Study On Dynamic Characteristics Of Metro Train Under Vibration Load

In recent years,with the rapid development of urban rail transit and shield construction,the urban line network has become more and more intensive,which inevitably leads to many shield Overlapped Tunnels in space.Because the surrounding rock in the overlapped section is relatively weak,with the long-term operation of the train,the vibration load of the train tends to appear stress concentration in the overlapped section of the tunnel,which will cause damage to the structure of the overlapped section of the tunnel and damage the train The safe operation of the car causes significant potential safety hazards.Besides,with the regional difference,the surrounding rock level of the tunnel,the running speed of the train and other differences,the dynamic response at the intersection of the tunnel and the service state of the vehicle tunnel system are also affected.Therefore,it is of considerable significance to study the dynamic response law and displacement damage characteristics of the Overlapped Shield Tunnel reasonably and comprehensively to ensure the long-term safe operation of the train in the tunnel.In this paper,the dynamic response law,deformation and damage law of the lining structure of the Overlapped Shield Tunnel under the action of the train vibration load are studied,and the main research work of this paper is as follows:(1)In order to simulate the real state of the Overlapped Shield Tunnel in the actual operation and accurately simulate the vibration load of the train,the continuous vibration load application mode in space is adopted,that is,the vibration load of the train is applied on the train axle in the form of vertical excitation load in the curve,and the train self-weight is applied on the train model.At the same time,the corresponding velocity field is applied to the train,which can effectively simulate the spatiotemporal change of load.(2)Based on the theory of dynamics and concrete damage,a refined three-dimensional tunnel model is established by using the finite element software.In order to reduce the error caused by the boundary deviation,a three-dimensional spring damping system is used to define the boundary conditions,which has good robustness.In order to ensure the continuity and accuracy of the data,the tunnel multi-section reversing method is adopted.(3)The dynamic response of the overlapped tunnel under the train vibration load is analyzed,including the vibration acceleration and the maximum principal stress.For the comparison and analysis of dynamic response under different working conditions,there is amplification effect on the dynamic response at the intersection of tunnels,in which the amplification effect of vibration acceleration is about 1.0-1.3 times,and the amplification effect of maximum principal stress is about 1.6-1.9 times;with the change of train operation speed and surrounding rock grade,there is a monotonous increase(decrease)trend,and the speed effect is greater than the surrounding rock grade effect.(4)The displacement and deformation of the overlapped tunnel under the trainvibration load are analyzed.The displacement and deformation of the overlapped tunnel under different working conditions are compared and analyzed,among which,there is amplification effect at the intersection of the tunnel,which is about 1.24 times of the amplification effect;the vertical displacement of the full section arch bottom of the tunnel is analyzed,and its curved thread is "parabola" shape,with the increase of the speed and the grade of the surrounding rock,the curvature increases with it,and the speed effect is greater than the grade effect of the surrounding rock.(5)According to the deteriorated concrete model,the damage rule of the overlapped tunnel is studied.The damage mainly occurs in the range of 130 °~ 140 °at the bottom of the tunnel,the overall tensile damage is higher than the compressive damage,and the overlapping section has amplification effect;the plastic damage occurs in the deteriorated concrete condition;the damage increases with the increase of train speed,and for the tensile damage of the overlapping section at the bottom of the arch under the non deteriorated concrete condition,the driving speed at 120 km / h is 8.46 times of40 km / h and 80 km / h respectively And 2.87 times.Through the analysis and research,the dynamic response law of lining structure,displacement deformation and damage law are obtained under different working conditions,which provides particular theoretical support for the dynamic response of critical parts in the subway operation process.