Study On The Mechanical Properties For Construction Of Asymmetric Neighborhood Tunnel In Water Rich Weathered Stratum

In the design of asymmetric neighborhood tunnel,the deep and shallow buried boundaries of the tunnel are the main basis for calculating the vertical load of the surrounding rock.The classification of asymmetric neighborhood tunnel can provide an important reference for the selection of retaining structure and the timing of the support structure.However,at present,there is no mature theory and relevant specifications for reference.In addition,with the construction of a large number of underwater tunnels,submarine tunnels and the underground railways built in water rich stratum,the seepage analysis,the fluid solid coupling analysis and the reinforcement technology of the bad strata are still to be studied.Firstly,based on the theory of collapse arch and plastic zone analysis,this paper makes a judgment on the depth and shallow burial of asymmetric neighborhood tunnel.It is determined the minimum net distance that the influence of asymmetric neighborhood tunnel is serious and should be avoided.Besides,based on the theoretical analysis of the law of strain energy density conversion,the simplified calculation formula of strain energy density and the classification of asymmetric small clearance tunnel are given.Secondly,through the numerical simulation of the finite element method,the deformation and stress of the initial support of the tunnel at different levels of the surrounding rock and the different excavation methods are studied,and the optimal construction method and the construction order of the left and right tunnel are put forward.The effects of grouting reinforcement and prestressed anchor on the stability of middle rock wall are studied,as well as the range of different grouting reinforcement,the layout of prestressed anchor and the main applicable conditions of various reinforcement methods.Thirdly,the steady state of seepage field after the excavation of the tunnel under the rainfall condition and the natural water surface is simulated and the change of seepage field after tunnel excavation is studied by the two-dimensional seepage analysis.The water inflow in the tunnel is calculated by theoretical formula and numerical simulation.Based on the analysis of fluid-solid coupling,the stress field and displacement field of the soil in front of the tunnel face were studied,and the influence of the tunnel face seepage on the stability of the tunnel face was studied by the Coulomb failure criterion.Finally,based on the principle of soil penetration and the constitutive modal of Bingham fluid,the diffusion model of viscous slurry in porous media at constant grouting rate was established.The spatial and temporal distribution equations of the diffusion pressure field and seepage field of the rock fracture in the two models are derived to study the diffusion process of viscous slurry in rock fracture and compared with the numerical results.Through the theoretical analysis and numerical simulation,the grouting pressure,grouting radius,porosity and permeability of different grouting speed at different times were studied,and the change law after fluid-solid coupling was considered.