Study On Deformation And Stability Of The Surrounding Rock In Subway Cross Tunnel Construction

As a structural form of a planar cross tunnel,The choice of the optimal intersection angle and the research on the deformation and stability of the surrounding rock of the cross tunnel are inevitable in the construction process of the transverse channel.Relying on the construction of transverse channel in Dalian subway as the engineering background,numerical simulation analysis of 7 different cross-angle cross tunnels using finite-difference software flac3d.The changes of the stress,strain and plastic zone of the surrounding rock and supporting structure of the cross tunnel during the transverse channel construction at different angles are studied and compared with the measured results in the field.The main research work and results achieved are:(1)According to the theory of close construction of tunnels,the influence of the near-connecting construction of the transverse channel on the surrounding rock and supporting structure of the main tunnel is divided into three affected zones:Strong influence zone,weak influence zone,no influence zone,The influence range of the three influence zones increases with the decrease of the excavation angle of the transverse channel.(2)The deformation of the surface,vault,arch base and arch waist of different angle cross tunnels varies with the angle of transverse channel excavation,The disturbance of 15°～45°transverse channel is obvious,the disturbance of 60°～90° transverse channel is smaller,and the choice of excavation angle of transverse channel should be greater than 45 °.The disturbance of the acute side surrounding rock of the cross tunnel is larger than the obtuse angle.Influenced by the excavation of the transverse channel,the surrounding rock of the main tunnel has different degree of disturbance with the influence of the zoning.The maximum of the vertical deformation and transverse deformation of the surrounding rock of the main tunnel appears at a certain distance from the center of the Cross tunnel in the strong influence zone,and the smaller the excavation angle of the transverse channel,the farther from the center of the intersection.Affected by the main tunnel support,deformation of surrounding rock in transverse channel is less than that of main tunnel surrounding rock.(3)The maximum and minimum principal stress of the surrounding rock,initial support and lining of the cross tunnel with different angles increases with the decrease of the excavation angle of the transverse channel.The surrounding rock stress of the initial supporting structure of the cross tunnel is obviously larger than that of the lining,and the maximum tensile stress appears at the vault and arch position near the center of the intersection of the Cross tunnel.The surrounding rock and lining of the cavern are mainly subjected to compressive stress,and the maximum compressive stress appears in the arch waist of the strong influence zone of the cross tunnel.(4)The plastic zone of the surrounding rock of the cross tunnel increases with the decrease of the angle angle of the transverse channel excavation.The plastic zone of the acute side surrounding rock of the cross tunnel is obviously greater than the obtuse side of the cross tunnel.Affected by the excavation of the transverse channel,The plastic zone on the right side of the main tunnel is greater than the left side.