Geological and hydrological study of a deep-seated toppling using time-lapse electrical resistivity tomography

The toppling stability is influenced by hydrogeology. However, the correlation between toppling and groundwater is complex and remains poorly be understood compared to the relationship between slides and groundwater. In this study, a geo-electrical investigation of the deep-seated Shidaguan toppling in southwestern China was conducted between April 2019 and May 2020. The material types of the toppling were determined and a morphological structural model was established based on drilling and apparent resistivity data. Time-lapse electrical resistivity tomography (ERT) was used to monitor the internal water flow processes within a large-scale deep-seated toppling. The processes of surface water infiltration and internal migration were captured, and a hydrological-mechanical coupling model was established. The model reveals that rainfall infiltrates the toppling body through priority flow paths, such as tension cracks, flexural fracture zones, and sliding surfaces, which leads to a reduction in shear strength along the basal surface. Furthermore, critical areas for monitoring and early warning of toppling were identified based on the evolution of deformation and water migration.