Study On Inversion Of Mechanical Parameters And Stability Prediction Of Surrounding Rock In Subway Tunnel

With the accelerating pace of modernization of the city, traffic congestion has attracted people's attention. Qingdao City is no exception,narrow road, vehicles are now facing problems of Qingdao traffic. So the development of underground traffic was put on the agenda. Construction of urban underground rail can ease congestion problems on the ground to a large extent, and can reduce the city noise pollution, urban appearance,and so on. The construction of a large number of subway tunnels has put forward higher requirements for its stability and the ability to analyze and predict the properties of surrounding rock. Based on the finite element strength reduction method and mechanical parameters inversion of surrounding rock, the stability of the surrounding rock is analyzed and forecasted, research contents are as follows:(1) Firstly, compares the computational advantages of the finite element strength reduction method, and the method is used to study the stability of surrounding rock of shallow buried subway tunnel in Qingdao. The failure mechanism of surrounding rock of shallow buried double-track tunnel is analyzed and the finite element software ANSYS is used to establish the three-dimensional numerical model. The development of plastic zone and the location of the damaged surface are simulated. The results show that the damage of the shallow tunnel is beginning with the arch of the middle rock mass of the two tunnels, and the stress of the vault is small, and the plastic zone of the middle rock mass is broken. The maximum point of plastic strain is the failure surface of the surrounding rock.(2) The reliability of the stability conclusion is verified by considering the factors. Considering the influences of different tunnel depth, different two-lane tunnel spacing on the tunnel stability, this paper analyzes the variation law of the surrounding rock safety factor under the condition of different burial depth and different surrounding rock types.The sensitivity of tunnel stability to the mechanical parameters of surrounding rock is studied, and a series of important conclusions are obtained.(3) An improved method for calculating the mechanical parameters of surrounding rock by combining the minimum safety factor method and the relative displacement method is presented. And the feasibility of the improved method in reversing the mechanical parameters is verified.Taking the Qingdao subway tunnel project as the background,the new method is used to invert the mechanical parameters of the surrounding rock of Qingdao subway tunnel, and the accuracy of the calculation parameters is verified.Finally, in this paper, based on the improved inversion method,mechanical parameters of surrounding rock is calculated. The stability of the surrounding rock of the tunnel to be excavated in Qingdao is analyzed and forecasted based on the finite element numerical simulation.The prediction conclusion provides the basis for the safe construction of the subway tunnel.