Vs measurements by seismic dilatometer (SDMT) in non-penetrable soils

This paper illustrates the procedure for obtaining measurements of the shear wave velocity Vs by seismic dilatometer (SDMT) in backfilled boreholes in non-penetrable soils. The possibility of such measurement descends from the fact that the path of the shear wave from the surface to the upper and lower receiver includes a short path in the backfill of very similar length for both receivers. The SDMT equipment/test procedure and the borehole backfilling technique are briefly described. The validation of the method by comparison of parallel profiles of Vs obtained in the "virgin" soil and in a backfilled borehole is presented. Vs profiles obtained by SDMT in backfilled boreholes at two test sites in central Italy, Sulmona (coarse gravel) and L'Aquila (calcareous breccia), are compared to Vs profiles obtained by the traditional Down-Hole technique and related to the stratigraphic profiles of the subsoil.