Seismic Response Analysis And Anti-seismic Measures Of Tunnels With Assembled Bottom Structure

The bottom structure of railway tunnel is one of the main components of tunnel structure,and is the foundation of tunnel structure.The key condition to ensure good track condition is that the bottom structure can be firm and stable.Compared with the traditional cast-in-place tunnel bottom structure,the prefabricated tunnel bottom structure has the advantages of high quality assurance rate,short construction period and less environmental pollution,and has broad application prospects.At present there are no relevant codes for seismic design of prefabricated tunnels in China,and the systematic research on seismic design and analysis of prefabricated tunnels is insufficient.Therefore,on the basis of previous studies,taking Luojiashan Tunnel of Zhengzhou-Wanzhou High-speed Railway as the engineering background,the prefabricated bottom structure tunnel is studied by numerical simulation.The main research work of this paper is as follows:(1)Establishing a three-dimensional refined model of prefabricated tunnel with bottom structure,inputting transverse seismic wave,discussing the influence of different lining strength,different surrounding rock grade and different peak acceleration on seismic response of tunnel,analyzing the distribution and variation of acceleration,displacement and maximum principal stress,especially the maximum principal stress of prefabricated tunnel with bottom structure,and according to calculation.Relevant suggestions are given to provide reference for engineering design and construction.(2)To study the effect of horizontal and transverse seismic waves on the seismic performance of tunnel structures,a shock absorption layer is set between the initial support and the second lining of the tunnel.The influence of different thickness of the shock absorption layer and stiffness of the shock absorption layer on the seismic performance of the tunnel structures is analyzed.It is proposed that the shock absorption layer with 20 cm thickness and 5 MPa stiffness should be adopted under the actual conditions of the project.(3)The numerical model of prefabricated tunnel joints with prefabricated bottom structure is established to calculate the maximum tangential stress of the joints under different lining strength,different surrounding rock grade,different seismic intensity and different thickness and stiffness of shock absorbing layer.It is concluded that the maximum tangential stress on the outer side of the joint contact surface is larger than that on the inner side when the shock absorbing layer is not installed.After the shock absorbing layer is installed,the distribution of the stress on the outer side and the inner side is basically the same.(4)When the cast-in-place structure at the bottom and the prefabricated structure at the bottom are adopted,the variation of the acceleration,displacement and maximum principal stress of the tunnel under the conditions of setting the shock absorption layer and not setting the shock absorption layer,and the prefabricated bottom structure as the tunnel base,can effectively improve the overall seismic performance of the tunnel lining and reduce the phenomenon of stress concentration at the bottom of the tunnel,but for the filling layer material.The quality requirement is high.