2 quiescent: Kd=2 qualitative recontruction infected clay (K D 2
due to active/quiescent slip surfaces)
Slide 53
Quantify ' h relaxation behind a landslide Case History:
Landslide in Milazzo, Sicily Horizontal Stress h Z (m) above sea
level 1 2 3 h obtained using K 0 from DMT RAILWAY 12 3 clay
Slide 54
Design of laterally loaded piles (Winkler) Three different
methods using DMT results for evaluating P-y curves for laterally
loaded piles: E s = constant Deflection y Soil reaction, p Linear
P-y curve E s = f (y) Deflection y Soil reaction, p Non Linear P-y
curve Recommended methods Gabr & Borden (1988) Robertson et al.
(1989) Marchetti et al. (1991)
Slide 55
Observed vs. DMT predicted pile deflections single pile, 1st
time monotonic loading In clay Validation of: 2 independent methods
(Robertson 1989 and Marchetti 1991) provide similar predictions, in
very good agreement with measured full-scale pile behaviour
(1989)
Slide 56
DMT for DESIGN of DIAPHRAGM WALLS Tentative correlation for
deriving the Winkler model springs for design of multi- propped
diaphragm walls from M DMT Indications on input moduli for FEM
analyses (PLAXIS Hardening Soil model) based on M DMT Monaco &
Marchetti (2004 ISC'2 Porto)
Slide 57
Linear elastic model: E 0.8 M DMT (Hamza & Richards, 1995)
DMT aims to calibrate FEM parameters PLAXIS hardening soil model: E
50,ref is correlated to M DMT (Schanz, 1997) FEM input parameters
Monaco & Marchetti (2004)
Slide 58
LIQUEFACTION RISK ASSESSMENT very cautious recommendations
using SPT and CPT Robertson & Wride (1998) CRR by CPT adequate
for low-risk projects. For high-risk: estimate CRR by more than one
method Youd & Idriss (NCEER Workshops 2001) use 2 or more tests
for a more reliable evaluation of CRR Idriss & Boulanger (2004)
the allure of relying on a single approach (e.g. CPT-only) should
be avoided Jamiolkowski (1985, 11 ICSMFE) reliable predictions of
CRR require the development of some new in situ device [other than
CPT or SPT] much more sensitive to the effects of past STRESS AND
STRAIN HISTORIES Leon et al. (ASCE GGE 2006) South Carolina sands.
Ignoring AGING and evaluating CRR from in situ tests insensitive to
aging (SPT, CPT, VS) underestimated CRR by a large 60 % Monaco
& Schmertmann (ASCE GGE 2007) Disregarding AGING omitting a
primary parameter in the correlation predicting CRR
Slide 59
Liquefaction: CRR from DMT Correlations for evaluating Cyclic
Resistance Ratio (CRR) from K D developed in past 2 decades,
stimulated by: 1.Sensitivity of K D to factors known to increase
liquefaction resistance: stress history prestraining/aging
cementation structure 2.Correlation K D Relative Density D r (Reyna
& Chameau, 1991, Tanaka & Tanaka,1998) 3.Correlation K D In
situ State Parameter (relative density + stress level) (Yu, 2004)
Intuitively K D expresses propensity/reluctance of sand to decrease
in volume ( !! )
Slide 60
Liquefaction: K D related to D r K D - D r correlation Reyna
& Chameau (1991) Tanaka & Tanaka (1998)
Slide 61
Liquefaction: K D related to CRR from Mayne 2009 LIQUEFACTION
NO LIQUEFACTION K d - correlation Yu (2004) theoretical = vertical
distance between the current state and the critical state line in
the usual v - ln p' plot
Slide 62
alone: incomplete indicator of Liquefaction resistance lacks
structure, stress history, aging: applying / removing load causes
only small e ( small ), but big CRR It does not appear illogical to
expect that Kd, being related to , but at the same time
incorporating stress history and aging, could be uniquely well
correlated with CRR governs the attitude of a sand to increase or
decrease in volume when sheared, hence it is strongly related to
liquefaction resistance
Slide 63
Have seen various reasons for expecting good Kd-CRR. But how to
translate the large experimental base behind Qc1-CRR? ( e.g. Youd
& Idriss 2001). Translation done by Tsai (2009). He first
determined a Kd-Qc1 correlation by running side-by-side CPT-DMT in
loose saturated clean sand. Then he used said Kd-Qc1 correlation to
replace Qc1 with Kd in Youd & Idriss, thereby obtaining a
correlation CRR-Kd.
Slide 64
Youd & Idriss 2001 Tsai translated the CRR-Qc database into
CRR-Kd Kd Side-by-side CPT-DMT parallel profiles of Qc1-Kd
Qc1=f(Kd) CRR=f(Qc1) CRR=f(Kd) (scatter)
Slide 65
At first sight one might consider doubtful the resulting Kd-CRR
correlation, being based on the highly dispersed Qc1-Kd
correlation. Not so. The scatter is just natural, is the consquence
of Kd reacting to factors unfelt by Qc1. E.g. for a same Qc1, there
can be many Kd - depending if the site has had Stress History.
Scatter is healthy. If there was no scatter : Qc1 and Kd contain
the same information, i.e. Qc1 reactive to SH as Kd. Not so.
Dispersion of the Qc1-Kd relation
Slide 66
Reason of the dispersion of the Qc1-Kd curve The fact that the
translation occurs via the average eliminates that part of scatter
due to the insensitivity of Qc1 to stress history. Hence expectable
Kd-CRR less scatter.
Slide 67
Dispersion of intercorrelations Qc1-Kd-CRR
Slide 68
SDMT for LIQUEFACTION Monaco et al. (2005) ICSMGE Osaka SDMT 2
independent evaluations of CRR from K D and V S (Seed & Idriss
1971 simplified procedure) Andrus & Stokoe (2000) Andrus et al.
(2004) CRR from VsCRR from K D
Slide 69
Jamiolkowski 1992 Soils & Foundations SDMT provides two
independent CRR estimates From Kd From Vs Sometimes different CRR.
We consider more reliable CRR(Kd) Vs insensitive to STRESS HISTORY
Waves produce strains far too small to initiate trend to
dilate/contract (essence of liquefaction) Vs measured on sand
specimen in the calibration chamber during loading and unloading
(Jamiolkowski and Lo Presti, 1992)
Slide 70
Vittorito LAquila (Earthquake, 6th April 2009) Kd Vs Moment
magnitude MW: 6.3 Distance from the epicentre: 45 km Peak ground
acceleration PGA: 0.065 g CSR Liquefaction case history in Italy
LAquila
Slide 71
Monaco et al. (2009, 2010) Liquefaction depth from Vs: 1-2.5 m
0 0.1 0.2 0.3 0.4 0.5 0.6 050100150200250 Normalized shear wave
velocity, Vs1 (m/s) Cyclic Stress Ratio, CSR or Cyclic Resistance
Ratio, CRR Fc = 35% LIQUEFACTION NO LIQUEFACTION Liquefaction depth
from K D : 2-6 m 0 0.1 0.2 0.3 0.4 0.5 0246810 Cyclic Stress R a
tio CSR or Cyclic Resistance Ratio CRR K D Proposed CRR-K D curve
(Monaco et al. 2005) LIQUEFACTION NO LIQUEFACTION Both Kd and Vs
indicated Liquefaction (red points) Liquefaction case history in
Italy LAquila
Slide 72
Liquefaction case history in Costarica Just a few weeks after
the SDMT execution, the cyclic wave action due to a storm induced
liquefaction of the soil deposit.. (Vargas & Coto 2012)
cofferdam Design Earthquake (M Richter = 7,5 and PGA = 0,25 g)
LIQUEFACTION NO LIQUEFACTION LIQUEFACTION NO LIQUEFACTION
Slide 73
Diagram groups results of 34 international sites in various
soils & geography SDMT same depth values for: Id, Kd, M, Go
(Vs) M, Id, Kd may provide rough Vs in previous DMT sites G 0 (Vs)
M = G0G0 constant G0G0 M 0.5 - 20 Correlation to estimate Vs (G 0 )
from mechanical DMT data (I D, K D, E D ) Marchetti et al. (2008)
Would it be possible predict Go from one-number test (no stress
history)?
Slide 74
G 0 /M DMT for detecting cementation as a consequence of these
data analysis, it becomes clear that both [G 0 /E D vs. I D ] and
[G 0 /M DMT vs. K D ] can be used to detect the presence of
cementation.. (Cruz, 2010)
Slide 75
measured by SDMT estimated from "mechanical" DMT data Vs
profiles Earthquake in LAquila, 6 April 2009 Monaco et al.
(2009)
Slide 76
Simplified use of Vs for Seismic Design Vs profile Vs 30 Soil
category (NTC08, Eurocode 8)
Slide 77
Vs for Seismic Design Go profile (Vs) EERA, ProShake (or
similar software) auxiliary input soil surface behaviour Input
motion Output motion Bedrock Soil Period, T AGI (2005)
Slide 78
SDMT small strain modulus G 0 from Vs working strain modulus G
DMT from M DMT (Marchetti et al. 2008) Tentative methods to derive
in situ G- curves by SDMT Two points help in selecting the G- curve
In situ G- decay curves by SDMT 0.05 0.1 % Mayne (2001) 0.01 1 %
Ishihara (2001)
Slide 79
Treporti Venice (Italy), Texas: SDMT vs observed settlements
LAquila (Italy): SDMT vs dynanic laboratory tests Western
Australia: SDMT vs SBP, SDMT vs triaxial tests In situ G- decay
curves by SDMT Amoroso et al. (2012) 2%
Slide 80
Conclusions 1/2 A CPT investigation costs less, but remains
orphan of capability of providing SOA predictions of settlements
220 papers ISC4: no one Qc for settlements Countless researchers:
Qc insensitive to Stress History W/o info Stress History,
impossible predict well settlements Robertson (1986) Prediction of
soil modulus from Qc can be rather poor, with a large potential
error This well known Qc weakness is no little thing. Often
settlement prediction is a > 50% task in a geo-report (Similar
considerations for liquefiability, where Stress History also
fundamental) pay less, get less - unless uninterested in
settlements
Slide 81
Conclusions 2/2 SDMT is simple, accurate, cost-effective,
repeatable and supplies results real time Practical : Any operator
gets same results. No need highly skilled workers. Short training
time Robust correlations to design parameters based on intermediate
parameters: Id, Ed and Kd Key parameter is Kd, which captures
stress history and is sensitive to aging, prestraining, cementation
and structure (fundamental for settlements and liquefaction) SDMT
provides two moduli in situ: G 0 (Vs) - low strain M DMT operative
(settlement prediction) Used in many everyday applications