Actual deformation mechanisms during sliding are a consequence of several interacting aspects: the geometry of the basal sliding surface, the degree of heterogeneity of the moving mass, the presence of internal weak or hard zones and the stress-strain behaviour of the involved materials. Except in simple cases (pure rotational or planar motions) the development of an admissible mechanism leads to internal shearing. As a result, extensive damage may result, especially in brittle materials. The paper examines the stability conditions and the post-failure behaviour of a compound landslide whose geometry is inspired by one of the representative cross sections of Vajont landslide. The effect of the rock brittleness and stiffness will be presented. A Mohr-Coulomb elasto-plastic strain softening constitutive model defines the rock behaviour. Strength parameters are made dependent of the accumulated deviatoric plastic deformation. The cases discussed were solved by the Material Point model which is well adapted to deal with large deformations and displacements within a general dynamic formulation.