隔河岩水利枢纽地下洞室施工的几个重大技术措施

Technical measures of underground opening construction for Geheyan Project

隔河岩水利枢纽电站引水隧洞群洞间距约一倍开挖洞径，后挖洞室爆破与已挖洞室混凝土衬砌施工互相制约，设计提出先挖导调后扩挖、全面锚喷、勤量测的优化方案，解决了施工期的安全问题，保证了工程质量与工期。该工程在强风化灰岩和软弱页岩层开挖大断面隧洞施工中，成功地利用短进尺弱爆破跳开马口和喷锚挂网以及钢拱架联合支护措施，解决了在不良地质区施工成洞的困难。

The Geheyan Hydropower Plant has four power tunnels. The net spacing between adjacent tunnels is approximately equal to the excavated diameter of the tunnels.Blasting action in post-excavated tunnels will produce unfavourable influence on the concrete lining in fore-excavated ones.To solve this problem, fore-excavating the heading,post-expanding,full-periphery shotcrete suppot were adopted. in addition,during the excavation process,a lot of construction monitoring were carried out.Through these measures good engineering quality and completion tunnel works ontime.have been achieved.The project's tunnels with large diameter pass through strong weathered limestone with weak shale strata. By meanS of short driving footage,weak blasting and shotcrete with steel arch truss support,formation of an exactly circular excavation cross section under unfavourable geological conditions has been achieved.