Examination of the Potential of the Seismic Dilatometer (SDMT) to Estimate In Situ Stiffness Decay Curves in Various Soil Types

This paper illustrates the use of the seismic dilatometer (SDMT) to assess the decay of in-situ stiffness with strain level in different soil types. The approach adopted in this study relies on the ability of the SDMT to provide routinely at each test depth both a small strain stiffness (Go from Vs) and a working strain stiffness (constrained modulus Mdmt derived from the usual DMT interpretation). At various test sites, working strain DMT moduli are compared with reference stiffness decay curves back-figured from (i) the behavior observed under a full-scale test embankment (at Treporti) or footings (in Texas), (ii) from laboratory tests (at L’Aquila, Fucino plain and Po plain) and (iii) various combinations of in-situ and laboratory testing techniques (Western Australia). Typical ranges of the shear strains gamma_dmt associated with working DMT strain DMT moduli are inferred to assist construction of stiffness - strain decay curves for different soil types.