seismic dilatometer (sdmt)cfpbolivia.com/2015/diego-marchetti/seismic-dilatome-(sdmt).pdfseismic...

Eng. Diego Marchetti 14 de Mayo 2015 www.marchetti-dmt.it

SEISMIC DILATOMETER (SDMT) Equipment, Test procedure, Results, Software

Santa Cruz de la Sierra Bolivia

2009 – Alexandria Egypt 17th Int. Conference on Soil Mechanics and Geotechnical Engineering State-of-the-Art Lecture

Mayne et al (2009)

SCPT & SDMT for every day field testing

TOO SLOW !

2012 – ISC’4 Brazil September 18-21, 4th International Conference on Geotechnical and Geophysical Site Characterization

Total 226 papers: 40 papers on SDMT, 57 references to SDMT

Lab Testing Direct Push (CPT and DMT) fast and convenient tools for everyday investigations

Introduction to DMT & SDMT Equipment

DMT (static)

Seismic (dynamic)

DMT equipment

DMT Flat Dilatometer equipment

BLADE

FLEXIBLE MEMBRANE (D = 60mm)

ALL MECHANICAL, NO ELECTRONICS Blade is like an electrical switch, can be only OFF or ON simple and robust

DMT Flat Dilatometer equipment

DMT Test Layout

blade

rods

penetration machine

pneumatic-electric cable control box

gas tank (air, nitrogen,etc)

Test Procedure stop every 20 cm A : Lift-off pressure

B : Pressure for 1.1 mm expansion

A B

Truck Penetrometer (most efficient)

Light Penetrometer (most common)

DMT independent from penetration method

CPT – measurements performed during penetration at a fix speed of 2 cm / sec (with some tolerance)

DMT Measurements when blade is not moving Penetration only to advance to next test depth

High flexibility to advance DMT in the soil

Ways of advancing the DMT (SDMT)

Driven by Spt tripod

Driven by drill rig

Pushed by drill rig Driven or pushed by light penetrometer

Pushed by a fixed platform Driven from a barge

SPT tripod (most economical)

Concepciòn Chile 2014

Membrane Calibration

The natural membrane position is somewhere between A and B

Definitions: ∆A = external pressure which must be applied to the membrane in free air to collapse it against its seating (i.e. A-position)

∆B = internal pressure which in free air lifts the membrane center 1.1 mm from its seating (i.e. B-position)

Membrane has non-zero rigidity

B

free A

seating

Membrane Calibration

Use syringe and short calibration cable for performing calibration

Membrane Calibration

ΔA: apply abbundant suction: signal ON

Slowly release: signal OFF ΔA

Slowly inflate: signal ON ΔB

Dilatometer Test Sequence

Readings: ON OFF ON (OFF) ON

Start inflation A (P0) B (P1) C (P2)

Audio signal:

start DMT Acquisition (signal ON)

Slowly inflate: signal OFF A

Continue to inflate (signal is still OFF)

Continue to inflate: signal ON B

Deflate immediately (autosave A & B)

Deflate completely – ready next depth

Time of DMT test execution

Time A, B readings each depth ≈ 30 s

Time to advance (2cm/s) 20 cm ≈ 10 s

Test speed ≈ 18 m/h

1 day ≈ 80-100 m of DMT

Example of Field Data

Z (m)

A (kPa)

B (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 …

Calibration: ΔA = 15 kPa ΔB = 40 kPa

A B

Calibration used for correcting field readings

DMT Field Readings

A

B

DMT Corrected Readings

P0: corrected 1st reading

P1: corrected 2nd reading

ΔA, ΔB

DMT Intermediate parameters

Intermediate Parameters DMT Corrected Readings

P0

P1

Kd: Horizontal Stress Index

Ed: Dilatometer Modulus

Id: Material Index

DMT Formulae – Interpreted parameters

Intermediate Parameters

Id

Kd

Ed

Interpreted Geotechnical Parameters

Cu: Undrained Shear Strength (clay)

Ko: Earth Pressure Coeff (clay)

OCR: Overconsolidation ratio (clay)

Φ: Safe floor friction angle (sand)

γ : Unit weight and soil description

M: Constrained Modulus

DMT Formulae (1980 - today)

Po and P1

Intermediate parameters

Interpreted parameters

ID contains information on soil type

Performing DMT, immediately notice that:

p

1

CLAY p p

0

SAND

p 0

p 1

p

SILT falls in between

ID = (p0 - u0) (p1 - p0)

ID contains information on soil type

SAND

CLAY

KD contains information on stress history

KD is an ‘amplified’ K0, because (p0 - u0) is an ‘amplified’ σ’h, due to penetration

KD = σ’v (p0 - u0)

p0

D M T

Definition of KD similar to K0:

Very roughly Kd ≈ 4 Ko E.g. in NC : Ko ≈ 0.5 and Kd ≈ 2

KD reflects ‘stress history’ (OCR)

Dep

th Z

Kd

KD contains information on stress history

2

KD = 2 in NC clay (OCR = 1)

NC

OC KD > 2 in OC clay (OCR > 1)

KD contains information on stress history

OC Kd > 2

NC Kd ͌ 2

Taranto 1987

KD correlated to OCR (clay)

Experimental Kamei & Iwasaki 1995

Theoretical Finno 1993

Theoretical Yu 2004

OCR = Kd

1.56 Marchetti 1980 (experimental) 0.5

KD correlated to K0 (clay)

Theoretical 2004 Yu

Experimental Marchetti (1980)

K0 = Kd 0.47

Marchetti 1980 (experimental) 1.5

0.6

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)

1.1 mm

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.

ED not directly usable corrections (penetration,etc)

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

ED (DMT modulus)

M Constrained

Modulus

KD (stress history)

ID (soil type)

Definition of M (no ambiguity)

Vertical drained confined tangent modulus (at σ'vo)

Same as Eoed, traditionally measured by oedometer

M = Eoed = 1/mv = ∆σ'v / ∆εv (at σ'vo)

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) 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

Cu from OCR Ladd SHANSEP 77 (SOA TOKYO)

Ladd: best Cu measurement not from TRX UU !!

Using m ≈ 0.8 (Ladd 1977) and (Cu/σ’v)NC ≈ 0.22 (Mesri 1975)

Cu σ’v OC

= Cu σ’v NC

OCR m OCR = 0.5 Kd

1.56

Cu = σ’v 0.5 Kd 1.25

0.22

best Cu from oed OCR Shansep

Cu comparisons from DMT and from other tests

Recife - Brazil

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

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

different CPT profile according to Nc value

(Nc 14-22)

A.G.I., 10th ECSMFE Firenze 1991 Vol. 1, p. 37

Cu at National Site FUCINO – ITALY

Interpretation of Soil Description & Unit weight

I )EQUATION OF THE LINES:

SOIL DESCRIPTION

0.6

Material Index

If PI>50, reduce by 0.1

D

Dila

tom

eter

Mod

ulus

0.1

and/orPEAT

5

MUD1210

20

50

( )1.5

0.2 0.5

MUD

A

B

C

0.33

1.6

1.8

1.7

1000

(bar

)E

100

200

D 500

2000

D

0.585

0.6570.694

CLAY

2.05

DC

AB 0.621

m

1.9

SILTY

2.0132.2892.564

1.737n

E =10(n+m log

3.3

1.7

γ

1

I2

D

0.8 1.2

1.6

1.7

1.8

5

SAND

2

1.8

1.9

2.15

1.95

1.8

2.1

SILT

CLA

YEY

SILTY

SAN

DY

D

and ESTIMATED γ/γwChart for evaluating:

ɣ unit weight ( σ'vo profile)

Soil description

as f (ID, ED)

Material Index ID

Dila

tom

eter

Mod

ulus

ED

(bar

)

Marchetti & Crapps 1981

Example red dot: ID = 1.6, Ed = 200 bar Ɣ = 1.8 Ɣw Soil description: sandy silt

C-Reading

Readings: ON OFF ON (OFF) ON

A (P0) B (P1) C (P2)

Audio signal:

C readings (in sand): pore water pressure

Schmertmann 1988 (DMT Digest No. 10, May 1988, Fig. 3)

SAND: C ≈ Uo drainage (≈ piezometer)

CLAY: C > Uo no drainage (≈ highlights ∆u)

∆u≈0

∆u≈0

∆u>0

UD = (p0 - u0) (p2 - u0)

Example of C readings

Catania Harbour - 2012

Example of C readings

Catania Harbour - 2012

Example of C readings and UD

wedge vs cone (dissipation)

Dissipation test in cohesive soils estimate coefficient consolidation & permeability

Time (min)

σ h

(kPa

)

Totani et al. (1998)

wedge From a ≈ mini embankment Larger volume in a less disturbed zone

cone From u(t) in a singular highly disturbed point

Acquisition DMT Dissipation (T, A)

DMT Dissipation Interpretation (Ch, Kh)

Validation of consolidation coefficient DMT vs. other dissipation tests

Totani et al. ISC '98 - Atlanta, Georgia (USA)

Graph available real time

DMT main graph grain size stress history compressibility strength

Data available real time

SDMT – Test Layout

Acquisition Board

DM

T Se

ism

ic p

robe

Top Sensor

Bottom Sensor

Plays a crucial role for: quality of test results maximum test depth (SNR – Signal to Noise Ratio)

Shear Wave Source

Pendulum Hammer Automated Hammer (Autoseis)

Remove pavement under SWS (if present) Apply load on SWS (i.e.

truck jacks). SWS transmits shear wave only if good adherence with soil Use rubber for decoupling

vertical load energy to soil not to load

Geometry & weight: influence only wave shape and max test depth (not Vs results)

Shear Wave Source (SWS)

Shear vs Compression wave

Shear Wave

propagation direction

Compression Wave

particle motion

particle motion

When the hammer head strikes the shear beam, the corresponding soil vibration generates both a compression wave (P) and a shear wave (S).

S-Wave

Shear Beam

P-wave P-wave

Hammer head

S and P waves generated by hammer + shear beam

soil vibration direction

S-Wave

Shear Beam

P-wave

P-wave

Hammer head

soil vibration direction

• Sensors record shear wave if: Z >> DSBR • If Z ≈ DSBR, sensors record combination of S and P wave Place shear beam as close as possible to rods (no contact)

Minimize distance from Shear Beam to Rods (DSBR) DSBR

Z

rods

Shear beam

TOP VIEW

Hammer head

Correct Placement Acceptable Placement

≈ 50° rods 90°

The hitting direction of the hammer should be perpendicular to the line from the rods to the center of shear beam

hammer hitting direction

SWS Placement & Orientation

sensor axis

SDMT has mono-axial sensors, soil movement detected only in one direction

Once SWS is placed, correct sensor orientation is determined: the hitting direction of the hammer must be (approximately) parallel to the axis of the sensors

Shear beam

TOP VIEW

Hammer head

hammer hitting direction

rod

sensor axis

sensor

SDMT Sensor Orientation

• Hammer hitting direction towards soil irregularity (wall, ditch, ..) • Sensor S1 receives direct S-Wave and reflected P-wave • Difficult Interpretation

Shear Beam

Hammer head

soil

irreg

ular

ity (i

.e. w

all)

soil vibration

S1

S2

Sum of direct S wave and reflected P wave.

S-Wave (direct)

P-wave (reflected)

SWS Placement and Orientation (1/2)

• Hammer hitting direction is parallel to soil irregularity • Sensor S1 receives direct S-Wave and reflected S-wave • Time delay similar for direct and reflected wave

S-Wave (direct)

S-wave (reflected)

Hammer head

soil

irreg

ular

ity (i

.e. w

all)

S1

S2

Shear beam

Direct S wave

Reflected S wave

Reliable interpretation

SWS Placement and Orientation (2/2)

Shear wave seismogram acquisition

295

40.50

Shear wave seismogram acquisition

depth of DMT blade (user deals only with 1 depth)

current Vs interpretation

Z: depth of midpoint between sensors

Vs assigned at Z

Vs repeated at Z (independent)

variation coefficient

Shear wave seismogram acquisition

Shear wave seismogram acquisition parameters

signal amplification in depth

sample time (microseconds)

n° samples (800-1800)

distance hammer - rods

trigger type

time shift after trigger event

Shear wave velocity measurement

Hammer generating shear wave

Data Acquisition is rapid (3-5 sec)

Vs interpretation real time

Automatic delay evaluation

Cross-correlation algorithm

shift red signal back towards blu signal, until best superimposition is obtained

Δt = wave delay

SDMT main features

Accuracy of delay (Δt) calculation • true-interval (2 receivers instead of 1)

• Trigger offset no influence on Δt calculation • Same wave to both receivers

• Signals are amplified and digitized in depth clean waves delay Δt very clear

• Vs interpretation • Automatic • operator independent • real time

• Test execution is rapid • no hole • no wait for cementation (e.g. crosshole, downhole)

SDMT

Seismograms

Summary table of Vs results

Word Report: Superimposed Graphs

Word Report: Cross Section Graph

Word Report: Vs tables

Word Report: Seismograms

Excel spreadsheet

Soils testable by DMT/SDMT

DMT • ALL SANDS, SILTS, CLAYS • Very soft soils (Cu = 2-4 kPa, M=0.5 MPa) • Hard soils/Soft Rock (Cu = 1 MPa, M=400 MPa) • Blade robust (safe push 25 ton)

SDMT • All penetrable soils (like DMT above) • Non penetrable soils (gravel, rock, ..):

inside a backfilled borehole Max depth: 135 m in L’Aquila (2009)

Vs in non-penetrable soils

Totani (2009)

Method (downhole):

Drill borehole careful backfill of borehole with

gravel (grains D = 5-15 mm) Vs in borehole

the sand travelpath is similar

Travelpath includes short path in the gravel backfill similar for both receivers delay Δt does not change

SDMT validation in non-penetrable soils

(only Vs in sandfilled borehole - no DMT !!!)

In penetrable soils both procedures are possible

results ≈ same

SDMT in borehole (140m) – Aquila (ITALY) SHEAR WAVE VELOCITY (m/s) Aquila (Earthquake – 2009)

Fill Material

Calcareous Breccia

LACUSTRINE DEPOSITS:

SILTY SAND and

CLAYEY-SANDY SILT D

epth

(m)

STANDARDS EUROCODE 7 (2007). Standard Test Method, European Committee for Standardization, Part 3: Design Assisted by Field Testing, Section 9: Flat Dilatometer Test (DMT), 9 pp.

ASTM (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.

ASTM (2011) – Standard Test Method D7400 – 08, “Standard Test Methods for Downhole Seismic Testing“, 11 pp.

NATIONAL STANDARDS: • Italy: Consiglio Superiore Lavori Pubblici (2009), Protezione Civile (2008) • Sweden: Swedish Geotechnical Society SGF report (1994) • France: ISO/TS 22476-11:2005(F) • China: TB10018 (2003), GB50021 (2003), DGJ08-37 (2012) • ..

(°) Algeria, Angola, Argentina, Australia, Austria, Bahrain, Bangladesh, Belgium, Bolivia, Bosnia, Brazil, Bulgaria, Canada, Czech Republic, China, Chile, Cyprus, Colombia, Costa Rica, Croatia, Denmark, Ecuador, Egypt, United Arab Emirates, Estonia, Finland, France, Germany, Greece, Guadalupe, Guatemala, Honduras, Hong Kong, Hungary, India, Indonesia, Iran, Israel, Italy, Japan, Korea, Kosovo, Kuwait, Lithuania, Malaysia, Mexico, Netherland, New Zeland, Norway, Oman, Pakistan, Peru, Philippines, Poland, Portugal, Romania, Russia, Saudi Arabia, Serbia, Singapore, Slovenia, South Africa, Spain, Sri Lanka, Sweden, Switzerland, Taiwan, Thailand, Tunisia, Turkey, United Kingdom, United States of America, Venezuela, Vietnam.

SDMT used in over 70 countries (°) (> 200 in USA)

Some SDMT test sites...

Via Fori Imperiali Piazza Venezia

Underground in Rome - Line C

SDMT - NASA Cape Kennedy (USA)

Juan Santamaria Intnl. Airport – Costarica

SDMT in SE LAGO – Mexico city

Palazzo Esposizioni - Rome

This building experienced a crack in the ceiling due to differential settlements

SDMT 1 (front) SDMT 2 (front) SDMT 3 (back) CROSS SECTION: CONSTRAINED MODULUS M (MPa)

SDMT at Zelazny Most – Poland Tests performed for monitoring copper waste dam

DMT Settlements software

Settlement prediction using DMT Settlements software from the Constrained Modulus obtained with the Flat Dilatometer in Bogotà last week in a 30 m SDMT test (4 hours demonstration)

SDMT Escuela Colombiana 9 May 2015

SDMT Escuela Colombiana 9 May 2015

SDMT Escuela Colombiana 9 May 2015

SDMT Escuela Colombiana 9 May 2015

SDMT Escuela Colombiana 9 May 2015

SDMT Escuela Colombiana 9 May 2015

uni file example (text file)

MDMT [MPa]

Sigma’v [kPa]

Z [m]

SDMT Escuela Colombiana 9 May 2015

SDMT Escuela Colombiana 9 May 2015

SDMT Escuela Colombiana 9 May 2015

END Thank you