Research On Propagation Rules Of Ground-borne Vibration Caused By Subway Trains In A Curved Tunnel

Due to the constraints of topography,geo features and different geological conditions in the urban area,the curved tunnel is widely applied in the subway line planning and design in order to meet the layout requirements of the existing urban railway layout and the passenger flow to the maximum extent.In addition,there are relatively few internal and abroad researches on the environmental vibration of curved tunnels at present.The measured data show that there are some differences in the laws of the surface environmental vibration caused by the running of subway trains passing through straight tunnels and curved tunnels.Based on the above background,this paper adopts the analytical coupling model of train and curved track and the periodic finite-infinite element coupling model of curve to study the ground-borne vibration propagation law of curved tunnel under train action.The main research contents and conclusions are as follows:1.Based on the theory of the periodic-infinite structure,the analytical coupling model of train and curved track and the periodic finite-infinite element coupling model of curve are combined properly,and a prediction model of environmental vibration caused by train operation in curved tunnel is proposed.2.Based on the measured soil layout parameters,the tunnel structure parameters and the train running speed of the curved tunnel section of Beijing Metro Line 15,the surface environmental vibration under the action of the curved tunnel train is calculated and analyzed by using the prediction model proposed in this paper.The rationality and feasibility of the combination of the two prediction models is verified by comparing the prediction results and the measured data of the ground surface vibration.3.Considering the influence of factors such as curve radius,train speed and soil layer parameters,the environmental vibration response of the outer surface points above the curved tunnel is calculated,and the sensitivity analysis of factors affecting the environmental vibration of the curved tunnel is carried out.It is found that the train running speed and the properties of the soil layer have great influence on the surface environmental vibration of the curved tunnel while the influence of curve radius is relatively small.4.The time history and 1/3 octave band of acceleration response and Z vibration level of the horizontal and vertical vibration of the surface points are analyzed.The difference of propagation law between the horizontal vibration and the vertical vibration with the distance from the center line is studied under different influence factors.The results show that:The RMS,1/3 octave spectrum of 20-100Hz frequency band and Z vibration magnitude of horizontal and vertical acceleration of each vibration pick-up point on the ground surface show an increasing trend with the increase of vehicle speed,and a decreasing trend with the increase of elastic modulus of soil layer(single soil layering),while the influence of curve radius change is relatively small.Whether in curved or straight tunnels,the vertical and horizontal vibration acceleration responses of the ground surface caused by train operation will generate vibration amplification near the 20m central line of the line.