Three-dimensional Numerical Simulation Research Of Excavation Of Large-scale Hydropower Tunnel

With the development of huge-capacity units of hydroelectric power stations and large-scale tunnels in China, the issues of the large section tunnels render a challenge for "underground workers". As a key part of the station, tunnel plays a particularly important role for diversion and flood-discharge. However, there are few research results of large section tunnels both at home and abroad, hence the corresponding construction experience is few to reference, as a matter of which, at present large-span tunnels are constructed with a certain degree of blindness. Through the analysis of excavation process and methods of large-scale tunnels, the distribution of the displacement field of large-scale tunnels can be obtained. And the analysis results have a significant importance in ensuring the construction safety and accelerating the construction speed.In this paper, a specific hydropower diversion tunnel is taken as a reference. The geometrical models of the tunnel are established. And the ANSYS software is employed to simulate the excavation process. The excavation methods of large-scale tunnels are analyzed according to the calculation results under different operating conditions. The specific works completed in this paper are as following:Firstly, according to the actual geological conditions and the cross section size of the selected diversion tunnel, three-dimensional geometric models of the tunnel excavation and tunnel rock mass are established, and the mesh of the models are generated.Secondly, ANSYS software is used in setting boundaries around the tunnels, selecting parameters, selecting calculation solvers, and so on. Boundary conditions of the meshed models are set, and calculation is started.Thirdly, the numerical calculation of the excavation process of tunnels is conducted. Through post-processing of the convergence results, vertical and horizontal displacement fields and displacement contours of rock mass during tunnel excavation under different conditions are obtained. And the changes of displacement under different conditions are analyzed.Finally, by comparing and analyzing the characteristics of tunnel excavation under different working conditions, the convergence change information of key parts of the tunnel is obtained, thus the rational construction method is selected.