Influence of heavy rainfall and different slope cutting conditions on stability changes in red clay slopes: a case study in South China

Heavy rainfall and engineering slope cutting are two key factors that trigger unstable red clay landslides with red clay soil as the sliding mass in the mountainous and hilly areas of South China. It is important to study the influence of engineering slope cuttings on changes in slope stability under heavy rainfall conditions. First, by summarising the main evolution and failure characteristics of landslides in Ganzhou City, Jiangxi Province, China, a general landslide physical model of red clay landslides with universal significance is constructed. Then, the rainfall characteristics of Ganzhou City are analyzed, and heavy rainfall occurring once in a period of 50 years is applied to the general landslide physical model. Concurrently, the influences of different engineering slope cutting distances and angles on the changes in slope stability are explored. Finally, saturated and unsaturated infiltration theory and nonlinear finite element analysis are used to calculate the stability and pore water pressure changes in the landslides under the above-described conditions of heavy rainfall and engineering slope cutting. The results show that: (1) When there is no rainfall, the stability coefficient of the red clay slope rapidly decreases with increasing distance and/or angle of slope cutting; for a certain slope cutting angle, the stability coefficients of the landslide show a convex upward decrease with increasing slope cutting distance; for a certain slope cutting distance, the stability coefficients show a linear decrease with a gradually increasing slope cutting angle. (2) Under 5 days of heavy rainfall reaching 210 mm, the engineering slope cutting forms have increasing influence on stability reduction in a red clay slope. For a certain slope cutting distance, as the slope cutting angle increases, the slope stability coefficient shows a slow decrease. For a certain slope cutting angle, a greater slope cutting distance means a faster decrease in the slope stability coefficient. (3) The pore water pressure along the potential sliding surface of the red clay slope under heavy rainfall gradually increases, and there is a good inverse correspondence between the changes in the pore water pressure and the stability coefficient.