Comparative analysis on numerical simulation of the impacts of different beach nourishment schemes on beach profile
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摘要: 大量工程实践表明,海滩养护是当前抵御海岸侵蚀的常见措施。通过人为地向海滩补充沙源,以达到海岸防护、修复沙滩等目的。本文建立了XBeach一维海滩剖面演变数值模型,并与物理模型试验结果进行对比验证;计算常浪条件下不同方案补沙后海滩剖面达到平衡状态的速率;通过对比补沙工况与未补沙工况的风暴后剖面,分析风暴作用下的防护效果。结果发现,补沙量较大时,沙坝向海侧位置补沙在常浪条件下补沙效率高于滩肩补沙,在风暴条件下防护效果优于滩肩补沙。此次研究对于在实际海滩养护过程中节约施工成本、提高施工效率有着重要意义,同时对于评估沙滩养护工程效果有一定的参考价值。Abstract: Numerous engineering projects show that beach nourishment is a common method against coastal erosion. Beach nourishment is an artificial process of adding sediment to a beach to increase beach width and protect it from erosion. In this paper, a 1D numerical model for beach profile was established and verified by the results of physical model experiment. In addition, the rates of profile change to equilibrium profile on different positions and different sand volume schemes were calculated, and the efficiency was compared and analyzed. To analyze the protection effects of beach nourishment, the profiles in nourishment schemes and no nourishment schemes after storm condition were compared. It turned out that when the nourishment volume was large the efficiency of bar nourishment under the calm condition was higher than of berm nourishment, and the nourishment effect under the storm condition was better. This study has important implications to save construction costs and raise working efficiency during the practical nourishment engineering. In the meantime, it sheds light on evaluating the effect of beach nourishment.
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Key words:
- beach nourishment /
- equilibrium profile /
- XBeach /
- numerical model /
- nourishment efficiency
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图 8 风暴作用下人工补沙剖面变化
a. 滩肩补沙(0.1 m3/m);b. 沙坝向海侧补沙(0.1 m3/m);c. 滩肩补沙(0.2 m3/m);d. 沙坝向海侧补沙(0.2 m3/m);e. 滩肩补沙(0.3 m3/m);f. 沙坝向海侧补沙(0.3 m3/m)
Fig. 8 Changes of artificial beach profile under storm
a. Berm nourishment (0.1 m3/m); b. bar nourishment to the seaward (0.1 m3/m); c. berm nourishment (0.2 m3/m); d. berm nourishment to the seaward (0.2 m3/m); e. berm nourishment (0.3 m3/m); f. bar nourishment to the seaward (0.3 m3/m)
表 1 人工沙滩稳定性试验验证工况
Tab. 1 Validation cases of artificial beach stability test
工况 试验水深/m 初始坡度 波浪类型 平均波高H/m 周期/s 滩肩宽度/m 作用时间T/h 一 0.5 1∶10 规则波 0.14 1.5 1.0 8 二 0.5 1∶10 规则波 0.14 1.8 1.0 8 三 0.5 1∶10 规则波 0.17 1.5 1.0 8 表 2 数值模型误差统计
Tab. 2 Error statistics of the numerical model
工况 BSS R2 SCI 一 0.972 0.978 0.081 二 0.951 0.968 0.107 三 0.986 0.993 0.061 表 3 数值模拟工况
Tab. 3 Numerical simulation cases
补沙位置 工况 波浪类型 波高/m 周期/s 补沙量/(m3·m−1) 模拟时间/h 剖面类型 模拟条件 未补沙 A1 规则波 0.08 2.0 0 8 过渡型 常浪 A2 不规则波 0.15 1.5 0 0.5 侵蚀型 风暴 滩肩 B1 规则波 0.08 2.0 0.1 8 过渡型 常浪 B2 规则波 0.08 2.0 0.2 8 过渡型 常浪 B3 规则波 0.08 2.0 0.3 8 过渡型 常浪 B4 不规则波 0.15 1.5 0.1 0.5 侵蚀性 风暴 B5 不规则波 0.15 1.5 0.2 0.5 侵蚀性 风暴 B6 不规则波 0.15 1.5 0.3 0.5 侵蚀性 风暴 沙坝向海侧 C1 规则波 0.08 2.0 0.1 8 过渡型 常浪 C2 规则波 0.08 2.0 0.2 8 过渡型 常浪 C3 规则波 0.08 2.0 0.3 8 过渡型 常浪 C4 不规则波 0.15 1.5 0.1 0.5 侵蚀型 风暴 C5 不规则波 0.15 1.5 0.2 0.5 侵蚀型 风暴 C6 不规则波 0.15 1.5 0.3 0.5 侵蚀型 风暴 注:规则波对应平均波高,不规则波对应有效波高。 表 4 模拟工况0~8 h内RMSE值变化率(单位:10−2 m/h)
Tab. 4 The change rate of RMSE value within 8 hours of simulation cases (unit: 10−2 m/h)
补沙量/(m3·m−1) 补沙位置 0~1 h 1~2 h 2~3 h 3~4 h 4~5 h 5~6 h 6~7 h 7~8 h 0.1 滩肩 0.10 0.12 0.07 0.07 0.02 0.02 0.01 0.01 沙坝向海侧 0.08 0.09 0.07 0.06 0.06 0.02 0.02 0.02 0.2 滩肩 0.24 0.22 0.18 0.14 0.09 0.10 0.03 0.01 沙坝向海侧 0.49 0.46 0.28 0.22 0.18 0.14 0.12 0.01 0.3 滩肩 0.34 0.22 0.08 0.20 0.15 0.09 0.07 0.01 沙坝向海侧 2.02 0.93 0.47 0.33 0.27 0.21 0.17 0.01 表 5 风暴后海滩边缘水平位置变化(单位:m)
Tab. 5 Changes of horizontal position of beach edge after storm (unit: m)
补沙位置 工况 Y=0.43 m Y=0.47 m Y=0.50 m 未补沙 A2 −0.20 −0.17 −0.14 滩肩 B4 −0.10 −0.07 −0.07 B5 +0.09 +0.09 −0.10 B6 +0.40 +0.37 +0.18 沙坝向海侧 C4 −0.14 −0.14 −0.07 C5 −0.07 −0.14 −0.11 C6 0 −0.06 −0.11 注:“+”代表向海扩宽;“−”代表向陆缩窄。 表 6 风暴后水下凹槽处床面高程变化(单位:m)
Tab. 6 Changes of bed elevation at underwater trough after storm (unit: m)
补沙位置 工况 X=15.5 m X=16.0 m X=16.4 m 未补沙 A2 +0.005 +0.004 −0.003 滩肩 B4 +0.001 −0.004 −0.008 B5 −0.008 −0.009 −0.005 B6 −0.011 −0.009 −0.006 沙坝向海侧 C4 +0.007 +0.006 +0.002 C5 +0.019 +0.017 +0.012 C6 +0.033 +0.029 +0.020 注:“+”代表高程增加;“−”代表高程减小。 -
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