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Workshop on Penetration Testing – University of Pisa, DESTEC Pisa – Italy, 9 th October 2014

Workshop on Penetration Testing – University of Pisa, DESTEC Pisa – Italy, 9 th October 2014. Flat dilatometer (DMT) & Seismic DMT (SDMT). Use of SDMT results for engineering applications. Sara Amoroso (Istituto Nazionale di Geofisica e Vulcanologia, L’Aquila, Italy)

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Workshop on Penetration Testing – University of Pisa, DESTEC Pisa – Italy, 9 th October 2014

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  1. Workshop on PenetrationTesting – Universityof Pisa, DESTEC Pisa – Italy, 9th October 2014 Flat dilatometer (DMT) & Seismic DMT (SDMT) Use of SDMT results for engineering applications Sara Amoroso (Istituto Nazionale di Geofisica e Vulcanologia, L’Aquila, Italy) sara.amoroso@ingv.it

  2. Outline of the presentation Flat dilatometer (DMT) Seismic dilatometer (SDMT) Interpretation of the parameters Engineering applications

  3. Flatdilatometer (DMT) & Seismic DMT (SDMT)

  4. DMT Flatdilatometerequipment BLADE FLEXIBLE MEMBRANE(D = 60mm)

  5. DMT Test layout & components Pneumatic – electric cable Pneumatic cable Control box Push force Gas tank Push rods DMT blade p0 Lift-off pressure p1 Pressure for 1.1 mm expansion Measurements performed after penetration  independent from insertion method

  6. DMT insertion with penetrometer Most efficient method: direct push with penetrometer

  7. A B DMT Workingprinciple Sensing disk (electrically insulated) Retaining Ring Membrane Sensing disk Blade is like an electrical switch, can be off or on NO ELECTRONICS  no zero drift, no temperature effects Nothing that the operator can regulate, adjust, manipulate

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

  9. (p0 - u0) KD = σ’v KD contains information on stress history DMT formula similar to K0: (p0 – u0)  σ’h KD is an “amplified” K0, because p0 is an “amplified” σh due to penetration p0 Very roughly KD ≈ 4K0 E.g. in NC K0 ≈ 0.5 and KD ≈ 2 KD well correlated to OCR and K0 (clay)

  10. Intermediate Parameters Id Ed Kd DMT Formulae – Interpretedparameters 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

  11. KDcorrelatedto OCR (clay) 1.56 Marchetti 1980 (experimental) OCR = 0.5 Kd Theoretical Finno 1993 Experimental Kamei & Iwasaki 1995 Theoretical Yu 2004

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

  13. DMT Formulae (1980 – today) Po and P1 Intermediate parameters Interpreted parameters

  14. DMT results KD=2NCclay ID  MCu   KD  soiltype (clay, silt, sand) common use shapesimilartoOCR helpsunderstandhistoryofdeposit Generally dependable

  15. Seismicdilatometer (SDMT)

  16. Seismic Dilatometer (SDMT) Combination S+DMT 2 receivers VS determined from delay arrival of impulse from 1st to 2nd receiver (same hammer blow) Signal amplified + digitized at depth VS measured every 0.5m DMT Marchetti 1980 SDMT Hepton 1988 ASTM D6635 – EC7 Martin & Mayne 1997,1998 ... TC16 2001

  17. Hammer for shear wave

  18. Example seismograms SDMT at Fucino Delay well conditioned from Cross Correlation  coeff of variation of Vs 1-2 %

  19. High repeatability SDMT results GO= ρ Vs2 DMT Seismic DMT

  20. Vs at National Site FUCINO –ITALY SDMT (2004) SCPT Cross Hole SASW AGI (1991) Fucino-Telespazio National Research Site (Italy) 2004 20

  21. Standards EUROCODE 7 (1997 and 2007). Standard Test Method, European Committee for Standardization, Part 2: Ground investigation and testing, Section 4. Field tests in soil and rock. 4.10. Flat Dilatometer Test (DMT). ASTM (2002 and 2007). Standard Test Method D6635-01, American Society for Testing and Materials. The standard test method for performing the Flat Dilatometer Test (DMT), 14 pp. TC16 (1997). “The DMT in soil Investigations”, a report by the ISSMGE Technical Committee tc16 on Ground Property, Characterization from in-situ testing, 41 pp. PROTEZIONE CIVILE Gruppo di lavoro (2008) – Indirizzi e criteri per la microzonazione sismica. Prova DMT pp. 391-397, Prova SDMT pp. 397-405 ASTM (2011) – Standard Test Method D7400 – 08, “Standard Test Methods for Downhole Seismic Testing“, 11 pp. Consiglio Superiore dei Lavori Pubblici (2008) –Istruzioni per l'applicazione Norme Tecniche per le Costruzioni NTC08. Circolare 02/02/09 , paragrafo C6.2.2

  22. Use of SDMT results for engineering applications

  23. Experimental interrelationship between G0 and MDMT • Data points tend to group according to soil type (ID) • G0/MDMT constant, varies in wide range(≈ 0.5 to 20), especially in clay • G0/MDMT largely influenced by stress history (KD) • By-product rough estimates of VS (when not measured) SDMT data from 34 sites Ratio G0/MDMT vs. KD for various soil types (Marchetti et al. 2008, Monaco et al. 2009) MDMT, ID, KD (DMT)  G0VS

  24. Experimental interrelationship between G0 and MDMT • COMMENTS • Use of cu (or NSPT) alone as a substitute of VS(when not measured) for seismic classification of a site (Eurocode 8) does not appear founded on a firm basis • If VS assumed as primary parameter for site classification, then a possible surrogate must be reasonably correlated to VS … But if 3 parameters (MDMT, ID, KD) barely sufficient to obtain rough estimates of VS, then estimating VS from only 1 parameter appears problematic …

  25. Estimates of VS from DMT data Comparison of profiles of VSmeasured by SDMT and estimated from mechanical DMT data (Monaco et al. 2013)

  26. Vs prediction from CPT and DMT • DMT predictions of VS appear more reliable and consistent than the CPT predictions (Amoroso 2014) • VS from DMT includes KD , sensitive to stress history, prestraining/aging and structure, scarcely detected by qc

  27. Main SDMT applications • Settlements of shallow foundations • Compaction control • Slip surface detection in OC clay • Quantify σ'hrelaxation behind a landslide • Laterally loaded piles • Diaphragm walls • FEM input parameters • Liquefiability evaluation • In situ G-γ decay curves • …

  28. Tentative method for deriving in situ G- decay curves from SDMT SDMT small strainmodulusG0 from VS working strainmodulusGDMTfrom MDMT (track record DMT-predicted vs. measured settlements) ? But which  associated to GDMT ?

  29. Shear strain "DMT" • Quantitative indicationsbycomparing at various test sites and in differentsoiltypesSDMT data + “reference” stiffness decay curves: • back-figured from the observed behavior under a full-scale test embankment (Treporti) or footings (Texas) • obtained by laboratory tests (L'Aquila, Emilia Romagna, Fucino) • reconstructed by combining different in situ/laboratory techniques (Western Australia) same-depth "reference" stiffness decay curve

  30. Typical ranges of DMT in different soil types "Typical shape" G/G0- curves in different soil types (Amoroso, Monaco, Lehane, Marchetti – Paper under review) Range of values of GDMT/G0 and corresponding shear strain DMT determined by the "intersection" procedure in different soil types

  31. Tentative equation for deriving G/G0- curves from SDMT SDMT data points used to assist construction of hyperbolic equation Roio Piano – L'Aquila Comparison between G/G0- decay curves obtained in Lab and estimated from SDMT by hyperbolic equation DSDSS (Double Sample Direct Simple Shear tests): University of Roma La Sapienza (Amoroso, Monaco, Lehane, Marchetti – Paper under review)

  32. Validation of in situ G- decay curves from SDMT (under study) • Comparison between HSS model – PLAXIS from SDMT parameters and monitoring activities for the excavation of Verge de Montserrat Station (Barcelona, Spain) Working group: Amoroso, Arroyo, Gens, Monaco, Di Mariano

  33. Validation of in situ G- decay curves from SDMT (under study) HSS model – PLAXIS G/G0 = 0.722 Assumptions: γ0.7

  34. Validation of in situ G- decay curves from SDMT (under study) • Preliminary results show an acceptable agreement between experimental data (monitoring activities) and numerical analysis (based on SDMT data) Phase 9 “Pumping down to a depth of 10 m”

  35. Concludingremarks • At sites where VS has not been measured and only mechanical DMT results from past investigations are available, rough estimates of VS (via G0) can be obtained from mechanical DMT data • SDMT results could be used to assess the decay of in situ stiffness with strain level and to provide guidance in selecting G- curves in various soil types, thanks to its ability to provide both a small strain modulus (G0 from VS) and a working strain modulus GDMT (obtained from MDMT derived by usual DMT interpretation) • Use of proposed hyperbolic relationship, which requires to input ratio GDMT/G0 + presumed "typical" shear strain DMT for a given soil type, can provide a useful first order estimate of G/G0- curves from SDMT (further validation needed)

  36. Thank you for your attention

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