Effect of Particle Shape on the Deformation and Stress Reduction of a Gravel Soil Due to Wetting

Abstract

In this paper, the effect of particle shape is investigated on the stress reduction and collapse deformation of gravelly soil using medium-scale direct shear test apparatus under different relative densities, normal stress, and shear stress levels. The Micro-Deval test was used to produce sub-angular particles from angular particles with continuous smoothening of the corners of the particles. Two series of soil specimens were obtained with the same rock type, particle size distribution, and relative density but different particle shapes. In addition to traditional direct shear tests on dry and wet specimens, a specific test procedure was applied to explore the stress reduction and collapse of soil specimens due to wetting. For instance, dry soil specimens under several normal pressure were subjected to shear loading while inundated at several levels of shear stresses. The results showed that the stress reduction and settlement due to wetting increased with vertical and shear stress level in both types of particle shapes, with higher values in angular particle shapes. The wetting of the samples had more impact on the particle breakage in angular gravel than sub-angular gravel, which increased linearly with the normal stress.