Geophysical Observation of Typical Landslides in Three Gorges Reservoir Area and Its Significance: A Case Study of Sifangbei Landslide in Wanzhou District

Landslide is one of the most serious geological disasters. Finding out the morphological characteristics of landslide and the formation mechanism of landslide is of great significance to landslide stability analysis, risk management of landslide hazards and government decision-making. Previous studies on landslide morphology and its formation mechanism are seldom combined with geophysical approach. The engineering geological profile drawing is limited to the acquisition of point-level information. The combination of geophysical measurement methods is conducive to obtaining more abundant landslide geological information from two-three dimension, and to quantifying the buried depth of sliding surface and perspective sliding bed morphology more accurately. In view of this, we take the hazardous Wanzhou area in the Three Gorges reservoir area as the research object, and apply high density grid resistivity method to measure resistivity values of different depth strata in the study area, to generate twodimensional resistivity profiles for the first time so that we can further construct three-dimensional shape of sliding bed. At the same time, the important factors affecting the landslide, such as the stratum structure, the depth of the slip surface and the shape of the slip bed, are comprehensively analyzed by integration of the electrical features of the section with the borehole data and geological survey data. The results show that the high-density grid resistivity method can accurately acquire the electrical structure characteristics of the stratum and construct a three-dimensional shape of the landslide body. The measured profile shows that the Sifangbei landslide belongs to an ancient landslide, and there exists the phenomenon of drawing crack trough. By calibrating the buried depth of the slip surface obtained from the measured profile and the three-dimensional slip bed configuration, the internal structure and material composition of the landslide body can be "perspective", which provides a basis for the analysis of the formation mechanism of the landslide, as well as theoretical guidance and technical reference for the evaluation and prediction of landslide stability in the other similar regional geological surveys. The theoretical method and technical route of revealing the threedimensional morphological characteristics of typical landslides in the Three Gorges Reservoir area by high-density electrical method are successfully introduced into the analysis of landslide formation mechanism, which can provide new ideas and approach for the study of landslide formation mechanism and theory, and can be widely used in many areas.