Showing papers on "Breakwater published in 1985"

Low-crest breakwaters, hydraulic performance and stability

Abstract: The research reported advances design methods for low crest and submerged breakwaters. This report reviews techniques available to predict wave transmission and overtopping effects and armour displacement. Hydraulic model test results obtained both at Hydraulics Research and in other labs are presented graphically in terms of appropriate non-dimensional parameters. Measurements of armour movement under random waves have also been analysed. The results have been presented graphically in terms of non-dimensional stability numbers.

Hinged Floating Breakwater

Abstract: An analytical model is developed to examine the response and efficiency of a rigid, hinged floating breakwater. The theoretical model is verified experimentally and is used to develop design curves which may be employed to estimate necessary physical breakwater characteristics to satisfy specified wave attenuation criteria. The utility of these curves is demonstrated in a design problem. It is shown that a structure of reasonable size is an effective dynamic barrier for high frequency waves and an effective kinematic barrier for low frequency waves.

A Harbor Ray Model of Wave Refraction‐Diffraction

Abstract: A harbor ray model has been developed which describes the combined wave effects of diffraction around breakwaters and depth refraction. Ray models are computationally well suited to determining the response of large harbor areas to short period waves. This is a situation for which alternative mathematical models can use prohibitively large amounts of computing time and storage. Diffraction caused by two types of breakwater layout, commonly found at harbor entrances, is shown to be capable of being modeled by a ray method. These breakwater layouts are: (1) A small gap between two straight breakwaters; and (2) a single, straight, semi‐infinite breakwater. A new ray system is presented for the semi‐infinite breakwater problem which overcomes the difficulty of modeling the region around the geometric shadow boundary. Unlike other techniques developed to resolve this difficulty, this method retains a ray plotting solution technique and therefore keeps the computational advantages of such a technique. A compari...

Breakwater using scrapped ship

Abstract: PURPOSE:To permit the mooring of a small ship by directing the tidal current downwards by providing wave-dissipating openings to the upper deck and side outer plate of the topside tank and the side outer plate of the double-bottom tank in a breakwater using a scrapped ship. CONSTITUTION:Filling soil 8 is packed into the center tank of a bulkcarrier hull 1, and the scrapped ship is used as a breakwater. In the top-side tank 4, a wave- dissipating opening 4a is provided in the upper deck 2, and an wave-dissipitating opening 5 is provided in the side outer plate 3. In the double-bottom tank 7, a wave-dissipating opening 6 is provided in the side outer plate 3. A wave-dissipating effect can thus be provided to the breakwater. Since the tidal current passes through the lower part, the small ship can be moored to the inland sea side of the breakwater.

Shore protection by offshore breakwaters

Abstract: This report reviews the information available for the design and use of offshore breakwaters in shore protection. As an introduction to the subject the physical processes occurring in the lee of an offshore breakwater are described with reference to natural examples. This is followed by a survey of case histories, and mathematical and physical modelling techniques for offshore breakwaters. Some of the methods which are available for the design of a breakwater system are reviewed. Possible future developments in the design process are described, and the areas in which further research on the effects of offshore breakwaters is required are highlighted.

Field assessment of a floating tire breakwater

Abstract: A field monitoring program of a Goodyear floating tire breakwater (FTB) was undertaken at La Salle Park, Burlington, Ontario, during 1981 and 1982. Incident and transmitted waves were measured with underwater pressure transducers. The resulting wave height transmission data compares favourably with previous results from model studies. Mooring loads on some anchor lines were measured with two electronic and four mechanical gauges. The resulting peak load data, corresponding to incident wave heights up to 0.65 m, are in good agreement with previous results from prototype scale model studies. Key words: coastal engineering, floating tire breakwaters, marinas, pressure gauges, mooring forces, waves.

Wave interception by sea-balloon breakwater.

Abstract: When a submerged, flexible bag is filled with air about 60~T0 % of its full volume ( it is called " sea-balloon " ), it has a stable shape with vertical axis of symmetry, on which several vertical wrinkles appear with folds of membrane. If two or more such sea-balloons are arranged to the direction of wave travel and connected pneumatically, balloons are deformed periodically and the air flows reciprocally in connecting pipe, following to the fluid pressure fluctuation due to incident waves. Such a system of sea-balloon intercepts incident waves effectively ( it is called " sea-balloon breakwater "). The wave interception by the breakwater is analyzed numerically by three-dimensional boundary integral method, assuming that the fluid motions both in- and out-side of the balloon are potential and that the tension in balloon membrane is proportional to the apparent elongation of membrane with virtual elastic constant. After analysis and experiments, it is made clear that in relatively long waves the incident wave is canceled by the radiation wave which is generated by volumetric change of sea-balloons, being affected by airflow resistance in connecting pipe. In short waves, sea-balloons seem to behave like as rigid piles and the incident wave is absorbed by airflow resistance in pipe and by the turbulence of fluid motion around balloons. Moreover, the effect of gaps between sea-balloons along wave crest on wave interception for relatively long waves is expressed by a simple empirical formula, by which the transmission coefficients at various types of sea-balloon breakwater is easily estimated by twodimensional computation. For the improvement of wave interception effect and from the point of practical use, the effects of other sea-balloon breakwater system are investigated by two-dimensional computation and experiments.

Breakwater Rehabilitation Study, Crescent City Harbor, California: Coastal Model Investigation.

Abstract: : An undistorted scale hydraulic model study was conducted to develop an adequate repair plan for a section of the Crescent City breakwater which as armored with dolosse. The damaged area was to be repaired with 42-ton dolos. It was desired to quantify the number of armor units required, the optimum slope on which to place the dolosse, overall constructability, and methods of stabilizing the transition areas. Based on results of model tests, a combination of trenching and buttressing with 25-ton armor stone is a constructable method of stabilizing the transition area.

Construction of breakwater structure

Abstract: PURPOSE:To easily construct a breakwater structure by a method in which a wave-dissipating part is fixed to a caisson installed on the foundation rubble, and concrete is placed to integrate the caisson and the wave-dissipating part. CONSTITUTION:A caisson 1 is installed on a foundation rubble 11, filling sand 6 is charged into the charging port 2a and packed into compartment chambers 2 and lower chambers 3, and a concrete cover 7 is covered on them. Wave-dissipating parts 4 are fixed to the upper outer wall of the compartment chambers 2 of the caisson 1 and the ceiling wall of the lower chambers 3 by fixers 5. Concrete 8 and 9 is placed to cover the fixers 5, and concrete 10 is placed on the upside of the caisson body 1. Since the caisson body 1 is separated from the wave-dissipating part for production, the delivery and construction of the breakwater structure parts can be made easier.

Erosion Control of Scour during Construction. Report 8. Summary Report.

Abstract: : When major stone structures such as jetties, breakwaters, or groins are erected in the coastal zone, they alter the existing tidal, wave-induced, or wind-driven currents that are in a dynamic equilibrium with the existing bathymetry. These altered currents and waves breaking on such structures under construction may change the existing bathymetry by causing bottom material to be suspended and transported from the region. The objectives of this research were to develop techniques and knowledge for estimating resulting wave characteristics and wave-induced current fields in the vicinity of major coastal structures. Both analytical and laboratory experimental studies were conducted during the investigation. The analytical developments regarding wave heights and wave-induced currents were verified by the use of precise experimental studies of shore-connected breakwaters. Additional underlayer stability experimental studies were conducted for estimating the size of stone comprising the foundation bedding material which would remain stable under various wave conditions. Originator-supplied keywords: Breakwaters, Coastal engineering, Hydraulic structures, Scour (Hydraulic engineering), Shore protection, Water waves.

Wave action at a series of offshore breakwaters: a mathematical model of wave diffraction and overtopping

Abstract: This report describes the development of a mathematical model of wave diffraction and overtopping by a series of offshore breakwaters. The method used combines the solutions of a number of insular breakwater and breakwater gap problems. For the case of a single insular breakwater or breakwater gap the results from this model are compared with published results. For a number of offshore breakwaters a preliminary comparison is made with the results from a physical model. The model is subsequently used to test the sensitivity of wave height in the lee of breakwaters to changes in incident period and direction, and adjustments in breakwater length: gap width ratio.

Scaling the Weight of Breakwater Armor Units

Abstract: The use of the stability parameter for calculating the weights of armor units in models of rubble mound breakwaters is shown to have little justification. An alternative scaling method based on similarity criteria is developed and the results of the two methods are compared. It is shown that the use of the stability number causes little error but that this is fortuitous rather than physically meaningful.

Research on the Development ofWai-Shan-Ding Barrier, SW Coast of Taiwan, R. O. C.

Abstract: Due to the abundant supply of sediment from the rivers, the west coast of Taiwan has shown a rapid accretion in history. As a result of this large areas could be reclaimed, such as the delta North of Putai -­Wai-Shan-Ding sand barrier. In recent years, however, sediment supply is reduced due to river training and flood control. Consequently, the coastal area is now subject to erosion as the net sediment transport exceeds the supply to the beach. Therefore, shore protection is going to be cultivating the Australian pine tree by the Chia-Yi County Government. Since the relatively well protected location of the area with regard to both waves and wind, no special navigational problems have to be envisaged. For the point view of whole development, it is easily planned the lee wind side of the delta as a marina, and wharf could be simply constructed as a floating type for sightseeing and cargo handling between this island to offshore island (such as P'eng-Hu or King-Meng, etc.). The main purpose of this marina is used for happy vacation time, such that the wharf is designed for the anchoring of yacht and hydro-foil cruiser, etc., the breakwater is need to constructed convenient to be fishing. Siwwing beach, beach park and some facilities for sightseeing are planned and designed in this offshore area for utility of the coastal management.