WO1990012155A1

WO1990012155A1 - Floatable breakwater

Info

Publication number: WO1990012155A1
Application number: PCT/GB1990/000548
Authority: WO
Inventors: Stephen Edward Jackman
Original assignee: Bandvulc Marine Limited
Priority date: 1989-04-13
Filing date: 1990-04-10
Publication date: 1990-10-18
Also published as: CA2062740A1; AU5520790A; GB8908311D0; GR900100268A; JPH04506689A

Abstract

A floatable breakwater consists of an array of flotation units (11) preferably used tyres (12) with a filling of buoyant material (13) flexibly linked together in two mutually orthogonal directions to form a module (21). Successive modules (21, 23, 24) may be linked together to any desired length or breadth. The flotation units are used to support a molluscs culture rope (16) and a gantry (33) may be positioned across the flotation units to work the culture ropes.

Description

FLOATABLE BREAKWATER

This invention relates to floatable breakwaters of the type for protection of aguaculture or coastal sites by attenuation of water waves or dissipating the energy therein.

It is known to provide artificial floating breakwaters for the purpose of protecting a section of shore or a floating installation, or for defining an aquaculture site and providing an area of relatively placid water therein. However, such structures are relatively expensive to instal and maintain and thus contribute significantly to the overhead costs of the enterprise.

It is an object of the present invention to provide a floating breakwater of the type described, which having been installed can be used to generate revenue.

According to one aspect of the present invention, a floatable breakwater comprises an array of flotation units linked together by flexible retaining means, in which in use the breakwater includes a plurality of substrates suspended therefrom for supporting marine organisms.

Marine organisms which may be supported by a floatable breakwater according to the invention may be deliberately placed or seeded on the substrates, on which they then grow by virtue of being held at the correct position in the water in relation to their food, typically plankton, and/or light. For example, mussels or commercially-available seaweeds may be seeded on the substrates. Alternatively, unseeded substrates may be suspended from the breakwater for supporting any local marine organism which comes in contact with the substrate and adheres thereto.

The flotation units are to be distinguished from known floats of for example cork in that they are sufficiently large and heavy that by their inertia they intrinsically provide a wave-attenuation or wave energy dissipation effect.

The suspended substrates may be filamentous and may comprise nets or discrete elements, for example ropes. We prefer to use discrete elements since such can more easily be raised clear of the water above the flotation units for servicing purposes.

Marine organisms which have been placed on or become supported on the substrates are generally sessile, for example molluscs or seaweed.

The suspension of substrates from floating breakwaters enables- the breakwater to have a revenue-earning capability in addition to its protective function, and additionally the suspended substrates enhance the wave-attenuation ability of the breakwater.

In order to service the substrates, that is, to lower a seeded or clean substrate or part thereof into the water and to raise it therefrom for harvesting the molluscs or other marine life-form attached thereto, a gantry may be supported on or across two or more flotation units. Preferably, each flotation unit is substantially planar or disc-like, that is, it has two major dimensions and a minor dimension, and the breakwater floats on the surface with the planes of the flotation units parallel with the surface, thereby to provide a more stable support for the gantry.

Individual flotation units may be buoyant per se or may be rendered or maintained buoyant by means of buoyancy elements to which they are attached, internally or externally. Conveniently, each flotation unit comprises a vehicle tyre, that is, a car, lorry or truck tyre the tread of which is worn, the tyre therefore no longer being utile for its originally-intended purpose. There are in fact enormous stocks of such tyres in the world which, since they are difficult to dispose of without creating pollution, present a considerable environmental problem; the invention therefore provides an economic way of using some of these tyres. To render the tyres buoyant, they preferably contain a buoyant material which may be natural, such as cork, but is preferably a synthetic air-entrapping material such as a foamed plastics material.

For the purpose of linking individual flotation units together, each unit may be provided with a passageway or conduit through which may be passed a flexible retaining element. Preferably, two such passageways or conduits are provided in each unit, arranged substantially in the plane thereof and in two respective directions which desirably are mutually orthogonal, thereby enabling individual units to be linked with neighbouring units in two directions, to provide a matrix of flotation units, preferably in a close-packed planar configuration.

Adjacent flotation units may be maintained in spaced-apart relationship by the use of one or more spacer elements carried by or threaded on the flexible retaining elements. Spacer elements may comprise discs, spheres or the like, are preferably resilient, and may extend wholly or predominantly below the water surface, preferably suspended from the retaining elements such that they can swing with the water movement to _ provide a further enhancement of the wave-attenuation effect. Conveniently, the spacer elements comprise further tyres arranged so that they extend predominantly below the water surface and with their plane substantially at 90° to the surface. Such tyres for use as spacer elements would not normally, of course, include any buoyancy material, although they may have at least a degree of buoyancy by virtue of the air entrapped in use in the uppermost arc of the casing.

A gantry may conveniently be supported on four adjacent flotation units which define the corners of a notional square or diamond within the matrix, an area of water surface being exposed in the central region of the square or diamond between the flotation units. Each leg of the gantry is supported directly or indirectly on a respective flotation unit and a hook or other connection member suitable for attaching to a substrate is suspended from the gantry above the said area of water surface. A substrate may be attached by support means to one of the flotation units, to be suspended in the water immediately beneath the said surface. The legs of the gantry may be attached to a base or frame which may be supported on the flotation units in the correct position for optimum stability and with the connection member overhanging the desired area of water surface. The structure is preferably portable so that it may be moved between successive pluralities of flotation units to work the substrates or parts thereof in turn. The legs of the gantry may be inwardly angled to form a pyramid and the substrate may be adjustably suspended, for example by a block and tackle, from the apex of the pyramid.

It is preferred that matrices of flotation units are pre-assembled to form modules of pre-determined size with spacer elements therebetween as required; modules of flotation units may then be linked together, for example with chains, to provide a floatable breakwater of the desired size for the intended application. Optionally, flotation modules may be towed by boat to the desired location and linked together on site. Once in position, they may be anchored by conventional means.

Advantageously, modules are detachably linked together so that a selected module may be removed in isolation from the breakwater and if necessary replaced with another, or the array of modules may be expanded or contracted.

For access to a substrate, to move a gantry, or to service, remove or re-connect a module, the flotation units when linked together according to the invention are sufficiently stable (given reasonable weather conditions) to be walked on, although it may be preferred to lay matting across the flotation units to provide enhanced stability.

The invention also provides, in another aspect, a floatable breakwater comprising repeating units of three or more, preferably four, flotation units arranged linked together in co-planar fashion in a close-packed configuration by flexible retaining means to expose in use an area of water therebetween. The close-packed arrangement may be triangular, square or diamond-shaped. Spacer elements, preferably arranged to depend below the plane of the flotation units below the water surface, may be supported by the flexible retaining means. The flotation units, flexible retaining means and spacer elements are substantially as described hereinbefore.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings, of which

Figure 1 shows an individual flotation unit attached to fragments of four similar flotation units;

Figure 2 shows an array of flotation units constituting a module, connected to adjacent modules;

Figure 3 is a plan view showing an array of flotation units carrying a base and a gantry; and

Figure 4 is a side elevation of the embodiment of Figure 3 , showing a culture rope suspended from the gantry, above the water level.

Referring to Figure 1, a flotation unit 11 consists of a vehicle tyre 12 with an inner disc filling 13 formed from a synthetic foam plastics material to render it buoyant. Metallic, or alternatively plastics, corrosion-resistant pipes or tubes 14, 15 are passed diametrically through the tyre and filling, mutually at 9 900 .. AA mmoolllluussccss ccuullttuurree rrooppee 1166 iiss detachably secured to the peripheral region of the tyre. The flotation unit is attached to neighbouring flotation units by means of hawsers 17, 18 which are passed through the pipes, thereby linking adjacent flotation units together in two mutually orthogonal directions to form a matrix. Adjacent pairs of flotation units may be separated by a vehicle tyre, as illustrated at 19; alternatively, separator collars 20 may be provided. In practice, it would not be usual to include separator tyres and collars in the same matrix.

Referring to Figure 2, an array 21 of flotation units forming a module of 10 by 10 units is shown, each unit being of the type described with references to Figure 1 and separated from its adjacent unit by spacer collars. However, vehicle tyres arranged to hang substantially vertically from the linking hawsers may advantageously be used instead, whereby they can swing in response to wave motion and enhance the energy-dissipating effects of the flotation units.

As shown, each module is attached by chains 22 to neighbouring modules 23, 24 to provide an extended line of modules of indefinite length, depending on the number of modules, constituting a floating breakwater when in use on the sea.

Referring to Figure 3, a platform 31 is positioned across four adjacent flotation units which are arranged as a square. The platform is itself square and has a central portion cut away to define a square central aperture 32 which overlies the space between the four tyres. A gantry 33 (see also Figure 4) consists of four inwardly-sloping leg members 34 meeting together at an apex 35 over the central aperture. A block and tackle 36 (Figure 4) may be slung from the apex to raise and lower the culture rope 37. In Figure 4, the culture rope is seen in the raised position, ready for harvesting the molluscs or other marine life attached thereto.

The entire platform and gantry assembly may be carried to successive culture ropes for harvesting or other servicing thereof.

Claims

1. A floatable breakwater comprising an array of flotation units linked together by flexible retaining means, in which in use the breakwater includes a plurality of substrates suspended therefrom for supporting marine organisms.

2. A breakwater according to Claim 1, in which each substrate is a discrete filamentous element.

3. A breakwater according to Claim 1 or Claim 2, in which each flotation unit is disc-like in form and in use the breakwater floats on the surface of water with the planes of the flotation units substantially parallel with the said surface.

4. A breakwater according to Claim 3, in which each flotation unit comprises a vehicle tyre containing a buoyant material.

5. A breakwater according to Claim 4, in which the buoyant material comprises a synthetic air-entrapping material.

6. A breakwater according to any preceding claim, in which each flotation unit includes a conduit or passageway and flotation units are linked together by means of a flexible retaining element passed through the passageways or conduits.

7. A breakwater according to Claim 6, in which each flotation unit includes two conduits or passageways arraged mutually orthogonally.

8. A breakwater according to any preceding claim, in which adjacent flotation units are maintained in spaced-apart relationship by one or more spacer elements.

9. A breakwater according to Claim 8, in which the flotation units are linked together by flexible retaining elements and the spacer elements extend wholly or predominantly below the water surface and are suspended from the said retaining elements.

10. A breakwater according to any preceding claim, in which a gantry is supported across two or more flotation units, a connection member being suspended from the gantry to service the substrate.

11. A breakwater according to Claim 10, in which the gantry comprises legs which are inwardly angled to form a pyramid, the substrate being adjustably supported from the apex of the pyramid.

12. A breakwater according to any preceding claim, in which matrices of flotation units are pre-assembled to form modules which may be detachably linked together.

13. A floatable breakwater comprising repeating units of three or more flotation units arranged linked together in co-planar fashion in a close-packed configuration by flexible retaining means to expose in use an area of water therebetween.