The Engineering Characteristics Of Granite Residual Soil And Slope Stability Analysis Under The Wetting-drying Cycles

Granite residual soil is widely distributed in southeast China,especially in Fujian region.As the granite residual soil slope is often directly exposed to the natural environment,slope soil experience wetting and drying for a long time influenced by seasonal climate factors,which makes the soil state in the process of alternating change repeatedly.The changes of soil affect its intensity which affects the stability of the slope furthermore.Therefore,in this paper,the typical granite residual soil in Fujian Province is taken as the research object.The rule of strength attenuation and permeability of granite remnant soil under wetting and drying cycles are discussed in depth from macroscopic and microscopic perspectives through the strength test,penetration test,SEM test,and further analyze the effect of slope stability under dry-wet cycle effect and rainfall infiltration.The main contents and results are as follows:(1)The strength test under wetting and drying cycles was carried out on the original and remodeled samples of granite residual soil.The variation of shear strength of residual granite soil with the number of wetting and drying cycles was analyzed.The cohesion c gradually decreases,and the internal friction angle ? is basically unchanged.On this basis,establish the empirical formula between the shear strength index of granite residual soil and the number of cycles,and the strength attenuation law of the granite residual soil is obtained.(2)The infiltration test under wetting and drying cycles was carried out on the original and remodeled samples of granite residual soil.The variation of infiltration of granite residual soil with the number of wetting and drying cycles was analyzed.With the increase of dry-wet cycles,the permeability coefficient k increases gradually.(3)The SEM test under wetting and drying cycles was carried out on the original and remodeled samples of granite residual soil to qualitatively analyze the strength deterioration mechanism of granite residual soil from the microscopic point of view.The macroscopic mechanics and microstructure of granite residual soil were studied by the method of gray relational analysis.The relationship between the shear strength of granite residual soil and the microscopic parameters under the wetting and drying cycle was established.(4)By combining the granite residual soil strength parameters under different numbers of wetting and drying cycles tested in the laboratory with the engineering practice data,and making use of Geo-Studio software to research into the practical slope,the influence of the strength parameters of granite residual soil under different dry-wet cycles on the stability of the slope and the slope stability analysis under the condition of seepage were analyzed.It is found that that slope safety coefficient gradually decrease under the effect of dry-wet cycles and the stability of slope is further deteriorated under consideration of rainfall infiltration.