Study On Dynamic Response Of Metro Tunnel Under Train Loads

ABSTRACT:During the whole working life of the tunnel,it is subjected to a long-term train dynamic load,and the increment of the train speed and operating frequency leads to a more and more considerable influence to the tunnel structure by the trains.There are lot of factors influenceing the vibration characteristics of the tunnel structure.In this paper,the three-dimentional finite element model is developed by numerical calculation,and a systematical study has been made for the dynamic response of the circular tunnel,the horsehoe tunnel and the rectangular tunnel under different velocity of the train,axle load and the structural style of the track.The main research contents are as follows:(1)The research status of the train load and the dynamic response of the tunnel under the train load is summarized.The calculation theory of structural dynamics and the analysis method of ansys transient dynamic analysis are introduced.(2)By using the analysis model of finite length train-rail coupling calculated the vibration load of the train,and also calculate the reaction force of the fastener under different train velocity,the axle load and the track structural style.The imposed load of tunnel is simulated by applying the reaction force of the fastener.(3)The finite element model of the tunnel-soil is established in ANSYS software,during which the input of the train loads and boundary of viscoelasticity are solved.Furthermore the model calculation is verified according to the field measurement.(4)The affecting factors of vibration characteristic of the tunnel structure is analyzed,and the vibration points are selected according to the dynamic response nephogram of the tunnel structure.The dynamic responses of circular tunnels,horseshoe tunnels,and rectangular tunnels at different train velocities,axle weights and track structural style are calculated.The changing rule of the acceleration,displacement,principal stress on every analysis point of the tunnel structure is analyzed contrastively with increasing of the train velocity,increasing of the axle load and two typical track structural styles.Also the dynamic responses of the tunnel structures with different cross-sections are analyzed.The results show that:the maximum dynamic response of the structure occurs at'the moment when the bogie passes through the crosssection of the detecting point,and the dynamic response of the tunnel structure shows a periodic change.The dynamic response amplitude of the bottom of the tunnel structure is much higher than those of the side wall and top side,so that the bottom of the tunnel structure is the key to design and the maintainance of the postoperation.It also shows an obviouse rising of the dynamic response during the increasing of the axle load and velocity of the train.The dynamic response also varies with different track structural style,that the response at the region with an unfavorable loading state of the rectangular tunnel is significantly greater than that of the horseshoe and circular tunnel.