Abstract:

The deformation effects of singletrack tunnels in soft ground constructed by traditional "top heading and bench" method, "archfeetwidened top heading and bench" method and "core soil top heading and bench" method are simulated by 3D numerical simulation methods. The following conclusion is drawn from the simulation: in case of tunnels in soft ground constructed by traditional "top heading and bench" method, the heavy reinforcement of the top heading is essential to the control of the large deformation; the extrusion deformation of the tunnel face is obvious in "top heading and bench" method, the stability of the tunnel face can not be ignored and the core soil is essential to the control of the tunnel face deformation and to the stability of the tunnel face; compared to the traditional "top heading and bench" method, the reinforcement by widened arch feet is more favorable to the convergence control and plastic zone development of the tunnel. The final conclusion drawn is that, for the singletrack tunnels in soft ground on LanzhouChongqing railway, top heading and bench method with widened arch feet and core soil is more faborable to the deformation control and tunnel stability.

Key words: singletrack tunnel in soft ground, "top heading and bench", method, widened arch feet, core soil, numerical analysis