Mechanical behaviour and shear localisation of gravel soils: experimental study and numerical modelling

Gravel soils are ubiquitous in nature, yet they pose significant challenges for laboratory testing and numerical modelling. Unlike pure soils, gravel soils comprise both fine-grained particles and gravel fragments, resulting in complicated behaviours affected by both the soil matrix and gravel. In this study, triaxial compression tests are conducted to investigate the mechanical behaviours of gravel soil with varying gravel shapes and contents. The failure mechanisms of gravel samples are further analysed through numerical simulation of plane strain tests using a hypoplastic model, considering various gravel contents, shapes, stress levels and soil densities. Both experimental and numerical results indicate that the presence of gravel enhances soil strength, as evidenced by increased stiffness and resistance. The angularity characteristics of gravel alter the failure patterns and propagation of the localised strains in the soil matrix. In addition, the enhancing effects caused by the initial dense state and high-stress condition contribute to the delayed progression of shear band formation.