The Study On Dynamic Response And Permanent Deformation Of Subgrade Under Vehicle Load

The vehicle load is a typical dynamic load,but the existing design code of subgrade and pavement still adopts the theory of elastic multilayer system under static vehicle load,which is not consistent with the actual situation.According to the survey data,at present,highway transportation has such characteristics as large tonnage,heavy axle load and large flow,and the influence of traffic load on subgrade is increasing day by day.Coarse grained soil is widely used in subgrade filling construction of South Expressway because of its large porosity,high permeability,high shear strength and high bearing capacity.The effect of vehicle load on the coarse grained soil subgrade is rarely studied,based on the National Natural Science Foundation project" Research on service performance evolution and state control technology of high coarse-grained soil embankment under dynamic wetting effect",first of all,the characteristics of vehicle load and the constitutive model of subgrade soil are analyzed,which provide the theoretical basis for numerical simulation;through the finite element software MIDAS/GTS analysis the influence of vehicle load(moving load)on subgrade;Finally use the results of numerical simulation as the basis of dynamic three axis test.discuss the influence of long term vehicle load on coarse grained soil subgrade,the research achievements are as follows:(1)The moving load is used to simulate the vehicle load,the subgrade is simplified as a 3D model,and the linear elastic and elastic-plastic constitutive model is adopted.The transient dynamic response of subgrade soil under vehicle load is studied by numerical simulation method.The attenuation law of dynamic stress and dynamic displacement of subgrade soil in different depth under the action of vehicle load is obtained.(2)The influence of vehicle type,speed and load on the dynamic response of subgrade is analyzed.The influence of vehicle type and load on subgrade is larger,and the speed of vehicle has little influence on Subgrade.(3)According to the results of numerical simulation and the previous research results,the test scheme of permanent deformation of coarse-grained soil was established.The prediction model of permanent deformation of coarse grained soil was obtained by fitting the cyclic loading test data.(4)Based on the prediction model of the permanent deformation of coarse-grained soil and the layered summation method,the deformation characteristics of coarse grained soil subgrade under long-term vehicle load are obtained.This project has important guiding significance for the design,construction and management of coarse grained soil subgrade of highway by studying the transient and long-term dynamic load of vehicle load on coarse grained soil subgrade.