Stability Influence of Over-crossing Existing Railway Tunnel on Newly Built Highway Tunnel
To clarify the influence of different factors ( e.g.,new tunnel construction,interlayer rock and soil thickness,and surrounding rock level) on the existing tunnel structure stability,based on the newly built highway tunnel over-crossing existing railway tunnel,by using numerical calculations method,this paper explored the influence of adjacent tunnel construction on the stress and deformation of existing tunnel structure with different interlayer rock and soil thicknesses and surrounding rock grades.The calculation model accuracy was verified through on-site experiments.Simultaneously,the safety factors of various parts of tunnel structure were checked to evaluate the construction safety of adjacent tunnels.The result indicates that the interlayer thickness between newly built highway tunnel and existing railway tunnel has a significant effect on the displacement of arch top and the rail bottom of existing railway tunnel.When the interlayer soil thickness is 0-16 m,the stress and deformation of existing structure are greatly affected by the newly built tunnel.When the thickness is greater than 31 m,it is basically not affected.The deformation of existing structure gradually decreases with the increase of soil layer thickness.The structural stress of existing railway tunnel increases with the decrease of surrounding rock level,but the nonlinear relation is that the stress of surrounding rock of grade Ⅵ and Ⅴ increase by 12.3％ and 36.8％ respectively compared with that of grade Ⅳ.On-site monitoring data show that the vertical displacement curves at arch and rail surfaces of existing tunnel both exhibit inverted W-shape.The deviation between measured and calculated deformation values is within 20％,which verifies the reliability of calculation model.The whole excavation process has little influence on the bearing capacity of existing tunnel lining structure,without crack or fracture,basically not changing the bearing capacity of existing structure,and the safety factor meets the requirements of relevant specifications.
NETL
NSTL
万方数据
