Research On The Strength And Deformation Characteristics Of Remolded Soil Under Particle Gradation Conditions

China has a vast territory and huge geological differences.The distribution of unsaturated soil is very extensive.The surface soil closely related to engineering practice is almost all unsaturated soil.It is widely used in engineering construction.Among them,unsaturated remolded soil as road and high-speed rail base filler.The demanding requirements for roadbed settlement and stability should be met in the construction of the project.The good engineering properties of the non-saturated remolded soil depend to a large extent on its particle gradation.Therefore,it is particularly important and urgent to study the strength and deformation characteristics of regional remolded soil under different grading conditions.In this paper,the reshaping sample of a disturbed soil in a construction site in Chongqing is taken as the research object.The combination of theoretical analysis,laboratory experiment and numerical simulation is used to carry out research work on the strength and deformation characteristics of remolded soil under different grading indexes.The main research results are as follows:(1)Based on the research of the history and current situation of shear strength theory,combined with the relevant geotechnical test data,the law of the influence of gradation index on strength is analyzed,and the empirical expression of the strength of remolded soil based on the influence of gradation index is put forward.(2)A series of laboratory tests of different grading indexes were carried out on the remolded specimens of disturbed soils selected from a project site in Chongqing.The dry density-water content curve,shear stress-shear deformation curve,soil-water characteristic curve(SWCC),shear strength curve,particle size distribution,water content-strength and shear strength of remolded soils were studied by controlling variable method.The results show that:(1)With the increase of curvature coefficient,the optimal moisture content of remolded soil increases first and then decreases,while the maximum dry density decreases first and then increases.(2)With the increase of curvature coefficient,the shear strength and cohesion of remolded soils decrease first and then increase,while the internal friction angle decreases;with the increase of non-uniformity coefficient,the shear strength and cohesion of remolded soils increase first and then decrease,while the internal frictionangle decreases first and then increases slightly.(3)With the increase of water content,the cohesion of remolded soil increases first and then decreases,and the difference between the beginning and the end decreases first and then increases with the increase of curvature coefficient,while the internal friction angle decreases first and then increases slightly.(3)Based on the regression analysis of geotechnical test data by using the software of Matlab,the soil-water characteristic curve function model of remolded soil is established,and the parameters of soil-water characteristic curve of other groups of remolded soil are predicted.(4)Through GeoStudio software,a series of direct shear tests under different particle gradation conditions are simulated.For this remolded soil,within a certain range of moisture content and particle gradation,the unit error of the results of empirical formula,experimental research and numerical simulation is small.The specific performance is that when the curvature coefficient is 1~3 and the non-uniformity coefficient is 4~6,the deduced strength formula has better applicability and meets the requirements of relative error in engineering.