探讨Ⅴ类围岩安全挂口进洞的施工措施

如何安全进洞是洞室正常施工的前提，也是隧洞施工的关键。选择隧洞进口的原则为“围岩完整、覆盖层厚度适当、地形合理”，但有些隧洞进口是根据施工布置进行的，局部范围调整仍无法避开不利地域时，就应考虑如何安全进洞。本文介绍了四川木里河上通坝水电站导流隧洞进、出口和引水隧洞（约22km）8个支洞口的安全进洞施工，提出一些经实践证明可行的施工技术，以供同类项目参考和借鉴。

Discussion on Construction Measures of Category V Surrounding Rock Safety Hanging Port Hole Stepping

Safe hole stepping is the premise for normal construction of chamber,and it is critical for tunnel construction. Tunnel hole stepping principles should be‘complete surrounding rock,rational thickness of coverage thickness and rational landform’.However,some tunnel ports are constructed according to construction layout.Adverse region cannot be avoided by local scope adjustment.Safe hole stepping should be considered.Safe hole stepping construction of eight branch caves, including inlet,outlet and water diversion tunnels （about 22km）in Tongba hydropower station of Sichuan Muli River,are introduced in the paper.Some construction techniques which are feasible in practice proof are proposed,thereby providing reference for similar projects.