以软岩单线铁路隧道为工程背景，采用三维数值手段对常规台阶法、扩大拱脚台阶法和预留核心土台阶法等典型工法的施工空间效应进行动态模拟。计算结果表明：对于软岩隧道，当采用常规台阶法施工时，加强上台阶围岩支护效果对大变形控制至关重要；在台阶法开挖过程中掌子面挤出变形明显，掌子面的稳定性不容忽视，而预留核心土在控制掌子面变形、确保掌子面稳定方面有明显的作用；扩大拱脚支护形式与标准断面相比更有利于控制隧道收敛变形和塑性区的发展。综合分析结果认为：兰渝铁路软岩单线隧道采用扩大拱脚支护形式结合预留核心土的台阶法更有利于控制变形和确保洞室稳定。

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.