Structural characterization and attempted displacement interpretation of the Baishuihe landslide using integrated geophysical methods

Abstract

The Baishuihe landslide, a typical large-scale deposit landslide in the Three Gorges Reservoir area, has attracted considerable societal and scholarly attention. Since 2003, 11 displacement monitoring points have been established on the landslide mass for monitoring displacement data. Displacement monitoring data from 14 years have been widely applied in landslide displacement prediction research. However, there is a lack of research involving interpretations of displacement data. To interpret landslide displacement from geological and hydrodynamic perspectives, we applied integrated geophysical methods, including electrical resistivity tomography (ERT), self-potential (SP), and surface nuclear magnetic resonance (SNMR), to model the landslide structure and investigate groundwater activity. The results indicate that the landslide deposit is predominantly located at the foot of the landslide, with a total volume of approximately 7.7 × 106 cubic meters. The thickness gradually increases in the eastern direction of the landslide along the sliding direction, while in the western direction, it initially increases and then decreases. The SNMR results reveal that groundwater is primarily situated in the gravel soil layer, demonstrating a volumetric water content of approximately 2.8% per unit volume. The SP results suggest that below an elevation of 190 m, the groundwater flow field is turbulent and irregular. Above an elevation of 190 m, the general direction of the groundwater flow field tends to align roughly with the sliding direction. Through the integration of GPS displacement monitoring data and comprehensive geophysical analysis, we discerned that the thickness of the deposit layer, the morphology of the sliding surface, and the interaction with groundwater recharge collectively exert significant influences on the displacement of the Baishuihe landslide. Generally, the thickness of the deposit layer and the morphology of the sliding surface determine whether the landslide will exhibit significant displacement. At a more detailed level, the weight of the accumulated mass and the influence of groundwater play a significant role in determining the displacement velocity.