金川水电站导流洞碳质千枚岩洞段施工技术

Construction Technology of Carbonaceous Phyllite Section in Diversion Tunnel of Jinchuan Hydropower Station

金川水电站导流洞碳质千枚岩分布洞段属于Ⅳ2类围岩,具有膨胀性和遇水软化、强度显著降低的特性,开挖施工松动圈快速扩展,自稳时间短。根据碳质千枚岩的工程特性,通过施工方案研究和现场试验,提出碳质千枚岩洞段采用保留核心土法施工,分层分部开挖施工方法,并采取超前小导管、钢拱架以及挂网、系统锚喷等支护措施,顺利完成千枚岩洞段施工。

The distribution of carbonaceous phyllite in the diversion tunnel of Jinchuan hydropower station belongs to class IV2 surrounding rock,which has the characteristics of expansibility,softening with water and significant reduction of strength.The loose zone of excavation construction expands rapidly and the self-stabilization time is short.According to the engineering characteristics of carbonaceous phyllite,construction scheme and field test have been studied.This paper puts forward the construction method of retaining core soil method,layered and partial excavation construction method.The supporting measures such as leading small pipe,steel arch frame,hanging net,system anchor and shotcrete,have been adopted.As a result,the construction of carbonaceous phyllite tunnel section has been successfully accomplished.