An experimental investigation on the arching effect of cohesive materials in trapdoor tests

Abstract

This study conducted a series of trapdoor tests on low cohesion material at different buried depths, the failure patterns and the variations of soil pressure were investigated, and the development of the arching effect in trapdoor tests was analyzed. The results showed two failure models for soils: when the buried depth ratio was smaller than 2, two rupture surfaces developed obliquely upward from two sides of the trapdoor and merged into one triangular rupture surface; when the ratio was greater than 2, two rupture surfaces developed vertically upward and merged into one tower-shaped rupture surface. As the burial depth increased, the inner boundaries of the soil arch moved upward, and the widths of the inner and outer boundaries expanded. Furthermore, the maximum arching trajectory, obtained by connecting the maximum tangential stress points, was closer to the inner boundary and shifted towards the outer boundary when the trapdoor was lowered. Based on the experimental results, a new composite arch model was proposed to calculate the soil pressure above a trapdoor, it can better describe the development of soil pressure in a trapdoor test.