Study On The Stability Of Loess Landslide In The Baota District Of Yan'an City

With the rapid development of economy in China and the implement of developing western region greatly, a lot of mountain cities in the west, like Yan'an, were forced to start to expanse to the mountain slopes. The Baota District of Yan'an City lies in the central of loess plateau and loess plateau is one of the most vulnerable ecological environment areas in China. Due to the special conditions of landform, fragile geological environment and aggravation of the human engineering economic activities, a large number of slopes instability is caused.On the basis of gathering relevant datum on regional geological environment of Baota district, the types of landslide and the factors influencing stability of the landslide were analyzed. Taking Wohushan landslide for example; study on the stability of loess landslide was made. Using geological analysis method, limit equilibrium method, the reliability analysis method and numerical simulation method, the stability of Wohushan landslide was made comprehensive demonstration. The main contents are as follows:(1) According to detailed investigation on Wohushan landslides, the basic characteristics of the landslide and its main influence factors and formation mechanism were revealed. The results show that loess with special structure provides the material basis for the formation of Wohushan landslide; topography and geomorphology, loess-bedrock provides boundary conditions and the inductive factors are the human activities and rainfall.(2) According to the tests and back calculation algorithms, shearing strength parameters of Wohushan landslide under the saturated state were determined reasonably. The stability of three profiles from this landslide was calculated by using the transmitting coefficient method. The results show that the stability of Wohushan landslide is poor under the saturated state, and Wohushan landslide may be easily collapsed in long-term function of negative factors such as rainfall.(3) Analysis to determine the reliability of stochastic factors of the Wohushan landslide are soil bulk density of sliding-zone soil (γ), internal cohesion (c) and internal friction angle (φ).On this basis, the stability factor was calculated by using probability estimates calculated moments method and there is larger possibility of instability of Wohushan landslide in saturated state.(4) Using the finite element software "Midas" /GTS to set up geological and the mechanical model, according to numerical simulations on Wohushan landslide in saturated condition and analyze the stress-displacement of Wohushan landslide soil, trailing edge deformation of the slope is greater and the completely transfixion sliding surface had been formed between the slip mass and slip bed. And the maximum shear strain zone extended to the edge of the landslide,The biggest shearing strain area to landslide after skirt expansion.