Study on the mechanism of excess void gas pressure in slopes under strong earthquake conditions

Abstract

Abstract Under strong earthquake conditions, excess void gas pressure is generated in slopes with cavities (without water), which accelerates tension cracking at the edges of the cavities and thus promotes slope failure. In this paper, a generalised model of a slope with cavities is proposed to explore the development of natural slope cavities, and large-scale physical shaking table tests and corresponding PFC numerical simulation tests are performed to study the formation mechanism of excess void gas pressure at depth. The following findings are obtained: (1) Sudden vibration loads of a certain intensity or sudden changes in the volume of the cavity can lead to the generation of excess void gas pressure in the cavity; (2) The deformation and damage of slopes with cavities under strong earthquake conditions can be divided into three stages: a. rupture of the top of the slope and the edges of the cavities; b. excess void gas pressure in the cavities, promoting crack propagation; and c. crack penetration, leading to overall damage of the slope; (3) Tension cracks caused by excess void gas pressure change the structure of the slope body, weaken the shear strength of the structural surfaces in the rock mass, and reduce the stability of the slope body. The above results are highly important for studying the initiation mechanism of seismically induced landslides on slopes.