【作者】 王峥；

【导师】 张庆河；

【作者基本信息】 天津大学 ， 水利工程， 2023， 硕士

【摘要】 由于海平面加速上升、风暴强度增加等全球环境变化,海滩侵蚀的危害越来越不容忽视,生态型防护措施因其对原有海岸生态扰动较小而越来越受到人们的关注。人工沙坝与岸上沙丘都是在近岸填充与岸滩性质相似的沉积物,在起到海岸防护作用的同时能够与当地生态环境相协调,因此对于这两种生态型防护措施的研究具有重要意义。本文基于XBeach建立了波浪-植物-泥沙耦合的数值模型,依托物理模型实验对模型的水动力特性和岸滩演变过程进行了验证,并对模型参数进行了敏感性分析。基于平衡海滩剖面和设计坡度建立概化沙滩地形,结合概化沙滩地形和高斯断面建立人工沙坝和岸上沙丘的模拟地形,并对波浪作用下两种地形的动力响应开展数值模拟研究,分析了波高和周期变化对水动力和岸滩演变规律的影响。定义了包含计算域内全部侵蚀量的总侵蚀量和衡量岸滩防护效果的后滨侵蚀量两种损失因子,并对其进行了定量分析。本文主要结论如下:(1)人工沙坝岸滩的模拟结果表明,波高、周期和水位的增大都会导致两种侵蚀量的增加;沙坝高度的增加会导致总侵蚀量的增加和后滨侵蚀量的减少;沙坝宽度的增加会导致后滨侵蚀量的减少;沙坝位置对于侵蚀量变化的影响则较为复杂,后滨侵蚀量随着离岸距离的增加呈波动变化的趋势。(2)岸上沙丘岸滩的模拟结果表明,植被的存在对于侵蚀量的减少具有显著效果,在相同的覆植沙丘地形条件下,波高和周期增大都会导致总侵蚀量和后滨侵蚀量的增加。当周期较小时覆植沙丘的存在对侵蚀现象的影响不大,当周期较大时,处于任意位置覆植沙丘的存在都能减小总侵蚀量和后滨侵蚀量,且覆植沙丘与滩肩距离越近、高度和宽度越大,减小侵蚀量的效果越好。(3)基于岸滩变化模拟结果建立了波高、周期与沙坝体积和后滨侵蚀量之间的拟合公式,该公式能够描述环境工况和地形参数变化对于后滨侵蚀量的影响,且有较高的拟合精度。更多还原

【Abstract】 Due to the impact of global environmental changes such as increasing sea level rise and storm intensity,the threat of beach erosion becomes more and more obvious at present.Ecological beach protection measures with small disturbance to the original coastal ecology,are attracting more attention.Artificial sandbars and dunes are built up by filling in sediments similar to the nature of original beach,so they can serve as coast protection measures and be coordinated with the local ecological environment.As a result,researches for these two kinds of ecological protection measures is of important significance.A numerical model of wave-plant-sediment coupling was established based on XBeach model,the hydrodynamic characteristic and beach evolution process of the model were verified by comparing with physical model experiment data,and the sensitivity analysis on model parameters was carried out.Generalized topography is established basing on equilibrium beach profile and designed slope,then topography of artificial sandbar and dune is established by combining the generalized topography and Gaussian function.Numerical simulations of the dynamic response to wave forcing were carried out based on these two topographies,and the effects of wave height and period on the hydrodynamics and beach evolution patterns were analyzed.Two loss factors were defined,one is the total erosion volume in the calculation domain and another is the backshore erosion volume to measure the effect of shore protection.The quantitative analysis was carried out for the two erosion volumes.The main conclusions of this thesis are as follows:(1)Simulation results of beach with artificial sandbar show that the increase of wave height,period and water level all contribute to an increase of total and backshore erosion volume.The increase in sandbar height leads to an increase in total erosion volume and a decrease in backshore erosion volume,while increasing the width of the sandbar leads to a reduction in backshore erosion volume.The influence of sandbar position on erosion is complex,the backshore erosion volume shows a trend of fluctuations with the increase of offshore distance.(2)Simulation results of beach with sand dune show that the presence of vegetation has a significant effect on the reduction of erosion.The wave height and period increases could lead to the increases of total and backshore erosion volume under the same dune conditions.The presence of vegetated dunes has a minimal impact on erosion phenomena when the wave period is small.However,for waves with larger periods,the existence of vegetated dunes at any position can reduce both total and backshore erosion volume.Moreover,the closer the vegetated dunes are to the berm in terms of distance,and the greater their height and width,the more effective they are in reducing erosion.(3)Based on the simulation results of beach evolution,a fitting formula is established to describe the relationship between wave height,wave period,sandbar volume and backshore erosion volume,which can describe the influence of environmental condition and the terrain parameters on backshore erosion volume.The formula shows high fitting precision.更多还原