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Influence of toe berm geometry on stability of reshaping berm breakwaters
Coastal Engineering ( IF 4.4 ) Pub Date : 2020-04-01 , DOI: 10.1016/j.coastaleng.2020.103636
Mehdi Shafieefar , Mohammad Reza Shekari , Bas Hofland

Reshaping berm breakwaters have been mainly designed and built for water depth less than 20 m. In such conditions, a toe structure may be needed to reduce bottom settlements and increase geotechnical stability in the loose subsoil condition. Also, a toe berm can be deployed to reduce the berm recession and increase the stability of the Reshaping berm breakwater, especially in deep water. Although many studies have been conducted to study the effects of toe berms on stability of conventional breakwaters, investigations on the influence of a toe berm on stability of reshaping berm breakwaters are rare. This paper presents results of an experimental work that has been carried out to investigate the influence of a toe berm on the hydraulic stability of reshaping berm breakwaters. In a 2D physical test setup in a wave flume, a total of 207 tests were conducted to systematically examine the effects of toe berm configuration on the reshaping of berm breakwaters with three types of armor stones. The experimental program covers the influence of different geometrical parameters of the toe berm on the berm recession under various sea state conditions. Comparing results of berm recession of the cases having a toe structure with the cases without a toe berm shows that the amount of berm recession with toe berm is considerably less than the analogous amount for without toe structure. It is observed that an increasing toe berm width and thickness both have considerable influence on recession reduction. However, the toe depth has a relatively larger influence on recession than the toe width, and the influence is larger for higher stability numbers. It is concluded that a toe berm in front of reshaping berm breakwater not only does have influence on recession due to the depth influence and the changing wave conditions, but also the toe depth has a direct influence on the reshaped profile by preventing the displaced rocks to fall down to deeper parts. Using the test results, a new formula is developed for estimation of berm recession by taking into account the influence of the toe berm configuration. Given an acceptable stability number (Ho) as a design criterion for reshaping berm breakwaters, the present method predicts that the recession can be reduced up to 35% by the application of a toe berm. Thus, the main berm width can be shortened, resulting in reduction of the required armor stones volume. So, by using a smaller stone size for the toe berm, the stability of the structure is secured and also the total cost of the breakwater can be reduced.

中文翻译:

护堤几何形状对重塑护堤防波堤稳定性的影响

整形护堤防波堤主要针对水深小于20m而设计建造。在这种情况下,可能需要趾结构来减少底部沉降并增加松散底土条件下的岩土工程稳定性。此外,可以部署脚趾护堤以减少护堤退缩并增加重塑护堤防波堤的稳定性,尤其是在深水中。尽管已经进行了许多研究来研究护坡对常规防波堤稳定性的影响,但关于护坡对重塑护堤防波堤稳定性影响的研究很少。本文介绍了一项实验工作的结果,该工作已开展以研究趾护堤对重塑护堤防波堤的水力稳定性的影响。在波槽中的 2D 物理测试设置中,总共进行了 207 次测试,以系统地检查脚趾护堤配置对使用三种类型的装甲石重塑护堤防波堤的影响。实验方案涵盖了在各种海况条件下护坡的不同几何参数对护堤退缩的影响。比较有趾结构的情况与无趾道的情况的护道退缩结果表明,有趾道的护道退缩量远小于无趾结构的类似量。据观察,增加脚趾护道宽度和厚度都对衰退减少有相当大的影响。然而,与趾宽相比,趾深对衰退的影响相对较大,稳定性数字越高,影响越大。结论是,整形护堤防波堤前的趾护堤不仅因深度影响和波浪条件的变化而对后退产生影响,而且趾部深度通过防止位移的岩石对重塑的剖面有直接影响。下降到更深的部分。使用测试结果,通过考虑脚趾护道配置的影响,开发了用于估计护道衰退的新公式。给定一个可接受的稳定数 (Ho) 作为重塑护堤防波堤的设计标准,本方法预测通过应用趾护堤可以将衰退减少多达 35%。因此,可以缩短主护堤的宽度,从而减少所需的护甲石体积。因此,通过在脚趾护堤上使用较小的石头尺寸,
更新日期:2020-04-01
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