Unveiling the Deformation Mechanism of Xiangping Mountain Expressway Landslide through Multi-Angle Deformation Monitoring

This study investigates the deformation patterns and mechanisms of the Xiangpingshan mega-landslide along the Wenshan-Malipo Expressway, with the objective of accurately identifying the sliding surface location to support effective mitigation and disaster reduction strategies for high-speed landslides. Through comprehensive field geological surveys and long-term deformation monitoring, we systematically analyzed macroscopic deformation features, surface displacement data, deep borehole displacement measurements, and deformation characteristics of anti-slide piles and retaining walls to elucidate the dynamics of the landslide. The results indicate that the Xiangpingshan mega-landslide is in an unstable to marginally stable condition and currently undergoing a creep-sliding phase as a mid-level landslide. The primary sliding surface is predominantly composed of strongly weathered carbonaceous weak shale layers, with localized evidence of dual sliding zones. Tectonic compression has induced bending deformation in steeply dipping shale strata toward free faces under the combined influence of tectonic stress and gravitational loading, resulting in the upper rock masses tilting gently inward while the lower strata retain their original steep dip. Weak and fragmented structural planes formed through tectonic weathering serve as potential sliding surfaces. The main driver of ongoing deformation is persistent groundwater activity. During prolonged wet-season rainfall, enhanced coupling between groundwater and weak rock layers leads to strata softening, increased pore water pressure, and elevated gravitational driving forces. This progressive process promotes the development of tensile cracks, intensifies water-rock interactions, and accelerates the formation and evolution of the sliding surface.