Study On The Effect Of The Large Longitudinal Slope And Small Track Shield Tunnel On The Railway Deformation

With the acceleration of China’s urbanization process,more and more people settle in cities,transportation and travel has become a hot issue hindering urban de velopment.As a means of transportation,the subway has the advantages of large transportation volume,convenience and speed,which has attracted the attention of urban rail transit planners.With the subway planning and construction,the line planning and shield environment is becoming more and more complex,and the number of projects of the lower-piercing buildings,railways and bridges is increasing,which puts forward higher requirements for the construction of the shield tunnel.In this paper,the railway under the large longitudinal slope and small track shield tunnel of a subway in Zhengzhou is used as the engineering background,and the change of track,road base and soil displacement caused by the railway construction caused by the large vertical slope small curved shield tunnel is studied by combining numerical simulation,site monitoring and theoretical calculation.The specific research content is as follows:(1)The influence factors and control value standards of soil,roadbed and orbit displacement.The influence factors of soil,roadbed and track displacement caused by different roadbed railways under the small curved diameter shield tunnel of large vertical slope are analyzed.And the control value standards of soil,roadbed and track displacement are put forward in combination with relevant norms or regulations,so as to provide a basis for numerical simulation analysis and evaluation of in-situ monitoring results.(2)Control measures for soil,roadbed and track displacement.Using Midas(GTS)to simulate and analyze the railway construction under the large vertical slope small curved shield tunnel.It is proposed to control the large slope small curved shield tunnel slope-facing thrust and steering demand over-excavation,which can effectively reduce the displacement of soil,roadbed and track,and strengthen the monitoring of the crossing pile foundation and box culvert part.(3)The change trend of soil,roadbed and orbital displacement.Numerical simulation and field monitoring results show that the construction of the left and right lines of the large slope shield tunnel causes the surface and track subsidence grooves to be asymmetrical “W”,and the surface and track subsidence decrease smaller with the increase of the distance from the center line of the shield tunnel.Compared with unreinforced soil,conventional reinforcement can reduce the vertical displacement of the soil by about 30%,while the reinforcement reduction can be as much as 50%.Compared with the ordinary shield tunnel,the soil,roadbed and track displacement spree caused by the construction of the large vertical slope small curved shield tunnel are about 30%.The first construction tunnel caused by soil solidification is 10%~30% larger than that of the post-construction tunnel.(4)The interrelationship between soil,roadbed and orbital displacement.Numerical simulation and in-situ monitoring show that the different soil load distribution is the main factor of the difference between soil and orbital displacement steamed under the shield tunnel,and the soil load distribution is mainly influenced by the roadbed form.Orbital stiffness has buffering and diffusion effect on surface subsidence,and the influence range of orbital subsidence is 25% wider than that of surface horizontal settlement.The shield tunnel curve has an aggravating effect on the tilt of the box culvert,and the upper track subsidence of the box culvert is mainly affected by the tilt of the box culvert.