Analysis of results and parameters derived from SDMT 6th February 2013 Reporter: S. Amoroso Banbury United Kingdom www.marchetti-dmt.it

SDMT Test Layout DMT (static) SDMT (dynamic) Measurements performed after penetration  independant from insertion method

DMT test: P0 & P1 every 20cm Z (m) P0 (kPa) P1 0.20 0.40 0.60 0.80 1.00 1.20 … 220 210 305 310 285 290 300 420 450 380 390

DMT Intermediate parameters DMT Readings Intermediate Parameters Id: Material Index P0 Kd: Horizontal Stress Index P1 Ed: Dilatometer Modulus

DMT Formulae – Interpreted parameters Intermediate Parameters Id Kd Ed Interpreted Parameters M: Constrained Modulus Cu: Undrained Shear Strength Ko: Earth Pressure Coeff (clay) OCR: Overconsolidation ratio (clay) : Safe floor friction angle (sand)  : Unit weight and description

DMT Formulae (1980) Po and P1 Intermediate parameters Interpreted parameters

ID contains information on soil type Performing DMT, immediate notice that: p 1 CLAY SAND p 1 SILT falls in between

ID contains information on soil type SAND CLAY

Reliability of material index ID Obviously ID 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 ID 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.

KD contains information on stress history σ’v (p0 - u0) D M T formula similar to Ko: (p0 – u0)  σ’h KD is an “amplified” K0, because p0 is an “amplified” σh due to penetration p0 KD well correlated to OCR and K0 (clay)

KD contains information on stress history Depth Z Kd 2 KD = 2 in NC clay (OCR = 1) NC OC KD > 2 in OC clay (OCR > 1)

KD contains information on stress history NC Kd ͌ 2 OC Kd > 2 Taranto 1987

Marchetti 1980 (experimental) KD correlated to OCR (clay) OCR = Kd 1.56 Marchetti 1980 (experimental) 0.5 Experimental Kamei & Iwasaki 1995 Theoretical Finno 1993 Theoretical Yu 2004

KD well correlated to K0 (clay) = Kd 0.47 Marchetti 1980 (experimental) 1.5 0.6 Experimental Marchetti (1980) Theoretical 2004 Yu

ED contains information on deformation Theory of elasticity: ED = elastic modulus of the horizontal load test performed by the DMT membrane (D=60mm, 1.1 mm expansion) D M T ED = 34.7 (P1 - P0) Gravesen S. "Elastic Semi-Infinite Medium bounded by a Rigid Wall with a Circular Hole", Danmarks Tekniske Højskole, No. 11, Copenhagen, 1960, p. 110. 1.1 mm ED not directly usable  corrections (penetration,etc)

Kd M Constrained Modulus Ed Id M obtained from Ed using information on stress history (Kd) and soil type (Id) Kd M Constrained Modulus Ed Id

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.

Ed must be corrected to obtain M M=Rm Ed with Rm=f(Kd,Id) Don’t use Ed as Young’s Rm has various correction tasks Distortion Horiz to vertical Drained Undrained Once Ed is converted to M, Young’s E’  0.8-0.9 M (elasticity)

M = Eoed=1/mv= 'v/v (at 'vo) May use M = constant if 'v large ? M = Eoed=1/mv= 'v/v (at 'vo)  Vertical drained confined tangent modulus (at 'vo) Same as Eoed, 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)

Ladd 1971 Terzaghi 1967 Compressibility of even good samples…

M Comparison from DMT and from Oedometer Virginia - U.S.A. ONSOY Clay – NORWAY Tokyo Bay Clay - JAPAN Constrained Modulus M (Mpa) Constrained Modulus M (Mpa) Failmezger, 1999 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 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

Cu correlation from OCR Ladd SHANSEP 77 (SOA TOKYO) Ladd: best Cu measurement not from TRX UU !! best Cu from oed  OCR  Shansep Cu σ’v OC = NC OCR m OCR = 0.5 Kd 1.56 Using m  0.8 (Ladd 1977) and (Cu/’v)NC  0.22 (Mesri 1975) Cu = σ’v 0.5 Kd 1.25 0.22

Cu comparisons from DMT and from other tests Recife - Brazil Skeena Ontario – Canada Tokyo Bay Clay - JAPAN Coutinho et al., Atlanta ISC'98 Mekechuk J. (1983). "DMT Use on C.N. Rail Line British Columbia", First Int.Conf. on the Flat Dilatometer, Edmonton, Canada, Feb 83, 50 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

“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 Bjerrum’s correction is often considered the best available Cu for stability analysis. The DMT 1980 correlations for Cu were developed using for calibration such “operative” Bjerrum’s-corrected Cu values. It is therefore Cu field vane uncorrected which is too high - in plastic clays.

Summary of DMT 2 step data processing DMT Readings Intermediate Parameters Geotechnical Parameters P0 P1 Id (soil type) Kd (stress history) Ed (elastic modulus) M Cu Ko OCR …

Main SDMT applications Settlements of shallow foundations Compaction control Slip surface detection in OC clay Quantify σ'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

Main Application: Settlement prediction Δσz LOAD SOIL DMT Boussinesq S = Δσz M Ʃ Δz Δσv Z 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

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)

Rectangular area: Settlement Prediction from DMT Fadum Abacus Rectangular area 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

Settlement Prediction from DMT 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 ISC’2 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)…………….

Summary of comparisons DMT-predicted vs. observed settlements 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 Monaco et al. (2006)

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

Treporti Test Embankment (Venezia) Before embankment construction After embankment removal Conclusion: OC increases stiffness especially at operative modulus (working strain)

(GeoRisck – ASCE – Failmezger & Bullock 2011) 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... Driller’s 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)

Settlement Prediction DMT vs SPT

Possible reasons DMT good settlement predictions Wedges deform soil less than cones Baligh & Scott (1975) Modulus by mini load test relates better to modulus than penetration resistance Stiffness  Strength measure zone measure zone 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…

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" OCR???

Effects of Stress History on CPT and DMT Lee 2011, Eng. Geology – CC in sand Effect of stress history on norm. Qc (x 1.10-1.15) on Kd (x 1.30-2.50)

KD ++ sensitive to Stress History and aging than penetration resistance Jamiolkowski (ISC'98 Atlanta) applied prestraining cycles in calibration chamber. Found : KD (DMT) 3 to 7 times more sensitive to AGING than penetration resistance CC TEST N. 216 IN TICINO SAND PRESTRAINING CYCLES  simulated AGING (similar mechanism: grain slippage) KD + 20 % qD + 3 %

Stress History also fundamental for liquefiability (e. g 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.

Example: Settlement Prediction from DMT

Example: Settlement Prediction from DMT

Example: Settlement Prediction from DMT

Example: Settlement Prediction from DMT

DMT for Compaction Control The high sensitivity to changes of stresses and density make the DMT particularly suitable for detecting benefits of SOIL IMPROVEMENT Depth (m) Compaction of a loose sandfill Resonant vibrocompaction technique Van Impe, De Cock, Massarsch, Mengé New Delhi (1994)

DMT vs CPT sensitivity to Compaction Schmertmann (1986) DYNAMIC COMPACTION of sand site. MDMT % increase  twice % increase in qc. Jendeby (1992) monitored DEEP COMPACTION in a sand fill by VIBROWING. MDMT increase  twice increase in qc. 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".

Compaction Control DMT vs CPT Jendeby (1992): Qc & Mdmt before & after compaction of a loose sandfill Before compaction After compaction

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)

Slip surface detection in OC clay slopes (Totani et al. 1997) DMT-KD method  Verify if an OC clay slope contains active (or old quiescent) slip surfaces

Slip surface detection in clay slopes Mine of lignite S. Barbara (San Giovanni Valdarno) SS. N. 83 “Marsicana” Gioia dei Marsi (2006) blocked

Validation of DMT-KD method LANDSLIDE "FILIPPONE" (Chieti) DOCUMENTED SLIP SURFACE LANDSLIDE "CAVE VECCHIE" (S. Barbara) DOCUMENTED SLIP SURFACE (inclinometers)

Reconstruction of multiple slip surfaces active: Kd=2 quiescent: Kd=2 qualitative recontruction infected clay (KD  2 due to active/quiescent slip surfaces) ‘healthy’ clay

Quantify σ'h relaxation behind a landslide Case History: Landslide in Milazzo, Sicily Horizontal Stress σ’h 1 RAILWAY 1 2 3 clay Z (m) – above sea level 2 3 σ’h obtained using K0 from DMT

Design of laterally loaded piles (Winkler) Es = constant Deflection y Soil reaction, p Linear P-y curve Es = f (y) Deflection y Soil reaction, p Non Linear P-y curve Three different methods using DMT results for evaluating P-y curves for laterally loaded piles: Gabr & Borden (1988) Robertson et al. (1989) Marchetti et al. (1991) Recommended methods

Observed vs. DMT predicted pile deflections Validation of: 2 independent methods (Robertson 1989 and Marchetti 1991) provide similar predictions, in very good agreement with measured full-scale pile behaviour (1989) single pile, 1st time monotonic loading In clay

DMT for DESIGN of DIAPHRAGM WALLS Monaco & Marchetti (2004 – ISC'2 Porto) Tentative correlation for deriving the Winkler model springs for design of multi-propped diaphragm walls from MDMT Indications on input moduli for FEM analyses (PLAXIS Hardening Soil model) based on MDMT

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)

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

Liquefaction: CRR from DMT 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 Dr (Reyna & Chameau, 1991, Tanaka & Tanaka,1998) Correlation KD – In situ State Parameter  (relative density + stress level) (Yu , 2004) Intuitively KD expresses propensity/reluctance of sand to decrease in volume ( !!)

Liquefaction: KD related to Dr KD - Dr correlation Reyna & Chameau (1991) Tanaka & Tanaka (1998)

Liquefaction: KD related to  CRR from  Mayne 2009 LIQUEFACTION NO LIQUEFACTION Kd -  correlation Yu (2004) theoretical  = vertical distance between the current state and the critical state line in the usual v - ln p' plot

 alone: incomplete indicator of Liquefaction resistance  governs the attitude of a sand to increase or decrease in volume when sheared, hence it is strongly related to 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

Have seen various reasons for expecting good Kd-CRR 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.

Tsai translated the CRR-Qc database into CRR-Kd Side-by-side CPT-DMT  parallel profiles of Qc1-Kd Qc1=f(Kd) Youd & Idriss 2001 CRR=f(Qc1)  CRR=f(Kd) (scatter) Kd

Dispersion of the Qc1-Kd relation 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.

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.

Dispersion of intercorrelations Qc1-Kd-CRR

(Seed & Idriss 1971 simplified procedure) SDMT for LIQUEFACTION SDMT  2 independent evaluations of CRR from KD and VS (Seed & Idriss 1971 simplified procedure) Andrus & Stokoe (2000) Andrus et al. (2004) CRR from Vs CRR from KD Monaco et al. (2005) ICSMGE Osaka

SDMT provides two independent CRR estimates From Kd From Vs Sometimes different CRR. We consider more reliable CRR(Kd) Vs insensitive to STRESS HISTORY Vs measured on sand specimen in the calibration chamber during loading and unloading Jamiolkowski 1992 Soils & Foundations Waves produce strains far too small to initiate trend to dilate/contract (essence of liquefaction) (Jamiolkowski and Lo Presti, 1992)

Vittorito – L’Aquila (Earthquake, 6th April 2009) Liquefaction case history in Italy – L’Aquila Vittorito – L’Aquila (Earthquake, 6th April 2009) Moment magnitude MW: 6.3 Distance from the epicentre: 45 km Peak ground acceleration PGA: 0.065 g CSR Kd Vs

Liquefaction depth from KD: 2-6 m Liquefaction depth from Vs: 1-2.5 m Liquefaction case history in Italy – L’Aquila Liquefaction depth from KD: 2-6 m 0.1 0.2 0.3 0.4 0.5 2 4 6 8 10 Cyclic Stress R a tio CSR or Cyclic Resistance Ratio CRR K D Pr o posed CRR - curve (Monaco et al. 2005) LIQUEFACTION NO LIQUEFACTION Liquefaction depth from Vs: 1-2.5 m 0.1 0.2 0.3 0.4 0.5 0.6 50 100 150 200 250 Normalized shear wave velocity, Vs1 (m/s) Cyclic Stress Ratio, CSR or Cyclic Resistance Ratio, CRR Fc <=5% Fc= 15% Fc >= 35% LIQUEFACTION NO Monaco et al. (2009, 2010) Both Kd and Vs indicated Liquefaction (red points)

Liquefaction case history in Costarica cofferdam Design Earthquake (M Richter = 7,5 and PGA = 0,25 g) LIQUEFACTION NO LIQUEFACTION “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)

SDMT  same depth values for: Id, Kd, M, Go (Vs) Correlation to estimate Vs (G0) from mechanical DMT data (ID, KD, ED) Diagram groups results of 34 international sites in various soils & geography SDMT  same depth values for: Id, Kd, M, Go (Vs) Marchetti et al. (2008) G0 M 0.5 - 20 M = G0 constant M, Id, Kd may provide rough Vs in previous DMT sites G0 (Vs) Would it be possible predict Go from one-number test (no stress history)?

G0/MDMT for detecting cementation “as a consequence of these data analysis, it becomes clear that both [G0/ED vs. ID] and [G0/MDMT vs. KD] can be used to detect the presence of cementation..” (Cruz, 2010)

Earthquake in L’Aquila, 6 April 2009 measured by SDMT estimated from "mechanical" DMT data Vs profiles Monaco et al. (2009)

Simplified use of Vs for Seismic Design Vs profile Vs 30 Soil category (NTC08, Eurocode 8)

EERA, ProShake (or similar software) soil surface behaviour Vs for Seismic Design EERA, ProShake (or similar software) auxiliary input soil surface behaviour Go profile (Vs) Input motion Output Bedrock Soil Period, T AGI (2005)

In situ G- decay curves by SDMT 0.05 – 0.1 % Mayne (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

In situ G- decay curves by SDMT Amoroso et al. (2012) 2% Treporti – Venice (Italy), Texas: SDMT vs observed settlements L’Aquila (Italy): SDMT vs dynanic laboratory tests Western Australia: SDMT vs SBP, SDMT vs triaxial tests

Conclusions 1/2 A CPT investigation costs less, but remains orphan of capability of providing SOA predictions of settlements 220 papers ISC’4: 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

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: G0 (Vs) - low strain MDMT – operative (settlement prediction) Used in many everyday applications

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