强浪环境下围堰龙口泄流与冲刷特性研究

Flow Discharge and Scour Characteristics of Cofferdam Closure Gaps under Strong-waves Condition

鉴于强浪环境下围堰工程附近的波浪、水流作用显著,对排水龙口的泄水能力及结构稳定均有重大影响。以某大型围海造陆工程为例,采用近海波浪模型及平面二维水流泥沙数学模型,量化围堰工程区域及龙口局部波高、流场及床面形态变化规律。结果表明,龙口设置于Q7围堤中线处受波浪影响最小,相比龙口设置于其他围堤的情景,其有效波高相对减小85%~92%,同时对比Q7围堤沿程有效波高分布情况,中线处波高在有无龙口设置时均较小;龙口布设后,大浪期围堰工程内存在越浪现象,排水龙口水流紊乱且流速增加,围堰内外55m范围床面发生冲刷,靠近围堤的前后两组板桩附近流场更为复杂,流速及冲刷深度达到最大。

Under strong-waves condition,waves and water flow close to cofferdam projects have great adverse impact on discharge capacity and structure stabilization of closure gaps.Taking a larger-scale land reclamation work as the research object,an near-shore waves numerical model and a 2-D flow sediment numerical model were applied to estimate the variation characteristics of wave height,flow field and river bed transformation in the cofferdam construction and closure gaps regions.Main findings of this study are as follows:It is more reasonable to build a closure gap in the median line of Q7 causeway.Compared with building the closure gap in other cofferdams,this can efficiently reduce the significant wave height around 85%-92%.Compared with building the closure gap along Q7 causeway,the wave height in the median line of Q7 causeway all decreased no matter having a closure gap or not.After building the closure gap,there exists a wave overtopping phenomenon in cofferdam regions during strong-waves period.The flow field becomes disordered with velocity increasing.Around the cofferdam regions with trange of 55 m,the river bed was scoured.In the meantime,flow directions becomes more complex around the two sheet-piles close to the dike body of the closure gaps,and the velocity and the river bed scouring depth both reach the maximum values.