Abstract: Mudstone, as the underlying bedrock layer of a slope, is often affected by changes in boundary conditions caused by water environment and excavation unloading, which often leads to instability and failure of the upper rock mass. An existing municipal highway slope treatment project in Guangxi is presented in this paper as the case history. Evaluation methods such as engineering geological investigation, laboratory rock testing, and slope deformation monitoring are performed to comprehensively analyze the failure mechanism of the highway slope in a hydraulic coupling environment. Research has shown that the mudstone rock layer on the slope undergoes significant creep deformation due to the saturation caused by waterlogging, as well as the release of boundary constraints and changes in upper loads. The accumulation of deformation reaches the failure threshold, leading to rock subsidence and ultimately causing tensile or shear failure of the upper rock layer. Based on this failure mechanism, the effective treatment was carried out on the slope in a controlled manner, thereby validating the mechanism analysis in this study, and having analogical and reference significance for similar projects.

Key words: Mudstone, Hydraulic Coupling Effect, Rheology