Probabilistic analysis of progressive slope retreats due to weathering: An improved discretized-UBLA approach

Abstract

Slope retreat phenomena have been a persistent area of interest for researchers; however, the majority of these studies have been conducted within a deterministic framework, thereby overlooking the numerous geotechnical uncertainties inherent in these scenarios. This study addresses this gap by considering the initial slope strength and its degradation rate as random variables, thereby enabling a probabilistic analysis of the progressive sliding behavior of a slope subjected to weathering. An upper-bound limit analysis (UBLA)-based discretized mechanism was established to serve as the deterministic model. This mechanism employs a ’point-to-point’ technique for generating the discretized sliding surface, effectively circumventing the limitations and complexity associated with the classic log-spiral mechanism. When integrated with time-varying slope strength, this model is capable of predicting the occurrence of each sliding event with remarkable accuracy and efficiency. To assess the likelihood of specific sliding events occurring at any given time, a reliability analysis was conducted using Monte Carlo simulation. The framework proposed in this study was validated through two case studies: one involving a homogeneous slope and the other a two-layered slope. These case studies produced a variety of reliability results of great value, including the time-varying failure probability (P_f) for each slide, the distance of slope retreat, and the probabilistic collapse within the slope. Additionally, this study also conducted a system reliability analysis. It is demonstrated that the variability in initial strength and degradation rate exerts contrasting effects on the time-varying slope strength. The variability in initial strength constricts the strength distribution, while the variability in degradation rate tends to expand it. Homogeneous and heterogeneous slopes exhibit distinct characteristics of slip surface degradation. These results provide novel insights into how the probabilistic characteristics of initial strength and degradation rate influence progressive failure. The proposed methodology provides a powerful tool for conducting probabilistic analysis of slope retreat resulting from weathering, and it has significant implications for regions that are prone to landslides.