土堤加糙透水式预制块护坡消浪效果模型试验

波浪爬高是确定土堤堤顶高程的重要参数之一,土堤坡面护坡的消浪效果将直接影响波浪的爬高,在土堤护坡工程中,光面混凝土预制块护坡应用最为广泛,但其消浪效果较差,为了解决这一的问题,该文以鄱阳湖上饶片区堤防工程为例,通过增加护坡预制块糙渗系数提出了凹槽嵌固式正六边形预制块、Z字型混凝土预制块和嵌固式四边形空心预制块等3种护坡体型,通过建立护坡消浪室内物理模型试验系统,对比分析了3种预制块相对于传统光面混凝土预制块护坡的消浪效果,提出了3种预制块糙渗系数计算取值。试验结果表明:与光面混凝土预制块护坡相比,该文设计的3种预制块护坡对波浪的爬高都有较大幅度的抑制,坡面上波浪爬高试验结果从小到大依次为凹槽嵌固式正六边形预制块、Z字型混凝土预制块、嵌固式四边形空心预制块、光面混凝土预制块;3种预制块护坡相对于光面混凝土预制块的波浪爬高衰减率(波浪爬高减小比例)依次为35.0%、30.2%和26.23%,计算得到对应的糙渗系数取值分别为0.76、0.77、0.79。综合消浪效果及节约工程成本分析,采用凹槽嵌固式正六边形预制块护坡最佳,具有良好的推广价值和发展前景。

Model test on wave dissipation effect of roughened embankment with permeable prefabricated block for slope protection

Abstract: Wave run-up is a key parameter in determining the crest elevation of earth embankments, and it is considerably affected by the wave reduction effect of protection slope. Smooth concrete prefabricated block is widely used in the slope protection of embankments. However, its wave reduction effect is relatively poor. To solve this problem, 3 new kinds of prefabricated blocks were designed to improve the wave reduction effect by increasing the roughness coefficient of the prefabricated block, including concave and embedded regular hexagon type prefabricated block, Z type prefabricated concrete block and embedded quadrangle type prefabricated hollow block. According to the formula in Handbook of hydraulic structure design, the thickness of prefabricated block was calculated, and then a laboratorial physical model experiment was performed in a wave flume for the slope protection and wave dissipation. Nine tests were carried out under 3 water depths (23.6, 30.6 and 37.15 cm) and 3 wave periods (1.5, 1.875 and 2.5 s). In the experiment, waves were produced by a wave maker, and the wave run-up was measured by a photogrammetric method. The wave reduction effects of the 3 new kinds of prefabricated blocks were assessed by the reduction ratio of the wave run-up compared with the smooth concrete prefabricated block. Additionally, the values of the 3 new kinds of prefabricated blocks'' roughness coefficient were proposed. The experiment results showed that, compared with the smooth concrete prefabricated block, the 3 kinds of prefabricated blocks proposed in this paper had obvious inhibiting effects on wave run-up. The concave and embedded regular hexagon type prefabricated block had the most inhibiting effect, followed by the Z type prefabricated concrete block and embedded quadrangle type prefabricated hollow block. Their wave run-up decay rates (the reduction ratio of the new designs to the smooth concrete prefabricated block) were 35.0%, 30.2% and 26.23%, respectively, and corresponding roughness coefficients were 0.76, 0.77 and 0.79, respectively. Finally, the economic benefits of the 3 kinds of new designed prefabricated blocks were analyzed in this paper. It was mainly divided into 2 parts, the revetment concrete amount with the same thickness, and the extent of crest elevation reduction by the wave reduction effects. According to the comprehensive comparison and analysis, the concave and embedded regular hexagon type prefabricated block consumed less concrete amount, which decreased by 17.13% compared with the smooth concrete prefabricated block, and wave run-up was more reduced. For example, if the wave run-up of the smooth concrete prefabricated block was 1.0 m, the concave and embedded regular hexagon type prefabricated block would be 0.65 m, the Z type prefabricated concrete block would be 0.70 m, and the embedded quadrangle type prefabricated hollow block would be 0.74 m. Consequently, considering the effect of revetment wave and economic benefit, the concave and embedded regular hexagon type prefabricated block is the best choice in the slope protection and has popularization value and development prospects.