Study On The Stability Of Tunnel By Adjacent Foundation Excavation And Jointed Fractured Rock

With the development of the city and country economy,convenient transportation plays an increasingly important role in the national economy.More and more crowded cities gradually turn to the ground to improve traffic condition.As the city excavation of foundation pit engineering environment become more complex,they often close to the existing subway tunnels underground.The excavation of foundation pit often make a certain adverse effects to the tunnel and constantly extending high-speed rail lines will inevitably pass through more tunnels in adverse geological conditions.So study the stability of tunnel by adjacent foundation excavation and jointed fractured rock has a very important significance in the practice of associated works.To solve the two complex engineering practices,this paper combines the method of theoretical analysis,numerical simulation and monitoring data to analyze the stability of the Tunnel affected by the near foundation pit and jointed fractured rock.This dissertation first relies on the deep foundation pit engineering of Central Plaza in Shenyang,through the finite element software Phase² to explore the influence of deep foundation pit parameters and supporting methods on existing subway tunnels.Sensitivity analysis is also performed concerning excavation depth,distance between the existed tunnel and pit,and the spacing between the two rows of piles.The results show that the double-row pile with bolts is more effective than the double-row pile in controlling the deformation of the supporting structure and surrounding soil,and succeed in limiting the displacement of the soil in the range of 3m away from the existed tunnel within 5mm.On the other hand,the excavation depth has the greatest influence on the horizontal deformation of the tunnel,the spacing between the foundation pit and the tunnel is the second,and the spacing of the double row pile is the least.Secondly,this paper takes the Guanshan tunnel as an example to discuss the numerical simulation method of the mountain tunnel in deep,high crustal stress and jointed conditions.Based on this simulation method,the effectiveness of the different excavation and supporting method is judged.Furthermore,the influence of Joint Roughness on surrounding rock deformation is studied.The results show that,the joint network finite element method can reflect the weakening effect of the joint on rock strength well.In jointed rock mass,the bench method has lost the original advantage over the full face excavation method,which induced the closed structure plane open under multi-disturbance.The maximum vertical settlement of the tunnel decreases with the increase of the roughness.When J_RC <12,the maximum settlement of the tunnel varies increased slowly with the increase of J_RC.While the maximum settlement drastically reduced with the increase of J_RC value when lower than 12.The horizontal convergence value is linearly decreasing with the increase of joint roughness.The research results of this dissertation are of great significance to ensure the safe construction of tunnels and improve the accuracy of numerical simulations,and can also provide reference for similar projects.