Study on landslide stability and prevention measures of Guang’an village landslide in Wuxi under different rainfall conditions

Slopes composed of overlying limestone and underlying thin weak shale are widely developed in Wuxi County, Northeast Chongqing. Such slopes are highly susceptible to sliding instability induced by rainfall with obvious delayed failure characteristics. Most existing studies focus on the control effect of total rainfall on slope stability, while systematic analyses of slope deformation and prevention measures under diverse rainfall temporal sequences are insufficient. Taking Zone III with severe deformation of the Guang’an Village landslide in Wuxi as the research object, this paper identifies the disaster-inducing differences of various rainfall patterns and optimizes targeted prevention and control measures. Based on multi-year measured rainfall statistical data, six typical rainfall temporal patterns including unimodal, front-peaked, rear-peaked, increasing, decreasing and uniform types are classified using K-means clustering algorithm. A two-dimensional slope model is established via GEO-Studio to carry out numerical simulations of seepage field and slope stability under different rainfall patterns. Numerical simulations are also performed for three treatment schemes, namely independent interception-drainage system, single anti-slide piles, and the combined scheme of interception-drainage plus anti-slide piles, to compare the reinforcement performance and working mechanism of each measure. The results show that: (1) The total rainfall infiltration volume is the dominant controlling factor for the instability of slopes with the structural combination of shale weak base and fractured limestone. The disaster-induced effects of the six rainfall patterns are significantly different. Among them, the increasing rainfall pattern exhibits the most prominent failure effect and can directly trigger landslide instability; the unimodal rainfall pattern weakens slope stability to a certain extent; the slope remains stable under the action of front-peaked, rear-peaked, decreasing and uniform rainfall patterns. (2) Under the condition of increasing rainfall, pore water pressure continuously accumulates along the potential sliding surface, forming a connected high pore water pressure zone at the landslide front. At the landslide rear, due to well-developed tensile fissures and favorable drainage conditions, the overall pore water pressure remains at a relatively low level. (3) The combined scheme of interception-drainage and anti-slide piles achieves the optimal landslide prevention and control effect, limiting the stability attenuation range within 0.32%, which is significantly superior to single engineering measures. Rainfall temporal patterns dominate slope stability by regulating the accumulation process of pore water pressure. The integrated prevention and control mode combining source interception for seepage control and deep rigid anti-slide structures can markedly improve slope stability under sustained heavy rainfall, which can provide references for early warning and engineering treatment of similar slope disasters.