大石峡水利枢纽工程导流洞进口围堰设计及施工

大石峡水利枢纽工程导流洞进口河床较窄,受下游电站运行河床淤积逐年抬高,开工时原设计预留岩坎挡水高程不满足全年挡水要求。结合导流隧洞和进水塔的施工时段,2018年导流洞进口采取过水围堰标准,2019年采取全年挡水围堰标准设计,堰型采用覆盖层上修建混凝土挡墙围堰的方案,围堰基础覆盖层采用控制性灌浆处理。混凝土挡墙围堰两年多运行安全可靠,且经受2019年汛期洪水考验,对类似狭窄河谷、河床覆盖层混凝土挡墙式围堰设计和施工有借鉴作用。

Design and Construction of the Cofferdam at the Inlet of the Diversion Tunnel of the Dashixia Water Control Project

The river bed at the inlet of the diversion tunnel of the Dashixia Water Conservancy Project is relatively narrow.Due to the siltation caused by the operation of the downstream hydropower station,the river bed has been raised year by year.The original designed rock sill retaining elevation at the start of construction is insufficient for the water retaining all the year round.In combination with the construction period of the diversion tunnel and the water intake tower,the inlet of the diversion tunnel is designed with the flood standard of the overflow cofferdam in 2018,and in 2019 the flood standard for water-retaining cofferdam all the year around is adopted.The cofferdam adopts the construction of concrete retaining wall on the overburden.The overburden of the cofferdam foundation is treated with controlled grouting.The concrete retaining wall cofferdam has operated safely and reliably for more than two years,and has withstood the flood in 2019.It can be a reference for the design and construction of similar concrete retaining wall cofferdams located in narrow river valleys with riverbed overburdens.