Deformation and failure mechanism of colluvial landslide under sustained rainfall-a case study of Xinzhan landslide in Tongzi County, China

Abstract

The failure mechanism of Xinzhan landslide were investigated systematically based on multiple-integrated geotechniques, including field investigations, monitoring, and numerical simulations. Xinzhan landslide is a typical colluvial landslide, composed of gravelly soil in upper part and sandstone interbedded with mudstone in underlying part. The sliding surface is closing to the soil-rock interface with average depth about 8 m and the main sliding direction 287°. The occurrence of Xinzhan landslide is attributed to its unique geological environment and sustained rainfall. The hydro-mechanical coupling results indicate that under sustained rainfall, the rainwater infiltrates into gravelly soil, rising the pressure and forming transient saturation zone near the soil-rock interface, where the strength parameter is weakened under effect of water. As a consequence, the plastic deformation is intensified. Additionally, the deformation evolution trend of landslide under different rainfall intensities is also studied. The results show that the greater rainfall intensity, the shorter rainfall duration required for the landslide to produce accelerated deformation. The rainfall intensity-duration curve is used to construct the critical rainfall early warning criterion of Xinzhan landslide. The R2 of the fitting formula is 0.971, which indicates that the formula can effectively serve the early warning and provide convenience for highway safety construction.

Keywords

• Colluvial landslide
• Sustained rainfall
• Failure mechanism
• Numerical simulations