The first part of the paper introduces previous past experience in offshore DMT and SDMT testing. The second part of the manuscript introduces the recently developed Medusa DMT. This device is a self-contained cableless probe that is able to autonomously perform dilatometer tests up to a maximum pressure of 25 MPa. Hydraulic pressurization is achieved with a motorized syringe, enabling volumetric control during membrane expansion. Initially conceived only for offshore testing, the Medusa DMT provides higher quality dilatometer data onshore, with the possibility of additional measurements not feasible with the traditional pneumatic equipment.
Mariano A., Amoroso S., Arroyo M., Monaco P., Gens A. (2018)
“Case Study: SDMT-based numerical analyses of a deep excavation in soft soil”
The paper illustrates how SDMT results were used to estimate the G-gamma decay curves to input in Plaxis, for the project of the excavation of Verge de Montserrat Station (Barcelona, Spain)
The estimation of building settlements on saturated sandy and silty soils are a relevant task for the structure serviceability and stability assurance. On these grounds, a need arises for the performance of in situ tests which disturb less the soil when it is explored to depths up to 30 m or more. Results obtained with the CPTU and DMT devices for an urban renovation project with buildings founded on saturated sands and silts in Concepción city, are presented. These results allow the estimation and comparison of structure settlements obtained from CPTU and DMT.
Sharif E. (2017)
“Early Applications of DMT in Arabian Gulf Area – Three Case Studies”
GeoMEast 2017, Sharm-El-Sheikh
DMT was used for three main applications in famous projects in Dubai, UAE and in Duqm Port in Sultanate of Oman in the Arabian Gulf. The first two applications were conducted in man-made sandy earthfill embankments formed by dredging from the sea bed and stabilized by deep ground improvement. In the Duqm site the DMT was used to confirm liquefaction analysis by CPT, in the Dubai site to confirm the over consolidated nature of upper sandy fill soil previously Vibro-Compacted (8–10 years before). The third project concerned the design of large diameter flexible steel oil storage tanks, based on controlled and strict, edge settlement requirements. Without DMT, the estimates of soil modulus exclusively based on SPT and CPT tests resulted in conservative estimates, suggesting the need for deep ground densification/improvement. A site specific correlation was developed between DMT based M and CPT tip resistance, resulting in about 50% increase over the CPT based modulus M.
Monaco P. et Marchetti D. (2017)
“Evaluation of OCR in sand from DMT & CPT”
6th International Workshop in Poznan (Poland), 26-27 June 2017
This paper is focused on the in situ evaluation of OCR in sands. In particular the correlation for estimating OCR in sand from the ratio MDMT/qt (“proxy” of stress history), involving the combined use of DMT and CPT/CPTU.
Li J. et al (2017)
“In situ shear modulus and shear strain decay curves in expansive soils and analysis of its characteristics”.
Chinese Journal of Rock Mechanics and Engineering 2017
To evaluate the characteristics of stiffness decay of expansive soil at the in-situ stress state under the small strain condition, the in-situ seismic dilatometer test and the resonant column test are carried out. The results show that both the stress state and stress history significantly affect the shear modulus of expansive soil.
Failmezger et al (2016) “Measuring and comparing soil parameters for a large bridge on East coast of the United States” Seismic dilatometer tests (SDMT), piezoconecone tests (CPTU), pressuremeter tests (PMT), vane shear tests (VST) and standard penetration tests (SPT) were performed at a bridge site on the East coast of the United States, where the subsurface soils varied from very soft clays to very dense sands. A large crane lowered the direct push ‘seafloor’ system to the mudline, for advancing the SDMT and CPTU probes. A custom designed hammer was used to generate the seismic waves for Vs measurements offhsore. At the main span, the exploration holes were clustered together and results of all the tests are compared.
Marchetti S. (2016) “Incorporating the Stress History Parameter KD of DMT into the Liquefaction Correlations in Clean Uncemented Sands” Jnl Asce GGE, 142, No. 2, 4pp Provides an updated KD-CRR correlation for estimating CRR from KD. Alternatively, the paper includes a chart for estimating CRR based at the same time on CPT and DMT. The paper also shows that CPT alone or DMT alone are not sufficient to estimate OCR in granular soils. In these soils OCR can be estimated using Monaco’s (2014) correlation OCR = f(MDMT/qc) based on both CPT and DMT. OCR = 0.0344 (MDMT / qt)2 – 0.4174 (MDMT / qt) + 2.2914
Marchetti S. (2016) “DMT in partially draining saturated silts (niche silts)” Unpublished Document. 3pp. DMT is executed, in most cases, in sands, silts and clays. In sands (“permeable”) and in clays (“impermeable”) the interpretation is simpler, because the test conditions during the ≈ 0.5 minutes duration of the test, are either fully drained or fully undrained. A specific “niche” of relatively permeable saturated silts requires a special DMT interpretation, because, during the test, there is partial drainage. It is important (a) To first recognize if the soil is a niche silt (b) Then, if the soil is recognized as a niche silt, to adopt a special interpretation. “A-only” short dissipations, when the soil is saturated silt, should be systematically executed. When ID and MDMT are very low, the operator should suspect niche silts.
Marchetti S. (2015)
“Flat Dilatometer (DMT). Applications and Recent Developments”
Proc. 50th Indian Geot. Conf. IGC-2015. Pune. 10pp.
This paper is a recent short general overview of DMT & SDMT. Description and main applications.
Bandyopadhyay K. et Bhattacharjee S. (2015)
“Correlation between flat dilatometer (DMT) index with insitu bearing strength for subgrade material”
Japanese Geotechnical Society Special Publication
In situ investigation of the soil characteristics offers significant promise for providing a reliable and economical method for obtaining strength and stiffness characteristics associated with pavement design. The investigation of the compressibility and compaction properties of a layer of soil below subgrade of an internal road was carried out in Salt lake campus of Jadavpur University (India). Flat dilatometer (DMT) was used to determine the different properties and moduli of foundation soil below the subgrade and also field CBR, DCP and field compaction tests were carried out to determine the bearing strength and compaction properties.
Marchetti S. (2015)
“Some 2015 Updates to the TC16 DMT Report“
3rd DMT Conf. Rome. pp. 43-65
This Report complements the previous TC16 2001 Report. It covers developments in the period 2001-2015. This 2015 Report plus the TC16 2001 Report contain most of what user’s need to know about DMT.CONTENT. Current trends and ongoing developments, Sensitivity of DMT and CPT to Stress History, OCR in sand, K0 and Ø in sand, Niche silts with partial drainage, Roots of the OCR and Su correlations, Displaying the DMT results, Similarity between KD and fs, Normalization exponent for KD, Settlements, Monitoring compaction, Go/MDMT vs (KD, ID) and Vs prediction, Cementation, Liquefaction, CRR by DMT, CRR by CPT and DMT combined, CRR from Vs (SDMT), State parameter, DMT execution in semiliquid soils, G-gamma decay curves, Intercorrelations CPT-DMT, Reliability of ID, Advancing speed, Tip resistance qc vs qd, Reason of the 1.1 mm displacement, Su field vane, Non textbook soils.
Mayne P.W. (2015)
“Peak friction angle of undisturbed sands using DMT“
Proc. 3rd Int. Conf. on the Flat Dilatometer DMT’15. Rome, Italy.pp.237-242.
Mayne undertakes a systematic validation of the Ø – KD eqn by Marchetti (1997): Ø = 28° + 14.6 log KD -2.1log2KD
by comparing the Ø values predicted by the eq. with the measured peak friction angles Ø on undisturbed samples of clean sands acquired using special field drilling methods, primarily freezing or special piston tube samplers. Mayne shows that the Ø estimated by the 1997 KD -Ø Eq. conservatively matches all the TRX Ø data.
Balachowski, L. and Kurek, N. (2015)
“Vibroflotation control of sandy soils using DMT and CPTU“
Proc. 3rd Int.nl Conf. on the Flat Dilatometer DMT’15. Rome, Italy. pp. 185-190
Confirms Schmertmann (1986) finding that MDMT is more than twice more sensitive than qc to compaction. And, similarly to Schmertmann (1986), replaces the compaction acceptance requirement from a minimum Dr to a minimum MDMT. It also uses the ratio MDMT/qc(a proxy of OCR) to estimate the gain in OCR in addition to the gain in M.
Castelli & Maugeri (2014)
Mechanical properties of Municipal Solid Waste by SDMT”
Elsevier (Vol. 34, Issue 2)
A comparative study between SDMT results and waste properties evaluated by laboratory tests was carried out in Municipal Solid Waste (MSW) materials of a landfill in southern Italy (“Cozzo Vuturo – Enna” – Sicily). According to the authors the SDMT results appear promising for the assessment of the friction angle of waste and the evaluation of the shear wave velocity in such hetereogeneous materials.
McNulty et al. (2014)
“Comparison of DMT and CPT Correlated Constrained Moduli in Clayey and Silty Sands”
This paper compares CPT and DMT correlated constrained moduli and laboratory test results from a geotechnical engineering investigation of a 40,000 m2 site in the Southeastern United States, that lies within the Atlantic Coastal Plain. This study includes 47 cone penetration tests (CPTs and SCPTs) and 13 flat-plate dilatometer tests (Seismic and non-seismic DMTs) and over 80 incremental and constant rate of strain consolidation tests. The comparative analyses show major differences and key similarities in the correlated values. This paper concludes that in contrast to the DMT,CPT/SCPT soundings and often laboratory consolidation testing underestimate key settlement parameters because of disturbance.
Monaco et al. (2014)
“Overconsolidation and Stiffness of Venice Lagoon Sands and Silts from SDMT and CPTU”
J. Geotech. Geoenviron. Engrg.140 (1), pp. 215-227
Identifies an approximate but solid relation between OCR and MDMT/ qc. Reconfirms findings by e.g. Jendeby (1992) and Jamiolkowski et al. (1985): (a) OCR is more sensitively reflected by KD than by qc (b) OCR increases modulus at a faster rate than penetration resistance.
Berisavljevic D et al. (2014)
“Characterization of collapsing loess by seismic dilatometer”
J . Engrg. Geology, Elsevier
Loess soil in Belgrade. Modulus from DMT is compared with oedometer modulus. The paper also proposes two possible ways of indentifying collapsing loess from DMT intermediate parameters and from the ratio G0/MDMT.
The SDMT provides routinely at each test depth the small strain modulus Go and the working strain modulus MDMT. The paper provides indications on typical ranges of the shear strains γDMT associated with working strain DMT moduli in sands, silts and clays. Values of γDMT are needed when constructing the G-γ curves based on Go and MDMT.
Lee, M. et al. (2011)
“Effect of Stress History on CPT and DMT results in Sand“
J . Engrg. Geology, Elsevier, 117, 259-265
Abundant literature demonstrates the higher sensitivity to Stress History of KD, compared with Qcn. Fig. 4(a) and Fig. 6 in Lee’s paper compare the two sensitivities by a comprehensive calibration chamber experimentation. Diagrams in the paper show that KD is much more sensitive to Stress History than qc and ED. The same diagrams demonstrate that OCR in sand cannot be obtained by Qcn alone, nor by KD alone. Qcn and KD depend each one, though in a different way, from two parameters, Dr and OCR. Two unknowns require two information. Another consequence of Lee’s Fig. 6 is that the KD – Dr relation for NC sands cannot be used in OC sand – it will overestimate Dr.
Tsai, P., Lee, D., Kung, G. T. and Juang, C.H. (2009)
“Simplified DMT-based methods for evaluating Liquefaction Resistance of Soils“
J . Engrg.Geology, Elsevier, 103, 13-22
This paper translates the CPT liquefaction correlation Qcn -CRR into a correlation KD – Qcn for predicting CRR by DMT. Unlike previous conversions, using elusive relative density Dr as intermediate parameter, Tsai’s translation proceeds as follows: (1) Run side-by-side CPT and DMT in order to obtain pairs of Qcn and KD (2) Interpolate a correlation KD – Qcn through said pairs (3) Use said correlation to replace Qcn with KD in the horizontal axis of the CPT liquefaction correlation Qcn-CRR (e.g. Idriss and Boulanger 2004). The innovation is to avoid Dr and to avoid the errors of the correlations CPT-Dr and DMT-Dr.