大断面黄土隧道台阶法施工数值模拟研究

针对新建忻州隧道工程，运用有限元通用软件ANSYS，对大断面黄土隧道采用台阶法施工的过程进行数值模拟，探讨了采用台阶法施工隧道的围岩、初期支护及二次衬砌应力场和位移场随施工步的变化规律。在此基础上，研究了隧道初期支护、二次衬砌的支护效果以及隧道开挖对已施作初期支护受力及变形的影响。结果表明:①隧道施作初支有利于降低地层压应力，减小隧道变形；施作二衬能有效降低地层和初支的主应力，对隧道变形影响不大；②隧道的进一步开挖将导致已施作初支的压应力及位移值增大，使初支处于更危险的状态。

Numerical Simulation Study on Bench Cut Construction Method in Large Section Loess Tunnel

The numerical simulation on the process of tunnel construction by bench cut method in large section loess tunnel is conducted by adopting the general finite element software ANSYS based on the newly-built Xinzhou Tunnel Project. The change rule with the step increment of stress field and displacement field in surrounding rock, primary supporting and secondary lining is explored on the basis of bench cut method in this paper. Furthermore, the support effect of primary supporting and secondary lining and the influence of tunnel excavation on the force and deformation of constructed primary supporting is studied. The results are as follows:①The construction of primary supporting can reduce the compressive stress in stratum and the tunnel deformation; The construction of secondary lining can effectively reduce the principal stress in stratum and primary supporting, but has little influence on tunnel deformation. ②The further excavation of tunnel can increase the compressive stress and displacement in constructed primary supporting, which makes the primary supporting more susceptible to be damaged.