Research On Dynamic Load Transfer Mechanism Of Single Line Subway Tunnel Under Moving Loads

With the rapid development of urban subways,the construction scale of subway tunnel projects will usher in a new height.At the same time,it also brings many technical difficulties for tunnel design,construction and subway operation and maintenance.Under the repeated action of the moving load of the subway train,the dynamic response of the tunnel structure and surrounding rock is particularly prominent.In this paper,based on the detailed geotechnical investigation report of a certain rail transit interval and the structural parameters of a subway tunnel,a three-dimensional track-tunnel-surrounding rock dynamic finite element analysis model is established to study the dynamic response characteristics of the subway tunnel under the action of moving loads.The law of dynamic load transmission,and the effects of different train speeds,train axle load,and elastic modulus of surrounding rock on the dynamic load transmission of subway tunnels are studied.The main conclusions are as follows:(1)In terms of time-domain response,during the process of moving loads,the vertical dynamic stress of the track slab,invert arch and surrounding rock unit directly under the rail is mainly under compression,and the vertical dynamic stress of the secondary lining and initial support unit Then the tension and compression alternate.The vertical dynamic stress of the secondary lining under the rail alternates between tension and compression.The vertical dynamic stress of the secondary lining of the arch sill and vault is mainly under compression,and the vertical dynamic stress of the secondary lining at other locations is under tension.Mainly.(2)In terms of spatial domain response,along the depth direction,the vertical dynamic stress at the peak time is transmitted downwards from the bottom of the rail along the depth,and then rapidly attenuates through the structural layer under the rail.The value when transmitted to the surrounding rock is already very small.At non-peak times,the distribution of vertical dynamic stress along the depth has no obvious regularity.The values of the vertical dynamic stress at different interfaces are different,because the elastic modulus of the structure at the interface is different,which results in the discontinuous vertical dynamic stress at the interface.Vertical vibration acceleration,vertical dynamic displacement,and vertical vibration speed have similar rules.(3)In terms of spatial domain response,along the lateral direction of the line,at different times,the location of the track slab at the bottom of the sleeper and the vertical dynamic stress on the surface of the overfill are similarly distributed along the lateral direction.The changes in the lateral direction are sharp,and they are rapidly increasing from one side,then rapidly decreasing,and gradually changing in the middle,then rapidly increasing,and then rapidly decreasing.The two peaks appearing are directly below the rail;no other depths Significant peak characteristics,the vertical dynamic stress changes little laterally,and can be regarded as uniform distribution.Vertical dynamic displacement,vertical vibration acceleration,and vertical vibration displacement also have similar rules.(4)In terms of spatial domain response,along the longitudinal direction of the line,the vertical dynamic stress at different times corresponds to the position of the applied load in space,and moves to the side of the larger value of the lateral coordinate with time,which can reflect the load movement process.At the position of the track slab and the infill of the vertical arch,the vertical dynamic stress has a clear peak value,which can reflect the characteristics of the 6-segment group of the subway train.Increase,the additive effect weakens.The dynamic stress values of the bottom surface of the superstructure are higher than those of the bottom structure.Vertical vibration acceleration,vertical dynamic displacement,and vertical vibration speed have similar rules.(5)As the train speed increases,the vertical dynamic stress and vertical vibration acceleration increase approximately linearly.The vertical vibration acceleration changes more strongly,while the vertical dynamic stress changes relatively less.As the axle load of the train increases,the vertical dynamic stress and vertical vibration acceleration increase approximately linearly,and the vertical dynamic stress changes more strongly than the vertical vibration acceleration.With the increase of the elastic modulus of the surrounding rock,the vertical vibration acceleration decreases approximately linearly,and the increase of the elastic modulus of the surrounding rock has little effect on the response of the vertical dynamic stress.