多个采砂工程对长江下游局部河段河势影响

Impacts from several sand mining projects on river regime evolution of local reaches of Lower Yangtze River

针对采砂工程对河势影响的研究大多聚焦于单一工程,多个大型采砂工程的实施将对河床造成更为复杂的影响,以长江下游局部河段(上起江阴鹅鼻嘴,下至长江口南支杨林站以及北支连兴港)为例,基于Delft3D软件建立了工程河段二维水沙数学模型,通过数值模拟研究了不同采砂方案实施后工程附近局部河段的河势变化,并探讨了多个采砂工程对河势影响的叠加效应。结果表明:(1)不同方案实施后分流比总体变化幅度较小,分流比最大变化值发生在落潮时刻,通州沙东水道减小约3.18%;(2)除通州沙西水道采砂工程的实施对河床冲淤的影响范围较大外,其余采砂工程实施对河道冲淤影响仅限于采区附近,多个采砂工程实施对彼此采砂区的叠加冲淤变幅的影响在0.1 m以内;(3)多个采砂工程实施后,浏海沙水道南岸顶冲点附近深泓线下移约83 m,通州沙汊道进口段、新开沙及狼山沙附近深泓线向右偏转,工程实施对工程河段深泓线变化影响幅度较小,河道格局不会发生明显变化。研究成果可为长江河道采砂许可管理及规划提供参考依据。

Most of the studies made on the impact from sand mining project on river regime focus on that from a single project,but the impacts from the implementations of several large scale sand mining projects on riverbed are to be more complicated,for which the local reaches of the Lower Yangtze River(from Ebizui of the upstream Jiangyin Reach down to Yanglin Station of the South Branch of the Yangtze River Estuary and Lianxing Port of the North Branch)are taken as the study cases herein,and then a 2-D water-sediment mathematical model is established based on the software—Delft3D,thus the changes of the river regimes of the local reaches near the sand mining projects after the implementations of various sand mining schemes are studied through the relevant numerical simulations,while the superposed effect from several sand mining projects on the river regime is discussed as well.The study results show that(1)the general changing amplitudes of the diversion ratios are less after the implementations of various schemes,while the maximum changing value of the diversion ratio occurs at the moment of ebb tide,of which the decrease is about 3.18%at the East Waterway of Tongzhou Sand Shoal;(2)except the larger range of the impact on the riverbed scouring and silting from the implementation of the sand mining project at the East Waterway of Tongzhou Sand Shoal,the impacts from the implementations of the other sand mining projects are only limited near the mining areas,while the superposed changing amplitudes of scouring and silting from the implementations of several sand mining projects in-between all the mining areas are within 0.1 m;(3)after the implementations of several sand mining projects,the top impacting point on the south bank of Liuhai Sand Shoal Waterway moves downwards about 83 m,while the inlet section of the branch of Tongzhou Sand Shoal and the thalwegs near both Xinkai Sand Shoal and Langshan Sand Shaol deflect toward right,and the influencing amplitudes are less for the changes of the thalwegs of the river reaches of the projects after the project implementations without obvious changes of the river pattern.The study result can provide the referential bases for the sand mining permission and planning of the Yangtze River.