中长周期波作用下斜坡堤稳定性与堤后次生波试验研究

Experimental study on stability of sloping breakwater and secondary wave under medium-long wave

孟加拉湾内的海浪受北印度洋涌浪影响,表现为中长周期为主的混合浪特征,其中平均周期10 s以上所占频率为42%、12 s以上所占频率为15%,波况复杂。针对该海域拟建工程所面临的波浪问题,通过波浪断面物理模型试验,验证了防波堤结构各部位稳定性,测定了堤后次生波传播变化规律,并对设计方案断面进行了优化。越浪水体冲击点位于堤内坡戗台附近,受越堤水流冲击附近块石发生位移,失稳率最高达到3.03%。优化方案调整迎浪侧坡度并增加护面块体和垫层块石重量,特别是降低戗台顶高使淹没水深增加,进而使越堤水体冲击减弱,稳定性得到明显改善。随着越堤后波浪传播距离的增加,次生波波高沿程变化呈现逐步递减趋势,沿程各测点中波周期为15.12 s所对应波高值均比10 s时更大,在低水位时这种现象更为明显。另外,不同波周期对于堤前爬高、越浪量和堤后次生波衰减速率也均有不同程度影响。

The waves in the Bay of Bengal are influenced by the surge waves in the northern Indian Ocean,showing the mixed wave characteristics dominated by medium and long period,in which the frequency with average period of more than 10 s is 42%,and the frequency with average period of more than 12 s is 15%,and the wave state is complex.Aiming at the problem of wave in the proposed project in this sea area,the stability of each part of the breakwater structure was verified by physical model test of wave section,and the variation law of secondary wave propagation behind the breakwater was measured,and the designed section was optimized.The impact point of the over-topping water body is located near the peak platform on the inner slope of the breakwater.The rocks near the impact of the over-topping water flow are displaced,and the instability rate reaches up to 3.03%.The optimized scheme adjusts the slope of the wave side and increases the weight of the protective block and cushion block,especially reduces the peak height to increase the submerged water depth,and then weakens the impact of the water body over the dike,so as to be significantly improved.With the increase of wave propagation distance after crossing the breakwaters,the variation of secondary wave height along the breakwaters shows a gradually decreasing trend.The wave height corresponding to the wave period of 15.12 s at each measuring point along the breakwaters is all larger than that at 10 s,and this phenomenon is more obvious at low water level.In addition,different wave periods also have different effects on the rise in front of the embankment,the amount of wave crossing and the decay rate of secondary waves behind the breakwater.