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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