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Workshop on Penetration Testing – University of Pisa, DESTEC Pisa – Italy, 9 th October 2014 PowerPoint Presentation
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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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slide1

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

slide2

Outline of the presentation

Flat dilatometer (DMT)

Seismic dilatometer (SDMT)

Interpretation of the parameters

Engineering applications

dmt flat dilatometer equipment
DMT Flatdilatometerequipment

BLADE

FLEXIBLE MEMBRANE(D = 60mm)

dmt test layout components
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

dmt insertion with penetrometer
DMT insertion with penetrometer

Most efficient method:

direct push with penetrometer

dmt working principle

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

dmt intermediate parameters
DMT Intermediate parameters

DMT Readings

Intermediate Parameters

Id: Material Index

P0

Kd: Horizontal Stress Index

P1

Ed: Dilatometer Modulus

k d contains information on stress history

(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)

dmt formulae interpreted parameters

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

slide11

KDcorrelatedto OCR (clay)

1.56

Marchetti 1980 (experimental)

OCR

=

0.5

Kd

Theoretical

Finno 1993

Experimental

Kamei & Iwasaki 1995

Theoretical

Yu 2004

cu correlation from ocr ladd shansep 77 soa tokyo
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

=

dmt formulae 1980 today
DMT Formulae (1980 – today)

Po and P1

Intermediate parameters

Interpreted parameters

slide14

DMT results

KD=2NCclay

ID

MCu

 

KD

soiltype

(clay, silt, sand)

common use

shapesimilartoOCR helpsunderstandhistoryofdeposit

Generally dependable

slide16

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

example seismograms sdmt at fucino
Example seismograms SDMT at Fucino

Delay well conditioned from Cross Correlation  coeff of variation of Vs 1-2 %

sdmt results

High repeatability

SDMT results

GO= ρ Vs2

DMT

Seismic DMT

vs at national site fucino italy
Vs at National Site FUCINO –ITALY

SDMT (2004)

SCPT

Cross Hole

SASW

AGI (1991)

Fucino-Telespazio

National Research Site (Italy) 2004

20

standards
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

slide23

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

slide24

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 …
slide25

Estimates of VS from DMT data

Comparison of profiles of VSmeasured by SDMT

and estimated from mechanical DMT data (Monaco et al. 2013)

slide26

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
slide27

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
slide28

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 ?

slide29

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

slide30

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

slide31

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)

slide32

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

slide33

Validation of in situ G- decay curves

from SDMT (under study)

HSS model – PLAXIS

G/G0 = 0.722

Assumptions:

γ0.7

slide34

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”

slide35

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)