长江口12.5米深水航道南坝田挡沙堤加高工程总平面方案研究

长江口12.5米深水航道2010年贯通后,发挥了巨大社会经济效益,同时航道回淤量大、维护压力大、维护费用高的问题突出。本研究基于北槽四边界水沙通量观测成果,分析提出了北槽航道回淤泥沙来源;针对回淤原因,在已建减淤工程经验总结的基础上,提出了本次减淤的研究思路,优化了减淤工程方案的比选指标体系;采用三维潮流泥沙数模、清水动床物模、经济技术综合分析等手段,通过"加高范围"、"加高高程"及"加高位置"比选,研究推荐了减淤工程方案。利用实测回淤量分析了工程减淤效果。研究结果表明,南导堤越沙是洪季北槽的重要泥沙来源,对北槽高浓度含沙量场有一定贡献。提出了可通过加高北槽南侧的导堤,实现减少通过南导堤越堤进入北槽的泥沙量,从而减小北槽含沙量水平,同时改善北槽下段流态,降低水沙横向输移,进而降低航道回淤的减淤思路。研究推荐的长江口12.5米深水航道减淤工程为南坝田挡沙堤加高工程及先期工程方案。先期工程位于S4～S9丁坝坝田,在现有南坝田挡沙堤的基础上加高S4～S8区段,并延长至S9丁坝,工程全长约23.8 km,高程+3.5 m。工程于2015年11月开工建设,2016年7月主体工程完工,工程减淤效果显著,2016—2018年年均减淤量约954×105m3/a,近三年已节省航道维护疏浚费用约5亿元。

The study on general plan layout of the jetty heightening project in the southern groin field of Yangtze estuary 12.5 m deep-draft waterway

The Yangtze estuary 12.5 m deep-draft waterway, once completed in 2010, has produced a huge social and economic benefit, at the same time, the amount of siltation, the pressure and the cost of water depth maintenance are serious. Based on four boundary tide and sediment flux observation results, the sediment source of the North Passage Waterway is put forward. For the sediment source, on the basis of engineering experience, the approach for studying the siltation reduction project is proposed. Using 3-D tidal current sediment mathematical model and physical model, comprehensive analysis of economy and technology and other technical means, optimizing evaluation indices system, and comparative study on heightening range, elevation and location have been carried out. Using the siltation data in field, project siltation reduction effect is analyzed. The sediment transported from the South Jetty is the important sediment source of the North Channel, and contributes to the high suspended sediment concentration in the North Channel. In order to reduce the channel silt, it is recomended to decrease the suspended sediment concentration level by reducing the amount of the sediment across the South Jetty to the North Channel, to improve the flow regime and reduce the horizontal transport of water and sediment in the lower part of the Northern Channel. It is recommend to carry out the siltation reduction project, the jetty project in the southern groin field, and its early implementation project of the Yangtze estuary 12.5 m deep-draft waterway, which heightens S4~S8 dike segment, and is extended to the S9 dike, with a total length of 23.8 km, and heightens elevation by +3.5 m. The project was started in November 2015, and finished in July 2016. The effect of reducing siltation that is about 9.54 million m³ per year is remarkable. In the past three years, it has saved about 500 million yuan RMB in dredging costs.