潮汐河口坝田长宽比对泥沙淤积特征影响试验研究

在航道治理工程中,往往通过丁坝群来实现其稳定航槽等目的,而坝田作为缓流区,其与主槽的水沙交换主要取决于横向的紊动交换。基于长江口北槽丁坝群实测资料分析和物理模型水槽试验研究发现不同长宽比坝田内的流态、淤积形态、坝田与相邻河段水沙交换的机理均不同,在长江口北槽丁坝群坝田建成后的淤积初期阶段,长宽比为0.30～0.40的坝田内的平均淤积强度最大。水槽试验研究表明,长宽比为0.50的坝田内淤积的主要部位即为主环流所在位置(坝田外侧),而在副环流位置,则出现微淤或冲刷的趋势;而长宽比为0.33的坝田内的淤积分布相对比较均匀。长宽比为0.33的坝田内淤积速率明显大于长宽比为0.50的坝田,长宽比为0.33的坝田达到冲淤平衡的时间较长。坝田淤积强度与随坝田回流强度、坝田与主槽水沙交换系数的增加而增加。

Experimental analysis of the effect of changing the length-width ratio of dam fields on sediment deposition

In waterway regulation engineering, groynes are often used to stabilize the navigation channel. As a slow flow area, the water and sediment exchange between the dam field and the main channel mainly depends on the transverse turbulent exchange. Based on the analysis of the measured data of the groyne group in the north channel of the Yangtze River estuary and the flume test of physical model, it is found that the flow pattern, siltation pattern and the mechanism of water and sediment exchange between the groyne group and the adjacent river section are different in different aspect ratios. In the initial stage of siltation after the groyne group in the north channel of the Yangtze River estuary is completed, the average siltation intensity in the groyne group with an aspect ratio of 0.30-0.40 is the largest. The flume test results show that the main part of the deposition in the dam field with a length-width ratio of 0.50 is the location of the main circulation (the outside of the dam field), while at the location of the secondary circulation, there is a tendency of micro deposition or erosion; and the deposition distribution in the dam field with a length width ratio of 0.33 is relatively uniform. The sedimentation rate in the dam field with an aspect ratio of 0.33 is obviously higher than that in the dam field with an aspect ratio of 0.50, and the time for the dam field with an aspect ratio of 0.33 to reach the balance of erosion and deposition is longer. The siltation intensity of batian increases with the increase of backflow intensity and water sediment exchange coefficient between batian and main channel.