Submerged breakwaters are important coastal structures that protect seashore from waves. The transmission coefficient increases at high tide in large tidal zones. So, when the water depth is large over the submerged breakwater, effective armor blocks are developed. Eddies form between the ripple-type armor blocks during the onshore and offshore semiorbital wave motions. Incident waves reduce these eddies over the armor blocks, and transmission coefficient becomes small.
In contrast to the variable and unpredictable nature of waves, the rise and fall of the tide is normally regular and predictable, but like waves it exerts a considerable influence on wave damping of submerged breakwaters. The depth of water on the submerged breakwater affects wave damping greatly. The calculation of the tidal level in some places was carried out in this paper. The height of the submerged breakwater can be chosen suitably from the figures made here.
A submerged breakwater, its crest nearly coincided with the H.W.L., was constructed off Hagino, the Iburi Coast in Hokkaido. Echo-freindly units were used for this “high crest” submerged breakwater. The new units have large empty spaces to allow sunlight to go through onto the rock mound. A study on organisms attaching themselves and macrobenthos in the surroundings was performed over a period of 3 years. Kelp (Laminaria angustata) forests formed on the insidewalls of both units and the rock mound. The standing crop was 10-25 times that found on flat crest blocks (used as a control). This distinction was due to the complex unit structure and the variation in depth substrata. As the sand particle size on the landward side of the breakwater increased slightly with every year, macrobenthos such as annelida became more abundant. In addition, rock fish were seen to frequent the breakwater. The “high crest” submerged breakwater using the new units functioned not only protected the coast, but also acted as a rocky ecosystem and feeding point on the sandy bottom.
We have been proposed the delta-type reef as the coastal structure to generate good waves for surf-riding. It is effective for a promotion of oblique wave breaking and an amplification of waves. Waves can be concentrated and amplified by setting up the crescent-type submerged mound in the front of the delta-type reef. In this research, the transformations of waves around these structures were calculated by the MSE numerical simulation. The properties of these structures were examined from the calculated results.
Hydraulic characteristics of a newly developed artificial reef breakwater are studied experimentally. The breakwater is composed of units which are utilized of the concepts of a perforated horizontal plate set in water and placed horizontally in 1-layer on a rubble mound. The superiority of the breakwater in hydraulic characteristics has been shown by comparing with those of conventional artificial reef breakwaters.
A lateral artificial reef systems is a group of submerged, broad-crested detached breakwaters, which dissipate the incident wave energy by depth-controled breaking over the crests. A longitudinal artificial reef systems is a grope of wave heights and wave braking process through the refraction effect. Numerical of wave heights and wave-induced currents around these reef systems has been proved in good agreement with laboratory data. Performance of two systems in wave and current attenuation is compared using both laboratory data and numerical predictions.
Suspending of cargo handling caused by moored ship motions is serious problem at sea berths facing to open sea area. In this paper, we focus on a tanker sea berth facing to the Pacific Ocean. And we research about the berth operation of the sea berth firstly. Secondly, we measure and analyze the wind waves and swell data at the berth. We simulate mooring ship motions under these waves and winds, then we compared with the hearing result from the berth master and the simulation result. Finally, we propose a berth operation support system for a safe berth operation.
A -12m deep quay wall at Shinko-east area is one of the 17 high earthquake resistant quay walls constructed in the port of Kobe for the restoration of the damage by the 1995 Hyogoken-Nanbu earthquake. An embedded steel-plate cell configuration is applied to this quay wall as a high earthquake resistant quay wall for the first time. This structure has following properties:(1) shorter construction time, (2) no seabed improvement, (3) higher earthquake resistance, etc. This paper presents some topics in design, construction and seismic characteristics of the steel-plate cell structure.
During the recent big earthquakes in Japan, significant damage was caused in the port and harbor facilities, especially in reclaimed lands. The survey was extensively carried out on the damages during the recent three big earthquakes in Hokkaido Island; i.e., 1993 Kushiro-oki, 1993 Hokkaido Nansei-oki, and 1994 Hokkaido Toho-oki Earthquakes. And the damages were closely examined based on the current seismic design code for quay wall. As a result, it is clarified that the occurrence and the intensity of the damage are strongly correlated to the occurrence of the liquefaction in the backfill grand.
This report presents the design method of ultimate horizontal strength of abutments supported by the batter piles to protect against damage by an earthquake. Given its plastic deformation ability, this design method is judged more reasonable than the seismic coefficient method for a huge earthquake. The plastic deformation ability is analyzed by static nonlinear FEM with elastic and plastic buckling, because the ultimate horizonal strength of abutments supported by batter piles is generally governed by the buckling of the batter piles.
This offshore berth was constructed for Idemitsu Hokkaidou Refinery to receive crude oil from 300, 000DWT class tanker. It is one of the largest jacket-type offshore berth in the world with 10, 000t steel. The crude oil was unloaded from the first tanker in Aug. 73, only 10 months after the beginning of construction. Its performance is sound through 24 years operation. On the basis of experiences of construction and operation, this paper presents the technical key suggestion that should be considered in planning, designing, operating and maintaining offshore berths and offshore facilities generally.
“Aquarobot” is a robot that has been designed for underwater inspection in place of divers in port construction works. It has six legs similar to those of an insect. It is able to perform various kinds of inspection tasks while walking on a sea bed up to a depth of 50m. The walking velocity on a rubble mound is 1.4m/min. The most important pint is that it is able to measure the unevenness of rubble mound by the motion of the legs.
In Japan there is a problem that a number of unauthorized mooring pleasure boats left in public waters is increasing because of the lack of marina facilities. However, it is difficult to provide enough facilities for financial constraints. In this paper, a new idea for solution is proposed to decrease the number of those pleasure boats by putting emphasis on developing a simplified moorage and also on establishing service network among marinas.
Traditonally, the environmental policies in Japan have been centered on overcoming pollution and protecting human life. Recently, in addition to those, it has, A, lso become important to cope with subjects such as water quality in closed water area and protection of wetiand, etc. Considering this situation, Ministry of Transport has reviewed the environmental policy in the ports and harbours. In this paper, both the concept of the new environmental policy and one of its porject are reported;“Eco-Port” and a study about the condition of growth of clams at tidal flat constructed in Mikawa port.
For a island-short nation like Japan, it is imperative to make use of coastal areas. But usable space is limited, necessitating coastal utilization to be pursued depending on the characteristics of each adjacent sea area, to meet the growing space demand. This paper deals with present development and utilization of artificial islands in Japan, which have been developed and planned to make effective use of coastal area. Keywords: artificial island
The possibility of the conception on an offshore thermal power plant (TEALAND) that does not depend on a conventional reclamation method is evaluated here for the purpose of reducing the cost to supply electric power. The special feature of this conception consists in paying attention to the space under the surface of water. In this conception, the sea occupation area of the power plant is reduced as much as possible by arranging the generation equipment into the layered inside box. Then it reduces the construction cost by constructing both the component and the generation equipment simultaneously at land and then shortening the construction time. In this paper, the possibility of an offshore thermal power plant that utilizes the space under the surface of water is evaluated in terms of layered arrangement of the generation equipment as well as stability for external forces. Also, the problems on the technical development are shown.
Effects of large scale reclamation on benthos are examined by using the report on the environmental observation by Kansai International Airport Co., Ltd. The number of body of small shellfish, called “shizuku-gai”, decreases after the start of the reclamation work of the airport island but recovered quickly after the closing of the surrounding seawall. Both the change of the sediment and the turbidity can not be the possible causes at this moment.
Seashore walk commemorating the national holiday of ‘Sea Day’ was carried out on July 20, 1996 at the Hayama coast in Kanagawa Prefecture. Around 60 participants walked along the shoreline while hearing explanation of physical features of sandy beaches and eroding sea cliff. This paper summarizes these activities and the results of additional field observation conducted on late August in 1996 after the event. Also aerial photograph showing the site is investigated to realize natural condition of the beach. Future perspective of this activity is also discussed.
Through a 7.5m deep under water observation.window provided in Monbetsu City, you can sec the turbid Okhotsk water. The substances that make the water cloudy are important sources of food for the lives of various marine species in the Sea. Thus the Sea abounds with sea lives and assures high fishery production. To make non-turbid seas much more productive, it would be of utmost necessity to direct our major efforts to study further so as to constructa large-scale facility for creating artificial streams of water containing rich dissolved oxygen and running upward through the water (up welling).
Shoreline of Japan was widely oiled by the spills of Russian tanker in January, and of Korean tanker in April, 1997. To protect fishery and tourist resources, many people participated in the cleanup activities. Differences on spilt oil quality, topographical shoreline, climatic condition at the spill sites, resulted to different application of cleanup methods. For instance, the cleanup at Tsushima during warmer season of April, cleanup using sawdust was attempted.
The effects of the multi-directionality on the wave field in front of a long straight breakwater are discussed based on experimental results in a wave basin. When the waves don't break, the multi-directional waves don't generate a clear coexistence wave field of the oblique incident and reflected waves. When the waves break in front of the breakwater, the multi-directionality have no significant effect. This is because the wave breaking decreases the degree of the wave reflection from the breakwater.
There are several numerical method to analyze the wave field in harbors for random waves; finite difference method, fmite element method and boundary element method, for example. In the case where the constant depth can be assumed, the boundary element method is most useful. In the present paper, we establish the method to analyze the random wave field with the boundary element method. In particular, we establish the formulation of the method with the spectral representation of random waves.
Open boundary condition used in the analysis of wave fields with the boundary element method is discussed. Hamanaka (1995) proposed a new open boundary conditon which is ideally appropriate for any wave condition. But this boundary condition is formulated under an assumption that an opening and two boundaries on both sides of the opening make a straight line. In actual harbors, most of the boundaries on both sides of the opening have a fmite angle. In the present paper, the validity of this condition is examined in detail, comparing with potential matching method. It is confirmed that this open boundary condition is still valid in such configurations of boundaries.
Amplification of water waves on a rectangular step with the vertical wall at the end is examined theoretically and experimentally. Resonance occurs when the step length is approximately an odd multiple of a quater wavelength on the step. The velocity potentials in the regions in front of and on top of the step are connected through the continuity conditions of surface elevation and horizontal velocity. Laboratory experiments have been carried out for a step with the length 1.00m, the height 0.305 m, the submergence depth 0.04m and 0.076m, for regular waves with the period ranging from 0.8-3.0s. Theorectical prediction of the amplitude amplification by resonace effect has been confirmed, and proposal is made for an empirical formula for resonace condition and a design diagram for resonance amplitude.
Long period waves with periods of 1-5 minutes sometimes terminate the cargo handling and cause the break of mooring ropes in Japanese several major ports. Such damages sometimes occur in Kasima-port located at the central part of Japanese main island A series of field observation for long period wave height was carried out in the port employing several wave gages. The observation results demonstrate that long period waves induce the large surging motion by resonance between the wave agitation and a mooring system consisting of vessel and elastic mooring ropes.The variation of bounded wave components included in the long period waves is also investigated in the paper.
Long period waves sometimes cause the termination of cargo handling and break of mooring ropes in Tomakomai-port.Characteristics of long period waves in the port are discribed from the statistical analysis of field observation.The long period waves are mainly induced by the set-down waves bounded with grouping waves for the case of large wind waves. An occurrence probability table for long period waves is proposed by employing continuous observation data in the port.
Several type of structures have been proposed to control the wave field unit now, for example, submerged plate and submerged breakwater. In this study, submerged flexible sheets which are composed of textile sheets in frames with elastic springs are studied for another type. A new method of analysis using the boundary element method with Green function for wave field around the this structure was reported by Sakikawa et al (1996). In this study, a few experiments were carried out to investigate the validity of analyzed results using 3-D wave tank. Compared with calculated results and experimented results, in figures of contours for wave distribution of wave field, it was found that both results agreed good with each other under same hydraulic condition. Consequent by, the validity of the method of analysis was confirmed, by experiments.
A non-linear model for a wave field coexisting with currents has been developed to investigate the influence of currents on waves propagation. A new form of dispersion relation is derived by extending for the wave-current coexistence field based on special type of depth-integrated Boussinesq equations (Madsen et al. 1991, 1992). The third spatial derivative of surface fluctuation, ∂3S/∂x3 is discretized in terms of surface curvature, ∂2s/∂x2 and subsequently is solved by the cubic spline method. The model is applied to wave propagation in a domain of variable depths with preexisting adverse and following currents of different magnitudes.
A density interface is formed to σt=27.0 in Sea of Japan near Hokkaido. The nutrients in a surface of the density interface is a regular value through a year w ith a phosphate-P 0.8-1.0μg-at/l, nitrate-N 10.0μg-at/l and silicate-Si 15.0μgat/l. The depth of the density interface is formed becomes shallow in the westside and alsb the north side of Sea of Japan near Hokkaido.The internal waves thatpropag ates during surface of a density interface is concentrating on the offshore of Syak otan Peninsula and also Ohuyu Cape by the hydraulic model test.
A survey of recreational and sport surf-riding in Japan produced a set of parameters corresponding to the skill-levels of riders and types of surfboard used, which may be applied to the planning and design of coastal and marine structures that may affect the shore morphology and hence the surf characteristics of recreational sites along the coast.
Concerning wave energy dissipations caused by flow separations and resultant vortex formations from sharp edges of an angular body, a twodimensional analysis on wave transformations and wave forces on an angular body has been developed. In the analysis, a damping wave model was newly proposed to account for the wave energy dissipation approximately. An equivalent linear damping coefficient of fluid and a spatial range of the damping fluid are necessary in the analysis. In order to figure out these factors, wave tank tests were carried out. Two different structural models, i.e., a curtain-walled breakwater and a semi-submerged rectangular body, were used in the experiment. It was confirmed that the numerical analysis developed here is useful for estimating wave transformations and wave forces about an angular body including the effects of wave energy dissipation due to vortex formations around the body.
In the present measuring system, sea water levels is stored as digital data or indicated in real time by computer system in addition to analogue recording chart. The tidal levels could automatically be calculated from the time series digital data of sea water levels contained variously short time period fluctuations. The tidal levels and the appearance times at high or low tide obtained from the digital data almost coincide with the values read from analogue recording chart by manual operation. As compared with the results of calculation and manual operation, over eighty percent of the time differences in appearance times at high or low tide were less than fifteen minutes. And over eighty ercent of the level differences at high or low water levels were less than one centimeter.
In recent years, various types of floating structures have been planned and constructed for the purpose of the effective utilization in coastal areas. The floating structures such as very large floating structures, floating bridges and submerged floating tunnels should be considered their flexible properties in the design. In this report, hydraulic: model tests of a long flexible floating body are carried out and the results of the motion and the deformation are analyzed in order to evaluate the effect of incident wave direction, wave height, wave period and rigidity.
When we evaluate the safety of activity on a floating pier or a small ship, it is important to know the characteristics of motions in ship waves. Because when ship waves come to a floating body, the motions become large unexpectedly. The main purpose of this study is to investigate the characteristics of ship motions in waves generated by a high-speed boat passing near the mooring small floating body. Ship motions in ship waves are measured by the field tests, the short period maximum motions are also investigated by the approximate calculations.
This paper presents development of a Higher Order Boundary Element Method (HOBEM) program for analyzing wave response of box-like Very Large Floating Structures (VLFS). In order to analyze such structures, the problems that 1) elastic deformation of the structure should be considered in the hydroelastic analysis, and 2) large size of its computation in CPU time and required storage size, should be overcome. The program, developed utilizes modal superposition method for both rigid body motions and bending modes of the floating plate in order to account for dynamic coupling between fluid and structure responses. The computation size has been reduced by employing higher order BEM which utilizes 2nd order 8-noded panels and utilizing double-symmetry with respect to χ- and y-axis. A box-like VLFS having the length of 2000m, the width of 400m, and the draft of 4m has been successfully analyzed up to L/λ= 50 (L: length of structure, λ: incident wave length).
Wave response analysis of a full scale floating bridge considering the effect of nonlinear characteristic of fenders and elastic deformation of the structural system has been studied in this paper. Wave response analysis of the Yumeshima-Maishima bridge which is projected by Osaka municipal office has been performed. Emphasis is placed on the effect of the characteristic of non-linear fenders (especially hysteresis) and the dynamic interaction of the elastic deformation of the structural system with fluids. The analytical results have shown that the characteristic of non-linear fenders and elastic deformation of the structural system influences significantly on dynamic responses of such a floating bridge.
Tsunami regarded as a long-period wave is bfought about a submarine earthquake. Tsunami's wave height becomes higher in shallower onshore area. Wave road from Tsunami has much influenced to the motions and mooring tensions of a moored floating structure in onshore area. For this reason, it is very important for submarine works to estimate the dynamic response of a moored floating structure under Tsunami. This study deals with the characteristics of motions and mooring tensions on moored floating rectangular body by means of the hydraulic experiments under solitary wave considered as tsunami.
In general, the motions and mooring forces of floating structure are evaluated on the assumption that the structure is rigid. But, on a slender structure, such as a floating bridge, the effect of its elasticity can be neglected no longer. This paper describes the computational analysis method to calculate motions, mooring forces, deformations and working stresses of floating bridge. As the results of the calculation for a model bridge by several methods, one is our analytical method and others are conventional ones, it is proved that the effect of structural elasticity must be taken into account properly.
Evaluation of values and functions of the area, which will be impacted by development, is a key to environmentally friendly practices in planning and design. This paper reviews the several assessment methods developed and used in the U. S., where more systematic environment protection scheme, including mitigation, is implemented. Each method differs in terms of area of interest, functions to be evaluated and evaluation process, but they have potential of evaluating Japanese wetlands especially if they are improved considering the characteristics observed in the Japanese coastal area.
Mitigation technology in the U. S.A. was investigated by the Japan Ocean Development Construction Association Inc. The delegate collected the state-of-art information about evaluation and monitoring techniques. A mitigation program associated with a construction plan at a coastal area is carried out after the permission given by COR The so-called “restoration programs” are implemented with more flexibilty, of which purpose are to restore the lost nature. The paper describes some examples of restoration programs as well as monitoring methods.
Field measurements of chlorophyll-a concentration are carried out in Mikawa Bay.Characteristics of horizontal, vertical and seasonal variations of the concentration are firstinvestigated. The distributions of chlorophyll-a concentration are compared with Landsat TM data and the possibility of qualitative and quantitative monitoring from space isdiscussed. Higher correlation is found with the difference of CCT counts between bandl andband3 although further study is required for the quantitative prediction.
In order to realize a very large floating structure for an airport and so on, in-situexperiments using a test model with the size of 300m x 60m x 2m (draft: 0. 5m) have beencarried out. In this paper, several results of the experiments concerning environmentalimpacts by the model are introduced. Main conclusions are as follows:(1) flow pattern isnot affected by the existence of the model, (2) there are no difference in water qualityand bottom materials between under and outside the model, (3) all over the bottomsurface of the model has been covered with attached organisms, (4) in spite of theexisteifee of attached organisms from the model, the water quality on the seabed hasmaintained a normal quality level
Tokyo-Port is located in the innermost environs of Tokyo Bay which is an enclosed area. Tokyo port's water front is a center of urban development, as well as a distribution basefor the greater metropolitan area. This paper investigate the relativity of the change of the sea bottom organisms andbenthos. We compared the shoals with the other areas that have the same bottom, and foundout the merit of the shoals in the enclosed area. We will apply a new method (CSD) in manypoints of Tokyo-Port. And then a environmental creation plan is suggested according tomitigation concept and CSD.
When public works are conducted, people recently tend to ask their entrepreneur for keeping good natural environment as much as possible. On that condition, we studiedthe subject when we introduce the concept of mitigation in shore protection project by Ministry of Construction, which has ensured the public safety behind the shore fromnatural disasters like storms. Through our study, numerical evaluation of physicalcondition and living features along sandy coast was tried. Finally a flow chart of the project with mitigation was experimentally gained when the method of their evaluation is established.
A biological model has been developed to simulate the water quality in a bay. The model is ahydrodynamical and ecological coupled model, and the ecological model includes the biological processin the bottom sediment. The vertical diffusivity is estimated by κ-ε turbulence model to simulate thevertical transport process with high accuracy. The model was applied to Tokyo Bay in summer, which isa typical eutrophicated bay in Japan. The numerical results showed good agreement with the observeddata. The model can simulate the formation of oxygen poor water in the bottom layer, which is the mostserious environmental problem in Tokyo Bay
This study examined the behavioral characteristics of juvenile Japanese surf clams Pseudocardium sachalinensis in relation to bottom disturbance under laboratory conditions, and estimated the fluid conditionsnecessary to wash the clams out of the sand. The juveniles burrowed in sand when their buried depth decreased to ‹1.5 times the shell length due to erosion, and more upward when the depth increased to ›2.5 times the length by deposition of sand. Burrowing and climbing speeds tended to be about 1.8 times faster than the speed of erosion or deposition of sand. The juveniles were washed out of the sand when the erosion speed rose above 3.5mm/min.
The author proposes a design method of a detached submerged breakwater system to improve the habitat environment of Spisula sachalinensis (Japanese surf clam), which is one of the most expensive bivalves in Japan. According to the recent investigations, a general description of the ecological condition of the bivalve is given, in which a hydrodynamic explanation on the phenomena of the winter casting-up of Spisula sachalinensis due to waves is also given. Then a general design method of a detached submerged breakwater system, which is suited to the propagation of thekind of bivalves, is shown. Wave force on cover stones through sea weeds, such as Eisenia bicyclis and Ecklonia cava, is made clear as well on the basis of wave flume experiments.
In early to late spring, spawning shoals of a squid, Lorigo bleekeri, migrate to the western coast of Hooked facing the Japan Sea. Breakwaters and other artificial structures of the harbors are suspected to be utilized for their spawning. Diving observations were conducted of breakwaters in nine harbors to confirm actually laid eggs and to characterize underwater conditions of the spawning sites. spatial features of these spawning sites and luminous condition were described. The selected depths and distribution of the spawning sites observed to be affected by waves, local currents and temperatures. Function of unexpected role of breakwaters as spawning sites of a squid, improvements of the breakwater and other seaside structures were suggested.
In recently, we realize that the problem of marine resources and environment has been engaged actively. In Marine Civil Engineering, new technology for the “algae reproducing structures” which enable marine life reproduction is under developing. In the process of this tecnology developing, we are now researching the numerical model which forecasts algae growth under the variable environmental and structures location factors in the ocean. This numerical model definitively needs the quantification of the algae reproduction and environmental factors. In this study, we analyze the data to clarify the relation between algae growth and trailing factors which has been our marine purpose on this field but never been clarified.
Physical environmental characteristics to be considered in the construction of shell gathering grounds as amenity spaces include sediment grain size and hardness, current condition and ground height. This study examined optimum conditions for these characteristics, from the viewpoints of short-necked clam habitats and user comfort.