Coupled processes during rainfall: an experimental investigation on a silty sand

he factors that contributed to the initiation of a triggering mechanism in a shallow landslides induced by rainfall are investigated in this work at laboratory scale. The aim of the work was to characterise the behaviour of the soil in triaxial tests, in the light of the possible failure mechanisms in a slope subjected to rainfall. The material study is a silty sand from a steep slope in Ruedlingen in the North-East of Switzerland, where a landslide triggering experiment was carried out. Conventional drained and undrained triaxial tests for the water phase were conducted to detect critical state conditions as well as peak shear strength as a function of confining pressure for three different water content related to the in situ one. Soil specimens with three different gravimetric water contents were exposed to stress paths simulating the in situ anisotropic compression followed by a decrease of mean effective stress at constant axial load. Possible unstable response along the stress paths analysed was investigated by means of second order work.