Analysis Of Dynamic Response Of Close Crisscross And Overlapping Tunnel Subjected To Moving Train Load

With the rapid growth of our country national economy, transportation facility demand increase for comprehensive development and utilization of underground space, the inevitable emergence of close crisscross and overlapping tunnel. The Xinmeihua Mountain Tunnel and Wumeng Mountain Tunnel project was taken as the background of this thesis, based on the main theory of the dynamic interaction between tunnel structure,track and rock, elastoplastic material DP is used to simulate the soil and linear elastic model as tunnel structure .This thesis uses ANSYS to establish three -dimensional finite element models to study the dynamic responses to moving train load. Firstly, according to the characteristics of train, vibration load start with the geometric irregularity which causes the vehicle dynamics, this thesis uses an exciting force corresponding with the manage standard of irregularity to simulate the vertical dynamic load of the train. Secondly, a viscous-spring boundary is applied in order to simulate the semi-infinity feature of the soil. The initial stresses of after excavation are calculated and the damp coefficients and the rational step time of vibration analysis are defined applying the subspace iteration method. Finally, based on Newmark Step-by-step time integration method, according to many compositions of the train vibration loads, the dynamic response of the system are analyzed under three load situations. The stresses, displacements and weak portions in the liner are determined under the vibration loads.Some useful conclusions on the influence of dynamic load to surrounding tunnels are obtained through contrast. The dynamic responses under the consideration of different work conditions are discussed in the thesis which includes acceleration response,displacement response,moment,axial force . These data are discussed and summarized so that the response curves of displacement and acceleration are obtained, the directional distributions of internal force are also obtained. The calculation results show that the maxim dynamic responses of tunnels appear later than the time when the moving loads arrive; especially, the dynamic stresses of inverts are affected furthest by load velocity. In addition, for the tunnel structure design, the static soil pressure is the key load, and the additional stress induced by the train's vibrating load is much smaller than the stress induced by the static load. The research results have important denotation not only for the dynamic stability evaluation of tunnel structures but also for the tunnel design and construction of railway.