Dynamic Response And Accumulative Deformation Characteristics Of Track-subgrade For High-speed Railway

As a major achievement of railway high technology,the construction scale of high-speed railway is an important symbol of railway modernization.The biggest difference between the high-speed railway and the traditional railway is that the high-speed train is fast,so strict limits are put forward to control subgrade structure’s vibration as well as its settlement.Therefore,studying the dynamic response and accumulated deformation of track-subgrade of high-speed railway.Aiming at the shortcomings of existing studies,considering that most scholars have simplified the vehicle load to uniform moving when studying dynamic response,in addition,in terms of experimental research,scholars have conducted more research on soft clay subgrade fillings,and dynamic experimental research on coarse grained soil fillings is relatively rare,this paper simplified the vehicle load to variable speed moving considering the actual situation.The dynamic response and accumulated deformation of high-speed railway are conducted by adopting theoretical analysis and tests.The main research contents can be drawn as follows:（1）The track is regarded as a finite Euler-bernoulli beam resting on Pasternak foundation with viscous damping.According to the equilibrium equation,the mode superposition method and the Duhamel integral are used to solve the equation,the integral solution of the deflection of the foundation beam under moving load is obtained.The integral was solved by using an adaptive Gauss-Legendre integration rule.Compared with the existing research results,the correctness of the proposed method is verified.In the parameter analysis,the influence of the initial velocity,the acceleration,the shear modulus of foundation,the elastic foundation coefficient and the damping of the foundation on the deflection of the foundation beam were analyzed.（2）Considering that the dynamic strain of subgrade soil is about 10^-4 during the operation of high-speed railway,it is important to analyze the dynamic modulus of elasticity and damping ratio in studying the dynamic response of subgrade.Therefor,GDS triaxial apparatus was used to develop laboratory test to analyze the effect of different dynamic strain,confining pressure,compaction degree on dynamic parameters of subgrade coarse grained soil,the research show that relationships between dynamic stress and strain can be described by Hardin-Drnevich Hyperbolic Model,and on this basis,an empirical formulas of dynamic elastic modulus and damping ratio with confining pressure and compaction degree was put forward.（3）The effects of different CSR（cyclic stress ratio）,confining pressures and compaction degree on the accumulative deformation characteristics of coarse grained soil were studied by dynamic triaxial test.Based on the test results,a model for predicting the accumulative deformation of coarse grained soil was proposed,which can consider the effects of CSR,confining pressure and compaction degree.The predicted results are similar to the test results.Based on the prediction model of the accumulative deformation of coarse grained soil and the layered summation method,the high-speed railway subgrade accumulative deformation is obtained.