Reliability Analysis of Anchored Slopes under Rainfall Infiltration Considering Multi-Parameter Influences

Abstract

Rainfall infiltration poses a critical threat to anchored slope stability, challenging traditional deterministic methods for long-term safety assessment. This study develops an integrated reliability analysis framework coupling unsaturated seepage flow, a segmented slip surface method, and Monte Carlo simulation. Applied to a typical anchored slope in the Three Gorges Reservoir Area, the framework fully accounts for the shear strength differences in multi-layer rock and soil masses. The calculated safety factor agrees with numerical simulations to within 0.4%, validating the proposed approach. Results reveal a hierarchical sensitivity of soil parameters: the influence of cohesion variability far exceeds that of the internal friction angle, with the reliability index β decreasing by approximately 79% when its COV increases from 0.1 to 0.5; when their coupled variability reaches medium-high levels, the reliability index β drops by over 60%. Rainfall parameters exhibit stochastic effects, where increased intensity and duration induce nonlinear deterioration of slope reliability. Critical geometric thresholds are identified - a slope gradient exceeding 45° or a height over 40 m causes a sharp surge in failure probability. Furthermore, when the slice width in limit equilibrium analysis exceeds 2m, the local failure risk is underestimated due to stress homogenization. Among support measures, increasing anchor cable tension markedly improves β, although economic trade-offs must be considered. The proposed framework provides a robust tool for evaluating the probabilistic stability of anchored slopes subjected to transient rainfall.