Study On Dynamic Response Of Tunnel Structure And Its Bottom Layer Under Train Vibration And Earthquake Load

In recent years,with the rapid development of China’s economy,in order to facilitate the travel of citizens,China has begun to build urban subway on a large scale,which has greatly improved the travel difficulties of citizens in cities.During the subway operation,the vibration of the train and the occurrence of the earthquake may cause some damage to the tunnel structure and the underlying soil layer,thus affecting the safe operation of the subway.In this paper,by means of data investigation and numerical simulation,based on the engineering background of xia`men metro line 6,the dynamic response characteristics of the tunnel structure and its bottom soil layer under the coupling effects of train vibration,earthquake,train vibration and earthquake load are studied.This paper focuses on the analysis of the effects of vibration loads at different speeds of trains,peak seismic acceleration loads,coupling effects of train vibration and earthquake loads,and different stiffness of tunnel segments on the dynamic response of tunnel structures and soil layers at the bottom.The main work and research results are as follows:(1)The vibration force generated by the train on the tunnel track is the most commonly experienced dynamic load during the operation of the subway.In this paper,the dynamic loads generated by the four kinds of trains running at the speed of each hour are quantified by the excitation force function,and the dynamic analysis is carried out at the track of the model tunnel structure,and the influence of different tunnel pipe stiffness on the dynamic response of the tunnel structure and the soil layer at the bottom is further studied.The results show that under the four kinds of train loads,the stress response characteristics of the tunnel structure are consistent,mainly under compressive stress.For different train speeds,the higher the speed of the train,the larger the dynamic stress peak and the vertical displacement of the tunnel structure will be.The dynamic stress response and displacement change rule of the soil layer at the bottom of the tunnel structure are consistent with the change rule of the tunnel structure.For the soil layer at the bottom of the tunnel structure,the influence of dynamic load of the train is gradually weakened as the distance from the bottom of the tunnel becomes more and more distant.In addition,the change of the stiffness of the tunnel segments does not have a significant effect on the tunnel structure and the soil layer at the bottom of the tunnel.(2)For more comprehensive consideration may encounter during the period of the subway operation influential dynamic load influence on tunnel structure and soil layer at the bottom,this article also to four different earthquake acceleration time history curve of frequency spectrum analysis,filter and correct,as the dynamic load on the bottom of the shield tunnel model of dynamic analysis,summed up the response characteristics of the model of shield tunnel.In addition,in order to study the seismic impact of tunnel segment stiffness on tunnel structures,the dynamic response of tunnel structures with different segment stiffness models and their underlying soil layers under the same seismic load was studied.The results show that under different seismic loads,the peak of the maximum first principal stress is at the arch waist of the tunnel structure.For the soil layer at the bottom of the tunnel structure,the dynamic stress and displacement responses become more and more obvious as the distance from the surface of the seismic wave is approached.By comparing the dynamic response characteristics of the tunnel structure and its bottom soil layer under different earthquake loads,the dynamic stress peak and vertical displacement of the tunnel structure both increase significantly with the gradual increase of the earthquake acceleration peak,and even damage may occur.The dynamic stress peak and displacement of the soil layer at the bottom of the tunnel structure also increased with the increase of the seismic wave acceleration peak.(3)During subway operation,it is possible to encounter the simultaneous occurrence of the above two kinds of dynamic loads,that is,the coupling effect of train vibration and earthquake load.In this paper,the dynamic response characteristics of four different seismic acceleration time-history curves acting on the shield tunnel model when the train speed is 80km/h are further studied,and the results are compared and analyzed with the calculation results of only seismic load.Results showed that the train vibration and seismic load working condition of(a)and the coupling effect only when the earthquake load working conditions(2)of the tunnel structure and the dynamic response of soil layer at the bottom of the rules,but both the dynamic response of the monitoring value condition of the working condition of a,shows that when the earthquake occurred,the operation of the train will produce adverse effect on the stress of the tunnel structure,so when the earthquake struck,as far as possible in a timely manner will be shut down the subway train.