Research On The Strength And Permeability Of Granite Residual Soil And Its Engineering Applicationin Guangxi

Due to its high strength,granite residual soil is often used for filling highway subgrade.However,due to its large particle size and small clay content,the soil has strong permeability,and the surface's ability to resist rain erosion is poor after filling,which affects the quality of the filling project.Therefore,by adding a certain amount of clay to improve its permeability and increase its surface resistance to rain erosion,better filling quality can be obtained.Through the screening test,permeability test,strength test and SEM scanning electron microscope test under different red clay contents,the strength and permeability of granite residual soil with different clay contents were studied from macroscopic and microscopic aspects.The following work was mainly carried out:(1)In view of the phenomenon that the surface of granite residual soil is easy to be washed by rain after filling,a certain amount of red clay is added to improve the soil properties.A constant head permeability test was carried out on the improved soil with different clay content,the permeability coefficient of the improved soil with different clay content was obtained,and it was found that the permeability coefficient decreased slowly with the increase of clay content.(2)Through SEM scanning and particle analysis of granite eluvial soils with different clay contents,the change of permeability coefficient was compared,and it was found that: the heterogeneity coefficient Cu of the improved soil increased with the increase of clay content,and the permeability coefficient decreased with the increase of the heterogeneity coefficient.The curvature coefficient Cc of granite residual soil decreases with the increase of clay content and the permeability coefficient decreases with the decrease of the curvature coefficient.SEM results show that as the non-uniform coefficient increase and the decrease of the curvature coefficient,contain clay granite residual soil particles of the particle size range,a gradual increase in particle size types are also increasing,make its skeleton intergranular pore effectively fill,which to a certain extent,reduce the permeability.(3)The unconfined compressive strength test,compaction test and permeability test were carried out for granite residual soils with different clay content to study the influence of clay content on the engineering properties of granite residual soils.The results show that the optimal content of red clay in granite eluvial soil is 40%,and the permeability coefficient of clay-bearing granite eluvial soil is 1.27×10-6m·s-1,and the unconfined compressive strength is 0.489 Mpa.The optimum compactness of alluvial granite is 96%.(4)Taking the GLC-TJ4 contract section of high speed GLC-TJ4 from guigang to longan in guangxi as an example,the field comparative test of improving the granite residual subgrade filling by adding clay particles was carried out,and the optimal clay content of the improved granite residual subgrade filling was verified.The research results of this paper are of great significance for granite residual fillengineering in rainy area.