Abstract:The composite joint tunnel is different from other public rail tunnel, and its dynamic response is also different under vehicle and train load. In order to study the dynamic response of the composite joint tunnel under the composite traffic load, the excitation force method, cellular automata and vehicle dynamic model were used to simulate the train load, vehicle flow and vehicle load, and the finite element software Plaxis3D was used to analyze the dynamic response of the tunnel under different loads and with or without cushion. The results show that the acceleration response of highway tunnel and railway tunnel is mainly to vehicle load and train load, respectively. The acceleration response of railway tunnel is significantly greater than that of highway tunnel, which is about 20 times of the latter. At different locations of the tunnel, the stress response of the two traffic loads is different. The stress response of the railway tunnel is mainly controlled by the train load, but when large vehicles pass through the highway tunnel, it will have a great influence on the stress response of the railway tunnel, and even play a leading role. Setting cushion between highway and railway tunnels will increase the dynamic response of highway tunnels, but it will also reduce the stiffness difference of the soil below the highway tunnel and then reduce its stress value. Under the combined effect, the stress state of highway tunnels will be improved after setting cushion.