Simple Shear Tests for Unsaturated Soils

Rainfall-induced landslides in Southern Italy often affect the pyroclastic soils produced by the past explosive activity of Vesuvius volcano. Along hilly zones these soils are mostly unsaturated and characterized by a metastable structure, which can experience static liquefaction upon shearing. Several authors studied the mechanical behaviour and the wetting-induced collapse through triaxial tests and direct shear tests. Here, a new series of tests is performed—on remolded specimens—through the Suction Controlled Simple Shear apparatus, which is particularly suitable to reproduce the in-situ stress–strain hillslope conditions and the strain/stress paths induced by rainfall during the failure and post-failure mechanisms. The results are discussed in terms of shear strain, axial strain and saturation degree.