波浪作用下考虑渗流影响的岸滩响应分析

发布时间：2018-03-04 00:11

本文选题：渗流　切入点：地下水位差　出处：《长沙理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：海岸带作为人类从事生产活动的主要区域,海岸发展对全球经济起着至关重要的作用,随着海岸的不断开发利用,全球海岸受到严重侵蚀,目前世界不少地区趋于通过抽取地下水来保护岸滩,其原理就是基于地下水渗流对泥沙运动和岸滩演变的影响。然而传统的海岸动力研究大多基于不可渗的海滩或者在可渗海滩中忽略渗流作用,因此开展渗流影响下的泥沙运动和岸滩演变规律研究具有重要的理论意义和社会价值。本研究通过开展波浪水槽实验,研究实验水深分别为0.4m、0.45m和0.5m情况下结合椭圆余弦波和孤立波的作用探讨不同波浪要素情况下沙质斜坡的水动力特性,人工降低地下水位以及椭圆余弦波作用下管渗对沙质岸滩剖面变化规律、泥沙分选规律以及孔隙水压力分布的影响。波浪水槽实验采用1：10单一斜坡概化沙质岸滩,选用2种波浪类型、3种实验水深改变波浪动力因素,分别在人工降低地下水位、管渗影响下对波浪在沙质岸滩上传播过程进行观测,测量波浪作用后岸滩地形变化、泥沙粒径组成以及岸滩内部孔隙水压力。实验结果表明：采用FFT和HHT理论分析渗流对能量的时域和频域变化特征影响,人工降低地下水位后,近岸区水流能量较自然渗流减小。椭余波作用下,相对于自然渗流,人工降低地下水位和管渗促进岸滩的冲刷,渗流管在水陆交界面处冲刷最严重,管渗条件下离岸区泥沙出现细化,波谷孔隙水压力平均值增加的幅值大于波峰孔隙水压力平均值,渗流力促进泥沙颗粒起动。孤立波作用下,地下水位下降后产生的渗流有利于泥沙淤积；相比于自然渗流,地下水位差增加了岸滩的非饱和度,入渗水流抑制了粗颗粒泥沙起动,岸滩近岸淤积位置粒径级配出现局部粗化。
[Abstract]:Coastal zone, as the main area of human being engaged in production activities, coastal development plays a vital role in the global economy. With the continuous development and utilization of the coast, the global coast has been seriously eroded. At present, many parts of the world tend to protect the shoreline by pumping groundwater. The principle is based on the influence of groundwater seepage on sediment movement and shoreline evolution. However, the traditional coastal dynamic research is based on the impermeable beach or neglecting the seepage in the permeable beach. Therefore, it is of great theoretical significance and social value to study the sediment movement and shoreline evolution law under the influence of seepage. The hydrodynamic characteristics of sandy slopes with different wave elements are studied by combining the effects of elliptical cosine wave and solitary wave under the experimental water depth of 0.4mg 0.45m and 0.5m, respectively. The effects of pipe seepage on the profile variation, sediment sorting and pore water pressure distribution of sandy shoreline under the action of artificial lowering of groundwater level and elliptical cosine wave are studied. The wave flume experiment is based on a single slope of 1:10, which is used to generalize sandy shoreline. Using two kinds of wave types and three kinds of experimental water depth to change the dynamic factors of wave, the wave propagation process on sandy shoreline is observed under the influence of artificial lowering of groundwater level and seepage, and the topographic changes of shoreline after wave action are measured. The experimental results show that FFT and HHT theory are used to analyze the influence of percolation on the variation of energy in time domain and frequency domain, and after artificially lowering the groundwater level, the sediment particle size composition and pore water pressure in shoreline are analyzed. Under the action of elliptical afterwave, compared with natural seepage, artificial lowering of groundwater level and pipe seepage promote shoal erosion, and seepage pipe scour is the most serious at the interface between water and land. Under the condition of pipe and seepage, the sediment in the offshore area is refined, the amplitude of the mean pore water pressure in the trough is larger than the average value of the pore water pressure of the wave peak, and the seepage force promotes the sediment particle to start. Compared with natural seepage, the difference of groundwater level increases the unsaturation of shoreline, and the infiltration water inhibits the starting of coarse sediment. Local coarsening occurs in the grain size gradation of shoreline near shore siltation position.
【学位授予单位】：长沙理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P748;P731.22

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