小湾水电站导流洞进出口围堰方案优化

小湾水电站导流隧洞进、出口均位于深切河谷的岸坡地带,岩石破碎。由于前期施工过程中石渣下江导致江水位抬高达10m左右,导流隧洞工程进、出口围堰按原设计的防洪标准,相应的水位应予提高。在确保永久建筑物设计功能的前提下,为使围堰建基于具有干地施工条件的完整岩石基础上,最大限度地将围堰位置向内侧移动,并对其进行分段设计和基础处理。尽管围堰体形不同程度地加大,但部分堰体按永久工程的标准进行设计与施工并予永久保留,因此围堰后期拆除工程量比合同工程量明显减少。该围堰方案的优化,保证了施工质量、工期,并节省了投资。

Scheme optimization of cofferdams of the diversion tunnels of Xiaowan Hydropower Station

Xiaowan hydropower station is located in a canyon with high mountains on its both banks. The inlet and outlet of its diversion tunnel are located at a riverside in a deep valley with deep weathered and fractured rocks. As the water level has risen about 10 m due to dumping excavated spoils into the river during the construction at its initial stage, the flood control level of the inlet- and outlet-cofferdam of the diversion tunnel should be raised accordingly. In order to allow the inlet- and outlet-cofferdam to be founded on intact rocks for the sake of performing their construction under dry condition, the scheme is optimized, i.e. the locations of both inlet and outlet of the tunnel should be shifted inward to a maximum, and they should be designed and foundation treated in stages as required as permanent structures on condition that the design functions of the permanent structures should be guaranteed. Although the cofferdams should be somewhat enlarged, part of the cofferdams is designed and constructed as permanent structures and will remain there forever and the quantity of the cofferdams to be removed at later stage will be significant reduced as compared with that stipulated in the contract. The optimization of the design of such scheme ensures the construction quality and completion in schedule as well as cost reduction.