The Flat Dilatometer and Seismic Dilatometer
The last decades have seen a massive migration from laboratory testing to in situ testing. The reason is that in situ tests are fast, economical, reproducible, informative, provide continuos profiles, exhibit reduced scatter and cost much less than the sequence of drilling, sampling and testing. Particularly in sand, recovering undisturbed samples is very difficult and expensive.
The Flat Dilatometer (DMT) and the Cone Penetrometer (CPT) are the two direct-push technologies that are commonly used for everyday site investigations. Laboratory tests remain fundamental for research and high risk projects.
The aim of this workshop is to describe the Flat Dilatometer equipment (DMT), its working principle and test procedure. The interpretation steps will be shown starting from the field readings up to the interpreted geotechnical parameters. Comparisons of the results will be shown with other investigation tools in well documented research test sites.
The Seismic Dilatometer (SDMT) will also be described. It is a seismic add-on module for measuring the shear wave velocity VS.
The presentation will illustrate the main applications for which this test is commonly performed, including:
- Settlement predictions (comparisons of DMT-predicted with measured settlements)
- Moduli before-after soil improvement
- Estimation of the liquefaction resistance CRR
- Slip surface detection
- Kh behind diaphragm walls from MDMT
- Moduli in roads subgrade
- P-y curves for laterally loaded piles
- FEM input parameters from DMT results (ex Plaxis)
- Combining the low-strain shear modulus G0 with the working strain modulus MDMT to estimate the G-Gamma decay curves
The workshop will also include the description of the most recent developments, including the Medusa DMT and the Seafloor DMT system for offshore investigations.
Eng. Diego Marchetti