Strength behavior of slip-zone soils of landslide subject to the change of water content

Landslides are the major natural hazards in many countries all over the world and are usually caused by heavy rainfall, water level change of reservoir, excavation, earthquake, etc. Whether the landslide occurs or not in rainfall season, the strength variation of slip-zone soils of landslide is regarded as the vital control factor. Thus, strength behavior for slip-zone soils of landslide subject to the change of water content is required to be evaluated in a potential landslide area. In this paper, the shear strength of typical slip-zone soil, six groups of 25 specimens of remolded clay samples from Daxishan reservoir landslide, was systemically investigated using the improved direct shear test apparatus in order to fully understand its physical and mechanical properties, and also the shear and failure behavior. Furthermore, the fitting equations for expressing the relationship between the shear strength (effective cohesion and internal friction angle) and vertical loadings, initial water contents of slip-zone clay were established based on the experimental results. In particular, a series of shear stress-shear strain curves under various vertical loadings and different water contents were observed. The results show that a softening stress-strain behavior is achieved for unsaturated slip-zone soil, while a hardening curve is found for saturated slip-zone soil.