A CASM-X constitutive model for unsaturated soils and its application to model wetting-induced slope collapse using SPH
Dinh-Tai Nguyen, Ha H. Bui, Yanjian Lian, Thang Nguyen, Giang D. Nguyen, Abdelmalek Bouazza
Abstract
Mesh-free methods, such as the Smooth Particle Hydrodynamics (SPH) method, have recently been successfully developed to model the entire wetting-induced slope collapse process, such as rainfall-induced landslides, from the onset to complete failure. However, the latest SPH developments still lack an advanced unsaturated constitutive model capable of capturing complex soil behaviour responses to wetting. This limitation reduces their ability to provide detailed insights into the failure processes and to correctly capture the complex behaviours of unsaturated soils. This paper addresses this research gap by incorporating an advanced unsaturated constitutive model for clay and sand (CASM-X) into a recently proposed fully coupled seepage flow-deformation SPH framework to simulate a field-scale wetting-induced slope collapse test. The CASM-X model is based on the unified critical state constitutive model for clay and sand (CASM) and incorporates a void-dependent water retention curve and a modified suction-dependent compression index law, enabling the accurate prediction of various unsaturated soil behaviours. The integration of the proposed CASM-X model in the fully coupled flow-deformation SPH framework enables the successful prediction of a field-scale wetting-induced slope collapse test, providing insights into slope failure mechanisms from initiation to post-failure responses.