Study On The Dynamic Response And Fatigue Cumulative Damage Of Cross Shield Tunnel Under Vibration Load

Aiming at the damage problems occurred easily in the long term operation of cross shield tunnel,the paper relys on the National natural Science Foundation Project of China(NO.51278425)and the dynamic response and fatigue cumulative damage of the cross shield tunnel were studied by using methods such as theoretical analysis and numerical calculation.Using the improved fatigue constitutive model and considering the driving effect of train,the fatigue life of cross structure with the connecting transverse passage and space-cross tunnel structure in short distance was calculated.What's more,aiming at these two kinds of cross shield tunnel,the dynamic response and fatigue cumulative damage were analyzed.The main research work and achievements are as follows:(1)Based on the uniaxial constitutive model of concrete in the current concrete design specification,taking stiffness degradation,strength decrease and residual strain increase of concrete into consideration,the fatigue constitutive model was improved.The model is suitable for the fatigue analysis of high-cycle train vibration;(2)The structure-cross and space-cross shield tunnel were built,respectively.Considering the driving effect of train,the whole process of train driving in the tunnel was simulated.Based on the dynamic response of the structure during the train driving in the tunnel for the first time,the fatigue life of two kinds of cross shield tunnel was calculated by nominal stress method;(3)Based on the improved fatigue constitutive model of concrete,dynamic response characteristics such as stress and acceleration of the structure-cross and space-cross shield tunnel were analyzed.Results show that the vibration of observation points is obviously phased during high speed train running.The vibration in the middle of the main tunnel where the train driving was intense,and the vibration of the adjacent tunnel was gentle.With the increase of train running time,stress and acceleration of structures increase in a certain degree.(4)Using the plastic-damage constitutive model of concrete,cumulative damage characteristics of the structure-cross and space-cross shield tunnel were studied.Results show that the accumulative damage of the main tunnel caused by train operation was characterized by two stages.However,the accumulative damage of the transverse passage was characterized by three stages.The accumulative damage of the main tunnel is focused on the inverted arch,and the accumulative damage of connecting transverse passage is focused on the corners of both sidewalls.The tension-induced accumulative damage is greater than the pressure-induced accumulative damage from the size and range of damage.What's more,the tension-induced accumulative damage of structures is the controllable factor which leads to structure damage failure.