Role of Geophysical Testing in Geotechnical Site Characterization

The lecture attempts to highlight the insights late Victor De Mello provided on some key areas. Considering the increasing role of the geophysical methods in the geotechnical site characterization, the writer focuses on the use of in-hole geophysical methods when assessing, both in field and in laboratory, the parameters depicting the soil state and its stiffness at small strain. With this aim the writer draws the attention to seismic transversal (S) and longitudinal (P) body waves generated both in field, during in-hole tests, and in laboratory using piezocristals. Within this framework the following issues are discussed: • Stiffness at very small strain as obtainable from the S and P velocities. • Difference between fully from near to saturated soils from the measured P-wave velocity. • Evaluation of undisturbed samples quality based on the comparison of S-waves velocities measured in field and in laboratory respectively. • Evaluation of porosity and void ratio from measured P and S waves velocity. • S-wave based evaluation of the coarse grained soils susceptibility to cyclic liquefaction.