Influence of 3D geometry and pore pressure distribution on the safety factor of a deep earthslide in a clay slope.

This paper reports the results of 2D and 3D theoretical analyses of pore pressure distribution and safety factor of a clayey landslide. 2D FEM analysis was carried out on the transient process between limit hydraulic conditions of null flux and null pore pressure on the ground surface (corresponding to dry and rainy weather respectively). The effects of the historical rainfall series of the site were also considered. Due to the very low hydraulic conductivity and to the significant depth of the slip surface, the 2D analysis provides negligible pore pressure variations due to rain in the axial section. The influence of rainfall on 2D results gradually increases in the lateral sections, as the slip surface approaches the ground surface. The analyses carried out by means of the two codes PLAXIS3D and STAB3D show a large difference of the safety factor with respect to the value obtained by the 2D analysis. The influence of the landslide