Soil Slope Instability Mechanism and Treatment Measures under Rainfall—A Case Study of a Slope in Yunda Road

Abstract

The unique geological conditions in Yunnan make it likely for landslides to occur there. For the purpose of exploring the soil slope instability mechanism, this paper takes a slope in Yunda Road, Chenggong, Kunming, as case study and establishes a slope model utilizing FLAC 3D coupled with Geo-studio software. The displacement, strain and deformation rate of the slope under the condition of rainfall are simulated, and the influence of rainfall and rainfall duration on rainfall infiltration is analyzed. The results indicated the following: (1) The effective stress on and shear strength of slope soil at the foot of the slope gradually decreased under rainfall, resulting in the loosening of the slope soil and slip at the foot of the slope. This affected the stability of the upper slope which, in turn, reduced the stability of the whole slope; (2) When the duration of rainfall reached 72 h, the slope stability coefficient Fs = 0.88, indicating a failure state. The increments of principal stress and shear stress at the foot of the slope were the largest, and the strain speed was the fastest, with the maximum values of principal stress and shear stress reaching 0.412 and 0.579, respectively; (3) The maximum total displacement was 2.177 m at the foot of the slope, the maximum vertical Z-axis displacement was 1.673 m in the negative direction of the Z-axis, and the soil at the foot of the slope was 0.6 m in the positive direction of the Z-axis. Our simulation results were consistent with the actual failure of the slope. After analyzing the slope mechanism and adopting targeted treatment measures, the slope was subjected to four rainfall cycles without any sign of landslips, indicating that the effect of our interventions was favorable.