滩槽泥沙交换对长江口北槽深水航道回淤影响的分析

Response of deepwater channel in north passage to water and sediment exchange between channel and shoal in the Yangtze estuary

黏性细颗粒泥沙在潮汐水流中运动的主要特性之一是存在多种不同尺度的输运形态。就长江口而言,其中1～2 m近底水流驱动下的高浓度悬沙输运应加重视。现场观测表明,近底高浓度悬沙的生成与黏性细颗粒泥沙在潮汐水流中的沉降特性有关,其输运对航道回淤的影响表现为滩槽之间的泥沙交换。初步估计横向水体高浓度悬沙输运造成12.5 m深水航道中段2 000万～3 000万m3的年回淤量是可能的。这可能是造成航道中段集中回淤的重要原因之一。

It is one of the important features for cohesive fine sediment that there exist different transport patterns under the effect of the tidal currents. As for the Yangtze estuary, the high-concentrated mud suspension（HCMS） is driven by near-bottom flow with the range from 1 to 2 meters, to which we should pay more attention. The field investigation reveals that the generation of HCMS is related to the settlement characteristics of the cohesive fine sediment in tidal current. The effect of the HCMS movement to the back-siltation in the deepwater channel registers as the water and sediment exchange between channel and shoal. It is estimated that the HCMS transport in the transverse current may increase the amount of the back-siltation in middle of the 12.5 m deepwater channel up to 20 million ～30 milion cubic meters. This would be one of the important factors resulting in back- siltation concentrated in the middle of the north passage.