【作者】 汪文诚；

【导师】 程永舟；

【作者基本信息】 长沙理工大学 ， 港口、海岸及近海工程， 2011， 硕士

【摘要】 波浪传播到近岸水深较浅处会发生破碎,海床破坏与破碎波浪冲击作用下孔隙水压力的分布有着密切的关系。本文采用理论分析、模型试验相结合的方法,揭示了波浪破碎、海床变形及孔隙水压力分布之间的关系,为海洋工程设计提供可参考的依据。本文基于1:30的斜坡床面上的波浪水槽试验,研究砂质海床上破碎波作用时海床孔隙水压力响应规律,观察波浪破碎区的地形变化并分析其形成原因。试验使用影像处理技术,观察底床受破碎波浪作用后的变形情况。由此找出扰动与未扰动砂层交界剖面,从中了解波浪对底床掏刷程度。试验将传感器埋设于破碎带区域,获得底床内部压力变化并进行分析。试验结果表明,在波浪破碎前后孔隙水压力变化不同。波浪破碎处地形变化剧烈,破碎带处孔隙水压力竖向衰减幅度均比破碎前、后大。孔隙水压力在沙床顶部的变化比底部变化明显。不同碎波形态的孔隙水压力横向沿程变化没有明显区别,但不同碎波形态对砂层作用的表现方式不同,波浪发生卷破时,主要表现为对砂层大幅度的掏刷与堆积;波浪发生崩破时,主要表现为对已破坏的砂层有一定程度的整平作用。破碎带内砂层掏刷,孔隙水压振幅变大;砂层堆积,振幅变小。若砂层处于掏刷作用后又堆积的情形,新堆积的砂层不如初始状态紧密,仍有较大的振幅,在波浪的持续作用下,振幅才明显减小。若初始孔隙水压力振幅大于该深度理论静土压力,波浪对底床有着较大的影响深度与砂层移动能力。破碎带内若传感器均处于未扰动砂层之中,上下两传感器间的压力梯度差值较小。而若上层传感器由于砂层在波浪的持续作用下开始松动,上下两传感器间有着最大的压力梯度差值。波浪的持续作用,上下两传感器间的覆土均被扰动,此时压力梯度差值较小。若波浪对底床的侵蚀作用持续,上述现象会发生于更深层的传感器之间。更多还原

【Abstract】 The breaking wave will occur when the wave propagates to the area of near-shore and shallow water. It has a close relationship between the seabed destruction and the distribution of pore water pressure under the action of breaking wave. The relationship between the breaking waves, seabed deformation and pore water pressure distribution are presented combined with theoretical analysis, model test method, and this may provide assistance for coastal engineering design.Based on the wave flume experiments, response pattern of pore water pressure is studied on a 1:30 slope sandy seabed under breaking wave action. The topographic change is observed and its causes are analyzed. It used the image processing technique, and the actual situation of movable seabed change could be calculated. It sets braces near surf zone, obtain the change of the pore pressure under the movable bed and analysis the relationship between moved sand and pore pressure.The results show that the pore pressure changes significantly differently before and after the wave breaking. The pore pressure reaches the maximum on the area away from the nearest bed surface of the breaking point in the whole process, and the vertical decay rate of pore pressure is larger than the before and after wave breaking in the breaking section. The pore water pressure increases significantly at the breaking point. The topographic change is greatly on the wave breaking section. Pore water pressure changing at the top is significantly higher than it is at the bottom. The changing of the pore water pressure has no relationship with the wave breaking pattern. The pore water pressure attenuates slowly before the wave breaking and attenuates rapidly after the wave breaking. The different patterns of the breaking wave have different performance on the sand. It mainly presented the substantial undercutting and accumulation on the sand when the breaking wave is plunging breaker, and it mainly presented that it has a certain degree of leveling effect on the destructed sand.When the sand scours, the amplitude of the pore water pressure increases; and when the sand accumulates, the amplitude of the pore water pressure decreases. When the amplitude of the initial pore water pressure is greater than static earth pressure theory, the wave has a greater impact on bed depth and sand mobility.When the pressure gauges are all in the sand, the upper and lower gauges have a low pressure gradient. And when the gauge in the sand continued to start loosening up and down under the wave action, the two gauges have the greatest pressure gradient. With the continuing action of the wave, the casing on the two pressure gauge is to be disturbed, the two gauges have the low pressure gradient. If the wave action continues eroding the bed, this phenomenon will occur in the deeper sand.更多还原