潮汐河口淹没丁坝群坝田淤积特征及成因分析

潮汐河口淹没丁坝群坝田水动力条件复杂多变,坝田复杂的水流结构决定了坝田内的泥沙淤积过程及淤积形态。以长江口北槽丁坝群形成坝田为例,分析坝田形成后淤积形态及淤积速率特征和规律。分析结果表明:随着时间推移,坝田内2 m等深线逐渐向距坝头0. 2倍坝长处靠近,5 m等深线逐渐向坝头处靠近;坝田的初始容积与冲淤平衡时的平衡容积呈对数关系;在丁坝间距为3～4倍坝长时,坝田内淤积分布最为均衡;坝田内淤积速率的拐点均出现在坝田形成后5～6 a。另外,从工程影响淤积丁坝布置参数方面探讨坝田内淤积特征的成因。

Characteristics and genesis of deposition in the field among submerged spur dikes in tidal estuary

The hydrodynamic conditions of the dam group flooded by the tidal estuaries are complex and changeable,and the complicated flow structure of the spur dikes field determines the siltation process and the form of siltation in the field.Taking the field formed by the spur dikes at the north passage of the Yangtze estuary for example,we analyze the deposition pattern,rate characteristic and regularity of the dam field after the dam formation.The result reveals that with the passage of time,the dam within 2 m isobath gradually closes to 0.2 times the distance from the dam head dam strengths,and 5 m isobath gradually closes to the dam at the head of the dam;there appears a logarithmic relationship between the initial volume of the dam field and balance volume at the scour sedimentation equilibrium;when the groin spacing is 3 to 4 times the length of dam,dam deposition distributes in equilibrium;the inflection point appears 5-6 years after the dam formation.Moreover,the causes of the siltation characteristics in the dike field are discussed in terms of the layout parameters affecting the silt dam.