The Dynamic Response Of Overlapping Tunnel Under Heavy Haul Train Load

The spatial form and mechanical mechanism of the cross tunnel are relatively complex,and the physical and mechanical parameters of different strata and the support structures have great influence on the cross tunnels.After the tunnel is completed,the excitation load of the train will further influence the stability of the cross tunnels.Therefore,the dynamic response characteristics of the cross tunnels under heavy and long duration load of heavy haul train are studied in this paper.A model test,numerical simulation and theoretical analysis are adopted to analyze the acceleration vibration time history curve of tunnel lining and the change law of dynamic soil pressure of the surrounding rock interlayer between the upper and lower tunnels.The main contents are as follows:(1)Based on the similarity theory,the cross tunnel surrounding rock and lining model are prepared.The acceleration vibration time history data of heavy haul trains are collected and applied to the lining of the upper tunnel in single point excitation.The soil pressure boxes are arranged in contact surface between the inverted arch of upper tunnel and the surrounding rock and in the surrounding rock interlayer.The floor of the upper tunnel,the vault of the lower tunnel and the floor of the lower tunnel are selected to arrange the accelerometers.A control test is further designed,the corresponding spectrum curves are obtained by using the FFT algorithm for the measured train acceleration time history data,and the main frequency and amplitude of vibration are extracted to apply a simplified train vibration sine wave.(2)According to the size requirements of the cross tunnel model,the corresponding three-dimensional numerical simulation model is established by the finite difference method.Multipoint train vibration loads are applied in the upper tunnel.Meanwhile,the monitoring results of the test and numerical simulation results are compared and analyzed in terms of the acceleration of the lining and the dynamic soil pressure of the surrounding rock.The feasibility of the numerical simulation method to study the dynamic response characteristics of the cross tunnel will be verified.(3)According to the surrounding rock grade,the interlayer thickness,the train load and the traffic mode,the change rule of the acceleration of the lining and the dynamic soil pressure of the surrounding rock is discussed.The cross tunnel has not been completed,the acceleration of the high speed train in the lower tunnel can not be collected.Therefore,a series of high speed train excitation loads composed of sine functions are applied in the numerical simulation.(4)The plastic superposition zone of the cross tunnel is studied based on the plastoelasticity mechanics method and the Mohr-Coulomb yield condition.The curves of the radius change of the plastic zone are drawn under initial ground stress,support resistance,cohesion and friction angle.The sensitivity of various factors to the radius of plastic zone is analyzed.