Ⅳ级围岩隧道两台阶法开挖进尺研究

以吉图珲高铁富岩1号隧道为工程实例,运用有限元分析方法对不同开挖循环进尺下的隧道两台阶法进行数值模拟,对比分析不同工况下隧道变形和应力的响应规律,得出工程适用的开挖循环进尺。研究结果表明:开挖进尺对围岩变形影响较大,两者呈线性正相关关系;在Ⅳ级较差围岩条件下,拱顶受拉破坏先于拱腰和掌子面的受剪破坏,拱顶掌子面后方1 m处第一主应力达到最大值;随着开挖进尺的增大,拱顶第一主应力和拱腰、掌子面处D-P值均增大,隧道更易发生破坏;Ⅳ级较差围岩,开挖进尺建议取2.0 m,Ⅳ级偏好围岩开挖进尺可增大至4 m。

Research on Excavation Footage of Tunnels in Ⅳ Rock with Two-bench Construction Method

Based on No. 1 Fuyan tunnel on Jituhui high-speed rail,the finite element method is applied to numerically simulate the tunneling with two-bench construction method in different excavation cyclical footage. Tunnel deformation and response regularity of stress are comparatively analyzed to obtain excavation cyclical footage suitable for engineering. The research results show that excavation footage poses greater impact on the surrounding rock,which is in a linear and positive correlation with excavation footage; in the case of poor Ⅳrock,tension-destroying in vault occurs before shear-destroying in haunch and driving face and the maximum first main stress is located 1m behind the driving face in vault; with the increase of excavation footage,the first main stress in vault and DP value in haunchand driving face are increased,making the tunnel more vulnerable to damage; the excavation footage in poor Ⅳ rock is recommended to be 2 m,while the value may rise to 4 m in good Ⅳ rock.