The Study Of Granite Residual Soil Landslide In Guangxi Influenced By Cutting Slope And Rainfall Based On Yulin District

For cutting slope and building up landslide disaster early warning and forecasting system, it is very important to analysis the influence of cutting slope and rainfall on the granite residual soil landslide in guangxi. Supported by the Land and Resources Department of Guangxi’s research project "Guangxi granite residual soil landslide disaster warning system development and application online ", which is presided in 2014. Data statistical analysis, laboratory test and numerical simulation are combinated to analysis the effect on slope stability under different cutting slope and rainfall conditions in the granite area of Yulin. The main research contents and results are as follows:1、The landslide data of Guangxi granite area from 2005 to 2013 were statistical analyzed. The results show that the rainy season was concentrated and human engineering activities are frequent in Guangxi granite area. Landslide damage occurred mainly in layer on eluvial area. The time of landslide occure conformed to the rainy season. Landslide is closely related to the cutting slope and the rainfall.2、The relationship of slope type and rainfall with Yulin granite landslides was statistical analyzed. Statistical results show that the Yulin granite landslides mainly occurred in the area of convex natural slope whose cutting toe is straight artificial slope. Incremental type torrential rain has good relativity with landslide and the landslide mainly relate to the rainfall of the day of landslide and two days before.3、The physical and mechanical properties of granite residual soil in Yulin was studied by laboratory tests. Penetration test results show that the permeability of granite residual soil in Yulin is good. The analysis results of Soil Water Characteristic Curve show that, the initial dry density’s effect on SWCC is higher than the initial moisture content’s. The lower initial dry density is, the faster dehydrated speed is and the weaker water-holding capacity is. Direct shear test results show that the shear strength of granite residual soil in Yulin is high, but the strength is lower significantly under the saturation. Along with the water content increases, cohesion increases first and then decreases, and internal friction angle decreases gradually.4、The effects of artificial cutting on the granite residual soil landslide in Yulin is simulated by Seep/W and Slope/W, Geo-studio software. The simulation results show that along with the increase of cutting slope degree and cutting slope height, the slope potential sliding surface moved to the superficial layer, and the stability coefficient of the slope reduce gradually. The slope stability reduced accordingly under the condition of rainfall. It’s suggested that the cutting slope gradient should be less than 55° and cutting slope height should be lower than 6m when the natural slope is less than 45° in the granite area of Yulin.5、The effects of different rainfall conditions on the granite residual soil landslide in Yulin was simulated based on the saturated-unsaturated seepage theory and strength theory of unsaturated soil. The simulation results show that the rainfall intensity, duration and rainfall patterns have significant influence on the slope stability. The incremental type rainfall is more likely to induce landslide. It’s suggested that the rainfall intensity’s thresholds should be 200mm/d,125mm/d and 65mm/d for natural slope of 35°,40° and 45° respectively in the granite area of Yulin when the cutting slope gradient is 55° and the cutting slope height is 6m.