闽江无闸低坝枢纽工程子围堰施工阶段水流研究

Water flow of sub-cofferdam in construction phase for Minjiang Hydropower Station with low head dam and non-gate

山区河流河窄水急,通航枢纽施工导流河道缩窄率可高达60%~70%,对施工导流期的泄流能力与通航水流条件的影响很大。根据流路阻力系数与过流能力成反比和能量方程等水力学原理,选择河岸切嘴顺坡、清底整平河床的方法,有效降低河道形状阻力,减小过流糙率系数,提升河道泄流能力;采用降低缩窄河底高程、增加过流断面的方法,减小流速、提升最高通航流量;采取延伸导流河底高程变化点至纵向围堰上下游端点外与缓和斜坡连接床底的方法,降低过水断面变率、减小过流卡口河段的壅跌水高度、平顺水流,实现改善通航条件的目的。结果证明该方法对于增加缩窄河道泄流能力、提升最高通航流量是切实可行的。

River in mountain area has the characteristics of narrow waterway and fast flow,especially in the construction diversion narrows the channel’[KG-*4]s width is as high as 60%-70%,which has a great influence on the changes of discharge capacity and the navigation flow condition.According to the basic hydraulics principles of energy equation and the relationship between flow resistance coefficient and flow capacity,we apply the approaches of cutting nozzle along the slope and leveling bottom to effectively reduce the resistance of the river shape and the roughness coefficient of the flow,and the approaches can enhance the discharge capacity of the river channel;we use the method of reducing the height of the narrowed bed for increasing the flow section to decrease flow rate and to increase maximum traffic flow;we take the measures of extending the various height’[KG-*4]s point in diversion bed to upstream and downstream endpoint for the longitudinal cofferdam and connecting the bottom of the bed with a gentle slope,and the measures can reduce the rate of change of flow section,the height of water and the water flow,also improve the navigable condition.The results show that the proposed method is feasible to increase the discharge capacity of narrowed channel and the maximum traffic flow.