Study On Stress Deformation And Ground Characteristic Curve Of Non-rotational Symmetry Tunnel

The surrounding rock is in an elastic state under the initial stress state,and the surrounding rock will loosen or plastically deform after excavation.Therefore,it is of great significance to study rock stress and deformation for tunnels with weak surrounding rocks or large buried depths.Most of the existing surrounding rock stress and deformation and surrounding rock characteristic curve analysis are established for strict axisymmetric conditions,without considering the non-rotational symmetry conditions of actual tunnels.Based on this,this article uses the Huangfeng Tunnel as the engineering background,and adopts a research method combining field monitoring,numerical calculation and theoretical analysis.A systematic study was carried out on the stress and deformation of surrounding rock and the characteristic curve of surrounding rock during the construction of non-rotational symmetry tunnels.The main research contents and conclusions are as follows:(1)Research on site monitoring during construction of non-rotational symmetry tunnel.On-site monitoring data showed that the maximum surface settlement displacement at the entrance of the cave was 20 mm,and the settlement displacement gradually stabilized after 3 months of excavation;the symmetrical position convergence displacement survey line of the tunnel section tends to be stable,and there is an unequal phenomenon,and the symmetrical position convergence displacement 2-1 survey line and 2-3 survey line have a maximum difference of 29.17%,and the symmetrical position convergence displacement 2-4 survey line and 2 The maximum difference of-5 survey line is 44.00%.It shows that the convergence displacement of the symmetrical position is not equal,that,the phenomenon of non-rotational symmetry appears.(2)Numerical simulation research on construction process of non-rotational symmetry tunnel.Analyzing the effects of different surface slope angles and different buried depths of tunnels on the stress and deformation of the non-axisymmetric tunnel construction process,the results show that the stress and displacement at the symmetrical position are not equal.The non-axisymmetric stress ratios at the arch shoulder,arch wall,and arch foot under different surface slope angles and different tunnel depths are not equal to 1.With the change of buried depth,the displacement of the symmetrical position convergence survey line is not consistent.When the buried depth is less than 10 m,the maximum convergence displacement of the symmetrical position 2-1 and 2-3 survey line differs by 11.60%,and when the buried depth is greater than 10 m,the symmetrical position 2-There is a 59.84% difference between the maximum convergent displacement of the 1 and 2-3 survey lines;the maximum convergent displacement of the symmetrical position 2-4 and the 2-5 survey lines differs by 73.67%.Numerical simulation results show that the stress and deformation of the surrounding rock of the tunnel are non-axisymmetrical.(3)Research on tunnel stress deformation and surrounding rock characteristic curve based on unified strength theory.According to the unified strength theory and nonassociated flow law,considering the lateral pressure coefficient,the intermediate principal stress of the surrounding rock,the tunnel azimuth angle,the dilatancy characteristics of the surrounding rock,the elastic modulus of the plastic zone and the elastic strain of the plastic zone,a non-axisymmetric tunnel is established.Analytical solution of rock stress and deformation and surrounding rock characteristic curve.Through the analysis of engineering examples,the influence of factors such as lateral pressure coefficient,intermediate principal stress effect parameter,tunnel azimuth angle,and dilatancy characteristic parameters on the stress and deformation of surrounding rock of nonaxisymmetric tunnel and the solution of surrounding rock characteristic curve are discussed.The results show that with the increase of the intermediate principal stress effect parameter b,the circumferential tensile stress of the plastic zone gradually decreases,the radial pressure gradually increases,the range of the plastic zone gradually decreases,and the displacement of the plastic zone and the characteristic curve of the surrounding rock gradually shift to the left to the maximum The displacement of the cave wall gradually decreases;As the lateral pressure coefficient λ increases,the circumferential tensile stress in the plastic zone gradually decreases,and the radial stress gradually increases;when λ<1,the vertical plastic zone gradually shrinks,and the plastic zone displacement and surrounding rock characteristic curve shift to the left,When λ>1,the plastic zone in the horizontal direction gradually shrinks,the displacement of the plastic zone moves to the right,and the surrounding rock characteristic curve moves to the left;As the dilatancy parameter β increases,the plastic zone displacement moves upward,the surrounding rock characteristic curve moves to the right,and the maximum cave wall displacement increases.Comparing the stress and deformation results of on-site monitoring,numerical calculation,and theoretical analysis,there is a non-axis symmetry.The research results can provide reference and reference for the support design and construction of non-rotational symmetry tunnels.