小湾水电站导流隧洞施工技术综述

小湾水电站导流隧洞两洞轴线距离仅48．0m，洞室纵横跨度均较大；围岩稳定性差，国内罕见的F7特大断层穿过，开挖成洞极为困难；因工期提前一年，施工具有工期紧、断面大、施工强度高、技术标准要求严等特点。在开挖支护及混凝土施工中，优化调整施工支洞及围堰布置方案，采用了“新奥法”进行开挖支护。在钢模台车设计时，兼顾了顶拱不衬段的施工，运用柔性搭接原理有效解决了常规钢模台车浇筑混凝土的错台问题，优质高效完成了导流隧洞混凝土施工，确保了大江提前一年截流工期目标的实现。

A Summary of the River Diversion Tunnel Construction Technology for the Xiaowan Hydropower Project

In the construction of the Xiaowan hydropower project the axes of the two river diversion tunnels are only 48. 0m away from each other, both longitudinal and transverse spans of the underground caverns are all rather large and their surrounding rocks stability is poor, and the extremely large fault F7, which is rarely seen in the country, runs through the tunnel area. All of this made either excavation or formation of the tunnels badly difficult; The construction is to be completed 1 year ahead of schedule. As a result the time limit for construction of the tunnels is made to be pressing due to their large cross sections, high construc.tion intensity and high technical standards. In order to complete the excavation, support and concrete placement work of the tunnels in an efficient way the layout of the construction adits and cofferdams was readjusted and optimized, the new Austrian tunneling method was used for the excavation and supporting work, Consideration was given to construction of the crown section without lining and the principle of flexible lapping was applied to solving of the staggering problem for concreting using traditional steel form jumbos in the design of the steel form jumbos, so that the river closure was accomplished 1 year ahead of schedule.