Katsutoshi Kimura

DESIGN AND CONSTRUCTION OF SEAWATER EXCHANGE BREAKWATERS

Detailed studies have been undertaken to assist in the design of major extensions to the port of Haifa. Both numerical and physical model studies were done to optimise the mooring conditions vis a vis the harbour approach and entrance layout. The adopted layout deviates from the normal straight approach to the harbour entrance. This layout, together with suitable aids to navigation, was found to be nautically acceptable, and generally better with regard to mooring conditions, on the basis of extensive nautical design studies.Hwa-Lian Harbour is located at the north-eastern coast of Taiwan, where is relatively exposed to the threat of typhoon waves from the Pacific Ocean. In the summer season, harbour resonance caused by typhoon waves which generated at the eastern ocean of the Philippine. In order to obtain a better understanding of the existing problem and find out a feasible solution to improve harbour instability. Typhoon waves measurement, wave characteristics analysis, down-time evaluation for harbour operation, hydraulic model tests are carried out in this program. Under the action of typhoon waves, the wave spectra show that inside the harbors short period energy component has been damped by breakwater, but the long period energy increased by resonance hundred times. The hydraulic model test can reproduce the prototype phenomena successfully. The result of model tests indicate that by constructing a jetty at the harbour entrance or building a short groin at the corner of terminal #25, the long period wave height amplification agitated by typhoon waves can be eliminated about 50%. The width of harbour basin 800m is about one half of wave length in the basin for period 140sec which occurs the maximum wave amplification.Two-stage methodology of shoreline prediction for long coastal segments is presented in the study. About 30-km stretch of seaward coast of the Hel Peninsula was selected for the analysis. In 1st stage the shoreline evolution was assessed ignoring local effects of man-made structures. Those calculations allowed the identification of potentially eroding spots and the explanation of causes of erosion. In 2nd stage a 2-km eroding sub-segment of the Peninsula in the vicinity of existing harbour was thoroughly examined including local man-induced effects. The computations properly reproduced the shoreline evolution along this sub-segment over a long period between 1934 and 1997.In connection with the dredging and reclamation works at the Oresund Link Project between Denmark and Sweden carried out by the Contractor, Oresund Marine Joint Venture (OMJV), an intensive spill monitoring campaign has been performed in order to fulfil the environmental requirements set by the Danish and Swedish Authorities. Spill in this context is defined as the overall amount of suspended sediment originating from dredging and reclamation activities leaving the working zone. The maximum spill limit is set to 5% of the dredged material, which has to be monitored, analysed and calculated within 25% accuracy. Velocity data are measured by means of a broad band ADCP and turbidity data by four OBS probes (output in FTU). The FTUs are converted into sediment content in mg/1 by water samples. The analyses carried out, results in high acceptance levels for the conversion to be implemented as a linear relation which can be forced through the origin. Furthermore analyses verifies that the applied setup with a 4-point turbidity profile is a reasonable approximation to the true turbidity profile. Finally the maximum turbidity is on average located at a distance 30-40% from the seabed.

Development of New Breakwater Construction Methods with Cellular Blocks

Most breakwaters in Japan are caisson breakwaters. However, the lower is the number of caissons constructed in a year, the higher is the construction cost per caisson, because the cost of floating dock operation is fixed, irrespective of caisson number. Therefore, a construction method was developed in which breakwaters are constructed not of caissons but of connecting cellular blocks. This paper proposes a design method for connecting cellular blocks and examines wave force characteristics in the construction stage by using hydraulic model tests. It was found that the proposed construction method could cut the project cost by 15% and could cut the project duration by 3 years at the Port of Setana.

Effects on Vehicle Traffic of Wave-Overtopping at Slipways Adjoining Coastal Roads

海岸施設の設計では,背後地の利用形態に応じた護岸 整備が実施される.しかしながら,近年の低気圧の大型 化や海面上昇に伴い,来襲する高波の頻度およびその規 模は増大しており,既設の護岸における越波被害が多発 している.一方,海岸道路では,延長が長く,海域利用 者との調整が難しく,適切な護岸改良が行えない場合が 少なくない.こうした状況下において道路管理者は,越 波による危険が生じる箇所に対して,気象・海象情報と 現地における目視調査の結果から必要に応じて徐行,片 側交互通行あるいは全面通行止めの規制を行っている. 越波による車両被害として,清水ら(2010a)は,越 波水塊の落水や衝突による車両破損のような直接的被害 の分析をしている.また,木村ら(2001,2003)は,越 波による飛沫成分の飛散による一時的な視界障害のよう な間接的な被害や,越波水塊の打ち上げ特性を分析し具 体的な恒久対策工について検討を行っている.さらに, 越智ら(2012)は,海岸道路における路肩欠損事例をも とに,高波浪時に大型土のうと消波ブロックを併用した 応急復旧工による越波対策工の効果を検証している.こ うした海岸道路における車両被害を減少させるために は,各護岸に対する越波現象の解明と予測手法の確立が 重要となる. 清水ら(2010b)は,日本海に面したA海岸を対象と し,現地観測結果に基づいて,直立護岸および背後地へ の越波流量と波圧の関係を明らかにし,越波による車両 脱輪事故の実験的な検討を行っている.しかしながら, 実際のA海岸においては,直立護岸に併設された船揚場 斜路に波が集中し,激しい越波となって車両に作用し, 脱輪を生じさせたと推測される. 本研究では,北海道を対象とした船揚場の実態調査を 行った上で,直立護岸に併設された斜路部の平面配置を 変化させた際の波の集中現象について,水理模型実験お よび数値波動水槽CADMAS-SURF/3D(2001)により明 らかにする.また,A海岸での車両脱輪事故時の越波状 況を水理模型実験により再現し,現地における対策手法 の提案を行う.

A STUDY ON DAMAGED SEASIDE HOUSES DUE TO WAVE OVERTOPPING

Seaside houses in Kamoenai Village were seriously damaged by Typhoon No. 18 in 2004. The damage patterns were classified according to wave overtopping rate and the distance from the seawall alignment. The wave overtopping rate and wave forces on the houses were reproduced by two dimensional model tests, and the critical condition of seaside houses behind the seawall was shown as the function of offshore wave height and the distance from seawall. Based on the results, the evacuation condition was recommended for the coastal residents in Kamoenai Village. It was also confirmed that the safety of seaside houses can be improved by wave absorbing revetments in front of seawalls.

Stability of Armor Units for a Leeward Mound of Composite Breakwaters

: The armor units on the rubble mound foundation of a composite breakwater should be of sufficient mass to ensure stability against storm waves. Toward this, the stability mass of seaward units has been calculated by an equation developed from hydraulic model tests and the mass of leeward units has been designed empirically as half mass of seaward units. This study uses numerical simulation to show that large eddies generated by wave overtopping results in a rapid caissonward flow above the leeward mound crown and that the velocity of this flow is a very important factor in the stability of armor units. Hydraulic model tests were used to formulate a function of wave conditions and structural geometry. From the balance of forces acting on an armor unit, the stability number NS in the Hudson formula was formulated to allow design of armor units on the leeward mound. INTRODUCTION The rubble mound foundation of a composite breakwater is covered with armor units of concrete or stone whose mass is sufficient to prevent wave action from displacing rubble stones. Tanimoto et al. (1982) and Takahashi et al. (1990) developed a calculation method for stable mass of armor unit using hydraulic model tests. The mass for leeward armor units has been set empirically at half that for seaward units. However, as there are few examples of damage to leeward armor units, it might 1 Port Planning Section, Hokkaido Regional Development Bureau, Ministry of Land Infrastructure and Transport, Kita 8 Nishi 2, Kita-ku, 060-8511 JAPAN 2 Civil Engineering Research Institute, Independent Administrative Institution, 1-3 Hiragishi Sapporo, 062-0931 JAPAN 3 Division of Environmental Engineering, Muroran Institute of Technology,27-1,Mizumoto-cho, Muroran, 050-8585 JAPAN 4 Division of Environmental Resources Engineering, Hokkaido University, Kita 13 Nishi 8, Kita-ku, 0608628 JAPAN

STABILITY OF ARMOR UNITS ON A HARBOR-SIDE MOUND AGAINST WAVE OVERTOPPING WITH BACKWARD PARAPETS

The high mound is sometimes constructed behind a composite breakwater in order to increase the sliding resistance and utilize the mound for an aquacultural purpose. The high mound must be covered by armor units with adequate weight to prevent from scattering by overtopping waves. However, the shallower is the submerged depth of the mound, the heavier become the armor units.This study proposed a backward parapet as a countermeasure to reduce weight of armor units. A numerical simulation showed the difference in the velocity field behind the caisson between the backward and forward parapet. With the backward parapet, large-scale eddies were not observed and the velocity on the mound was slower than that of the forward parapet. Furthermore, hydraulic model tests showed that the stable weight was approximately 40% less than that of the forward parapet.

Prevention Method of Long Period Waves by Construction of Breakwaters

Termination of cargo handling caused by long period waves sometimes occurs in a port.The estimation method of the rate of effective cargo handling days for long period waves is derived from the characteristics of long period waves observed in Tomakomai-port.The countermeasures by breakwaters is proposed to improve the rate.

Characteristics of Long Period Waves by Field Observation and Statistical Analysis of It's Propagation in Harbor

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.

Wave Forces and Armor Stability of Breakwaters on Steep Slopes

A design method for breakwaters on steep slopes has not been established, because the wave forces have been unable to be estimated accurately.In this paper, the stability of wave dissipating blocks and wave forces acting on breakwaters on steep slopes have been investigated experimentally.The common formula is applicable in estimating wave forces acting on breakwaters covered with wave dissipating blocks, but under some conditions, a stronger than usual wave pressure acts. When the incident wave height is large relative to the water depth, the blocks at the end of the slope suffer great damage.