Study On Stability Of Soil-rock Composite Slope Considering Rainfall And Phreatic Water Effect

China is one of seriously geological disasters countries in the world. In2010China’s actual geological disaster ranking top three are landslide, collapse and mudslides. How to reduce the harm to society from geological disasters becomes important issue for governments. Therefore the research of the slope stability considering rainfall and phreatic water has important academic value and engineering significance.Adopting the improved direct shear test and modified permeability test, the paper studies the soil-rock composite slope’s the strength properties and infiltration characteristics. Based on adopting landslide model testing indoor considering rainfall characteristics and geology characteristic, the paper studies the soil-rock composite slope’s failure mechanism and failure morphology, and the changes of the water content and other parameters. The main conclusions and findings obtained are as follows.(1) Based on the improved penetration test, coarse grained soil permeability test was carried out. The results show that coarse grained soil infiltration properties consistent with Darcy’s Law when the hydraulic gradient is low, and coefficient of permeability is less than normal when high hydraulic gradient. Permeability coefficient and stone content is an exponential relationship. When stone content increase or permeability coefficient lessens or non uniformity coefficient increases, the permeability coefficient increases.(2) Through improved direct shear test indoor, the study on coarse grained soil direct shear test shows that strength failure criterion conforms to the coarse grained soil shear strength theory. Relationship of stress and strain is strain-hardening effect, and this conclusion and the phenomenon of shear failure plane non smooth surface is consistent. Friction angle and cohesive strength increase when stone content increases or water content reduces. Water content changes mainly cause cohesion changes, however stone content changes lead the cohesion and friction angle change large. When vertical stress is low, soil initial shear modulus decreased at first and then increases with increasing content of stone, while at higher vertical stress instead. Overall, the change of the initial shear modulus from the stone content does not change significantly.(3) Based on homemade rainfall equipment, the indoor model experiment studies the slope damage mechanism and morphology under the rainfall effect. The result of earth pressure, water content and slope body settlement’s monitoring shows that the rate of the volumetric water content descent decreases and the gap of upper and lower layer’s water content declines after the repeated rainfall. The reason for this phenomenon is slope body structure’s changes. Soil pressure and ground settlement’s changes are not obvious in the whole process. Slope failure pattern is related to rainfall characteristics and grain composition. Phreatic water plays limited role on the contact surface impact, even to lose effectiveness.(4) The water infiltration simulation use two phase flow module in FLAC find that simulation data has a good agreement with the model test results contrast analysis. Water-phase and gas-phase motion characteristics have a close relationship to piping phenomena in model experiment. Numerical simulation about having phreatic water or not discovers that there are a certain relationship between phreatic water and the position of slope’s destruction.