长江口深水航道三期工程后北槽洪枯季水沙运动特征研究

利用长江口深水航道三期整治工程前后,北槽洪枯季各测点水沙资料初步探讨了北槽洪枯季水沙运动特征。研究结果表明,北槽洪枯季潮周期平均含沙量分布自上而下总体呈"低-高-低"的分布态势,中段含沙量较高。洪季北槽各测点潮周期平均含沙量与潮周期平均流速相关性较差,北槽泥沙输运以平流输移为主。枯季两者相关较好,北槽泥沙运动则以起悬输运为主。北槽悬沙输运主要以欧拉输运为主,洪季北槽悬沙净输运率要明显大于枯季。洪季北槽中段潮泵及垂向环流作用最为明显,枯季,除北槽上段外,潮泵及垂向环流作用较小,水沙输运方向较为相近。造成洪季北槽中段潮泵作用及垂向环流输沙较大的原因是由于北槽中段滩槽泥沙交换频繁,涨潮流经南槽拦门沙及九段沙滩面后,挟带一定高含沙水体进入北槽,进而造成北槽中段潮泵及垂向环流输沙明显。

Analysis of the sediment motion at north passage in flood and dry season after 3rd phase engineering of the deep waterways in Changjiang Estuary

In this paper, the sediment motion at north passage has been analyzed on the basis of the observations of water current and sediment concentration before and after the third phase engineering of the deep waterways in Changjiang Estuary. The result shows that:the distribution of the sediment concentration of north passage in both flood and dry season appears low-high-low pattern from the upper stream to the down stream where the midstream region of north passage has the highest sediment concentration. The correlation of sediment concentration and water current averaged in a tide cycle is poor in the flood season so that the sediment advection.plays a more important role in north passage while in the dry season, the correlation is good so that the sediment suspension plays more. The main form of sediment transport in north passage is the lagrangian advection. The net sediment transport in the flood season is bigger than the dry season. The tidal pumping effect as well as the vertical-circulation effect are big in the midstream of north passage in the flood season while in the dry season, they are so small that make the water and sediment move nearly in the same direction excluding the upper stream of north passage. The reason that the tidal pumping effect as well as the vertical-circulation effect play an important roles in the midstream of north passage is that the sediment exchanging is very frequent in the midstream of north passage where there exist a high concentration of sediment flowed into north passage generated from both the mouth bar of south passage and Jiuduansha tidal shoal in a flood tide.