| Tunnel construction under the conditions such as topography,geology,using the natural exhibition of line and long tunnels have been unable to overcome the line between control points in height,spiral tunnel has better line conditions and meet the linear indicators of potential,more and more be taken seriously.However,the application of the spiral tunnel is still relatively small,so it needs further research.The based on the Dahua road,Yuzhong District,Chongqing City,the engineering background of this project.Using the finite element method,the linear curvature of the spiral tunnel,excavation methods,left and right line spacing,construction and other aspects of the monitoring have carried out a detailed study,the main research contents and conclusions are as follows:(1)The optimum curve radius of the spiral tunnel is determined.Spiral tunnel with the decrease of the radius of the linear exhibits the following rules: the surrounding rock stress is getting worse;plastic zones from nothing to have the plastic area is increasing;the asymmetric deformation of tunnel lining shows more and more obvious,the beginning of the force support system is increased.When the condition is limited to the use of the spiral tunnel form,the proposed combination of terrain conditions try to select a larger linear radius,so that the linear relatively flat.(2)The reasonable excavation method is confirmed.Through the whole section method,step method,CD method under three kinds of working spiral tunnels force and deformation analysis can be obtained: in the process of excavation and surrounding rock deformation of supporting structure in the early approximation under three kinds of method,and the plastic zone have appeared.Which CD method under the surrounding rock and primary support structure deformation smaller,reflecting ability to control surrounding rock deformation.From the structure stress distribution at the beginning of three kinds of systemic method to the difference in the order is the CD method,steps,method and whole section method.Considering the stress of the spiral tunnel asymmetry,should choose construction method of deformation is relatively flat,to avoid the occurrence of rapid deformation,lest cause instability of surrounding rock.(3)The safety distance between the excavation face of the tunnel around the left and right lines is determined.The structure of the surrounding rock and initial supporting structure with the distance between the left and right lines are less affectedby the accumulated deformation and stress.The deformation of surrounding rock and initial support structure has great influence on the deformation process.When the distance between the left and the right line is 5m,the deformation process of the tunnel is fluctuating,which is caused by the interaction between the left and the right holes.With the increase of the distance between the left and right lines,such as 15 m and 25 m,the deformation curve of the key points of the tunnel is not fluctuating,and the interaction between the left and the right holes is very small.(4)By comparing the simulation results with field monitoring measurement data,the tunnel deformation trend approximation,to demonstrate the validity of the numerical simulation research.In the recommended flow of road tunnel design and construction method,the tunnel hole in advance and subsequent hole vault subsidence,horizontal convergence,the accumulative deformation does not exceed the standard rules allow deformation,the large road tunnel design and construction scheme is feasible.(5)Through the above research conclusion,flow of Yuzhong district in Chongqing road screw the specific guidance significance to the design and construction of the tunnel. |
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