Study On The Dynamic Response Of The Spatial Cross Shield Tunnel Of Subway Under Train-induced Vibration Load

Based on indoor model test and numerical simulation,this thesis analyzes the dynamic response and its transmission characteristics of the spatial cross shield tunnel under train-induced vibration load.The influence of the joint structure on the structural dynamic response is also discussed in this thesis.Considering the effects of chloride,an analysis and evaluation system for shield tunnel is stablished to analyze the changes in dynamic response,inner forces and bearing capacity in different corrosion ratio.The main research results are as follows:1.Under the vibration load of train,the changes of frequency spectrums and energy spectrums of the monitoring points in the spatial cross shield tunnel are basically the same,and the peak values of the spectrums are appeared at the same frequency.In the frequency domain of 0-100 Hz,the transfer rate functions of each monitoring point at the bottom of the upper tunnel are relatively slow,and the transfer rate functions of the lower tunnel are fluctuating decreasing.The frequency of applied vibration load and the magnitude have nothing to do with the transfer rate function.2.The joint structure obviously influences the dynamic response of the structure.Joints reduce the acceleration of the upper tunnel and enhance the acceleration of the lower tunnel.The longitudinal joint structure strengthens the concentration of dynamic stress in the vault of the upper tunnel arch and the lower tunnel as well as reduces the distribution of dynamic stress in the other areas of the tunnel,but it has no significant influence on the dynamic strain.The dynamic strain of the tunnel is greatly reduced by the circumferential joint,but it has little effect on the strain of the tunnel,and the stress is strengthened in the dome and the arch of the tunnel,but it has little influence on the stress of the tunnel.3.With chloride,as the corrosion ratio grows,the acceleration and strain amplitude of the upper tunnel increase,and the stress amplitude of vault and arch reduce.The lower tunnel’s acceleration amplitude at the arch and the bottom is not obviously affected by the growth of corrosion,and the acceleration amplitude at the vault is increasing.With the increase of the corrosion ratio,the stress of the lower tunnel decreases while the strain increases.The dynamic coefficient of the structure increases with the rising of corrosion ratio,and the dynamic coefficient at the bottom of the tunnel is far greater than that of the other parts of the tunnel.4.Based on the limit state analysis method of bearing capacity considering the effects of chloride,the bearing capacity of the segments and joints are significantly reduced because of the chloride.The train vibration load strengthens the tension safety of the upper tunnel segments,and the higher the corrosion ratio is,the more the train vibration load reduces the tension safety of the lower tunnel segments.The train vibration load has little influence on the shear safety of segments.