- 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.
- 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. (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
- 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.
- 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 Unpublished Document. 3pp.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.
- McNulty et al. (2014). “Comparison of DMT and CPT Correlated Constrained Moduli in Clayey and Silty Sands” Geocongress 2014. 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.
- Amoroso S. at al. (2014). “Examination of the Potential of the Seismic Dilatometer (SDMT) to Estimate In Situ Stiffness Decay Curves in Various Soil Types“.
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.
- 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.
- 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.
- 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.