RESULTS Obtained Parameters

SEISMIC DILATOMETER (SDMT)

SEISMIC DILATOMETER (SDMT)

SETTLEMENTS, LIQUEFIABILITY, Parameters M and Cu,

Vs Shear Wave Velocity, G-Gamma Curves

Choice G-gamma curve

FLAT DILATOMETER (DMT)

Repeatibility of Vs 1-2%

FLAT DILATOMETER (DMT) DMT determines in a quick, precise, simple and economical way various important parameters used in geotechnical design. The results are highly repeatable and independent from the operator.

The blade is advanced in the soil by pushing the rods with penetrometers or drill rigs, or a variety of field machines. In this way boreholes and sample disturbance are avoided. The measurements are carried out directly on the in situ soil. The results are immediately available in a report format, containing graphs and tabular outputs.

The DMT is used in 50 countries. It is standardized in the ASTM (USA) norms and in the Eurocode.

The equipment and test procedure are described in detail in the Report ISSMGE Committee TC16 (2001), downloadable from the website.

APPLICATIONS - Settlements prediction - Operative modulus M - Undrained shear strength Cu - Soil Type (sand, silt, clay) - Compaction control - Detection of slip surfaces in slopes - P-y curves for laterally loaded piles - Liquefaction potential - Coefficient of consolidation and permeability (clays) - phi in sands - OCR and Ko in clays - Subgrade reaction modulus for diaphragm walls - Choice of Input parameters for Plaxis - Subgrade reaction modulus for pavements

Settlement predictions The DMT provides estimates of operative moduli and settlements of superior accuracy, initially documented by Schmertmann 1986, Lacasse 1986, Sallfors 1988, Leonards 1988, Hayes 1990, subsequently by a summary of numerous case histories by Monaco et al. “DMT-predicted vs observed settlements” in the Proceedings of “Washington DMT 2006” Conference.

The superior accuracy of the DMT settlement prediction is due to the lower distortions caused by the blade penetration compared with the distortions caused by conical tips, to the fact that the modulus Mdmt is derived by a “miniload test” rather than by the penetrometric resistance at rupture, to the availability of the “Stress History Index” Kd, strongly related to OCR. Thanks to Kd, estimating the moduli, notoriously highly dependent from stress history, is univocal, avoiding arbitrary factors as in the case of penetrometric tests.

SEISMIC DILATOMETER (SDMT) SDMT is the combination of the standard Flat Dilatometer (DMT) with a seismic module. Such module is a probe outfitted with two sensors, spaced 0.5 m, for measuring the shear wave velocity Vs. From Vs one can determine the small strain shear modulus Go.

APPLICATIONS of SDMT The modern norms increasingly require seismic analysis, for which the basic parameter is Vs. SDMT provides profiles of Vs in a quick, precise, simple and economical way. Repeatability of Vs 1-2 %.

For complete seismic analysis it is necessary, besides Vs (or Go obtainable from Vs), the complete G-Gamma decay curve. At the moment SDMT is the only in situ test, besides the self boring pressuremeter, providing the low strain Go and the working strain M, hence two points in the G-Gamma curve. The availability of two points helps in the choice of the proper G-Gamma curve, unlike tests determing only Go.

SDMT provides, besides Vs, all the information obtained by the traditional DMT.

Liquefaction potential. SDMT provides at each depth two independent estimates of the liquefaction resistance, one derived from Vs, the other from Kd. Kd is sensitive to factors almost unfelt by other tests, in particular aging, a factor that may increase the liquefaction resistance even by 60% in loose sands (see Leon et al. Jnl ASCE GGE March 2006, evaluating the seismic risk under existing nuclear reactors in South Carolina).

Seismic codes. According to Eurocode 8 all new contructions should be preceded by an analysis of the local seismic response, requiring Vs from ground surface to 30 m depth.

Use of SDMT. Used worldwide, often in important projects, among others the Barriers for protecting Venice (Italy), Barcelona harbour and airport, the New Shuttle Cralwerway at Nasa Cape Kennedy, the San Andreas Fault area in California, Marina Pez Vela project in Quepos Costa Rica, big Power Plants, high speed Railways and Metro, in various Harbours Nearshore, numerous research projects by Universities etc..

References. -TC16 (2001) "The DMT in Soil Investigations", A

Report by the ISSMGE Committee TC16, 41 pp.

-Washington DMT 2006. 2nd International Conference on the Flat Dilatometer (DMT). 50 papers describing experiences worldwide – see website.

-Seismic Dilatometer. Additional information at website.

EUROCODE 7 Part 2 (2007)

ASTM- Standard D6635 (2007)

ISSMGE – TC16 Report (2001)

www.marchetti-dmt.it tel +39 06-303 11 240 – +39 06-303 60 107

WAYS OF INSERTING THE BLADE

“TORPEDO” INSERTION METHOD

Pushed by truck Pushed by a drill rig Driven by a drill rig

Pushed froma fixed platform Driven by SPT Tripod

Driven or pushed by astatic/dynamic penetrometer

TorpedoL ≈≈≈≈ 3 m

N e e d t od e t e c t

Formation of Kd = 2 (NC) zones

Kd = 2 denotes NC clay

Kd by DMTZ(m)

Kd = 2 active/quiescent slip surface

1. SLIDING 2. REMOULDING

3. RECONSOLIDATION(NC STATE)

4. INSPECT Kd PROFILE

active: Kd=2quiescent : Kd=2

slip surfaces ?

LIQUEFACTION bySEISMIC DILATOMETERTwo independent CRR evaluations

www.marchetti-dmt.it

Light earthquakes

Strong earthquakes

CRR from VsSDMT

CRR from KdDMT

Andrus and Stokoe 2000

Monaco 2005

Ref. Monaco (2007) "Evaluating Liquefaction Potential by Seismic Dilatometer (SDMT) accounting for Aging/Stress History" 4th Int. Conf. Earthquake Geotechn. Eng. -Thessaloniki

S D M T

Telescopicguide tube

Shear Wave Source

BARGEWaves0.5 m

30- m

NO JACKUP

CONE

Distortions caused by penetration of cones and wedges in real clay.Baligh & Scott (Nov. 1975) "Quasi-Static Deep Penetration in Clay",Jnl. ASCE Geot.Eng.Div.

SETTLEMENTS

Bullock & Failmezger (Porto 2004)

Higher accuracy of DMT believed due to:

1. DMT contains information on Stress History

2. Wedge shaped tips deform less than conical tips

3. Modulus obtained by loading the soil (mini-load test) is more closely related to Modulus than Penetration Resistance

SPT predicted Settlements

measured (mm)

pre

dic

ted

(mm

)

sands

Burland andBurbridge (1985)

DMT predicted Settlements

measured (mm)

pre

dic

ted

(mm

)

sands

Schmertmann (1986)and Hayes (1988)

DISTORTIONS IN CLAYWEDGE

Which soil investigation

should I use?REFERENCE: State-of-the-art Lecture No. 1

Geomaterial Behavior and Testing, 17th Int. Conf. SoilMechanics and Geot. Engng, 2009, Alexandria, Egypt

Mayne P.W. Georgia Institute of Technology, Atlanta, USA

Coop M.R. Imperial College, London, UK

Springman S.M. Swiss Federal Inst. of Technology, Zurich, CH

Huang A.B. National Chiao Tung Univ., Taiwan, China

Zornberg J.G. University of Texas, Austin, USA

“Soil borings … laboratory testing … SPT …pressuremeter (PMT) … vane (VST) … crosshole(CHT) … Taken together, all of these are suitable …yet at considerable cost in time and money …”

“... In this fast-paced world, … SCPT and SDMT should serve as the basis … in routine daily site investigation practices …”

Direct-push

Seismic

Dilatometer

www.marchetti-dmt.it