Use of the seismic dilatometer (SDMT) to estimate G-gamma decay curves in different soil types

This paper illustrates the use of the seismic dilatometer (SDMT) to assess the in situ decay of stiffness with strain level (G-γ curves or similar) 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 (G0 from VS) and a working strain stiffness (constrained modulus MDMT from usual DMT interpretation). At various test sites working strain DMT moduli (GDMT or EDMT, derived from MDMT by elasticity theory) have been compared with same-depth reference stiffness decay curves back-figured from the observed behavior under a full-scale test embankment (Treporti) or footings (Texas), obtained by laboratory tests (L'Aquila) or reconstructed by combining different in situ/laboratory techniques (Western Australia). Typical ranges of the shear strain γDMT associated to GDMT in different soil types have been inferred from the intersection of the DMT data points with the reference stiffness decay curves.