Failure mechanism of a loess-red silty clay interface landslide on the Heifangtai platform, China

Abstract

Loess-red silty clay interface landslides are one of the most widely distributed types of loess landslide disasters in China. In this study, field investigations, numerical simulation, model tests, and microscopic tests were conducted to reveal the failure mechanism of the loess-red silty clay interface landslide that occurred on the Heifangtai Platform on 1 April 2023. The findings revealed that the landslide, which was characterised by high speed and long distance, exhibited remarkable features. It lasted 39 s, during which the maximum sliding velocity reached 14.2 m/s. The maximum thickness of the deposits resulting from the landslide was 6.94 m, and the sliding distance exceeded 250 m. A large number of cracks were distributed around the edge slope of the landslide; these served as primary pathways for infiltration. Furthermore, the difference in permeability between the loess and red silty clay led to the accumulation of water at the bottom of the loess. This increased the water content of the loess and decreased the soil strength, thereby initiating the landslide. During the seepage process, water infiltration carries many fine particles in loess, accumulating at the interface between the loess and red silty clay, causing blockages. This accelerates the gathering of water flow at the interface, contributing to decreased soil strength. In additon, the pores in the loess undergo significant changes, with large pores in the soil decreasing and small pores increasing, forming a flocculent structure. These findings provide scientific evidence for the failure mechanism of loess interface landslides.