Evaluation of porosity and degree of saturation from seismic and electrical data

The characterisation of unsaturated intermediate and coarse-grained soils faces some practical difficulties because undisturbed sampling is not easy. Geophysical methods provide useful information as they can be applied on site for testing geo-materials in their natural state. Moreover their repeated application over time is effective and efficient for monitoring purposes. A procedure for evaluating porosity and degree of saturation on the basis of electrical resistivity and wave velocities measurements is proposed. The approach is based on an electro-seismic model that utilises Archie's law to describe the electrical behaviour of soils and a recent formulation of elastic wave propagation in unsaturated soils. The proposed procedure is applied to laboratory data, and shows promising results.