Studies on optimum design and conservation of artifical reefs

目的是通过水工模型试验，明确浅海区人工鱼礁等人工构筑物防倾覆、防掩埋的优化设计和养护方法。特别是本研究涉及的水力学问题是波浪控制和引起泥沙输移的牵引力。（1）Ohashi和Kainou在20 m × 15 m的近岸波浪试验池中，对濑户内海岛屿上常见的袋状海滩建立了固定床模型。这个模型按比例缩小到原型的四十分之一。主要是通过设置具有鱼礁功能的透空式防波堤来控制波浪，并进行了规则波试验。从实验结果来看，可以清楚地看到改进的效果，仅在防波堤的中心周围被识别。因为t的存在 ...更多信息 渔港和海滩两侧的小岬对该海域的波浪状况影响较大，因此，对进一步的改善措施进行了研究。考虑到复杂的波浪特性（如三维绕射波和越浪率分布等），最后确定了防波堤的最佳长度和开口宽度。(2)Ohashi和Fujihara在不规则波试验池中设置了4种不同类型的礁石（顶宽分别为30 cm、50 cm、70 cm的台阶型和条形礁石），进行了波高衰减试验。在两个不同的能量水平下进行了7-9个水位（间隔2cm）的试验，共测量了8个点的波高。根据试验结果（波浪反射率、有效波高、最大能量、总能量和起升值），探讨了各类礁体作为防浪建筑物的最佳水力条件，这些结果不仅可作为风浪时的防御措施，也可从休闲角度作为平静时的利用措施。少

The aim is to make clear the optimum design and conservation method to keep the man-made structures (e.g.artificial reefs) set in the shallow sea area from overturning and burying thorough the hydraulic model experiments. In particular the hydraulic problems concerning to this study are the wave control and tractive force which induces the sediment transport. Their hydraulic characteristics are revealed experimentally in this research(1) Ohashi and Kainou constructed the fixed bed model of the pocket beaches, which are commonly seen at the islands in the Seto Inland Sea, in the coastal wave test basin (20m*15m). The model is scaled down to one-fortieth of the prototype. Mainly to control the waves by setting the permeable offshore breakwater, which can function as fish reef, the experiments with the regular waves were conducted. From the experimental results, it was clear the effect of the improvement, was recognized only around the center of the breakwater. Because the existences of t … More he fishing port and the small promontory at both sides of the pocket beach affect largely the wave condition in it. Therefore, further improvement were examined. Considering the complex wave characteristics (e.g.three dimensional diffracted wave and the distribution of overtopping rate, and etc.), the optimal length and opening width of breakwater were finally decided.(2) Ohashi and Fujihara experimented the decay of wave height by setting the four types of reefs (step type and bar type with 30cm, 50cm, 70cm of crown width) in the irregular wave test tank. The experiments under two different energy levels with 7-9 cases of water level (2cm interval) were conducted and wave heights were measured at 8 points. The Optimal hydraulic conditions of each type of reefs as wave control structures were investigated from the experimental results (wave reflection ratio, significant wave height, maximum energy, total energy and set-up value).These results are useful not only for a defending measure when stormy, but also for a utilizing measure when calm from the point of leisure. Less