Displacement Back Analysis of Shallow Double-Arch Tunnel and Its Numerical Simulation of Construction Process

According to the real condition of Jie Pai Ao tunnel on the Huaihua-Xinhuang Highway,using test points' displacement of the field loading test,the tunnel crushed zone rock mass parameters were inversely computed out by the FEM inverse theory's simulated annealing approach in this paper.Jie Pai Ao tunnel construction steps' 2D elastic-plastic FEM computation model was set up by using these surrounding rock mass parameters.The stress and strain of surrounding rock and middle wall have been studied when the tunnel was constructed by the three-pilot drift construction method.The results indicate that the constructions of the two main tunnels' arch rock mass are the two key steps during the double-arch tunnel construction process.The displacement of two tunnels' vault rock mass and the plastic strain of the right tunnel's left spandrel rock mass are very big,which may cause the landslip or destruction of tunnel.For the bias of mountain body and the asymmetric construction of tunnel,the middle wall was at basically eccentric compressive state during the whole tunnel construction.