Research On Surrounding Rock Long-lasting Stability Of Non-symmetric Double-arch Tunnel In The Complicated Geological Condition

With the development of expressway, a great number of highway tunnels have been constructed or under construction, and, it is difficult to avoid the bad environment, such as soft rock, joint, crack and soft interlayer; the new supporting theory is proposed along with "NATM" applied widely, so the old design theory can't meet present engineering; more double arch tunnels are constructed due to their particular advantages, however, the works are complex and disturbed each other. Especially, it is difficult to construct unsymmetrical double-arch tunnels, with their applied stress complex and variational.Based on the problems above-mentioned, the thesis set the research subject of the rock mass time-dependency of non-symmetric double-arch tunnel and performed a creative research on analysis and back-analysis. At first, on the basis of that the data is dealt with and analyzed, the appropriate viscoplasticity model is selected; then, the complex conformal transformation is used to map the considered region in the physical plane onto a circular ring region in the image plane, and the displacement analytical method of rock mass is drawed; the next, work out GA program in real coding, and works on the program to inverse the mechanical parameters; at last, simulate the practical tunnel by using Flac, and the result is as like as the result than gets from monitoring measurement in site. It shows that the research in the paper is rational. Through analyzing stress performance of the tunnel and rock mass during the tunnel construction, optimizing supporting opportunity of secondary lining and analyzing long-lasting stability of rock mass, the result indicates that viscoplasticity performance must be considered for soft rock mass, which affects the stress performance and stability of the tunnel in a great extent.