| In this paper,based on the strength reduction method,the influence of the excavation side of the tunnel under different structural integrity,different surrounding rock level,different tunnel section,different overburden load and different initial burial depth is calculated and analyzed.The main conclusions are as follows:(1)Based on the strength reduction method,the stability of the surrounding rock is analyzed by means of Flac3D finite element software and the displacement mutation is used as the criterion of tunnel instability.The safety factor is 1.35.(2)Witih the increase of the degree of tunnel deterioration,the safety factor is decreasing as a whole under different structural soundness.When the depth is shallow,the safety factor of the tunnel is greatly influenced by the structural soundness.With the increase of the buried depth,the influence of the structural soundness is getting smaller and smaller,and the overall safety factor is decreasing.When the structural soundness is higher than that of the surrounding rock,the safety factor decreases with the increase of the buried depth,and the safety factor increases first and then decreases with the increase of the buried depth.Under different surrounding rock grade and different tunnel sections,the calculated safety factor of tunnels is basically the same as law of different structures soundness.(3)Under the different overburden load,with the increase of the overburden load,the safety factor as a whole showed a decreasing trend.When the depth is shallow,the safety factor of the tunnel is greatly influenced by the overburden load.With the increase of the buried depth,the influence of the overburden load is getting smaller and smaller,and the overall safety factor increases first and then decreases.When the structural soundness is higher than that of the surrounding rock,the safety factor decreases with the increase of the burial depth,and the safety factor increases first and then decreases with the increase of the buried depth.The peak size of the safety factor is related to the overburden load.The larger the overburden load,the greater the buried depth of the safety factor.(4)At different initial burial depths,with the increase of the initial burial depth,the safety factor of the tunnels is decreasing as a whole.When the depth is shallow,the safety factor of the tunnel is greatly affected by the initial depth.With the increase of the buried depth,the influence of the initial burial depth is getting smaller and smaller,When the filling height is not more than 10m and the initial burial depth is more than 40m,it can be considered that the initial burial depth has no effect on the tunnel structure.When the depth is more than 80m,the filling height can be considered to have no effect on the tunnel structure.When the excavation height is not more than 10m and the initial burial depth is more than 50m,it can be considered that the initial burial depth has no effect on the tunnel structure.(5)The influence zoning standards of the filling and excavation above the tunnel is given,and the demarcation values of the influence zoning are given at the different surrounding rock grade,different structural soundness,different overburden load,different tunnel sections.It is proved that the method of partitioning is reasonable by analyzing the horizontal convergence,orbital settlement and structural stress data of the cross section of the Wenxiang tunnel and the Hanguguan tunnel. |
