Study On Construction Stability Of Open Excavation Tunnel

At present,China is a big country in tunnel construction.The tunnel construction method has the open excavation method,the undermining excavation method and so on.The open excavation method is often used in tunnel construction.The key to the construction of open cut tunnel is to ensure the stability of the foundation pit,and the instability of foundation pit will cause unnecessary casualties and property loss.In this paper,based on the construction of the tunnel excavation,the stability of the open cut tunnel is studied.Specific research results are as follows:(1)In this paper,the ratio of the safety factor in the stability analysis of the foundation pit is compared by the method of the slice circular slip surface of the limit equilibrium principle and the finite element strength reduction method.The safety factor of the foundation pit calculated by the method of circular slip surface is generally less than the result obtained by strength reduction method.The method of circular slip surface in engineering measures is safe and not very economical.(2)Based on the theory of limit equilibrium of mechanics,the method of circular sliding surface is adopted and different slope ratio is adopted.It is proved that the design of tunnel foundation pit of the MingZhu tunnel is reasonable.(3)Relying on the MingZhu tunnel project,the construction simulation is carried out by using the finite element strength reduction method.The safety factor of the tunnel is greater than 1 during the whole construction process,and the tunnel foundation pit is stable.Through the analysis of tunnel excavation stability under multiple load analysis shows that with the increase of excavation depth,the safety factor of foundation pit will be reduced,and the stability of foundation pit will be worse;with the decrease of excavation slope,the safety factor of foundation pit increases;safety factor as the foundation pit surrounding rock cohesion and friction angle increased;the safety coefficient of the seepage of water will greatly reduce the foundation,reduce the stability of foundation pit.(4)By analyzing the construction technology of the MingZhu tunnel,the construction technology of enclosure and support system for excavation of open pit tunnel under complex environment is put forward.Combined with the experience of support project,the monitoring of retaining structure should be strengthened in the construction of open cut tunnel,and the drainage inside and outside the foundation pit should be strengthened to ensure the construction quality of the retaining structure of the foundation pit so as to ensure the safety and stability of the construction.(5)According to the monitoring results of the MingZhu tunnel and comparing the numerical analysis results,it proves the stability of the MingZhu tunnel in the foundation pit construction process.Based on the background of the MingZhu tunnel project,this paper summarizes the deformation law of the tunnel.By means of finite element analysis,the construction process of the MingZhu tunnel is verified.There are many factors influencing the stability of foundation pit.The influences of excavation depth,excavation slope,strength of surrounding rock and seepage on the stability of foundation pit are analyzed.