Small- and large-strain soil properties from seismic flat dilatometer tests

The seismic flat dilatometer test (SDMT) provides downhole shear wave velocities (V-S) in supplement to conventional inflation readings (p(0) and p(1)). Soil stratigraphy and strength parameters are evaluated from the pressure readings while the small-strain stiffness (G(0)) is obtained from in-situ V-S profiles. A modified hyperbola is used for modulus degradation in order to span from nondestructive- to intermediate-to failure-level strains. Comparisons are made between the derived stress-strain-strength curves from SDMTs and laboratory tests on soft varved lacustrine clay and residual silty sand. The approximate nonlinear approach is also applied to a load test case study involving shallow foundation displacements.