中文摘要：

丁坝是航道整治工程中广泛采用的一种整治建筑物,然而丁坝坝头复杂的水流结构,常导致坝头局部冲刷,易诱发丁坝水毁。为减弱坝头的水流动力,提出了设置台阶式坝头的新型丁坝结构形式,并通过水槽试验研究了台阶式丁坝的水动力特性及冲淤特征。研究表明,台阶式坝头能逐级分散坝头的集中绕流,消弱坝头脱离涡的涡量强度,而台阶的台面也能逐级阻挡坝头下潜流,消弱其对床面的直接冲击;同时,台阶台面具有挑流作用,使得最大流速或最大紊动强度区相应外移,也有利于坝头的稳定。试验还研究了台阶级数、宽度以及坝身下游边坡是否设置台阶等对控制局部冲刷坑的影响。试验发现,台阶级数相对越多,宽度越宽,其减小局部冲刷的效果越好;坝身下游边坡设置台阶增大了台阶台面阻挡下潜流及挑流的面积,也有利于控制局部冲刷的发展。

英文摘要：

The spur dikes are widely used in the waterway regulation engineering. However, the emergence of complex three-dimensional flow fields around the groyne head usually leads to the develpement of a local sour hole which may cause failure of the whole works. In this paper, a new type of spur dike with stepped head is proposed to weaken the flow dynamics at the groyne head, and a series of flume tests have been conducted in order to study the hydrodynamic characteristics and the scour characteristics of this new structure. The analysis results show that with the stepped head, the concentrated flow and the down-flow at the groyne head is dispersed progressively, and the formation of the shedding vortex is also reduced effectively. All of these lead to a reduction of the flow dynamics around the groyne head, and consequentially, the local scour is reduced. In addition, the flow can be deflected by the countertop of the steps. As a result, the local scour hole is pushed away from the groyne head, which is favorable to the stability of the groyne head. The studies also show that the protective effect of this new structure is related to the number of the steps, the width of the countertop and whether there are steps set up at the downstream slope of the groyne body. Experimental analysis results indicate that as the number or the width of the steps increases, the effect to control the local scour increases. Also, steps set up at the downstream slope of the groyne body protect the site downstream of the groyne head directly where the shedding vortex and the down-flow act, which seems more favorable to the reduction of the local scour hole.