| Along with the development of urban metro,the rail transit has developed on a speedway in recent years,Shield construction has the advantages of safety,environmental protection,fast and reliable,it has been widely applied in the construction of metro interval tunnel.Segment lining is the main supporting structure of shield tunnel,it is a continuous stable structure connected by the bolts,due to the poor quality of construction and the exterior loads,segment lining has damage problems such as segment dislocation,angle,crack etc.Focusing on segment dislocation and the lining ellipticity,the paper analyzed and summarized the impact on the segment stress.Segment lining is the main supporting structure of the tunnel,it has many joints,it’s not a homogeneous or continuous structure,the computation model is very complicated,the common models includes isotropic circular model,hinged circular model,beam-spring model,shell-spring model and block model.In order to simulate longitudinal mechanics effect of segment lining,this paper build three-dimensional shell-spring model,use shell element simulates segment,spring element simulates bolt and the contact between segment.By adopting reversing thinking,the paper analyzed the impact of segment dislocation and ellipticity,the main research content is as follows:(1)With three-dimensional shell-spring model,the paper analyzed the inner stress and deformation of segment.The study shows that the bending moment and axial force of the adjacent two rings are not consistent in the longitudinal of the tunnel.The paper also analyzed the influence of different position or different degrees of segment dislocation on the inner stress of segment,the results show that the segment dislocation on top or side of tunnel are more unfavorable to the segment stress.When the displacement of segment move to the inside of the tunnel,the checking results show that the maximum crack width is 0.157 mm,the displacement move to the outside of the tunnel,the maximum crack width is 0.196 mm.The effect on the adjacent ring is mainly around the dislocation,which has little influence on the security of the adjacent ring.(2)Building a model which has a existing dislocation between adjacent segment ring,analyzed the influence of four different dislocation on the inner stress of the segment.The research shows that with 15 mm segment dislocation,the dislocation in top and left side of the tunnel are most unfavorable to the structure stress.Compare to the position of the dislocation near the joint,the structural stress is more unfavorable when the dislocation is located in the middle of the segment.When 15 mm segment dislocation occurred at the top of tunnel,the maximum crack width is 0.187 mm,when occurred at the left side of tunnel,the maximum crack width is 0.198 mm.Analyzed the impact on adjacent segment,the distribution of bending moment and axial force on the adjacent segment ring is obvious,but there is little change in the numerical value.(3)Building four different lining ellipticity models,according to the calculation results,analyzed the influence of different ellipticity on the inner stress of segment.From the numerical point of view,the circumferential and inner stress of the segment are all increased with the increase of the ellipticity of the segment ring.The distribution of the inner stress of the segment under each dllipticity is roughly the same,but with the increase of the ellipticity,the segment joints show different characteristics in different position of the segment ring.When the ellipticity is close to or exceeds 6‰,between the top block and the adjacent block,may exist segment dislocation or fragmentation.The width of the maximum crack in 6‰ is 0.195 mm,which is close to the limit of the standard. |
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