Study Of Characteristics Of Slip Surface And Slope Stability For Accumulational Landslide In Three Gorges Reservoir Area

The landslides in our country have characteristics that large scale, complex mechanism, catastrophic losses, difficulty prevention, and the system of research and treatment started late. Because of the complexity and diversity of the prediction, it is difficult to forecast and preventation. The characteristics of the landslide should be further deepened, and the landslide zone of slope should be broaden, and the strength parameters of slip zone should be analyzed for the study. The formation of sliding soil, material composition, micro-structure are diversity, so we can reveal the macroscopic and microscopic characteristics of sliding soil in order to analyze their stability, and thus provide a theoretical basis for landslide prevention. The contents and results were as following:(1) Research of Landslide Characteristics of sliding surface geometry. Taking the space geometry from the sliding surface characteristics, features sliding surface scratches for example, analysis the landslide sliding surface geometry features of accumulational landslide in Three Gorges Reservoir Area (circular arc type, linear type, ladder type and combination type).And taking the North Garden landslide as an example, reveals that the landslide surface scratches was mirror-like surface scratches, linear scratches, uneven shape and the combination of form, the different forms of scratches reflecting the different stages of the landslide sliding.(2) Research of Landslide sliding surface mineral composition and micro-structure. Using scanning electron microscopy and X-ray diffraction analysis the soil micro-structure and mineral composition of North Garden landslide zone,and come to conclusion that the mechanical properties of various external loads have unearthed the under performance of its micro-structure is essentially a changes of the macroscopic reflection.And it also reveals that the sliding soil mineral compositioned mainly by large number of montmorillonite, they were softening and water swelling, their shear strength is low,and structure is inattentive, while lots of the micro-pores and micro-fissures development, so they belong to the slide rock group.(3) Research of The stability analysis of different sliding surface morphology. Use transfer coefficient method and Geostudio slope/w module modeling software to calculate the various forms of sliding surface stability factor, then analyzed,and concluded as follows:In circular arc type sliding surface, the radius of the circular arc were different forms, the stability coefficient decreases and then increases as the radius of the circular arc reduce.In linear type sliding surface, the stability coefficient under different forms of the leading edge angle is gradually increasing.In ladder type sliding surface,the stability coefficient under different steps form increasing gradually as the number of steps gradually increase. In combined type sliding surface, the stability coefficient contain one step and different radius of curvature gradually increases as the decrease radius of the circular arc;the stability coefficient contain two steps and different radius of curvature decreases and then increases as decrease radius of the circular arc.(4) Research of the landslide sliding surface morphology and stability of North Garden landslide.Tests cohesion force and internal friction angle under different moisture contents, use the transfer coefficient method and Geostudio slope/w module software calculate and analysis its stability. Moisture content have a great impact on the stability of North Garden landslide. The landslide’s stability increase and reach the peak value when it has a lower water content,The landslide’s stability decrease sharply when it has a high water content,which limit moisture content is 18.68%. Different types of sliding surface also affect the stability of the landslide. The linear type sliding surface is most volatile, then circular arc type, the stability of ladder type sliding surface’ slightly higher than circular arc type,and the combination type sliding surface is most stable.