Development Characteristics and Mechanism of Slope Geological Hazards Controlled by Two Typical Strata in Eastern Dongting Basin

The Dongting Lake area is an important ecologically sensitive area in the Yangtze River Economic Zone. It is very important to identify the development characteristics and disaster mechanism of landslide and collapse geological disasters which are easily affected by frequent extreme rainfall in the region. In the eastern margin of Dongting Lake, the main types, scale and distribution characteristics of geological hazards have been identified through detailed field investigation. The geological hazards are collapse and landslide, small and micro in scale, mostly developed in high and steep slopes formed by artificial cutting. Through the analysis of geology, topography and development characteristics of the most widely developed collapse disasters, it is found that the disasters are mainly controlled by geological strata, namely the Dongtinghu Formation and Miluo Formation, and the triggering factors are mainly engineering excavation and precipitation. However there are different disaster mechanisms in the collapses developed in the two formations. The lithology of Dongtinghu Formation is dominated by reticulated red clay, and vertical joints are developed. After repeated drying and wetting of precipitation, the joints become fractures, and the fractures continue to expand, resulting in toppling collapse on the slope. But the lithology of Miluo Formation is composed of gravel, sand, silt and clay, and the gravel layer is an aquifer. Under the action of precipitation, the fine components of silt and clay in the slope aquifer are constantly taken away, resulting in washing collapse. On the basis of clarifying the mechanism of the disaster, the prevention and control measures of this kind of geological disaster in this area are proposed.