Experimental Study Of Characteristics Of Granite Residual Soil Under Drying And Wetting Cycle

There is a large area of residual granite soil in southern of Jiangxi Province,and it is widely used in engineering construction.In the south of Jiangxi Province,the rainwater is abundant and the sunshine is abundant.When the rainy season comes,the groundwater level rises,and the residual soil of granite is soaked by water and the water content increases.When the dry season comes,the groundwater level drops and the water content drops.In fact,the reduction and increase of water content is the process of drying and wetting cycle.During the drying and wetting cycle,many engineering problems will occur,such as the reduction of the mechanical properties of granite residual soil,which will affect the safety and stability of the project construction.Therefore,it is necessary to study the characteristics of granite residual soil in the south of Jiangxi Province under the condition of drying and wetting cycle and make a useful exploration for engineering practice.In this paper,the granite residual soil in the southern part of Jiangxi Province is taken as the research object.The experimental characteristics of the residual granite soil in the the southern of Jiangxi Province under the condition of drying and wetting cycle are studied and analyzed.Then the slope stability analysis is performed.The main research results of this article are as follows:(1)In the drying and wetting cycle conditions,the test characteristics of granite residual soils at different initial dry densities and different fiber contents were studied through a consolidation drainage test.Some conclusions are drawn:attenuation rates of the cohesion force and the internal friction angle are the highest at the first wet-dry cycle,and then the attenuation tends to be gentle,and a cohesion and internal friction angle are proposed as mathematical formulas;the increase in cohesion and internal friction angle of fiber to the granite residual soil can be approximated as a constant,not changing with the number of cycles;the increase in initial dry density and fiber participation can effectively improve the cohesion and internal friction angles slow the attenuation of the cohesion and internal friction angles of the drying and wetting cycle.That is to improve soil compaction and mix certain fibers can reduce the influence of drying and wetting cycle on the cohesion and internal friction angle of soil,improve the safety and stability of the project,and provide theoretical guidance for practical projects.(2)Through unconfined compressive strength test,it is found that when the fiber content is the same,with the increase of the drying and wetting cycle times,the unconfined compressive strength of the sample gradually attenuates and the first drying and wetting cycle attenuates the fastest.Under the same fiber content,the unconfined compression strength is exponentially related to the drying and wetting cycle times,and through the fiber content.A mathematical formula for predicting unconfined compressive strength is proposed,which can guide engineering practice and application.(3)The self-made disintegration test device was used to test the disintegration characteristics.It was found that the average disintegration rate first decreased with the increase of fiber content under the same number of drying and wetting cycles,and finally approached stability;then a prediction was put forward.The formula of the average disintegration rate can predict the disintegration rate and guide the soil and water conservation management.(4)It is found that the permeability coefficient of granite residual soil can be reduced by increasing the initial dry density and increasing the content of mixed fiber in the drying and wetting cycle condition.In a certain range,two mathematical relations are put forward,one is about the mathematical relation between the coefficient of permeability and the number of drying and wetting cycles and the initial dry density.The other is the mathematical relationship between the permeability coefficient and the number of drying and wetting cycles and fiber content.(5)Through the use of professional software for slope stability analysis,the stability of the granite residual soil slope under different drying and wetting cycle times and initial dry density conditions and under different drying and wetting cycle times and fiber content was analyzed,and it was found that the initial dryness was increased.Density,mixing appropriate amount of fiber content,can increase the safety factor,and then enhance the slope stability;under drying and wetting cycle conditions,mixing appropriate amount of fiber can effectively improve the safety coefficient of the roadbed slope of granite residual soil,making it finally tend to stability,thereby improving its safety and stability.