As the number of promenade breakwaters increases, the various risk to which sightseers are exposed becomes increasingly important. In this paper, one of the crucial dangers, falling on the breakwater due to wave overtopping is discussed, and a method to evaluate the relationship among wave height, overtopping rate, and the risk of falling is proposed.

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The bottom standing type of pendulor wave power system developed at Muroran Institute of Technology in 1979 had been revealed to be one of the most promising wave energy converter. And it had the function of breakwater too. But in case the system is installed at greater water depth, considering the horizontal wave force against them, it requires large caisson structures. Therefore, the uplifting type which has vacant space below the chamber may not require as heavy as the bottom standing type and the construction cost of the uplifting type is cheaper than of the bottom standing type. This experimental study has been conducted to make sure the function of breakwater and to get primary conversion efficiency. As a result of this study, reflection coefficient has been decreased with motion of the pendulum. And the uplifting type's conversion efficiency is as good as the bottom standing type's for the case of d/h≥0.5.

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Interlocking properties affecting stability of rubble mound breakwaters are investigated. Stability tests of ripraps against wave attack are performed by changing disposition patterns. Another stability tests are carried out to examine stabilizing effects by using stuffing stones. These results show that the stability of ripraps strongly depends on the interlocking properties which may be parameterized in terms of void fraction, coordinate number, diameter ratio for two particle system and angle of repose.

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The stability of artificial concrete blocks covered the upright breakwaters havebeen invesitigated by irregular-wave model tests. To assess the stability of theblocks, the colored blocks wewe arranged with stripes on the wave breaking works. The damage ratio was determined by the wave height was gradually increased in 2-cm increments. The stability factor of the artificial concrete blocks (specific gravity: 2.3, 2.6 and 2.9) at 5% damage ratio of slope 1:1.5 can be obtained as in Fig.12.

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Stability of concrete blocks ‘CRABLOCK’ for a gentle slope seawall were investigated experimentally in an irregular wave tank. The lift force acting on a block was measured with pressure gauges and the relationships between a damage of blocks and the lift force were studied. When the surf-similarity parameter is close to 1, the lift force becomes large and the critical wave height becomes small. The limits curves for the stability of the block were obtained in the case of both regular waves and irregular waves.

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Irregular-wave model tests of the stability of armor units for submerged breakwaters were conducted. To assess the stability of the armor units, armor units segmented with colored stripes for reference were arranged on the surface of submerged breakwaters, and the wave height was gradually increased in 2-cm increments to determine the damage ratio. The required weight for an armor unit can be obtained by Hudson's formula. The stability factor of the armor stone (specific gravity: 2.6) at a 5% damage ratio can be obtained as in fig. 8.

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Submerged floating tunnels have been proposed for many strait crossing projects, but seismic response of the tunnels have not been investigated in detail. This paper presents analytical method to estimate response of submerged floating tunnels to vertical seismic excitations. Based on the one-dimensional wave propagation method, response of seabed and sea water to the input earthquake motions is calculated. Also hydrodynamic force of the tunnel is numerically evaluated by the boundary integral method using the Green's function. Then the equation of motion for the tunnel is established and response of the tunnel acceleration and the tendon forces is calculated by solving the equation.

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To evaluate the lateral resistance of single piles for dolphins under repeated loads and large deformations, lateral loading tests were carried out for model piles embedded in sandy soil in a laboratory. The model piles were made of high-tensile steel plates 2500mm in length and 200mm in width. The conclusions of this study are as follows: 1) the test results of the relationship between soil reaction p and pile deflection y show that Kubo's formula (pocy^0.5) is applicable to large deflection under the initial loading phase of each package of cycles. 2) the deflections and inclination angles of the pile increase with the loading cycles. Increasing ratios have linear relations to the logarithmic number of loading cycles when the magnitude of the load is kept constant.

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A granular air-mortar is a light weight backfill material and it's unit weight and strength can be control. Therefor it is estimated to reduce earth pressure acting on the revetment and the retaining wall. In the case of using this light weight material at a revetment, liquefaction and seismic earth pressure of backfill are difficult planning problems. And so static and cyclic triaxial tests and shaking table tests were performed on a granular air-mortal. This report deals with the shear characteristics and the seismic earth pressure acting on the retaining wall.

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Stability of a composite breakwater which consists of a caisson and a rubble mound is discussed. Stability against sliding is conventionally estimated by the following formula, H=tanδ·V where V, H and tanδ are vertical load, horizontal resistance force and apparent friction angle between a caisson and a rubble mound. The value of tans used for design is 0.6 which is an empirical constant. From geotechnical point of view, this stability problem is equivalent to a bearing capacity problem of a shallow foundation subject to combined loads. By introducing macroscopic failure locus of a cassion-rubble mound system in 3-dimensional load spaceV-H-M/B, it can be easily explain that tanδ depends on loading conditions. Non-linear FE analysis is performed to evaluate a bearing capacity characteristic. The numerical results show that tanδ reduces owing to existence of a moment load around a base of a caisson. For breakwater problems, a horizontal component of wave loads also cause moment loads because they are working at some heights from the base. The importance of an applied height of a horizontal load is highlighted for rational estimation of sliding resistance of the breakwater system.

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Recently, various types of tension leg platform (hereinafter called “TLP”) have been proposed, designed, and constructed for deep sea oil drilling and production platforms. This paper first presents a basic concept of a TLP with a mechanical damping system (hydraulic damper). Next, the basic planning on a prototype model of TLP with a mechanical damping system is briefly described. Finally, the results of an in-laboratory dynamic loading test, which was performed to verify the performance of hydraulic damper selected an optimum system, are also introduced.

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When we perform a drilling and soil investigation in the water areas of more than 15m deep, steel platforms or guide tower platforms have been commonly used. However, these platforms have often been restricted to apply by some field conditions.
Accordingly, we have continued the development of a new drilling derrick to improve the safety for such restriction as bad weather and sea conditions, or ship navigation.
We have developed a new type of drilling derrick with no anchor wire named the Spar-Buoy Boring Derrick (BB Derrick), which is simple-designed and easy to transport, install and operate. Further, we have developed a stabilizer system for current force and wave motion. We have demonstrated that the BB derrick with the newly designed stabilizer could operate under tidal current of more than 2kt and increased the stability against the wave motion.

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Under Water Strutted Steel Structure System is a new type quay wall which was developed by Port and Harbour Research Institute and Nippon Steel Corp.
The deformation and stress distribution of the system against lateral load which are acting on the wall are measured and analyzed in this report.

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In recent years, a number of composite breakwaters with concrete armor blocks piled up just in front have been constructed. These are considered effective to suppress wave pressure on the caisson and wave reflection.
The new type is a composite breakwater, that is caisson on rubble mound type, with detached submerged mounds of armor units which are otherwise to be placed just in front of the caisson. The hydraulic characteristics are investigated with two- and three- dimensional hydraulic model experiments.
As a result, this new type breakwater gives more stable environment that will be favorable to marine fishery resources with a minimum increase in construction costs.

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A new procedure for improving sea bed condition using a gridfence is proposed. The grid fences set on the bottom covered by sapropel has a function flow down the sapropel by creating local scouring around them and improve sea bed condition into a favorable one for the growth of benthos.
The mechanism of local scouring and the shape of the local scouring are investigated through two dimensional experiments using wave and current. The maximum local scouring depth is expressed by the unique function of Shield's number.

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Study on the control of environmental conditions has been carried out to enhance fishery productivities as such sea urchin, abalone and others. The open spaces along shore platform of the Japan Sea is selected as one of grounds to develop for aquacultural pond.
Hydraulic model tests, numerical simulations by time-dependent mild slope equation method were carried out to plan optimum layouts of breakwaters for favorable conditions of aquatic organisms in aquacultural pond.

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Fish have been known to aggregate and school around rocky outcroppings, deployed ships and concrete blocks. One of the reasons of the fish abundance have been considered to be the underwater sound. This paper deals with the underwater acoustics generated by the fish aggregation devices through the laboratory tests. The acoustic pressure measured in the tank tests and analyzed by the spectrum estimator. The results indicate that the underwater sound generated by the fish habitat seemed to be a very important parameter for the attraction to the marine fish.

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Natural environments and marine organisms in the artificial lagoons atthe Tannowa-Hakozukuri Coast facing Osaka Bay are investigated. At first, changes of meteorological and oceanographic conditions and water quality were measured. And, also the habitable conditions of marine organisms in two tide pools were observed in the case of one opening and two ones. Consequently, the characteristics of vertical and horizontal distributions of marine organisms were made clear in these tide pools. Moreover, the marine organisms in the pools were compared with those in concrete-made detached breakwater.

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The buoyant jets issuing vertically upwards into stagnant ambient fluid, which we call “water curtain”, are expected to utilize as a fish screen to control fish behavior by fencing a water body with the buoyant jets. There have been many studies of vertical buoyant jets, in the previous studies, the Gaussian error curve is assumed to give an adequate approximation to the actual velocity and concentration distribution. In the present paper, we develop theoretically the diffusion problem of jets by assuming the discontinuity of density on the boundary between jet and ambient fluid, which is verified by experiments.
The equations deduced to evaluate the entrainment of ambient fluid, velocity and density are showen to be very simple in comparison with the usual equations, and have good accuracy for practical use. The experiments using fish (red sea breams) show that the control efficiency is very good to young breams.

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A model to predict the change in ecosystem associated with the construction of detached breakwater was developed. Coastal zones in Japan were classified into 41 types with respect to the coastal morphology, wave climate and the characteristics of bottom material. The influences to the coastal environment due to the construction of detached breakwaters were estimated with reference to the formation of void, calm wave zone, nearshore circulation and fine sand zone behind the detached breakwater. In each type a predictive model of change in ecosystem was given.

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Land development has seen river mouth facilities put in place to prevent blockage of the river mouth, thus preventing flooding and dissipating the very wet marshlands. Preventior of blockageof the river mouth and lowering of the water level of the Yasshushinai River leads to the surface of the water in the Yasoshi Marshes situated along the Yasshushinai River dropping and becoming affected by tides.
Nature conservation groups involved in bird watching of either the birds which fly into the lagoon or live along the river area protested against the construction of river mouth facilities.
Agreement was reached at meetings resulting in construction being initiated following a mitigation programme drafted with regard to ducks and snipes.

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