Dynamic Response Analysis on the Subgrade of the Existing Speed Increase Jinshan Railway

Based on the infinite artificial boundary and the substructure system of the bed-embankment-field,a finite element model of the existing Jinshan railway subgrade in Shanghai was established.According to the measured response characteristics of subgrade,the function of moving load on the bedding surface was built to simulate the actual dynamic loads produced by trains with the current speed.The dynamic response of the ordinary subgrade was analyzed under the moving loads produced by trains from the current speed 43 km·h-1 to the target speed 160 km·h-1.It is found that,if the train speed is increased to 160 km·h-1 from 43 km·h-1 without reconstructing the existing subgrade,the peak value of the dynamic stress on the bedding surface will increase by about 17%.The vertical dynamic stress on the subgrade surface declines with the depth below in the form of exponential decay.Compared to 6.2 m below the bedding surface under the present speed,the influence depth has increased 1.2 m after speed increase.