Analysis Of Soil Slope Stability Under The Condition Changes Of Unsaturated-Saturated State

With economic developing, more and more attention draw to the issue of unsaturated soil, the security question of slope in unsaturated is an urgent problem to be solved. Instability of unsaturated soil slope will not only caused huge losses to property as well as causing serious harm to human safety. Rainfall and other reasons will cause the change of water content of soil, and lead the shear strength of slope to changes. The study of influence on slope stability that changes from unsaturated to saturated has important engineering significance.For the problems of unsaturated soil slope stability analysis, moisture content, cohesion, matrix suction and internal friction angle are important physical and mechanical parameters that are interrelated. Wherein matric suction is the root reason that cause the difference between internal unsaturated soil with the saturated soil, when the water content changes. The matrix suction of unsaturated soil changes accordingly, and the distribution of matrix suction in different depth changes also; As a composition of shear strength of the soil under unsaturated, the change of matrix suction directly affect the shear strength of soil, determine the stability of soil slope.Based on the soil skeleton stress state, the unified shear strength formula of saturated and unsaturated soil is applicable, combining the matrix suction with SWCC, and dealing with shear strength formula of unsaturated soil, the equivalent cohesive force of the soil is obtained. Finally, obtained a parameter that can reflect association between the change of soil state from unsaturated to saturated and shear strength—equivalent cohesive force. According to the soil stated changes from unsaturated to saturated, the distribution moisture content and matrix suction is different, the equivalent cohesive force of slope is assigned by using the computer program. By calculating the initial balance, fluid balance, the safety coefficient and redistributing the equivalent cohesive force, the slope stability under unsaturated-saturated soil is analyzed.According to the numerical simulation of slope under different conditions of infiltration depth, analyzed distribution of pore-water pressure and matrix suction in different soil, shear strain increment cloud and safety coefficient. Research the change rule of soil slope stability while the soil state changes from unsaturated state to saturated state because of infiltration. Analysis the influence on slope safety due to the change of the equivalent cohesive force and the changes of the slope slip surface in the process of slope soil state changed. Based on the results of numerical calculation, obtained the changing rule of the soil slope stability under the condition of unsaturated-saturated state changed. and the internal relations among water content, the matrix suction, equivalent cohesive force and slope stability, furtherly, obtained the change law of slope safety factor in the transition process of soil from slope unsaturated state to saturated state. The above research can provide guidance and technical support for prevention of slope instability disasters and optimization the design and construction scheme of engineering slop.