ABSTRACT
ABSTRACT: A theoretical interpretation of observed shear responses upon wetting of two unsaturated pyroclastic soils is reported. The experimental observations have been obtained by direct shear tests performed on specimens at natural water content and on saturated specimens. In some cases natural water content specimens have been wetted during shearing stage at peak strength. This procedure has been used to analyse all the phenomena that occur when complete saturation is performed in proximity of shear failure. In every test the wetting process produced either a reduction of shear strength either a modification of dilatancy. The observed behaviour has been interpreted in the framework of critical state soil mechanics as originally extended to unsaturated soils by Alonso et al. (1987) and, subsequently, improved by a number of other authors.
