分汊河段船闸引航道整治试验研究

大洑潭枢纽位于沅水上游,处在山区限制性河道,其通航水流条件十分复杂,不利于通航。针对上、下游引航道口门区和连接段水流条件差、横流较大、洲尾通航困难及小流量下通航水深不足等问题,设计和修建大洑潭枢纽船闸整体物理模型,并结合船模航行试验,对船闸引航道口门区、连接段及洲尾处通航水流条件进行系统的试验研究。模型试验结果表明,船闸枢纽平面布置存在缺陷,上游船闸引航道口门区及连接段水流条件易受江心洲分汊口斜流影响,尤其左右两汊同时泄流下,船舶航行难度较大。整治方案采取加长导航墙和修建丁坝、顺坝及开挖航槽等措施进行试验研究,发现优化方案④下的通航、船模水流条件得到明显改善,确定了在该条件下的最大通航流量,并论证了在此方案下通航的安全性和工程可行性。

Physical Model Test on Regulation and Optimization of Navigation Lock Approach Channel in a Branching Reach

Located in the upstream of the Yuanjiang River, Dafutan navigation-hydropower project is in mountainous restrictive channel with complex flow condition unfavorable for navigation. The entrance and connection segments of the upstream and downstream approach channels are featured with unfavorable flow condition, large transverse flow velocity, and insufficient water depth for navigation under low flow. In view of this, we designed and constructed a physical model of the shiplock of Dafutan project to comprehensively investigate the navigation flow condition in the entrance and connection segment of approach channel and the sandbar tail. Ship model test demonstrated that the original layout of the project and the navigation structures are unreasonable. The navigable flow condition of the entrance and connection segment of upstream lock approach channel is subjected to the cross current at the middle sandbar under the circumstance of simultaneous discharge of left and right branches, difficult for ship navigation. In order to improve the flow condition, we take measures such as elongating the navigation wall, building spur dike and longitudinal dike along the bar tail, and excavating the navigation channel. We found that the navigation condition and the flow condition of ship model had obviously improved under the optimized layout scheme 4. In addition, we determined the maximum navigable discharge under the optimized scheme 4, and demonstrated the safety and engineering feasibility of the optimization.