Modelling of unsaturated slope failures induced by water pipe leakage using smoothed particle hydrodynamics

Underground water pipe leakage can critically undermine slope stability. Water leakage rapidly reduces matric suction in unsaturated soils and weakens shear strength. In severe cases, it can trigger slope failure without visible surface warning signs. Comprehensive studies on pipe leakage-induced slope failures remain limited, and existing methods often fail to capture the post-failure process. This study employs the smoothed particle hydrodynamics (SPH) method within a fully coupled hydro-mechanical framework to investigate unsaturated soil slope failure mechanisms induced by pipe leakage. An advanced unsaturated constitutive model based on the critical state clay and sand model (CASM) is adopted to capture the effects of matric suction and soil density on shear strength. The SPH model is applied to a field case study involving unsaturated sand and clay, successfully reproducing the slope failure initiation and post-failure process, capturing the evolution of pore water pressure, effective stress, and saturation. A systematic parametric study highlights the critical roles of key factors such as leakage pressure, drainage capacity, and soil compaction in controlling slope stability. Higher leakage pressures accelerate localised slope failure and alter the overall failure characteristics, whereas improved drainage and enhanced soil compaction significantly increase slope stability and mitigate the onset of failure.