Study On Space Effect,influence And Control For Surrounding Rock Deformation During The Tunnel Construction Underpassing

With the improvement of transportation infrastructure, due to the terrain and topography of space be limited, overlap or cross each other between highway problem constantly emerging, causing through both building of tunnel construction appears many difficulties and problems. For this complicated conditions type of tunnel, In order to put forward more reasonable support form, the designers urgently need to be aware of surrounding rock deformation and the subgrade layers regular of change with the constraints advancing process. On-site construction personnel need to use a part of the surrounding rock deformation of field monitoring to predict final deformation of surrounding rock. Longitudinal deformation profile and ground response profile of tunnel are important part of the convergence-confinement method. However, under the condition of hydrostatic pressure, discussing the middle principal stress and loss factor Λ which considering the effect of constraints space constraints impact surrounding rock characteristic curve of circular tunnel and analysis curve of LDP rule in the tunnel of weak surrounding rock, putting forward the concrete methods of how to effectively control surrounding rock’s stability, which are all still need to further research.Therefore, in this paper, through combination the way of theoretical analysis, field measurement data analysis and numerical simulation to study on space effect,influence and control for surrounding rock deformation during the tunnel construction underpassing. Firstly, based on unified strength theory, considering the constraint loss factor Λ the influence on space effect of tunnel face.In order to get the theoretical solution of stress and displacement of surrounding rock of circular tunnel in the hydrostatic pressure and plane strain problem which are based on the unified strength criterion and considering constraint loss factor Λ. Clarifying relationship between displacement release coefficient λ and constraint loss factor Λ. It is effective ground response profile to analysis parameter b which considering the intermediate principal stress and constraint loss factor Λ. Then, the tunnel of 324 National line through under Shen Hai highway is regarded as an engineering background. Through combination the way of field monitoring and the finite element software ABAQUS of numerical simulation, It analyzes how LDP curve is changing in the process of tunnel construction. And then, to further analyze how LDP curve is changing, the different measures of reinforcement on surrounding rock in front of tunnel face, different ways of tunnel excavation and different car load by ABAQUS software simulation are taken as analysis. Finally, combination with the above the study on practical engineering tunnel, putting forward the specific measures on how to control the deformation of surrounding rock and analyze how to control the effect. The results of this study to improve the convergence constraint method, to understand the law of tunnel surrounding rock deformation and to guide control surrounding rock deformation is great significance.The main research results are as follows:(1)When tunnel in the elastic deformation stage, it has nothing to change ground response profile with parameter b. When the tunnel in the stage of plastic deformation, with the increase of parameter b, the slope of ground response profile is increased. Considering constraint loss factor Λ calculate the maximum radial displacement of surrounding rock mass UR,max less than not, 22.24%,and the smaller the radial displacement value of surrounding rock under the same σR/σ0.(2)By actual monitoring data analysis,in front of the double hole diameter of constraints location, surrounding rock start to be disturbed and appear deformation; in behind of the double hole diameter of constraints location, surrounding rock is disturbed obviously, at the same time, this area is also affected by the constraints of space effect obviously.(3)To establish three-dimensional finite element model of the tunnel construction, surrounding rock deformation, on the whole, moving towards airport surface after tunnel excavation release stress. Space effect distance about before and after constraints [-1.5D,2.0D] through the key position of surrounding rock deformation and displacement release coefficient λ of change curve. Among them, Slow growth zone of surrounding rock deformation during the before and after constraints [-1.5D,-0.74D]; The deformation of surrounding rock increase sharply during the before and after constraints [-0.74 D,1.0D]; The deformation tends to be stable after constraints 2.0 D.(4)Forepole wall rock area,the longer distance constraints began excavation after grouting, the tunnel vault subsidence, hance horizontal convergence displacement is smaller, but not influence on displacement release coefficient λ of surrounding rock. When simulating the effect of reinforcement measures in advance which using the equivalent thickness of wall rock circle, with the greater the equivalent thickness of wall rock circle, the maximum vault subsidence of tunnel exponentially appears decreasing trend and maximum horizontal displacement of hance appears linear decrease trend.(5)The excavation footage speed of pilot tunnel make little effect on disturbance of surrounding rock in front of the constraints, but it make a big difference on that in back of constraints. Tunnel excavation, using pilot tunnel method get displacement release coefficient λ of the vault subsidence,is smaller than using the whole section method in the range of Z < 11 m, and when Z = 0 m, it reached 23.7%; Within the range of the Z > 11 m, it is bigger than excavation by whole section method. Tunnel excavation, using pilot tunnel method get displacement release coefficient λ of hance level convergence,is smaller than using the whole section method in the whole process of tunnel excavation, and when Z = 0 m, it reached 42.9%.(6)When car loading on Shenhai high way above tunnel is calculated by pseudo static method, car loading make effect on vault subsidence, and it also make effect on Hance horizontal displacement of surrounding rock in back of the tunnel constraints.(7)The wall rock reinforcement measures choice in front of constraints should mainly consider increase the equivalent thickness of reinforcing ring;Tunnel excavation method choice should first consider the effect of excavation area.