A boundary-element method is developed for computing the wave-height distribution in harbors to account for permeable breakwaters and walls of imperfect left-lettlection. The method is examined in view of accuracy to predict the wave deformations due to the diffraction, left-lettlection and water-depth change by comparing with the results of the method of matched asymptotic expansions. Where the method of matched asymptotic expansions is applicable, the solutions by both methods coincide with errors of a few percents, provided the element-lengths are less than one tenth the wavelength. A technique is also presented to apply the method to a huge harbor using the virtual permeable breakwaters.
Until now, offshore areas of Hokkaido coast faced on the Okhotsk sea have rarely been utilized in winter seasons because of pack ice driven to the coast. To utilize the sea areas more fully, it is necessary to control sea ice by ice barriers.The more the sea surface off the coast is covered by the sea ice, the more the wave heigh near shore is damped. Authors experimented on the attenuation of wave height due to ice cover by using model ice plates. Finally, the relations between the transmission coefficient under the various wave and ice conditions have been found.
This paper aims to discuss the characteristics of velocity field of the partial clapotis, based on the laboratry experiments and a newly developed third order theory. As the relative water depth decreases and the wave steepness increases, the crest of the time history of horizontal velocities is steepned and its trough is flattened, while the wave form bends forward in vertical velocities. In addition, as the left-lettlection coeffient is more than 0.8, the second harmonic component wave appears to be prominent in water surface profiles and vertical velocities at the node.
The problem of variation of w ater surface displacement and left-lettlection coefficient of partial standing waves on a vertical wall is basic subject to be solved for the design of offshore breakwater. The phenomenon of left-lettlection coefficient of partial standing waves is a non-linear boundary problem, it has been examined both theoretically and experimentally using the equation of third order approximation for finite amplitude standing waves, Healy's method and ratio of the water surface displacement in changes of vertical wall height. The left-lettlection coefficient with the increase of vertical wall height was in good agreement with the results of calculation shown in the each diagram.
Waterfront development in Japan is remarkably expanded in these days. On the other hand the mean sea level rise due to greenhouse effect is seriously concerned by the govermental agences and is expected to be 20-110cm in 2030. Considering the present circumstances the precise evaluation of wave overtopping is of extremely importance for the future planning of coastal protection in Japan. In this paper a new method is presented to calculate the wave overtopping rate of sea wall which is located on a complicative bottom profile of sea coast. The proposed method was applied to the cases in laloratory as well as in field. The agreement between the expected values and the available data was favourable good.
Recently, waterfront developments have been noticed, and it has become important to develop a countermeasure on wave overtopping. In this paper, next two points are investigated. (1) Applicable methods to estimate the wave run-up height and the rate of wave overtopping. (2) Appropriate methods to evaluate the effect of wave dissipation by typical structures. And the following conclusions are obtained. (1) It is possible to apply the equation proposed by Yamamoto to the calculation of the wave run-up height. (2) The method by Yamamoto and Horikawa can be applied to the calculation of the rate of wave overtopping. (3) The experiments indicate that the vertical revetment of energy dissipating blocks has a considerable effect on reducing the rate of wave overtopping.
This paper deals with the development of a new model fish aggregation device which prevents trawlnet entanglement. Labolatory experiments were carried out to measure hydrodynamic forces acting on a submerged hemisphere in a flow and under regular waves. The obtained results are summarized as follows; The drag and lift coefficients in a flow are constant. The measured longitudinal wave force is decomposed into the drag and the inertia forces by means of the Morison equation. As K. C. number increases, the longitudinal maximum wave force decreases almost proportionally. The vertical maximum wave force varies from 2 to 10 times of the longitudinal maximum wave force. The longitudinal drag and inertia coefficients under regular waves are given as a function of K. C. number, h/D and h/gT2.
This study is intented to investigate theoretically and experimentally the dynamic behavior of a semi-submerged rectangular floating structure with a pressurized air-chamber and wave transformation. The Dividing Region Method which is based on the linear wave theory is employed in order to evaluate the wave left-lettlection and transmission, the rolling, heaving and swaying motions and the tension force of mooring line. An air compression model is developed to evaluate the dynamic air pressure in the chamber, assuming the adiabatic change of the ideal gas state. Moreover, viscous resistance force is introduced to prevent the divergence of solution at resonant frequency in rolling motion. The numerical solution is in good agreement with the experimental values, except some small differences around the natural frequency of the floating body, which confirms the validity of the theory developed in this study.
The problem of the dynamic behaviour of a floating fish habitat by ocean waves is investigated theoretically in this paper. A mathematical model for determing the dynamic displacement of a aquaculture are derived by using a empirical relationship of wave force acting on the plain net. The culclations resits arecompared with the wave tank tests under various wave conditions and they show good agreement. Also, a new field measurement system of the movement of fish farm structure is developed and results of laboratory tests of the system are presented.
The Ministry of Transport publicized “The Harbor in the 21st Century” as a part of a harbor improvement policy. Accordingly The Third District Port Construction Bureau designed The Floating Pier in Hiroshima Port on the largest scale in Japan. A structual form which can split the whole body into five parts consists of Prestressed Concrete.
The pile moored sandwich type pontoon is one of the newly developped pontoon for small to medium sized vessels, which enables smooth embarkation, disembarkation and cargo handling at any tidal lebel in sea areas with large tidal range. The authors installed this pontoon off the Port of Kanda, Fukuoka Pleft-lettecture and conducted field test. As a result, it was proved that the pile moored sandwich type pontoon could keep good conditions for cargo handling because of small pitching and rolling even in wavy conditions.
In addition to conservative way of massive development, contemporary planning of fishing port facility requires more consciousness of qualitative factors, such as safety, effectiveness, and comfort. This report introduces research and development for two kinds of floating type structures, namely mooring wharf and breakwater, and explains the state-of-the-art research. It also shows some application examples at fishing port areas in Japan with their investigation results.
Recently, the water front development grows remakably and ocean leisure becomes popular. A yacht basin and marina are typical facilities for that purposes. For mooring yachts in the basin, the arrangement such as breakwaters, mooring spaces and pontoon bridges are needed. Among of them the arrangement of pontoon bridge is the most important. This paper reports the comparison results of the pontoon bridge stucture inspection which were carried out in four principal yacht basins in Okayama, Osaka and Kanagawa Pleft-lettecture, with emphasis on their safety, durability, utility, cost and sight aspects.
Caissons for outer breakwater of the port of Hirara are being fabricated by use of floating docks (hereafter FD). FDs used to left-lettuge to Okinawa island or Ishigaki island when a typhoon seemed toattack the Miyako island, and the fabrication work ought to be interruped and postponed for one or two weeks for every typhoon. If it is possible to moor FDs during typhoons are influening the Miyako island, the days of interruption must be shorten. Then, the examination was made on the safety of mooring of a FD during typhoon with numerical simulation method then 4, 800 ton FD has beenmoored safely during typhoon since1989. In 1990, it was planned to replace the 4, 800 ton FD by 6, 000 ton FD, theleft-lettore the examination was made on the safety of mooring of 6, 000 ton FD with the same manner. Then the 6, 000 ton FD has been moored since June, 1990. Several typhoons attacked the Miyako island in 1990, however, the FD was moored safely. Motions of the FD were measured during typhoons. This paper describes the procedure and the results of the examination on the safety of mooring of 6, 000 ton FD and the results of the observation.
In recent years coastal development projects including man-made islands are carried out in Japan. In these projects floating bridges as the access road is considered to be more economically constructed than usual types of bridge under the severe conditions such as deep sea area and soft seabed. Theleft-lettore Ministry of Transport makes researches on applicability of floating bridges from technical and economical point of view. According to the results of case studies, floating bridges are applicable at the relatively calm sea area like an enclosed bay where the depth from water surface to support layer is larger than 15m.
Silt protector sheets are widely used in order to prevent environments of surrounding area to underwater construction sites from diffusion of rolled up sediment load by the execution of works. Infiltration capacity of the silt protector sheets which being applied at present are almost the same as Darcy's permeability coefficient of fine sand. So that, caleft-lettul consideration is necessary to install the sheets at the place of high flow velocity. High permeable silt protector sheets were developed for the place of big discharged such as inflow point, junction. Hydraulic experiments were carried out in order to prove the permeability and silt diffusion protection capacity of new high permeable silt protector sheets. Permeability of new sheets are more ten times of usual sheets, and silt diffusion protection capacity are 1/3 of usual sheets.
When a dredging or reclaiming is carried out in a sea, turbidity is usually generated. To prevent the surrounding sea from pollution by turbidity. Silt curtains are usually used. When the silt curtains are placed in the sea, impact tensional forces are offen generated on upper and lower cables which fix the silt curtain. From the eneineering point of view, it is necessary to estimate the magnitude of the impact force in the design of the silt curtain. In this study, a numerical model for predicting impact force on the cable is proposed, and the applicability of the model is tested through experiment.
A long flexible floating board made of the complex of needle-trees has been developed to moor small vessels like pleasure boats. The present paper investigates experimentally the wave transmission and left-lettlection of the board. The transmission coefficient KT and left-lettlection coefficient KR do not depend on the relative width of the board (width/wave length) but on the incident wave steepness. The value of KT decreases and KR increases as the wave steepness becomes large. The wave transmission coefficient becomes much smaller as the draught of the front float is deepened.
Experiments are carried out in a wind water tunnel. Model wind fences with 50% of fence-density are used. When a wind fence is put on the water front, the wave distribution behind the fence is separated into two parts, i.e., non-wave-developed area and wave-developed area. By arranging of the location of the several float type wind fences in a particular distance, the wide range of non-wave-developed area is obtained. Characteristics of the distributions of wind and wind waves behind each fence are discussed.
After drawing up the left-lettraction diagrams for variable incident waves at the famous surf-riding points in East Shikoku, it was found that the wave convergence and the peel angle (left-lettraction angle at breaking point) were important factors at surfriding. Further, the characteristics of breakers and their peel velocity were measured at straight reef models exposed obliquely in the incident waves.
Classified three types of seawalls, which are effective to decrease wave over-topping even with their lower crown heights, are newly developed. One type is with steps on the front face, second one is with a chamber behind slits on the front face and third one is with wide plane area between front and rear steps. The effect of these on the decrease of wave over-topping is verified by experiments.
The permeable breakwater which can be calmed severe wave condition's coastline down and having a water circulation system to prevent the deterioration of water quality, has been developed. This structure is composed of pleft-lettabricated multiple horizontal and vertical plates which is aiming the pleft-lettab works. This paper deals with the hydraulic model test in order to select the most suitable structural-form for the wave dissipation.As the results of tests, characteristics and mechanism of wave dissipation are cleared, and obteined the satisfactory structural-form.
A new type of submerged breakwater, named SURF, has been developed. SURF is made up of a caisson with a top plate and several sills, and quite effective on the reduction of wave height in spite of it's small dimension. In this study, a mechanism of wave energy dissipation and, characteristics of transmission and left-lettlection coefficients are discussed based on the results from twodimensional model tests. Furthermore, the design method is proposed by using the experimental results.
Recentry it has been necessary the purification of mooring basin water in fishing ports for new use, such as stock of fishes in living or intermediate breeding. The authors proposed a new method for interchanging sea water in which fresh sea water is drawn into the port by raising the mean water level through the wave breaking process over the submerged mound. A hydraulic model test was executed to prove this method to be useful for interchanging sea water and to present appropriate profile and plane designs such a structure .
The Ministry of Transport is currently developing a wave energy absorption type caisson breakwater called a wave power extracting caisson. The aim of developing this type of breakwater is to improve its performance such as stability against waves by providing air chambers which serve as energy converters, a d to reduce costs for wave power generation through use of breakwater. This report describes the field experiment of the breakwater at Sakata Port and its results.
paper concerns the stability of caissons during wave loading. The damages induced to Stretches B and C of the Shin-Nagasaki South_breakwater during Typhoon 8712 are outlined. This is followed by a theoretical discussion of the overturning behaviour of caissons, with the inertial resistance being properly allowed for. The expression for the lower bound of driving moments sufficient to overturn a given caisson is derived. The limiting driving moments obtained for Stretches B and C are then converted to the destructive wave heights, with the aid of Goda's (1974) wave-pressure formulae.
Linearized friction coefficient was examined experimentally for permeable breakwaters with precast concrete armour unit in shallow water region. The equation proposed by Sollitt et.al. was applied for calculating the friction coefficient from transmission coefficient. The friction coefficients obtained were less than 14 and varied with following parameters: ratio of incident wave height to block scale, HI/d, ratio of breakwater's width to wave length, B/L and wave steepness, HI/L. The parameter HI/d strongly affected the friction coefficient. The friction coefficient varied in the small range of 0 to 4 when the Reynolds number, ud/ v, was greater than 3×104.
This report presents the design method for mild-slope revetment by taking into account the beach evolution model. According to the previous investigations, it has been shown that it was not adequate to construct the mild-slope revetment in the beach where alongshore sediment transport is large. In the beach investigated in this study, the change of sediment transport along a beach is seasonal. Theleft-lettore, the shoreline changes were surveyed every season over a year. The results were compared with those predicted by one-line theory and then it was clear that the severe beach erosion was induced by the wave height with the return period of 10 years. Finally, it is shown that the structure constructed in the beach side should be designed so as to be safe for the beach erosion due to the wave characteristics mentioned above.
This paper researches numerically by finite element method about responses of coastal dikes under shock pressure of breaking water waves. It was found that the tension and shear failure developed in the supper part of back-filling soil by shock pressure waves. The generation of the excess pore water pressure causes to scour in the toe and suck out in back-filling soil. Coastal dikes become dangerously when the breaking wave height and the breaking water depth are large. the angle of dike is sleep, the penetration depth is small and the thickness of concrete wall is thin.
Two types of concrete block for gentle slope seawalls are newly developed and their hydraulic characteristics are revealed by experiments in a wave flume. These blocks, settled on a gentle slope, form inner layer for return flow. ' This layer contributes to reduce disturbance on the slope and increase the stability of blocks. Reflection coefficients of slopes covered with these blocks can be decreased to be 0.1-0.3. The relationship between wave run-up and wave steepness is shown using relative depth as a parameter.
The revetment of the artificial island in Trans Tokyo Bay is constructed by forming several gigantic steel jackects into a ring. A high accuracy of location and level is necessary for setting these jackets because of maintaining toughness by forming a ring, ensuring verticality for lagging and tunnelling through steel piles. The accuracy demanded the work was within ±10cm for location and ±5cm for level. In the installation work, the jacket is hung and moved by a crane or shifted by an anchor operation to the planned position. If the survey is carried out after the installation, we must repeat installation and survey works till satisfing the accuracy. Theleft-lettore we have developed three dimensional navigation system that can navigate jackets with a real time and a high accuracy using two total stations.
VTR-Pictuers taken under water are contain valuable and various information. Forevaluating quality of the pictuers, and studying about a model of light-transmission, experiments and real-sea obse vations are done. New evaluate method that uses a pattern-boad ispresented. Motion-analysis of suspended tracers are attempted for its application.The methodis based on travel distance between a pair of serial scenes.This method is applied for thestudy of velocity near the sea-bed.It shows good ability of advanced application of the pictuers.
Remotely sensed bathymetry in Kin Bay, Okinawa main-island, Japan was performed using digital data of a single band (band 2) of Landsat-5 Thematic Mapper (TM). Models were developed considering the bottom features of coral reef-bright sand type and sand mud-mud sand type.The Bottom features (coral reef and bright sand) greatly influenced the results, especially in shallow waters.For depth less than 18 m the root mean square (r.m.s.) error of predicted depth was 2.9 m and 6.1 m for coral ree-bright sand type and sand mud-mud sand type, respectively.But for depth more than 18 m, the bottom influence was decreased, and the r.m.s. error was measured 1.4m and 1.1 m, respectively.
Large impulsive tensions are exerted on a mooring chain when large waves attacks to a Catenary Anchor Leg Mooring buoy installed at a berthing area facing to an ocean.The sinker of the buoy may be moved and some of joints may be broken off by the large impulsive tension even if the maximum tension is smaller than the breaking load of the chain.The maximum tension is related to the wave energy expressed as the product of the square of wave height and the wave length.The impulsive tension can be reduced by employing an elastic'rubber chain'as a part of the buoy mooring chain
In this paper, we presents the results of calculations to examine the role of variable thickness in limiting the strength of multiyear ice floe.We model a multiyear Ice floe with bottom roughness both in the form of sine curve and in two beam sections of variable thicknesses with/without an elastic foundation.It is shown that the roughness amplitude and thickness of the floe over which compressive loads are applied to the boundary are the most important variables in determining the force which can be transmitted through the floe to an offshore structure in Arctic waters.
Estimating the ice forces acting on offshore structures constructed in cold region, it is very important to forecast the emvironmental force acting on ice floes and their drifting velocity. This paper deals with the wind force and fluid resistance acting on ice floes and their drifting velocity and systematic experiments on wind force, fluid resistance and velocity were carried out.
It is desired that a method can grasp a first stage estimation of ice force on pyramid shaped arctic structures. To work out this task, making use of the Ralston's theory for conical shaped structures is seemed to be better way. In this study, relationship between Ice force calculated from the Ralston's theory for conical structures and ice forces on three types of pyramid shaped structure was examined experimentally. As a result, the coefficients for practical use, which is able to use the ice force calculated from the Ralston's theory, for conical, quadrangular and octangular pyramid shaped structures were proposed.
In cold regions, changes in water level can induce vertical forces on offshore structures when sea ice cover interact with the structures.A rise in water level generates an upward force on a downward- breaking conical structure;likewise, a drop generates a downward force on a upward- breaking conical structure.These forces are induced on conical structures even if sea ice cover to structure adfreeze bonding is not present.The authors have proposed a method of calculation that estimates the vertical ice forces on conical structures taking the bending failure of the ice cover.
Currently, breasting dolphins of deepwater terminals are designed so as ship's berthingenergy shall be absorbed mainly by fenders. As for a singel pile structure (SPS) whichconsists of high-tensile steel, ship's berthing energy shall be absorbed mainly by piles.Major subjects to be cleared for design ofSPS are the lateral load-deflection characteristicsof piles against large deformation, estimatation of residual deformation underrepeated loads and evaluation the safety for fatigue. In this report, both residual deformationand cumulative fatigue damage ratio within a lifetime are computed with considerationof ship's berthing and mooring forces. The lateral load-deflection characteristicsof SPS against large lateral repeated loads which are obtained from the field tests andmodel experiments are taken into consideration in this study.
Abration of heavy-duty coated steel pipes due to littoral drift was studiedexperimentally and theoretically. Since steel pipes coated with anti-abrationurethane are very lower in abration rate than steel pipes, they are thought tobe suitable for use in coastal zone with severe sand transport. Abration rateis nearly proportional to collision energy of sand particle. Sand collisionenergy is related with the ratio of particle size to pipe diameter.
A five-years exposure programe has been started to clarify the durabilitycharacteristics, such as, weather and sea-water resistance of concrete usinghematite aggregate, with the object of studying the applicability of such concretein marine structures. Beams with concrete using these aggregates have been exposedin marine environment and this report has been prepared on the basis of the resultsobtained after one year. It was found that on the basis of crack propagation andcorrosion of the reinforcing bars embedded in concrete, it can be said that thedurability of concrete using hematite aggregates is at least comparable to that ofnormal concrete.
Abrasion resulting from movement of sea ice sheet must be considered during thedesign of concrete offshore structures for regions where the sea freezes in winter.Such areas include the Arctic Ocean, the sea of Okhotsk, the Gulf of Bohai and theBering Sea. Theleft-lettore, it is very improtant in the design of concrete structures forvery cold region to estimate the abrasion amount due to a movement of sea ice sheet.
Questionnaire test for the pleft-letterence for coastal atmosphere and utilizationwas carried outfor the residents in Ibaraki Pleft-lettecture. It is found that theresidents living near the coastvisit the coast more often than those living far from the coast. People highly pleft-letter the coastalatmosphere expressed by the words such as 'grand'. natural or 'open'. and such pleft-letterenceswere categorized by the sample's age and the distance between the residence and the coast. Itis also found that people highly pleft-letter the coastal utilization such as 'taking a walk' and 's eafood tasting', and such pleft-letterences were categorized by the sex distinction and the age. Furthermore, questionnaire for the primary school students shows that the difference of the pleft-letterencefor coastal atmosphere and utilization exists between the students and the adults.
In order to investigate the feasibility of the application of Marine Multi Zone (MMZ) plan to the actual coast, a case study was carried out at Kujukuri Coast in Chiba Pre-fecture facing the Pacific Ocean. Present situations of the coast were analyzed firstand various problems to be solved were pointed out. Marine resort plan was proposed notonly to solve those problems, but also to create coastal zone for the recreational usageIn this plan various recreational facilities were planned. Furthermore to create a calmwave zone, which is useful for the marine recreation, a new-type offshore breakwater wasintroduced. It is shown that this structure is useful not only for the creation of calmwave zone, but also for the shore protection.
There are many isolated coral reefs around the Okinawa Islands, and most of themhave configuration of circular plateau with diameter about 400-2000m. The depths ofwater on the coral reefs are about 2m at high tide and become about 0.5-1.0m at lowtide. Up to this day, high utilizations of the coral reefs have been proposed, oneof them is an application of a method developing artificial beach along open sea coast. Because of existance of strong longshore currents induced by high incident waves, generally, a natural beach is not formed on the coaral reef. In this study, a method ofdevelopment of artificial beachs along open sea coast for making beachs on the reefsis proposed.
The objective of this study is lay the island type offshore fishing ports plan. This developmentplans of fishing ports (Kutuo fishing port and Mitikawa fishing port) which is adaptableto drift sand, is able to accommodate fishing boats safety, and causes least effectsagainst topographic change.
Comparison of the coastal utilization in Japan and U. S. A. was made throughthe experience of the field trip to the West Coast in U.S.A. Coastal observationwas made in July, 1990 in an area between San Diego and Pt. Reyes north of SanIFrancisco. The differences of the coastal protection works and the coastalenvironment between two countries are emphasized. These fundamental informationsare useful for the future planning of the coastal works in Japan.
Under the following hypothesis that the seaside service facilities such as foodshops, cottages and amusement spots are a major factor to control the motivation ofgoing sea bathing, comprehensive field studies were done in summer season at twoseaside resorts located coast around Osaka bay. The service facilities as well astransportation access and natural environment are remarkably important in theplanning of construction or improvement of seaside resorts located in the suburbsof urban area.