The authors have been developing a non-wave overtopping type seawall with a deep circular cross section (referred to a flaring shaped seawall (FSS) ). The seawall effectively controls waves by reversing incoming wave's motion on its curved face. This seawall creates a safe and useable space on top with a lower crest height compared to a conventional upright seawall. The basic characteristics of the FSS, such as wave overtopping, wave force and wave reflection, have been investigated through a series of experiments.
Practical construction of the FSS has been scheduled in Beppu bay. However, because in practical situations wind is blowing, it is necessary to investigate the effect of wind on an FSS. In this study, the hydraulic model used in the experiments is scaled down from an actual site and we predict the wind effect on water spray and wave overtopping when the planned FSS is constructed on site.

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A Flaring Shaped Seawall (FSS), a new type of one, can drastically reduce a crest height and wave overtopping quantity in comparison with a conventional upright one. The FSS will usually be set on a mound from the point of a cost of manufacturing and construction. Thus, in this paper, effects of the mound on hydraulic characteristics of the FSS (a wave overtopping rate, a wave run-up height and a reflection coefficient) are clarified from experiments using a two-dimensional flume. Furthermore a method for the FSS on the mound is proposed, and it is shown that the method is adequate under the condition of experiments in this paper.

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　護岸の補修・改良事業において一部区間をフレア型護岸に置き換える場合がある．施工箇所によっては改修区間のフレア型護岸法線が未改修区間の直立護岸法線と隅角部を形成し，隅角部での越波量の増大が懸念される．護岸隅角部での越波量の増大が懸念される場合には，一般的には必要個所を消波ブロック等で被覆する対策がとられるが，フレア型護岸前面を消波ブロック等で被覆すると円弧断面部での波返し運動が阻害され，護岸本来の越波低減機能の低下が懸念される．本研究では消波ブロック被覆工を用いないフレア型護岸隅角部の越波処理対策を検討することを目的に，天端張出工を設けたフレア型護岸断面を提案し，その越波低減機能を水理模型実験により評価した．また，越波低減機能の強化を目的に天端張出工に隔壁工を併用した対策工の効果を評価した．

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A Flaring Shaped Seawall (FSS) can make reduce crest height rather than conventional seawall in rough sea. However, the FSS has not been sufficiently made a study of application for road seawall in the neighborhood of shoreline.In order to clarifyt he hydraulic characteristics of the FSS as road seawall in that sea, two-dimensional wave experimentsw ere carried out, and wave run-uph eight, overtopping rate, pressured istribution and others were measured.It is confirmed that the characteristics of the FSS are more superiort o the verticalw all, and that are almost similar to the vertical wall protected with block mounds. So it is found that the FSS is suited to road seawall without wave-dissipating blocks.

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This study conducts two series of hydraulic experiment under some oblique incident wave conditions. One of the purposes of these experiments is to obtain the coefficient of equivalent crown height on Flaring Shaped Seawall. The other one is to clear the characteristic of wave overtopping at the joint section between Flaring Shaped Seawall and vertical one. The coefficient of equivalent crown height on Flaring Shaped Seawall shows different character under the oblique incident waves in comparison with conventional vertical seawalls. This study indicates that the value of Flaring Shaped Seawall could be taken as β=1.0 in the cases of longer incident wave period, such as T=1.6 sec. and 2.0 second. On the other hand, the coefficient tends to increase, β=1.15-1.3 with increase of incident wave angle under the shorter wave period. The increase of wave overtopping was observed at the joint section due to the run up of stem waves onto the wave dissipating blocks, though the wave dissipating works reduce the wave disturbance in front of the joint section.

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A Flaring Shaped Seawall (FSS) can drastically reduce a crest height and waveovertopping quantity incomparison with a conventional upright one. In this study, systematic hydraulicexperiments by irregular waves were carried out using a two-dimensional flume. As a result, a diagram to estimatethe crest height and overtopping rate of the FSS was made, and it is found that the overtopping rate and reflectioncoefficient of the FSS are almost similar to those of an upright seawall covered with wave-dissipating blocks. Furthermore pressures by regular waves were compared with ones by irregular waves, and a wave force formula for the FSS in an extreme shallow sea was investigated.

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マウンド上に構造物がある場合, 構造物に作用する波はマウンド高さや肩幅, あるいはマウンド上の水深等に応じて変化するので, 作用波圧や越波流量の特性はマウンドの諸元に強く影響される. このことはフレア型護岸においても同様で, マウンドの設置による衝撃砕波圧の発生や護岸越波流量の増大は実務上の問題となる. 本研究は, マウンド上に設置したフレア型護岸に作用する波圧と越波流量の特性を把握することを目的に実施した. 具体的には, 作用波圧および越波流量に対するマウンド法先水深や肩幅の影響を明らかにするとともに, 直立堤の波圧算定式から得られる波圧に対する計測波圧の比 (割増係数) を検討した.

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著者らは, 護岸上を安全で快適な親水空間として利用する目的で非越波型護岸 (フレア型護岸) を提案し, その越波阻止機能や耐波安定性について研究を進めてきた.安全で快適な海岸空間を確保するためには, フレア型護岸の越波制御機能や耐波安定性に加えて, 護岸背後への飛沫の輸送特性や低減対策についても十分に検討しておく必要がある.本研究では, フレア型護岸の飛沫輸送特性を明らかにするとともに, 飛沫を制御する方法として護岸頂部に上部直立壁を設けることを提案し, その効果を検討した.その結果, 上部直立壁を設置することで背後地への飛沫輸送量が大幅に低減でき, フレア型護岸が越波と飛沫に関して高い制御機能を持つことを明らかにした.

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Hydraulic characters of a non-wave overtopping type seawall installed on a moundare investigated through experiments with a two-dimensional wave tank. A critical wave height, which is defined as a maximum wave height on which no wave overtopping occurs at all, was measured on different incident wave conditions as well as mound configurations. The wave reflection coefficient and wave pressure distributions on the seawall were also measured when the waves with the critical waveheight act on the seawall. In this study, the characteristics of the critical wave height and wave reflection coefficient are discussed under various incident wave conditions as well as mound configurations. And then, characteristics of wave pressure distributions are also discussed with comparing the design wave pressure act on the vertical seawall.

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　2012年，熊本高等専門学校（熊本高専）と八代河川国道事務所は連携協定を結び，特に球磨川流域における防災・減災について共同で研究・教育を実施してきている．熊本県の球磨川流域にある球磨村渡地区では，出水時に家屋浸水被害が多く発生しており，この地区に対する防災減災対策を共同で検討した．該当地区における水理模型実験を実施し，その対策工を検討する一方で，実験には多くの住民や学生にも参加してもらい，被災のメカニズムや対処方法といった点を中心に防災教育も並行して実施した．この官学連携の取り組みを通し，渡地区には実験結果を元にして導流堤が実際に施工された一方，参加した学生の防災減災に対する意識も向上しており，ハードとソフトの両面から成果を挙げられた．

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Hydraulic Characteristics of Flaring Shaped Scawall (FSS) in deepwater were investigated experimentally. A minimum crest height on which no wave overtopping is allowed, a reflection coefficient and a wave overtopping rate were measured for two types of FSS with aquadrant circular cross section and a semicircular one. Above three factors of FSS were compared with those of a conventional vertical seawall to clarify efficiency of the proposed seawall in deepwater. The minimum crest height of FSS is smaller than that of the vertical seawall and this effectiveness becomes large with increase of offshore wave steepness. The same results were obtained for the wave overtopping. The reflection coefficient of FSS with a semicircular cross section becomes smaller than that with a quadrant circular cross section and the vertical seawall.

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A Flaring Shaped Seawall (FSS) can drastically reduce a crest height and wave overtopping quantity in comparison with a conventional upright one. In this study, a series of hydraulic experiments were carried out using a two-dimensional flumeto apply the FSS to practical use. As a result, armor stones on the rubble moundfoundation were stabilized for a series of irregular waves. Flow velocities of wave in front of the FSS were measured to investigate scour. These were almost same as those of the upright seawall, and an average value of flow velocity indicated in the direction of onshore. Furthermore an impulsive breaking wave pressureby regular wave was measured and was about 4.5 times larger than one by Goda's formula. Finally, a diagram to estimate the crest height and wave overtopping rate of the FSS was made.

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Authors proposed a non-wave overtopping type seawall (refer as Flaring Shaped Seawall: FSS) with a deep circular cross section. Through a series of studies, they had already confirmed that the FSS satisfies a non-wave overtopping condition with an extremely lower crown height in comparison with a conventional wave absorbing upright seawall. In this study, the reduction effects of both wave overtopping and water spray by the FSS were investigated through hydraulic experiments. And then, in order to reduce the water spray on the FSS effectively, we proposed a vertical wall attached at the tip of the FSS as a technical device. It was confirmed that the vertical wall effectively reduces the spray on the FSS, and the quantity of spray becomes smaller than that on the upright seawall.

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　護岸隅角部の越波処理では，護岸を消波ブロックで被覆する対策が一般的であるが，フレア型護岸を消波ブロックで被覆すると，護岸局面部での波返し運動と消波工の相互作用によってフレア型護岸の越波低減効果が損なわれることが懸念される．この問題は，護岸に沿い波が発生する条件でより顕著になると考えられる．本研究では，フレア断面を含む護岸隅角部の越波低減対策として，消波ブロック被覆工の適用方法を水理模型実験により検討した．また，消波ブロックを用いない対策としてフレア型護岸に隔壁工を設ける対策を取り上げ，その効果と適用性を検討するとともに，隔壁工および隅角部付近の護岸部に作用する波圧特性について検討した．隔壁工は，沿い波の影響が比較的小さい条件では一定の越波低減効果が見られるが，沿い波が顕著になるとその効果は小さい．このような条件では，直立護岸側に加えてフレア型護岸側も消波ブロックで被覆する対策が有効となる．隔壁工には入射波高相当の静水圧の数倍程度の波圧が作用する．

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Flaring Shaped Seawall (FSS) can drastically reduce a crest height and wave overtopping volume in comparison with a conventional upright one, and a top area of the FSS can be used effectively. In this study, hydraulic experiments and numerical simulations for the FSS on the mound have been carried out using a twodimensional flume model. As a result, the wave overtopping rate and flow velocity by the numerical simulations are in agreement with those by the experiments. Good agreement between numerical results and experimental ones is found in not impulsive wave pressure. However, it is necessary to investigate an impulsive wave pressure furthermore.

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Authors have proposed a non-wave overtopping type seawall (Flaring Shaped Seawall) with deep circular cross section in order to facilitate a safe and excellent use of coastal space for various purposes. The seawall satisfies a non-wave overtopping condition with extremely lower crown height in comparison with conventional upright seawall. In this study, wind field near the seawall, water spray transported behind the seawall and sounds when waves running up were measured in the experiments, and compared with an upright seawall.

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Flaring shaped Seawall was adopted as the Osako port in Kurahashi-cho for the first time in the country in consideration of low height, scene nature, preservation of sands, and economical efficiency, etc. The height of flaring shaped seawall was decided to be +6.0m using the wave overtopping rate presumption diagram ofit. Although we conducted the two-dimensional wave tank model in the proposal section and the wave overtopping rate (0.0002m³/m/s) checked that it was1/50 of the permissible value, the breaking wave pressure became large shockingly, it was about five times the Goda equation wave pressure. Structure of flaringshaped seawall was made into the composite construction of steel and concrete. The structure design was performed in finite-element analysis by making this shockingly breaking wave load into static load and was able to be designed rationally. Since composite structure was adopted, construction of flaring shaped seawallwas able to be performed very easily.

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