Mechanical Analysis Of Excavation Problem Of Semi-infinite Plane Double/Porous Tunnel

Due to the influence of route selection,topography,hydrogeology and other conditions,subway tunnels are generally arranged in the form of double/porous tunnels.The disturbance of adjacent construction of double/porous tunnels on surrounding rock is much greater than that of single tunnel,which may cause large deformation of surrounding rock and even cause surface subsidence.In this paper,based on the previous studies,the complex variable function combined with Schwarz replacement method is proposed to solve the semi-analytical solution of the three-hole tunnel under uniform load,the semi-analytical solution of the shallow double-hole tunnel considering the weight of the soil layer and the grouting pressure,and the semi-analytical solution of the non-uniform deformation around the cavern under the displacement boundary condition of the double-line tunnel.The computer programming language MATLAB is used to solve the calculation.Finally,the displacement and stress solutions of the surrounding rock under different boundary conditions are obtained.The feasibility of the theoretical calculation is verified by engineering examples,experimental data and numerical simulation.The main research contents and results are as follows:(1)The complex variable function solution of the excavation mechanics problem of shallow three-hole tunnel is solved by using the complex variable function and the replacement method.The final solution is obtained by computer programming.The calculated value is compared with the centrifugal test,numerical simulation and field measured value to verify the feasibility of the calculation method.Finally,the contour map of stratum displacement produced by shallow-buried three-hole tunnel construction under different arrangement modes is obtained by using this method.(2)According to the actual construction process of shallow-buried shield tunnel,the surrounding unbalanced force and its distribution caused by tunnel excavation under the action of surrounding rock self-weight stress field are calculated,and the influence of shield tail grouting pressure is also considered.Under the two stress boundary conditions,the complex function and alternative method are used to solve the elastic solution of the double-hole shield tunnel excavation problem under arbitrary arrangement.The semi-analytical solution of the double-hole shield tunnel is obtained by computer programming.The numerical simulation and specific engineering examples verify the feasibility of the theoretical calculation method.Finally,using the above theoretical methods,the differences of ground deformation under different buried depth,spacing and arrangement of double-hole tunnels are discussed.(3)Considering the interaction between two-hole tunnels,combined with the actual convergence deformation mode of two-hole tunnels,the complex variable function expression of tunnel horizontal deformation is derived,and the influence of different tunnel convergence deformation(such as radial shrinkage and elliptical deformation)on ground displacement is further discussed.Finally,based on Park’s four single-hole convergence deformation boundary conditions,the surface deformation distribution of double-hole tunnels with different deformation boundaries under different horizontal deformations is studied.