粉细砂地层隧洞初期支护沉降变形侵限处理

Treatment of Invading the Boundary due to the Settlement Deformation of the Tunnel Initial Support in the Fine Sand Formation

粉细砂地层隧洞在地下水条件下的开挖施工,极易发生因洞底基础软化导致的隧洞初期支护整体沉降变形,造成隧洞初支侵限衬砌断面等问题,在这种恶劣地质条件下的隧洞初支拆换,施工难度大、安全隐患高。山西省小浪底引黄工程2#隧洞土洞段,在粉细砂地层初期支护沉降变形洞段采取隧洞基底加固、拱部超前密排管棚加固等措施,并结合隧洞变形监测数据,对初支侵限洞段进行换拱处理。该措施保证了隧洞换拱施工的安全进行,可为同类隧洞工程变形侵限处理提供参考。

In the excavation of the tunnel under the condition of underground water,the overall settlement deformation of tunnel initial support is easily caused by the softening of tunnel bottom foundation.lt will cause some problems,for example,the location of the tunnel initial support invades the boundary of the lining section.It is difficult to disassemble and replace the initial support of the tunnel under such harsh geological conditions,and the safety hidden danger is high.On the soil tunnel section of No.2 tunnel of Xiaolangdi Diversion Project in Shanxi Province,the measures such as tunnel basement reinforcement and advance densed-pipe shed reinforcement at the arch are introduced in the initial support and settlement deformation section of fine sand stratum.In combination with tunnel deformation monitoring data,the treatment of arch replacement for the initial support invading the boundary tunnel section is conducted.This measure ensures the safety of tunnel arch replacement construction and can provide reference for the treatment of deformation invasion boundary of similar tunnel projects.