超大跨度小净距公路隧道洞口段施工方案

Research on Construction Scheme of Portal Section of Highway Tunnel with Super Long Span and Small Spacing

以老虎山隧道为实例,对超大跨度公路隧道洞口小净距段的施工方案进行研究。结果表明:洞口段超前大管棚进洞和掌子面超前小导管加固措施能够控制围岩变形,减少对中岩柱的影响;控制左、右线先导洞掌子面之间的施工间距,并对中岩柱水平注浆小导管加固,可有效提高中岩柱的整体性与稳定性;初期支护阶段拱部最大变形量为28 mm,远小于设计预留变形量,状态稳定。

Based on the practice of Tiger Mountain Tunnel,the construction scheme of portal section of highway tunnel with super long span and small spacing was studied.The results show that in the portal section,the reinforcement measures of leading steel pipeline shed and leading conduit were adopted to strictly control the surrounding rock deformation,which was beneficial to reduce the influence of construction on the middle rock pillar.The process of construction strictly controlled the spacing between the left and right line pilot holes,meanwhile,reinforcement measures were applied to the horizontal grouted pipe so as to effectively improve the integrity and stability of the middle rock pillar.In the initial support stage,the maximum deformation of the arch was 28 mm,which was much smaller than the designed value of 200 mm,and the surrounding rock was in a stable state.