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吉田 秀樹, 清水 利浩, 伊部 知徳, 山田 貴裕, 片野 明良
2008 年 55 巻 p.
751-755
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
In Niigata west coast, integrated shore protection system by large-scale submerged breakwater has been applied. The topography change in the site is characterized by the belt-shaped scour extends along the submerged breakwater and land subsidence. This study intends to the above two typical process. By analyzing sounding survey data behind the submerged breakwater, it is confirmed that the scour depth of the belt-shaped scour relates to the speed of the submerged breakwater extension. Also, by analyzing the cross-shore profile, it is found that the cross-shore profile change which includes the effect of the land subsidence is quite similar to that by sea level rise predicted using Bruun's law.
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福島 眞司, 熊切 良行, 福濱 方哉, 山田 浩次, 有村 盾一, 山田 文則
2008 年 55 巻 p.
756-760
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
Fuji coast has several submarine canyons with steep slope. According to the previousurveys one of them located in front of Yoshiwara may cause the material of beach nourishment to move offshore. In this study the effect of the submarine wall proposed as the countermeasure were investigated using the 2-D hydraulic model test with sandy bed. As the results, it is found that the eddy yielded nearby the wall caused by waves has a significant effect on the sediment movement, and that effect depends on the location and the height of the wall.
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澁谷 容子, 黒岩 正光, 松原 雄平
2008 年 55 巻 p.
761-765
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
This study is concerned with a N-line model that takes into account contour line changes after beach nourishments. The behavior of the sand materials after beach nourishments is represented using two-dimensional advection diffusion equation in the horizontal plane. The effect of grain size of the nourished sand was considered in the advection diffusion equation. The contour line changes were calculated solving the fundamental equation for the conservation of bedmaterial, which adapts the effect of the advection diffusion equation. Firstly, model tests were carried out in orderto investigate the influence of grain size. The effect of grain size for beach nourishment was investigated. Secondly, the model was applied to preservation of eroded beach using a sand recycle method measures, and then the applicability was discussed.
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野川 康利, 宇多 高明, 松浦 健郎, 阿部 良, 長山 英樹, 大木 康弘
2008 年 55 巻 p.
766-770
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
Field investigation on the effect and stability of gravel nourishment was carried out on the Jinkoji coast facing the Pacific Ocean. 33, 000 m
3 of gravel was nourished on the shoreline, and subsequent beach changes were monitored by topographic surveys. Gravel layer was very stable while depositing along the shoreline. Fine sand layer on the shoreline was replaced by the nourishment gravel, leaving gravel layer below the fine sand layer as a foot protection in front of the seawall. A steep slope of 1/7 formed was effective to dissipate rough waves and to prevent wave run-up.
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野川 康利, 宇多 高明, 松浦 健郎, 阿部 良, 熊田 貴之, 長山 英樹
2008 年 55 巻 p.
771-775
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
Field experiment on changes in thickness of the sand mixing layer was investigated on the Jinkoji coast, where beach nourishment using coarse material has been carried out. Four trenches were excavated on the shore face, andcoarse material, fine sand and their mixture were filled in each trench, and subsequent mixing due to waves were investigated. Comparing the mobility of sandy beach composed of various materials, minimum mobility was obtained at gravel, and the mobility of the beach composed of the mixture of sand and gravel was the largest, implying that the effect of the beach nourishment using the mixture of sand and gravel is inferior to that using gravel only.
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宇多 高明, 田代 洋一, 長山 英樹
2008 年 55 巻 p.
776-780
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
Offshore beach nourishment using 2×10
4m
3 of dredged sand was carried out off the Ichino-miya coast on south Kujukuri Beach, and subsequent movement of sand was investigated through the filed observation using a narrow-multi-beam measurement. After the beach nourishment, sand movement was traced for three months, despite the attack of rough waves generated by typhoons. Nourishment sand was gradually transported shoreward with gradual diffusion alongshore, implying the effectiveness of offshore sand nourishment as a method for shore protection. Meandering of offshore contours around the tip of the artificial headlands was also observed by this measurement.
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宇野 宏司, 辻本 剛三, 徳田 一樹, 柿木 哲哉, 出口 一郎, 有田 守
2008 年 55 巻 p.
781-785
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
To clarify the relationship between the colonization of coastal vegetation and sediment dynamics at the Fukiage beach which is located in the southwestern part of Awaji Island in west Japan, the cluster analysis, field observations and the estimation of the amount of wind-blown sand were carried out. The sediment dynamics at the Fukiage beach has been in equilibrium all over the place in past 36 years, however, the colonization of coastal vegetation has been different from place to place. In winter, the winds in NW direction stand out and it carries the microscope sediment particles from east to west. Hence, the sediment tends to be miniaturizing from east to west in the beach. The seasonal wind in winter and strong wind caused by typhoon in summer might be important for the sediment transport at the Fukiage beach.
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有田 守, 出口 一郎, 芝崎 拓弥
2008 年 55 巻 p.
786-790
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
The method of forecasting the proper land in the Zostera beds by considering the physical limitation element has not been established. This paper propose the method of the proper land selection that considers an effect of the waves attenuation and a physical condition in this theory, and to clarify which factor becomes the obstruction factor of the Zostera growth.
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山田 文彦, 柴田 康晴, 田端 優憲, 玉置 昭夫
2008 年 55 巻 p.
791-795
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
Three-dimentional Laser and X-ray Computed Tomography (CT) Scanners have been applied to investigate a time-space evolutions of wave-generated ripple geometry and vertical sediment structures of intertidal mudflat with non-destructive conditions at Shirakawa River mouth. Field observations were conducted in two places where there are many Ruditapes philippinarums (clam-dominant area) or not (calm non-dominant area). Time-space evolutions of wave-generated ripple geometry at non-dominant area were found to be larger than those of calm-dominant area. Reconstructing threedimensional images using CT value, retention water in the intertidal sediment at calm-dominant area existed up to 6cm below the sediment surface during dry cycle of tide motions.
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平山 克也
2008 年 55 巻 p.
796-800
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
A Boussinesq-typ.wave transformation model which can calculate shoaling and breaking of nonlinear waves has been applied to the estimation of harbor tranquility. However, in a conventional procedure of harbor tranquility analysis, the nonlinearity of harbor waves is ignored because it is based on linear theory. In this paper, a new procedure of harbor tranquility analysis is proposed in order to consider the nonlinearity of harbor waves calculated by using the Boussinesqtyp. wave transformation model. The applicability of the new analysis method of harbor tranquility is demonstrated in two harbors where some storm waves penetrate to a reef, while the wave heights and spectra in front of wharves on complex bathymetry are calculated with good accuracy.
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吉田 明徳, 西井 康浩, 山城 賢, 加嶋 武志, 太田 一行
2008 年 55 巻 p.
801-805
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
On ship motions in harbors, a method for estimating diffraction forces from wave field calculations with the Boussinesq model is considered based on potential theory. Since the potential and its normal derivative on any arbitrary boundary enclosing the ship is obtained from the Boussinesq model as time histories of the water surface oscillation and the depthaveraged velocities at each grid point, the incident wave potential along the ship is calculated through Green's Identity Formula. Then a boundary value problem on the diffraction potential is formulated using the method of matched eigen function expansions. By solving the problem, the diffraction potentials are determined, and the ship motions are estimated through the retardation function method using thus obtained diffraction forces.
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浅川 耀賛, 岡本 弘, 関 克己, 水口 優
2008 年 55 巻 p.
806-810
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
Wave reflection from compound slope is studied experimentally. When the water depth is small, breaking and reflection occur on the offshore mild slope and little reflection is observed. When the water depth is large, reflection occurs on the steep slope with high reflection coefficient. For the intermediate water depth, relatively high reflection with significant high frequency components is observed. These high frequency components introduce space variation of local wave height of reflected waves. Energy-based reflection coefficient is evaluated and compared with hypothetical single slope method for wave run-up with some success.
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永瀬 恭一, 平石 哲也, 押村 嘉人
2008 年 55 巻 p.
811-815
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
Long period waves cause large surging motion in mooring cargo vessels due to resonance. This can cause interruption in cargo handling and even break mooring rope when the ship surging motion becomes extremely large. A new type of sea wall composed of a double faced slit caisson backed by a rubble layer has been proposed in order to reduce the long period wave height in harbor. However this structure is very large and it can be difficult to construct in existing harbor. So, some alternative, more feasible proposals were assessed in terms of wave performance model experiments and numerical analysis.
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本田 隆英, 伊藤 一教
2008 年 55 巻 p.
816-820
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
CADMAS-SURF is a useful tool to evaluate wave actions for coastal structures. However, there are few studies concerning irregular waves by using CADMAS-SURF. The aim of this paper is to examine the applicability of CADMASSURF for the wave overtopping rate caused by irregular waves. The wave overtopping rate was calculated for uniform and sloped bottom conditions by using CADMAS-SURF. The calculated wave overtopping rate was compared with existing formulae. It is shown that CADMAS-SURF is capable of estimating the wave overtopping rate by irregular waves under broad condition with almost the same accuracy of existing formulae. It is also possible to determine the short-term overtopping rate caused by wave irregularity.
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村上 啓介, 新田 純也, 真木 大介, 上久保 祐志, 片岡 保人
2008 年 55 巻 p.
821-825
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
Hydraulic performances of a non-wave overtopping type seawall were investigated on a supposition of the sea level rise that might occur near future. Two-dimensional hydraulic experiments were carried out under some different water level conditions, which reproducing the sea level rise, to clear the effect of the sea level rise on the hydraulic performances of the non-wave overtopping type seawall. Furthermore, this study proposes an appropriate countermeasure against the sea level rise to maintain an excellent checking effect of the wave overtopping of the seawall. Both the efficiencies of the proposed countermeasure and characteristics of the maximum wave pressure acting on it were evaluated through hydraulic experiments.
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齋藤 英治, 平石 哲也, 稲垣 茂樹
2008 年 55 巻 p.
826-830
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
Several offshore airports in the Japanese coasts are often damaged+these days by the wave overtopping due to storm s. One of the problems in such offshore airports is the limitation of seawall crown height derived from the width, height and distance of runway. Minami et al.(2007) have proposed a new typ. seawall with a wide permeable layer behind the front parapet to reduce the wave overtopping rate. In this paper, an experiment in a directional wave basin is carried out to determine the most appropriate width of permeable layer and height of its backward parapet. The experimental results reveal that the wave overtopping rate becomes smaller than the allowable level as the permeable layer becomes wider than 6m. The backward parapet has to be higher than 2.5m to prevent the overflow into runways.
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川崎 浩司, 菊 雅美, 笹田 泰雄, 眞栄里 和也, 内間 安治, 嶋田 宏, 五味 久昭, 三浦 健悟, 柴田 哲郎
2008 年 55 巻 p.
831-835
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
The purpose of this study is to investigate the effect of bottom topography and revetment configuration on wave deformation and wave overtopping characteristics around a revetment in regular or irregular wave field by conducting hydraulic model experiments and numerical computations with a CADMAS-SURF. The results revealed thatwave deformation over a reef has an effect on wave overtopping rate and a semi-circle type revetment is efficient in reducing wave overtopping rate. It was, therefore, confirmed to be important to consider the wave deformation so as to take countermeasures against wave overtopping in a coral reef sea area. The computational results also showedthat the CADMAS-SURF is a useful tool to estimate the wave overtopping rate of specially-shaped revetment over complicated bottom topography.
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後藤 仁志, 五十里 洋行, 安岡 恒人, 奥 謙介
2008 年 55 巻 p.
836-840
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
At a low crown caisson seawall with a large-size wave overtopping drainage, the pick-up of blocks on a caisson mound is one of the important issues. In a previous paper, it was conducted to predict the pick-up of blocks by using the C. E. R. C formula and the simulation by the MPS method, however, in order to predict more precisely, the movement of blocks should be tracked. Therefore, in this study, a simulation by the DEM-MPS hybrid model is carried out. In this model, fluid is calculated based on the MPS method and blocks are tracked by DEM. In a calculated result, blocks around the top of mound slope were picked up. This fact shows a good agreement with the hydraulic experiment.
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中條 壮大, 重松 孝昌, 坂下 直也, 辻本 剛三, 竹原 幸生
2008 年 55 巻 p.
841-845
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
The effect of oscillatory flow properties, the Reynolds number and the KC number, on turbulence generated by a porous media was investigated by hydraulic experiment. Violent turbulence was generated when interstitial velocity exceeded a critical level. Turbulent energy generated in pores increased as the Reynolds number increased. In a porous media, difference between minimum and maximum values of turbulent energy was increased as the KC number increased. And outside porous media, turbulent energy spread widely as the KC number increased. Under unsteady oscillatory flow, maximum turbulent energy was larger than that of unidirectional steady flow.
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渡部 靖憲, 田中 康文
2008 年 55 巻 p.
846-850
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
Fundamental optical responses of bioluminescent dinoflagellates, Pyrocystis lunura under impacting water pressure were measured in the imaging experiment. Effects of biological parameters, such as fatigue andbiorhythm, to the responses were also examined. A good correlation of the bioluminescent intensity and the dynamic pressure was obtained on the basis of our proposing statistical image preprocessing, indicating a possibility to develop new bio-measurement tool for acquiring spatial distributions of hydro-dynamic pressure.
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木岡 信治, 森 昌也, 山本 泰司, 竹内 貴弘
2008 年 55 巻 p.
851-855
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
In 1952, ice floes due to Tsunami, originated in the sea off the coast of Tokachi, caused serious damages to private houses, especially in Hamanaka town. Therefore, the ice impact force due to Tsunami during iceseason should be considered for the design of structures, especially important structures or their protective structures near the coast or port and harbor. We performed a medium-scale model test on the ice impact to a structure by free-fall of the ice floe. The influences of kinetic energy of ice floe and ice temperature on the impact force were clarified. Wealso developed a fundamental numerical simulation method for the ice impact to a structure based on the DEM with tension resistance among particles. The method was confirmed to be appropriate if mechanical parameters were properly given.
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森 昌也, 山本 泰司, 木村 克俊, 渡辺 慎也
2008 年 55 巻 p.
856-860
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
A high mound composite seawall, which has a permeable front wall with a dissipation chamber on the superstructure, was newly developed as a revetment for reclaimed land. Several studies have focused on the hydraulic characteristics of high mound seawall; however sufficient examination has not been carried out on the oblique wave conditions. Threedimensional hydraulic model experiments were conducted to investigate the wave force characteristics and wave overtopping characteristics under oblique wave conditions. Based on the phase difference of impulsive wave force acting on superstructure, wave force reduction coefficients for oblique waves were proposed. Furthermore, influence of incident wave angle on wave overtopping rate and wave run-up height were studied.
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下迫 健一郎, Giovanni CUOMO, 高橋 重雄
2008 年 55 巻 p.
861-865
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
Recent failures of coastal bridges during extreme storm events have focused attention on the need for research on wave loading of coastal structures suspended slightly above the still water level. This paper presents findings from large-scale experimental work carried out in the wave basin. Measurements from physical model tests are used to gain insights on the dynamics of wave-loading of coastal bridges and to derive prediction methods for both quasi-static and impulsive wave loads. The effect of openings in the bridge deck is also discussed, and guidance derived for design purpose.
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荒木 進歩, 中嶋 悠, 出口 一郎, 伊藤 禎和
2008 年 55 巻 p.
866-870
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
Horizontal and vertical tsunami fluid forces acting on a bridge beam near the river mouth were measured with and without river flow in hydraulic experiments. Very large impulsive force was measured. Vertical tsunami fluid force increased with the increase in the tsunami wave height over the bridge beam. Horizontal tsunami fluid force (wave pressure) increased under the condition that the top of wave crest hit the bridge beam. Generally, horizontal tsunami fluid force (wave pressure) in the cases of river flow was smaller than that in the cases of no river flow. Although it is difficult to estimate impulsive fluid force, the wave pressure after the impulsive component was able to be estimated by the equation that has been already proposed for structures on the ground.
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福山 貴子, 池谷 毅, 福本 幸成
2008 年 55 巻 p.
871-875
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
Regarding the isolated offshore structures, e. g., bridge foundations, sea berths or an offshore wind farm, the plural structures are constructed in an offshore area, and sometimes the collapse of one structure loses the important function of the facility. We propose the method for evaluating the probability distribution of wave force acting on the isolated structure and the probability of destruction of one or plural structures. To calculate the probability distribution of wave force, we set the log-normal distribution to the wave force acting over the still water level, and the normal distribution to the wave force acting under the still water level. The calculated distribution well agreedwith the experimented data. This method can be applicable to the isolated structures of arbitrary shape.
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長谷部 雅伸, 大山 巧
2008 年 55 巻 p.
876-880
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
Three-dimentional expanded mild-slope equation models were applied to seismic response analysis of semi-submersibletype isolation structure. Against horizontal vibration, damping effects caused by wave generation calculated by the 3Dmodel was relatively weak, and the peak of magnification factor indicated larger value than the results of 2D-model. We also estimated axial forces of rubber bearings under vertical and horizontal external vibration, and found that not only heaving but also rocking motion increases axial forces.
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大垣 圭一, 米山 治男, 鈴木 貴志
2008 年 55 巻 p.
881-885
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
We studied the most effective mooring method of a ship against a tsunami based on the numerical simulations. First, we set the ordinary mooring method and four mooring methods proposed as the countermeasures against the tsunami. And then, we performed the ship motion simulations by using the tsunami waves as the external forces and evaluated these countermeasures. The main results are: 1) The surging is the significant motion of the moored ship because the tsunami flows along the quay, 2) Although the motions of the ship becomes large when we set the mooring ropes long, we can reduce the effects on the mooring system (the mooring ropes and fenders), and 3) The method that the mooring ropes are set long is the most effective mooring method against the tsunami.
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米山 望, 永島 弘士, 戸田 圭一
2008 年 55 巻 p.
886-890
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
The main purpose of this study is to develop a numerical analysis code for the prediction of drift behavior in a tsunami inundation. The features of this code are that the FAVOR method is applied to set the boundary between a fluid and an obstacle, and that the VOF method is applied for a flow involving a free surface. The code was applied to a hydraulic experiment on an object drifted by a tsunami inundation. As a result, the code simulated the drift motion, and the obtained numerical solution of the drift velocity agreed well with the result of the experiment.
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李 光浩, 水谷 法美, 後藤 政雄
2008 年 55 巻 p.
891-895
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
In the present work, an Immersed Boundary (IB) method is applied to the numerical simulation of dynamic behavior of a tension leg floating body, which is vertically moored. The main feature of the tension leg floating body is the mooring system that maintains tension because of the excess buoyancy. The moving solid interface is represented by a distributed force term in the Navier-Stokes equations, which guarantees implementation of boundary condition over the solid-fluid interface. These equations are discretized on the Cartesian grid, using the finite difference method. The finite displacement of the breakwater, sway and heave, is computed in every time step, using the force balance acting on the floating body. Numerical results are compared with available experimental data and good agreement is achieved.
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外村 隆臣, 江島 隆晃, 今村 格, 津嶋 了, 辻本 剛三, 由比 政年, 沖 和哉, 山田 文彦
2008 年 55 巻 p.
896-900
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
Wave energy dissipation mechanisms of the Double Barrier Floating Breakwater (DBFB) have been examined using numerical analysis. The DBFB has a rectangular body and double vertical plates to make energy dissipation with vortex flow around the tip of plates. In the field observations, transmitted wave heights behind the breakwater were reduced during storm conditions. The numerical model solves two-dimensional, unsteady Reynolds averaged Navier-Stokes equations in the vertical plane. The k-ε Aturbulent model is also used for the computation of Reynolds stresses as well as the Volume Of Fluid method for tracking the variation of the free surface. The attached plate at the both side of floating body significantly enhances the efficiency of the floating body.
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五十里 洋行, 後藤 仁志
2008 年 55 巻 p.
901-905
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
Because a moored ship can be drifted and stranded when a mooring chain is broken due to a high wave, it is important to predict the movement of a moored floating object under acting such a high wave. Some of numerical prediction has been conducted, however, there is no model to simulate a floating object appropriately under a high wave. Therefore, in this study, a simulation model based on a particle method is developed. In this model, a mooring chain is tracked by a springmass model. As to the track of a floating object and the tension acting on a chain, calculated results show good agreement with experimental results in the previous studies.
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有川 太郎, 中野 史丈, 菊池 喜昭, 小林 真, 木原 一禎, 櫻井 良宏, 虎石 龍彦
2008 年 55 巻 p.
906-910
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
This report describes the results of the large scale model tests on the buoyancy-driven vertical piling breakwater by using the buoyancy-driven piles. This breakwater consists of rows of steel pip. piles and each pile consists of upper and lower steel pipes. The overall performance of this breakwater has been verified, but the relation between stress and wave power is not cleared at the part of lap joint between upper pipes and lower pipes, at which large stress may be occurred. So, the large scale model tests by using the buoyancy-driven piles were conducted. Main results of this paper are that movement of the upper pile under waves is confirmed and the relationship between the strain at the lap part and the wave power is clarified qualitatively.
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平石 哲也, 春尾 和人, 横田 弘, 長谷川 巌, 稲垣 茂樹
2008 年 55 巻 p.
911-915
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
Large jacket-type structures are employed in the construction of the forth runway, Tokyo International Airport (Haneda). The runway is located at the mouth of Tama River flowing into the Tokyo Bay and the jackets are employed in the one -third part of runway so that the flood from the river may not be disturbed by the runway. Meanwhile many timbers may be floated from the upstream in the flood and they may cause the collision on a pier composing the jacket structures. This paper describes at the first an experiment for the probability of collision by the drifting timber in a basin with the scale of 1/25. The horizontal motion of five model timbers is analyzed using the 3-D video camera tracker. Secondary an experiment for the collision force measurement is carried out in a channel with the scale of 1/10. The model test result shows that the high risk of collision by the drifting timber exists. A calculation formula of collision force is proposed.
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中村 孝幸, 中村 淳一, 兼貞 透
2008 年 55 巻 p.
916-920
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
The authors have developed a water exchange breakwater of water chamber type, in which the piston mode wave motion in the chamber is used as a major driving force for generating mean flows by waves. In this study, intending the development of a gravity type water exchange breakwater on a rubble mound, stability of amour concrete units of a rubble foundation has been examined experimentally. As a comparison test, stability of the same amour units for an impermeable caisson breakwater was also examined. It has become known that the jet flow from the gap under the front curtain wall of the water exchange breakwater has close relations to the stability of amour units on the rubble foundation. It was seen that the critical wave height for stability of the amour units for the water exchange breakwater was comparatively small.
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高山 知司, 辻尾 大樹, 安田 誠宏
2008 年 55 巻 p.
921-925
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
Recently, caisson sliding failures affected by large waves have occurred. The damage of the breakwaters in Susami port due to Typhoon 0423 is a typical sliding failure and the caissons were tilted down in the rear of rubble mound. The damage at Fushiki-Toyama port on February 2008 is also another typical sliding failure and concrete blocks were settled down. The present paper describes the factors of their caisson sliding failures affected by damage of armor concrete blocks. It concludes that the caisson sliding failure at Susami port was caused by insufficient weight of the caisson. Even if heavier concrete blocks are placed as armors, the caisson would be slid. The numerical simulation suggests that the caisson sliding failure at Fushiki-Toyama port was caused by the combination of three factors of large wave height, long wave period and duration time.
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有光 剛, 尾西 宙郎
2008 年 55 巻 p.
926-930
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
In the repair of damaged wave-dissipation works, the stability of wave dissipation blocks is expected to be improved by the use of blocks larger mass than the required mass in the initial design. However, although the wave-dissipation blocks used for the repair are heavier than the weight calculated by the Hudson equation, the damage of the blocks has occasionally occurred near the crest of wave-dissipating works. This paper aims to elucidate the damage mechanism of wavedissipation blocks used for the repair at the crest of wave-dissipating blocks of a low-crested seawall by conducting hydraulic model experiments. It is found from the experimental results that the wave pressure in the vicinity of the discontinuity of the mass of blocks causes the block damage near the water surface.
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久保田 真一, 下迫 健一郎, 浜口 正志, 松本 朗, 半沢 稔, 山本 方人
2008 年 55 巻 p.
931-935
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
A rubble mound of composite breakwater is usually covered with armor blocks and foot-protection blocks to prevent its deformation. Although the design method for armor blocks and foot-protection blocks seems to have been almost established, nowadays, the site conditions are becoming severer. Therefore more rational design methods are required. The purpose of this study is to obtain the new knowledge correlating to the stability and cost reduction for the foundation of composite breakwater. Wave forces acting on the armor blocks were measured and the rational shape of block which reduces the uplift force was proposed. Hydraulic stability tests for foot-protection blocks with various scales were conducted and the rational designs were investigated.
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諸星 一信, 小濱 英司, 渡部 昌治, 清宮 理, 菅野 高弘, 宮田 正史, 山本 修司, 佐藤 成
2008 年 55 巻 p.
936-940
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
The construction of a high seismic resistant quay, MC-3 began in February 2008 at Minami-Honmoku Pier of Yokohama Port. The large steel celitype quay with 24.5m in diameter and 32m in height is designed in conformity with the new technical standard for port and harbor structures revised in April 2007. Deformation and damage of structures must be evaluated accurately, based on performance-based design introduced to the new standard. Two-and three-dimensional finite element analyses and model shake table tests are conducted in this study, to evaluate performance ofthe quay during L2 earthquake.
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長尾 毅, 吉岡 健, 尾崎 竜三
2008 年 55 巻 p.
941-945
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
The Monte Carlo Simulation method is widely used for the evaluation of failure probability of breakwaters in view of sliding displacement. The method might be used more frequently in the future as the new technical standards for port and harbor facilities employ the performance-based design methodology. The accuracy of the result of the simulation depends on the pseudorandom number generating method and iteration number. This study aims at presenting the appropriate pseudorandom number generating method and iteration number for the evaluation of failure probability of breakwaters in view of sliding displacement.
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有光 剛, 安岡 恒人, 川崎 浩司
2008 年 55 巻 p.
946-950
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
The Hudson equation is, in general, employed to estimate the minimum weight of an armor unit on rubble mound foundation. However, the damage of the units is occasionally found at the toe of the foundation while the weight of armor units is larger than the one calculated by the Hudson equation. This paper aims to elucidate the damage mechanism of armor blocks at the toe of rubble mound foundation of a composite caisson-typ. breakwater by performing hydraulic model experiments and numerical computations with a numerical wave flume “CADMAS-SURF” under irregular wave actions. It is found from the numerical and experimental results that the increase of horizontal velocity and the decline of wave pressure in the vicinity of the blocks cause the block damage at the toe of the foundation.
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西村 大司, 河合 尚男, 堀井 義一, 森川 高徳, 吉田 要
2008 年 55 巻 p.
951-955
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
In recent years, there have been an increasing number of projects that adopt “wave absorbing slit caisson breakwater” to reduce construction cost in deep sea. This type of structure tends to receive strong wave force at upright wall. On account of this, there is a case study that replace upright wall with sloping wall, but it has quickened transmitted wave. Accordingly, this study was conducted to elucidate transmitted wave characteristic about “wave absorbing slit caisson breakwater with sloping top wall” of hydraulic model tests. The basic data obtained is expected to be greatly helpful in future breakwater design.
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山本 泰司, 木村 克俊, 南部 裕之, 高橋 元樹, 今村 晃久, 熊木 功治
2008 年 55 巻 p.
956-960
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
The traffic suspension due to wave overtopping is happened on the coastal road of National Route No.231 at Yudomari district along the Sea of Japan in Hokkaido. In this paper, the relationship between the wave run-up height and the offshore wave height was shown based on the field observation. It was also revealed that the wave splash acted on passing vehicles when the offshore wave height exceeded 3-4 meters. Hydraulic model tests on wave overtopping were conducted to find the necessary height of the wave splash barrier in order to protect the coastal road against storm waves. The characteristics of wave force on the vertical wall of the seawall were also examined by the hydraulic model tests. Based on the test results, the use of transparent material such as aramid fiber sheet was proposed for the wave splash barrier.
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原田 英治, 後藤 仁志
2008 年 55 巻 p.
961-965
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
For economic construction of a landfill and an artificial reef, blocks are dumped into sea by a barge. An improvement of an accuracy of prediction of sedimentation process of blocks leads to a significant cost saving. We have developed the DEM-base solid/liquid two phase flow model to solve rigid particulate flows with high resolution and performed a direct numerical simulation for sedimentation process of an armor block unit. In this paper, a flow structure around blocks in sedimentation process is shown in detail.
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吉永 宙司, 大下 善幸, 渡辺 義, 高本 康貴, 高野 剛光
2008 年 55 巻 p.
966-969
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
Stabilization of the seawalls is required for protecting the important facilities along the coast of the Fukui Port. Since 2004, Ministry of Land, Infrastructure and Transport has commenced the projects for improvement of the existing seawalls for scouring and liquefaction protection, and for construction of new submerged breakwaters. Construction of “two-crested submerged breakwaters, ” which have two parallel crests along the coast, was newlycommenced in 2006. The ministry realized that stability of the submerged breakwater needs to be examined because the submerged breakwater experiences winter stormy waves while the construction of the breakwater is not yetcompleted, i. e., the total length of the breakwater is 45m compared to the designed total length of 200m. This paper presents a survey result of location of concrete armor blocks for the submerged breakwater on partial completion with using Real-Time-Kinematic GPS.
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トラップ式ダブルリーフを対象として
斎藤 武久, 砂原 啓人, 市川 督人, 福本 正, 間瀬 肇, 石田 啓
2008 年 55 巻 p.
971-975
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
This study aims to develop a highly accurate method for an estimation of hydraulic characteristics around an artificial reef by using an artificial neural network, instead of a conventional method using a regression analysis. The wave trapping artificial reef is chosen as the structure of an artificial reef, and transmission coefficient and wave setup behind the reef are focused as hydraulic characteristics. For the training of the artificial neural network, the Levenberg-Marquardt method with Bayesian regulation is employed. Predictions of transmission coefficient and wave setup from the trained network agreed well with the experimental results comparing with predicted ones from the method using a regression analysis.
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藤原 隆一, 川崎 浩司, 藤間 功司, 馬場 慎太郎
2008 年 55 巻 p.
976-980
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
There are mainly two ways to compute wave overtopping phenomena. One of them is a numerical method which employsa non-linear wave transformation equation combined with an overtopping formula. Another is a direct numericalmethod for solving Navier-Stokes equation. Only a few numerical studies with the direct numerical method have so farbeen made on irregular wave overtopping. In the present study, the applicability of the CADMAS-SURF, which is basedon the VOF method, for the numerical simulation of irregular wave overtopping of an upright seawall has been verifiedby comparison with the hydraulic model experiments. Moreover, some consideration for calculating irregular waves hasbeen shown.
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平石 哲也, 平山 克也, 加島 寛章, 春尾 和人, 宮里 一郎
2008 年 55 巻 p.
981-985
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
The performance design code has been proposed in the coastal and harbor structureconstruction. In the new designcode, the design wave with a return period employed in the former design method is defined as the variable wave load. Meanwhile the accidental wave load that occurs in a low probability but causes a serious damage is considered in thenew design code to secure the safety and reparability of the structures. The specification of accidental wave load, however, is not clearly indicated in the new code. This paper describes the characteristics of structure damages caused bythe recent stormy waves with long period swells and proposes the application of such waves as the accidental waveload. The long period swell becomes the critical load when the breakwaters are constructed in the surf zone.
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川崎 浩司, 村上 智一, 戸田 圭亮, 大久保 陽介
2008 年 55 巻 p.
986-990
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
This paper intends to develop a three-dimensional material transportation model which is composed of an Atmosphere-Ocean-Wave coupled model and two types of particle tracking models with water and soil particles. The model wasused to estimate seawater exchange and soil transport in Ise and Mikawa Bay areas during Tokai heavy rain. The numericalresults revealed not only the quantitative estimation of the seawater exchange among Ise Bay, Mikawa Bay and Open Sea but also the dynamic behavior of freshwater particles from rivers. Furthermore, the transportation and sedimentationof soil particles as well as flow and density structures at the head of Ise Bay were examined in detail basedon the results of numerical simulation with fine grid meshes.
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金 キョンヘ, 駒井 克昭, 日比野 忠史
2008 年 55 巻 p.
991-995
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
The Seto Inland Sea, which 21 1st grade rivers are flowing into, is a semi-enclosed shelf sea connected to the Pacific Ocean through two open boundaries. It is considered that current is controlled by the difference in sealevel between two boundaries accompanied by the variation of Kuroshio path. And the sea level height is variedby the distribution of salinity formed by the current characteristic. In this study, we investigated the relation ofsalinity distribution and boundary sea level height in the whole area of the Seto Inland Sea using field observationdata and numerical calculation in order to analyze the sea level variation characteristics.
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安達 貴浩, 登川 武司, 大山 俊昭, 山城 徹, 櫻井 仁人
2008 年 55 巻 p.
996-1000
発行日: 2008/10/10
公開日: 2010/06/04
ジャーナル
フリー
In order to make clear the characteristics of water exchange at the entrance of Kagoshima bay in the season of stratification, the field observations on the velocity and density fields were carried out, and then the results on the residual currentswere examined. As a result, the following findings were obtained; 1) Two kinds of flow pattern of residual current “inflow at the upper layer and outflow at the lower layer” and “outflow at the upper layer and inflow at the lower layer” were observed. 2) The residual currents are regarded as the density-induced current, because those vertical patterns havestrong correlation with the vertical profiles of the horizontal gradient of baroclinic pressure.
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