Decoupling Analysis Method for Rain-Induced Failure of Shallow Expansive Soil Slopes Considering Swelling and Strength Softening

Abstract

Rain-induced shallow failures in expansive soils often occur on gentle slopes with slope ratios of 1:2–1:6, resulting in highly complex stability issuesThis study established an equivalent theoretical model for the swelling behavior of expansive soils based on the similarity theory of temperature and humidity fields. A numerical simulation approach was developed using a model with consistent nodes and the conversion of seepage results and swelling loads, allowing for the decoupling analysis of slope seepage–deformation–stress considering swelling and strength softening. Numerical analyses were conducted on a specific slope profile in a case study, analyzing the distribution and evolution of the slope seepage, deformation, and shear stress. The findings revealed that changes in moisture content at the slope toe have the most significant impact, with infiltration depth and strength attenuation being the largest. Horizontal and vertical deformations were also highly influenced by the reduction of shear strength. The uneven water absorption and swelling of expansive soil slopes resulted in shear stress concentration areas on the slope, leading to local failures near the slope toe and eventual overall instability of the slope. This study provides valuable insights into the complex behavior of shallow failures in expansive soil slopes.