Experimental studies on stability of riprap revetment on fringing reefs
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摘要: 岛礁地形是一种特殊的海岸形式,国内外学者对波浪在岛礁地形上的传播变形研究较多,但对于岛礁地形上的护岸工程研究较少,缺乏对关键设计参数的研究。以马尔代夫机场岛护岸工程为例,通过比例尺为1:10的波浪水槽物理模型试验,分析研究了3种不同岸坡宽度、4种不同水深和波浪组合工况下的护面块石稳定性。结果表明,前沿岸坡宽度,即护岸坡脚至礁缘之间的距离是影响抛石护岸稳定性的重要因素。在同样水深、波况及护岸块石质量条件下,护面块石的失稳率随岸坡宽度的增加而减小。进一步分析发现,为保障护岸安全,抛石护岸外坡坡脚宜布置于波浪破碎点之后,且与破碎点之间距离不应小于浅水波长的26%,即0.26T$ \sqrt{g h_{\mathrm{e}}}$。Abstract: The fringing reef is a special coastal topography. Many scholars at home and abroad have studied the propagation and deformation of waves on the fringing reefs, but few have studied the revetment engineering on the fringing reefs, hence lack of understanding of the key design parameters. For this reason, taking the revetment project of the Maldives Airport island as an example, some analyses and studies of the stability of the armor blocks under the conditions of three different bank widths, four different water depths and wave combinations are carried out through the physical model test in a 1:10 scale wave flume. The test results show that the bank width, that is, the distance between the toe of the riprap revetment slope and the reef edge, is an important factor affecting the stability of the riprap revetment. Under the same water depth, wave condition and weight of the revetment blocks, the instability rate of the revetment blocks decreases with the increase of the width of the bank slope. Further analysis of the test results shows that in order to ensure the safety of revetment, the toe of slope outside the riprap revetment should be placed behind the breaking point of wave, and the distance between the toe of the slope and the breaking point is recommended not to be less than 0.26 times the shallow water wave length of reef flat $T \sqrt{g h_{\mathrm{e}}} $. This key design parameter has important guiding significance for the design of similar bank protection works in the future.
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Key words:
- fringing reef /
- riprap revetment /
- stability /
- bank slope width /
- model test
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表 1 试验水深和波浪要素
Table 1. Water depths and wave parameters for experimental studies
项目 工况 d/m H1%/m H4%/m H5%/m H13%/m H/m T/s 原型值 1 14.00 3.09 2.61 2.53 2.11 1.33 5.61 2 13.55 3.07 2.60 2.51 2.10 1.33 5.60 3 13.00 3.04 2.57 2.49 2.07 1.30 5.53 4 12.37 2.93 2.48 2.39 2.00 1.26 5.46 模型试验值 1 1.400 0.309 0.261 0.253 0.211 0.133 1.77 2 1.355 0.307 0.260 0.251 0.210 0.133 1.77 3 1.300 0.304 0.257 0.249 0.207 0.130 1.75 4 1.237 0.293 0.248 0.239 0.200 0.126 1.73 注:本工程《设计波浪要素推算报告》[15]中计算点处高程-19.0 m。表中d为水深, Hi%为累计频率为i%的波高, H为平均波高, T为平均波周期。 表 2 护面块石稳定情况汇总
Table 2. Stability of armor blocks
工况 试验断面1 试验断面2 试验断面3 护面块石滚动个数/个 失稳率/% 是否满足稳定性要求 护面块石滚动个数/个 失稳率/% 是否满足稳定性要求 护面块石滚动个数/个 失稳率/% 是否满足稳定性要求 1 7 7 否 3 3 否 无 0 是 2 7 7 否 2 2 临界稳定 无 0 是 3 无 0 是 无 0 是 无 0 是 4 无 0 是 无 0 是 无 0 是 注:试验中护面块石总数为98个,所有块石均经严格挑选,满足质量要求。 表 3 各工况下坡脚与破碎点之间距离的计算值
Table 3. Calculated values of distance between slope toe and wave breaking point under working conditions
工况 试验断面1 试验断面2 试验断面3 xt xt/($ \sqrt{g h_{\mathrm{e}}}$) 是否稳定 xt xt/($ \sqrt{g h_{\mathrm{e}}}$) 是否稳定 xt xt/($ \sqrt{g h_{\mathrm{e}}}$) 是否稳定 1 1.7 0.05 否 6.7 0.22 否 11.7 0.38 是 2 2.1 0.08 否 7.1 0.26 临界稳定 12.1 0.43 是 3 2.8 0.11 是 7.8 0.32 是 12.8 0.52 是 4 3.5 0.18 是 8.5 0.43 是 13.5 0.68 是 -
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