The seismic dilatometer is an add-on module that may be combined with the dilatometer or with the CPT for measuring the shear wave velocity Vs (SDMT) and compression wave velocity Vp (SPDMT)
Thanks to the true-interval test configuration (two receivers), the repeatability of the VS measurements is very high, approximately 1 %, i.e. a few m/s.
The Vs values are calculated automatically and displayed in real time, at a cost and time considerably lower than Downhole or Crosshole.
SDMT provides the small strain modulus Go and the working strain modulus MDMT, i.e. two points of the G-γ The availability of two points is helpful while selecting the design G-γ curve. (Amoroso et al. 2014).
Based on SDMTs executed in many different soils and geographical regions, a chart (Fig. 5, Marchetti 2008) has been constructed permitting estimates of Vs from just mechanical DMT results.
A Vs profile can be obtained in impenetrable soils by executing the test in a borehole backfilled with gravel (Fig. 7, Totani et al. 2009).
Seismic dilatomer composition
The SDMT is the combination of the flat dilatometer with an add-on seismic module for the measurement of the shear wave velocity. The seismic module (Fig. 1a) is a tubular element placed above the DMT blade, equipped with two receivers located at 0.5 m distance. When a shear wave is generated at surface, it reaches first the upper receiver, then, after a delay, the lower receiver.
