Formation And Evolution Mechanism Of The Loess-Red Beds Interface Landslide

It has been greatly concerned to study the formation and evolution mechanism of landslide. Landslide is one of the most serious geological disasters because the geological environment is fragile In the loess plateau region. Besides the formation and evolution mechanism of landslide is theoretical foundation in order to predict, forecast, prevent and control effectively the landslide disaster. It is also very important to evaluate landslide stability or predict sliding speed or sliding distance. However, There is less study on taxonomic research of the formation and evolution mechanism of the loess-red beds interface landslide in loess landslide research area.Relying on the point of the earth system science and various factors coupling, taking the example of the loess-red beds interface landslide in Changjiahe town in Tongwei county in Gansu provice, taking the way that a combination of field survey and laboratory test, the thesis studies the distribution, classification and forming conditions of the loess landslide in Changjiahe town, and then researehes the formation mechanism and evolution process of three types of the loess-red beds interface landslide. The work is not only important for the risk evaluation and prevention and control planning of geological hazards in Changjiahe town, but it will further improve the research of the formation and evolution mechanism of loess landslide as well.The main results of research as follows.(1) The loess landslide can be divided into four basic types in Changjiahe town. They are homogeneous loess landslide, loess-red beds interface landslide, loess-red beds bedding landslide or loess-red beds cutting layer landslide. Furthermore, the loess-red beds interface landslide can be divided into linear type, fold line type or wavy type landslide.(2) The study on the formation mechanism of the loess-red beds interface landslide mainly consider the effect of river erosion, earthquakes and rainfall. The free face formed by river erosion leads to slope stress conducive to the sliding direction. The earthquake leads to the disintegration of the loess structure and the formation of new cracks and expansion and deepening of existed cracks in the loess. The rainfall infiltrates into the top surface of the red beds through the loess cracks, joints or the sinkholes, which softens the rock and soil, reduces their shear strength and finally promotes the formation of the slip surface.(3) Linear type landslide formed under the action of creep and fracturing is a tractive landslide. Fold line type formed under the action of creep and fracturing is a tractive landslide. Wavy type landslide is divided into two grades. The first half formed under the action of creep and fracturing is a tractive landslide. The second half formed under the action of creep-sliding and fracturing and snipping is a tractive and impellent landslide.