KEY INFLUENCING FACTORS BASED DISTRIBUTION REGULARITY AND DEFORMATION AND FAILURE RESPONSE OF COLLUVIAL LANDSLIDES IN THREE GORGES RESERVOIR AREA

Geological disasters occur frequently in the Three Gorges Reservoir Area(TGRA). Colluvial landslide is the most common type of landslides with the largest total amount. Information of 145 colluvial landslides on the reservoir bank in TGRA are systematically collected. This paper selects landslide topography, geological lithology, and slope structure as the controlling factors, and precipitation and reservoir water fluctuation as the main inducing factors. It characterizes the distribution and deformation and failure response of the landslides under these factors. The mechanisms of landsliding are analyzed. The main conclusions are as follows. (1)Under the dominance of regional tectonics and bedrock stratigraphic lithology, the occurrence frequency and scale of landslides have obvious spatial differences along Yangtze river. (2)Lithology combinations of sandstone and mudstone intercalated with shale and coal seams(SC), and marl and shale intercalated with mudstone(MSM) are the most harmful to landslide stability. The existences of soft rock,"soft-hard" interbedded dual structure, and water-rock(soil) interaction are the main influencing factors that dominate the development of landslides. (3)Most of the landslides are wade into river, locate on the slopes of 10°~30°, and have the elevation of the front edge mainly concentrated at 100~175 m above sea level. These slopes are seriously affected by the fluctuation of reservoir water. The river sides and slope structures have no obvious effect on the colluvial landslide development. (4)The landslides are mainly caused by the joint influences of rainfall and reservoir water drew-down. The joint influences can result in the slip-cracking deformation at the front of sliding body, which triggers retrogressive landslides. There are obvious differences in the pattern and extent of the impact of rainfall and reservoir water fluctuations on landslides. The research results are expected to provide scientific guidance for the overall targeted landslide prevention and control in the TGRA.