Analysis Of Stability Wuai Landslide Under Different Rainfall Conditions

Wuai landslide is located in Wuai town, Nandan County, Guangxi province. There is Hilly slope transition zone between Yunnan-Guizhou Plateau and Northwest Guangxi, and Hilly topography is widely distributed, and the slope surface is covered with eluvial soil. Northwest of Guangxi is landslide-prone areas, it occurred mainly in continuous rain, heavy rain periods. There is less related research in Northwest of Guangxi. So the research of Wuai landslide can exclude its security threat to the people, and provide reference of stability analysis for the local district similar landslide.This thesis use Wuai landslide as the object of study, through field reconnaissance and drilling, we have identified the boundaries, shape and size characteristics, structural characteristics and deformation characteristics of landslide. Evolution and deformation mechanism of deformation and failure mode of landslide has been analyzed. Fiel test and soil test were used in analysis of landslide. By using the limit equilibrium method and the finite difference method, the stability analysis and the analysis of the stress and strain of the landslide under rainfall conditions are carried out. Main conclusion and cognition as follows:(1) Site survey show: Wuai landslide located in the low mountain valley topography, steep slope, the presence of two obvious slumps, and the trailing edge of the landslide obvious tension cracks.(2) By drilling, identified landslide formation and composition of matter. In situ loop test had a sliding measuring the permeability of the soil, which belongs to moderate permeability. The underlying bedrock is weak permeable sandy mudstone, which plays the role of a relatively impermeable, which is conducive to the enrichment of groundwater in the landslide body, which is detrimental to the stability of the landslide.(3) For local climatic conditions, taking into account different rainfall conditions, groundwater and negative pore water pressure of Wuai landslide were analyzed:(1) The greater the rainfall intensity, the faster the groundwater table rises in the same time, the less the negative pore water pressure decreases,the greater the degree of curvature of the negative pore water pressure;(2) Under the same rainfall intensity, with the rainfall duration increasing, the negative pore water pressure of the landslide is gradually smaller, and the groundwater table is gradually rising;(3) Under the same total rainfall, Small rain, long duration rainfall is more fully penetrated into the landslide body; And strong rain, short duration rainfall, make the surface of slope become transient saturated zone rainfall is not sufficient infiltration slope;(4) After the rain stopped, the infiltration of rainwater and surface water of the landslide slope is still to transport the body, within a certain time, the groundwater table will slow uplift, negative pore water pressure of landslide body been gradually reduced, with the excretion of groundwater, the groundwater table of landslide body will slowly return to the initial state.(4) Based on unsaturated soil mechanics theory, the landslide stability under different rainfall conditions was analyzed:(1) Within 48 hours, the greater the rainfall intensity, the greater the decline landslide stability coefficient, the faster the rate of decline;(2) As rainfall duration prolonged stability of landslide coefficient decreases, up to a certain time, Landslide in less stable state;(3) Under the same total rainfall, the small intensity and the duration of rainfall is more unfavorable to the stability of landslide;(4) During rainfall and rain stopped after one day, landslide stability coefficient showed a decreasing trend. One day after the rain stopped, landslide is in the unstable state. The rain stopped after 3 days, Wuai landslide stability coefficient of slow recovery.(5) Considered natural state and rainfall conditions, deformation and stability of numerical simulation study of Wuai landslide, shows that under the natural state, Wuai landslide in stable state, Under the conditions of rainfall occurs slowly sliding, pulling the trailing edge deformation, and squeeze the leading edge, which is in good agreement with the field investigation.