Dynamic stability analysis of unsaturated slopes triggered by high gas pressure: Critical pressure threshold and progressive failure evolution

Landslides triggered by high gas pressure represent a distinct geotechnical hazard, especially in scenarios without significant rainfall. Recent studies have revealed that high-pressure gas accumulation within slopes can be a dominant trigger for large-scale failures although the processes behind this remain not well understood. This study examines how unsaturated soil slopes fail under high gas pressure using a combination of laboratory experiments and numerical simulations. A key discovery is that gas pressure changes slope stability by redistributing pore fluids and altering effective stress, with distinct depth-dependent effects. Moreover, a novel concept of critical stable gas pressure ( P_ac ) is proposed as a practical threshold for stability assessment, which is depth-dependent, with extreme values at shallow and intermediate depths, reflecting the interplay between gas diffusion and overburden resistance. This study advances the mechanistic understanding of gas-induced slope instability and offers actionable benchmarks for managing related risks in engineering projects including waste landfill management and shale gas operations.