Study On Vehicle-Induced Vibration Response Of Transfer Passage Closely And Perpendicularly Undercrossing The Existing Metro Station

Due to factors such as track irregularity,the train operation process to produce vibration force,and through the orbit,ballast bed to tunnel structure to generate vibration response,which affects the safety and stability of the structure.However,for the short-distance,or even zero-distance,close cross tunnel structures of urban subways.the upper vibration action load will not only produce vibration response to its structure,but also directly affect the underlying structure.Moreover,the vehicle-induced vibration response will be superimposed and coupled in the cross section,and the influence rules are more complex.Therefore,this paper takes the Chengdu Metro Line 8 Nijiaqiao Station transfer passage closely and perpendicularly under the existing Line 1 metro station as the background,combined with theoretical analysis,onsite test and numerical simulation,to explore the dynamic response characteristics and transfer rules of transfer passage structure under the upper vibration load,and obtains the following research results and conclusions:(1)The field vibration test analysis of the transfer passage structure under the upper vibration action load shows that the vertical response of the roof of the transfer passage is the strongest,and the lateral vibration of the side wall is weaker than that of the middle wall due to its larger thickness.The frequency response range of the structure is 50～200Hz,the strong frequency response range is 50～100Hz,and the frequency at the peak amplitude is 65 Hz.(2)A three-dimensional finite element model of station-passage-stratum is established,and based on the train-rail coupling model,considering the track irregularity factor,the timehistory spectrum of the train vibration load at different speeds is simulated,and the mobile application of the train vibration load is realized.Meanwhile,the correctness of the simulation method and parameter setting of the numerical simulation is verified by comparing with the field test results.(3)Considering the traffic conditions of the existing station and the lining parameters of the transfer channel,from the perspective of time domain and frequency domain,the characteristics of the vehicle-induced vibration response of transfer passage closely and perpendicularly undercrossing existing metro station are explored as follows:(1)The vehicle-induced vibration response of the transfer passage by the two-way trains in the existing metro station is larger than that of one-way train,but the growth rate of the response intensity at the same train vibration load is less than 5%,that is,the vibration superposition effect of two-way trains is not obvious compared with one-way trains.(2)The vehicle-induced vibration response of the transfer passage is positively correlated with the train speed in the existing stations,and the growth rate decreases gradually.The response intensity of each part is roof > middle wall transverse > middle wall vertical > side wall vertical > side wall transverse > bottom plate.The corresponding frequency response ranges of the train at 40km/h,60km/h and 80km/h are 40～180Hz,50～200Hz and 40～160Hz,indicating that the train speed has a great influence on the frequency response distribution of the structure vibration.(3)The vehicle-induced vibration response of the transfer passage is negatively related to its lining thickness ratio,and the deceleration gradually decreases until “the thickness ratio of the roof of the transfer passage to the floor of the existing station”is 1.5,and “the thickness ratio of the middle wall to the side wall of the transfer passage”is 1.0.The frequency at the peak amplitude of structure is usually 65 Hz or 130 Hz.As the lining thickness ratio increases,the high-frequency response attenuates and all the frequencies at the peak amplitude drops to65 Hz,indicating that enhancing the lining thickness ratio can effectively suppress the highfrequency vibration of the structure.(4)The vehicle-induced vibration response of the transfer channel is positively correlated with the void rate of the upper roof,and it increases approximately exponentially.When the void ratio reaches 20%,it enters the rapid growth area,and the amplifying effect of the void on the vertical vibration of the structure is higher than that in the lateral direction.During the process,the maximum increase of the vibration acceleration level is 9.7d B,indicating that the void of the structure can greatly increase the vibration energy,which is not conducive to the stability,concrete density should be strengthened or grouting behind lining should be compensated to eliminate void.(4)The multi-factor parameter sensitivity analysis method is adopted to rank the sensitivity of each factor on the peak acceleration of the transfer passage under the reference state.Specifically: train speed > “the thickness ratio of the roof of the transfer passage to the floor of the existing station” > the void rate of the upper roof of the transfer passage > “the thickness ratio of the middle wall to the side wall of the transfer passage” > the train traffic mode.