Underwater modular structure, module of or for said underwater modular structure and method of constructing an underwater modular structure

An underwater modular structure includes a plurality of modules, a connector that interlocks the modules and a labyrinth defined by contours of the modules. Each module includes a connector insertion opening to receive a connector therethrough. The connector is an elongate member arranged through a connector insertion opening of each module thereby interlocking the modules. The labyrinth can be defined by outer and/or inner contours of the modules. A module of or for an underwater modular structure A method includes sinking a plurality of modules to a seabed, each module includes a connector insertion opening, and interlocking the modules with a connector that is an elongate member, by arranging the connector through at least one connector insertion opening of each of the modules, to form a labyrinth defined by contours of the modules. Such method may further include filling at least part of the underwater modular structure with a filler.

This application is a national stage filing under 35 U.S.C. 371 of International Application No. PCTNL2020/050686, filed Nov. 4, 2020, which claims priority to Netherlands Patent Application No. 2024156, filed Nov. 4, 2019, the entirety of which applications are incorporated by reference herein.

The invention relates to the technical field of underwater structures and methods of constructing underwater structures.

Various known underwater structures are used to protect coasts. Such underwater structures are generally constructed in the form of a dam, which may or may not extend above the surface of the water. In either case, when a wave of the water moves towards the dam, it is urged upwards and may pass over the dam in addition to being partially reflected off the dam. Said wave may reach and impact on a coast or structure beyond the underwater structure. This process encourages undesired alterations of the coast or structure such as erosion and deposition of sediments, deterioration of coastal protection installations such as dikes, floods of hinterland and/or disturbances of an underwater environment.

A purpose of the invention is to provide an underwater structure which is improved relative to the prior art and which abates incoming wave energy. Such underwater structure may thereby protect a coast beyond said underwater structure.

This is achieved by an underwater modular structure according to the invention, which underwater modular structure comprises a plurality of modules, at least one connector that interlocks the plurality of modules and a labyrinth defined by contours of at least the plurality of modules, wherein each module comprises at least one connector insertion opening configured to receive a connector therethrough and the at least one connector is an elongate member arranged through at least one connector insertion opening of each of the plurality of modules thereby interlocking the plurality of modules.

The purpose is also achieved by a method of constructing an underwater modular structure according to the invention, which method comprises the steps of sinking a plurality of modules to a seabed, wherein each module comprises at least one connector insertion opening, and interlocking the plurality of modules with at least one connector that is an elongate member, by arranging the at least one connector through at least one connector insertion opening of each of the plurality of modules, to form a labyrinth defined by contours of at least the plurality of modules.

The invention further relates to a module of or for an underwater modular structure as described in this application.

Advantageous embodiments of the invention are the subject of dependent claims and may also be learned from the following description and appended figures.

The underwater modular structure forces incoming water to pass through the labyrinth, thereby dissipating wave energy. Wave energy may be dissipated, for example due to turbulence and friction, as the wave is at least in part directed along and/or through the labyrinth. Dissipating wave energy has the effect of reducing wave impact beyond the underwater modular structure, for instance on a nearby coastline or structure. This reduces the erosion of said coastline or structure, especially when this involves sandy beaches. Furthermore, the upwards urge of the wave as it moves towards the underwater modular structure is reduced compared to conventional underwater structures, such as a dam.

The labyrinth is defined by contours of at least the plurality of modules and may be further defined by the at least one connector.

The term labyrinth in this context is employed to indicate a continuous space defined by contours of at least the plurality of modules. Such continuous space may be filled with water when the underwater modular structure is positioned underwater. The labyrinth may thus comprise paths along which the water may flow both through as well as past the contours of at least the plurality of modules. The labyrinth comprises said paths along which water may flow past the contours to the extent in which these contours affect the flowing past of water, for example through generating turbulence and friction. Further, such water flow favours water quality and nutrient distribution within the underwater modular structure1, thus stimulating a local ecosystem.

The at least one connector that is an elongate member configured to interlock the plurality of modules may be of a substantially solid form, such as a pipe, rod, beam, hook, rail or plank, and/or of a substantially flexible form, such as a chain or cable. Preferably, the plurality of modules as well as the at least one connector are made of materials suitable for underwater use as known in the art, such as concrete, cement, durable plastics, copper, steel and stainless steel. The material for the plurality of modules need not be the same as that for the at least one connector. For example, modules may comprise concrete while the at least one connector may comprise stainless steel. Furthermore, the at least one connector may at least partly be incorporated in at least one of the plurality of modules.

The underwater modular structure may serve various ends, including coastal protection, protection of off-shore structures, coastal preservation, supporting an underwater ecological habitat and/or forming an artificial reef. These ends may be served by the underwater modular structure in combination or simultaneously. For example, the underwater modular structure may be formed as a breakwater to protect a coastline while also preserving a sandy beach from eroding and further forming a support structure for development of a reef ecosystem. In a further example, the underwater modular structure may form a barrier around an off-shore windfarm to reduce incoming waves and promote a reef habitat for local species. The underwater modular structure may also be advantageously employed around individual monopiles in order to reduce erosion or scour at a base of the monopile.

The following reference numbers are used in the figures as well as in the accompanying description:1underwater modular structure,2module,3connector,4labyrinth,5contours,6seabed,7coast,8outer contour of module,9inner contour of module,10wave,11connector insertion opening,11-1inward taper or recess,11-2outward taper or protrusion,12outer contour of connector,13inner contour of connector,14tortuous path,15underwater ecological habitat,16chamber,17filler,18sediment,19module parts,20outer wall,20-1rounded edge,21inner wall,21-1inner wall defining module part of first type,21-2inner wall defining module part of second type,21-3tapered end,21-4first type panel,21-5second type panel,22slots,23outline,24anti-scour apron,25anchoring,26three-dimensional geometric complexity,27textured surface,28porous surface,29interconnected inlets and outlets,30cavity,31reef-forming species,32dam,33spacer.

InFIG.1, an underwater modular structure1is shown while being constructed at an underwater construction site. The underwater structure1comprises a plurality of modules2, at least one connector3that interlocks the plurality of modules2and a labyrinth4defined by contours5of at least the plurality of modules2. The underwater modular structure1is shown as being constructed on a seabed6near a coast7. Typical depths at which the underwater modular structure1may be constructed range from 2 to 10 m below sea surface.

The modular nature of the underwater modular structure1presents advantages, for example that the structure1is adaptable to local situations, that it is scalable and may be assembled on-site, even under water. Furthermore, local sediments18may be used in its construction, as illustrated inFIG.1, which saves transportation efforts and limits introduction of potentially harmful elements to the underwater construction site.

Interlocking of the plurality of modules2by means of the at least one connector3ensures stability of the underwater modular structure1. The at least one connector3may thus prevent movement and/or displacement of the underwater modular structure1and modules2thereof.

The labyrinth4of the underwater structure may at least in part be defined by outer contours8and/or inner contours9of the plurality of modules2. The seabed6may also in part define the labyrinth4. When a wave10approaches the underwater modular structure1, it is forced to pass through and/or past the labyrinth4and thus at least some of the wave energy of wave10is dissipated. This is further explained in relation toFIG.3below.

The plurality of modules2may comprise at least one connector insertion opening11. Additionally, the at least one connector3may interlock the plurality of modules2via the at least one connector insertion opening11. Preferably, connector insertion openings11are provided in a sufficient number of the plurality of modules2so that the plurality of modules2are fully interlocked by means of the at least one connector3through the at least one connector insertion opening11. This enhances stability of the underwater modular structure1. More preferably, the connector insertion openings11are provided in each module2of the plurality of modules2. This facilitates compatibility between the plurality of modules2, enhances variability of the underwater modular structure1and reduces constructional effort at the underwater construction site.

The at least one connector3may be an elongate member. Preferably, the at least one connector3is a hollow member. The at least one connector3may thus be both elongate as well as hollow, though either elongate or hollow is also possible. For example, the at least one connector3may be a pipe with a perimeter of circular, rectangular or polygonal shape and may be a rail, hook or bar. When a connector3is designed as a hollow member, such connector3may be inserted into connector insertion openings11of modules2and thereby retain passage through these modules2when interlocking these modules2through their connector insertion openings11.

Alternatively or additionally, the at least one connector3may comprise a mating recess and protrusion, preferably comprised with the plurality of modules2. Upon engaging two of the plurality of modules2, one comprising such recess and the other comprising such protrusion, the recess and protrusion may interlock. The mating recess and protrusion may be provided on each of the plurality of modules2to ensure mutual interlocking.

In an advantageous embodiment, the mating recess and protrusion are provided on outer contours8of modules2at the connector insertion openings11. This facilitates alignment of the connector insertion openings11of the plurality of modules2when construction the underwater modular structure1, especially when this is performed underwater with limited visibility. The at least one connector3may then be readily introduced through the connecter insertion openings11, their alignment being assured through the mating recess and protrusion.

The labyrinth4may at least partly be defined by outer contours12and/or inner contours13of the at least one connector3. For example, when the at least one connector3is the hollow member, it may contribute to the labyrinth4with its hollow interior. In other words, when the at least one connector3is hollow, it further defines the labyrinth4.

At least one of the modules2may further comprise a tortuous path14further defining the labyrinth. The tortuous path14may be internal to the at least one of the modules2. The tortuous path14adds complexity to the labyrinth4, thus offering an increased number of possible paths for the wave10to pass through, thereby enhancing dissipation of wave energy of the wave10.

Furthermore, the tortuous path14may be configured to allow passage of underwater life into and out of the underwater modular structure1and/or to offer shelter for underwater life. The underwater modular structure1may thus foster underwater life of or for an underwater ecological habitat15, in contrast to conventional underwater structures that generally reduce or damage such underwater life and underwater ecological habitat15.

The underwater modular structure1may further comprise at least one chamber16that is at least partly filled with a filler17. The at least one chamber16may be comprised within individual modules2and/or connectors3. Alternatively or additionally, the at least one chamber16may be comprised between the plurality of modules2or may be defined by the plurality of modules2. Preferably, the at least one chamber16is comprised within at least one module2of the plurality of modules1of the underwater modular structure1.

The filler17may be used to add mass to the underwater modular structure1, so that it is not easily worn down, moved or displaced by movements of the water, such as arising from waves, tides and passing of ships. Known underwater structures are generally made from solid concrete to prevent such structure from being affected by movements of the water. Solid concrete structures require a large amount of raw materials and correspondingly large transportation and installation equipment resulting in large costs and high environmental impact.

Preferably, the filler17is a sediment18. The sediment18may be taken from the seabed6on or near the underwater construction site at which the underwater modular structure1is built and/or positioned. This allows for easy provision of additional mass to sink and/or stabilise the underwater modular structure1. Alternatively or additionally, the sediment18may be taken from dredging activities or other convenient sources. In this way, residual material may be repurposed.

Furthermore, the modules2and/or connectors3may be executed in a hollow or light-weight fashion, so that transportation and production effort may be reduced, thereby also reducing associated carbon emissions. For example, some of the modules2may each comprise the chamber16so that these modules2may be configured as substantially empty for transportation to the underwater construction site to be filled at the underwater construction site. This limits transportation and installation efforts for such modules2and thus also for the underwater modular structure1as a whole.

InFIG.2A,FIG.2B,FIG.2C,FIG.2DandFIG.2E, embodiments of the module2are illustrated. Though these five embodiments are presented separately, features of these embodiments may be combined at least in ways that follow from the dependencies in the claims. It should in particular be noted that the plurality of modules2may comprise several types of modules2and that within each type different versions of modules2may be employed. For example, the embodiments ofFIG.2AandFIG.2Bmay represent two versions of a first type of the module2, whileFIGS.2C and2Dmay represent two versions of a second type of the module2andFIG.2Emay represent a third type of module2.

FIG.2Aillustrates an embodiment of a module2comprising module parts19that are configured for assembly into said module2. An assembled view as well as an exploded view of said module2are shown at the top and bottom ofFIG.2A, respectively. At least one of the modules2of the underwater modular structure1may thus comprise module parts19that are configured for assembly into said at least one of the modules2. The at least one of the modules2comprising a tortuous path14may be the same as or distinct from the at least one of the modules2comprising module parts19.

The module parts19may be configured in various ways, examples of which are presented inFIG.2A-2D. The module parts19may be configured for assembly into the module2by means of mating edges and/or known fastening elements.

Preferably, the module parts19define at least one of an outer wall20of said module2and an inner wall21of said module2. The modular parts19that define the outer wall20of said module2may mutually engage, mate, interdigitate or couple to form the outer contour8of said module2. The modular parts19that define the inner wall21of said module2may equally engage mutually to form the inner contour9of said module2. Furthermore, the module parts19may mutually engage to form both the outer wall20as well as the inner wall21of said module2. As shown inFIG.2A, the outer wall20comprises the at least one connector insertion opening11of the module2.

In the example ofFIG.2A, the module parts19are illustrated to define both the outer wall20as well as the inner wall21of the module2in its assembled state. Furthermore, the outer wall20may define the outer contour8and the inner wall21may define the inner contour9of such module2.FIG.2Ashows three inner walls21defining module parts19, two of a first type21-1, having five orthogonal openings, and a second type21-2, having four orthogonal openings. Alternatively, this example may be modified to contain only three inner wall21defining module parts19, all of a third type having six orthogonal openings, said third type ensuring mutual interconnection along the longer axis of the illustrated module2.

In an advantageous embodiment of the module2, the chamber16may be formed by the module parts19, for example between the outer wall20and the inner wall21of said module2. One of the module parts19may be configured for closing the chamber16after the chamber16is filled with the filler17, for example as illustrated inFIG.1.

FIG.2Billustrates another version of the module2ofFIG.2A, to which the foregoing description is also applicable. However, in contrast to the module2ofFIG.2A, the module2ofFIG.2Bcomprises rounded edges20-1, here by way of non-limiting example comprised on the outer wall20of the module2. The rounded edges20-1of the module2have three main advantages:First, improved hydrodynamics by making it easier for water to flow past and through the structure, resulting in a lower drag force. A lower drag force results in an overall better stability of the underwater modular structure.Second, the rounded edges20-1reduce sediment accumulation.Third, once multiple modules2with rounded edges20-1are assembled in contact, their rounded edges20-1provide additional voids, contributing to the labyrinth4that dissipates wave energy and/or supporting development of an underwater ecological habitat15.

Further, the module2ofFIG.2Bhas at least one connector insertion opening11that is tapered inwards, defining an inward taper or a recess11-1. Such inwardly tapered or recessed connector insertion opening11advantageously defines a guide for inserting the connector3therein. The inward taper11-1is here illustrated as conical and surrounding the connector insertion opening11. Though the taper11-1is preferably smooth, it may comprise abrupt or stepped changes in diameter. Further, the inward taper or recess11-1need not cover the full circumference of the connector insertion opening11but may be limited to parts of said circumference.

The module2as illustrated inFIG.2Bfurther comprises at least one connector insertion opening11that is protruding outwards, defining a outward taper or protrusion11-2. Such outwardly tapered or protruding connector insertion opening11is preferably configured to correspond to the inward taper or recess11-1, so that an outwardly protruding connector insertion opening11of one module2can be slotted into an inwardly tapered connector insertion opening11of another module2. This facilitates alignment of modules2. Thus, an outward taper or protrusion11-2may couple to an inward taper11-1on a similar module2.

In other words, the outwardly and inwardly tapered connector insertion openings11are configured to mutually engage. Preferably, an inwardly tapered connector insertion opening11is arranged opposite an outwardly tapered connector insertion opening11on the same module, so that a guide is provided for arranging a connector3through said module2. This facilitates assembly of the underwater modular structure1.

ThoughFIG.2Billustrates only outward tapers11-1on one side of the module2and only inward tapers11-2on the opposite side of the module2, any side of the module2may comprise any one or both of inward and outward tapers11-1,11-2.

The inward tapers or recesses11-1form a guide for inserting the connectors3. When also employing outward tapers or protrusions11-2on the plurality of module2, alignment between modules2is further facilitated. When the inward and outward tapers11-1,11-2are also arranged on opposite sides of the modules2, a guide is formed for inserting a connector3through the modules2. These arrangements are particularly advantageous when installing an underwater modular structure1below the water surface, where currents may act on the various components (modules2and/or their module parts19as well as the connector3) while moving these into position.

For example, once a module2with at least one inwardly tapered connector insertion opening11is in position on the seabed6, a connector3(being an elongate member) may be moved in approximate position and then be guided by the inward taper11-1into said connector insertion opening11and thus into said module2. Instead of or preceding the connector3, another module2with an inwardly tapered connector insertion opening11may be coupled to the module2with the inwardly tapered connector insertion opening11. The coupled tapers11-1,11-2may increase stability of the underwater modular structure1, even during assembly thereof.

The inner wall21of module2ofFIG.2Bforms internal tubing with tapered ends21-3for connection to the outer wall20. In particular, the tapered ends21-3of the inner wall21are configured to engage inwardly or outwardly tapered connector insertion openings11in the outer wall20. In the illustrated example, the inner wall21comprises circular tubing with conical ends configured to couple to conical edges of circular connector insertion openings. This configuration allows simplified underwater assembly of the module2from module parts19. Other shapes are also envisaged, including square (for example as inFIG.2A), rectangular or oval.

Preferably, at least the outer wall20of the modules2ofFIGS.2A and/or2Bcomprise a textured surface27, further explained in relation toFIG.2E.

The examples ofFIGS.2A and2Bshow modules2with a dimension ratio of width:height:length equal to 1:1:3. Other ratios may be employed, such as 1:1:1 (cubic form), 1:1:2, 1:2:2 and 1:1:4. Preferably, a connector insertion opening11is arranged at each end of the module2and/or equidistant along its sides. Preferable sizes of an elongate module2are 1 m width, 1 m height and 3 m length.

An elongate form is preferred so that overhangs, bridges, tunnels and the like can be achieved in the labyrinth4of the underwater modular structure1. Further, the underwater structure1is made to be adaptable, scalable and versatile even when only one type of elongate module2is used. Incoming waves may be better dissipated and passage of larger species, such as predatory fish, through the underwater modular structure1is made possible while providing necessary structural stability even to increased heights compared to existing artificial reefs.

In general, the underwater modular structure1according to the invention may comprise at least one connector insertion opening11that is inwardly tapered to define a guide for connector insertion into said module2. That is, one or more of the at least connector insertion opening11of the underwater modular structure1may be inwardly tapered. The at least one inwardly tapered connector insertion opening11facilitates insertion of a connector3therein, and thus into and possibly through the module2which comprises said inwardly tapered connector insertion opening11.

Additionally or alternatively, the underwater modular structure1according to the invention may comprise at least one connector insertion opening11that is outwardly protruding. That is, one or more of the at least connector insertion opening11of the underwater modular structure1may be outwardly tapered. The at least one inwardly tapered connector insertion opening11facilitates insertion of a connector3therein, and thus into and possibly through the module2which comprises said inwardly tapered connector insertion opening11.

Preferably, the inwardly tapered connector insertion opening11and the outwardly protruding connector insertion opening11are arranged on opposite sides of the same module2to mutually extend the guide defined by the inwardly protruding connector insertion opening11to guide the connector out of said module2. When multiple modules2are configured in this way, the inwardly and outwardly tapered connector insertion openings11of different modules can aid mutual alignment of the multiple modules2. Following alignment, a connector3may be inserted through the aligned module2, thus facilitating construction, especially under water.

FIG.2Cillustrates another embodiment of a module2which comprises module parts19that are configured for assembly into said module2. An assembled view as well as an exploded view of said module2are shown inFIG.2C. Here, the module parts19comprise slots22configured for mutual engagement. The module parts19with the slots22mutually engage or interdigitate to form said module2. Such module parts19may advantageously be formed in a board-like shape with slots cut into sides of the board-like shape. Additionally or alternatively, such module parts19may comprise an outline23. The outline23may be configured to fall within the outer contour9of other modules2so that, for example, the various illustrated embodiments of modules2are mutually compatible.

As illustrated inFIG.2C, upon assembly of the module2comprising of module parts19with slots22, said module2may comprise connector insertion openings11. The slots22of the module parts19are spaced apart to obtain appropriate dimensions for the connector insertion opening11.

ThoughFIG.2Cshows six module parts19, this is an example only and other numbers of module parts19with slots22may be employed. For example, the slots22may be configured with twice the number of modules parts19shown inFIG.2Cwhile decreasing mutual spacing between the module parts19within the module2, thereby creating smaller openings, paths and/or channels through said module2adding to the labyrinth4. The slots22may thus be configured in different arrangements that create openings of different sizes, further dissipating wave energy. Such openings have the effect of reducing drag forces, thus increasing stability of the underwater modular structure1. In addition or as an alternative, such arrangements which may be optimised for fish and other marine species to shelter and thereby foster the underwater ecological habitat15.

FIG.2Dillustrates another embodiment of a module2, which also comprised module parts19with slots22for mutual engagement of the module parts19. A connector3is also shown passing through connector insertion openings11of the module2. The example illustrated inFIG.2Dshows a module2having multiple inner walls21in the form of horizontal and vertical panels that are coupled via slots22. The placement of the panels may be variable, as illustrated, by selecting particular slots22so that the internal structure of the module2is adaptable, for example, with respect to the location and function of the module2in the underwater modular structure1. The inner walls21are configurable to create cavities30of variable dimensions in order to provide a suitable habitat for marine life and to further define the labyrinth4to dissipate wave energy. Further, the inner walls21may be provided with openings or cavities30, for example according to specific target species.

The inner walls21may comprise first type panels21-4, that are configured to couple to the outer walls20of the module2, and second type panels21-5, that are configured to couple to the first type panels21-4, preferably by means of the slots22. Such arrangement increases ease of assembly under water and provides flexibility to create cavities30and tunnels (interconnected inlets and outlets29and/or tortuous paths14) of different sizes, for example to provide shelter for juvenile fish. The module2is shown with two connector insertion openings11through which an elongate connector3, here illustrated in the form of a hollow tube, can be arranged. For this purpose, the first type panels21-4also comprise connector insertion openings11. Inward tapers11-1and outward tapers11-2are also illustrated on the outer wall20of the module2around its connector insertion openings11.

The various modules2disclosed here are preferably configured as mutually compatible. For example, the various modules2may be used with the same connectors3, be placed substantially flush against each other and/or support each other. Furthermore, the various modules2may be provided in dimensions such that these are mutually compatible. For example, the modules2illustrated inFIGS.2A,2B and2Edelineate three times the volume of the module2illustrated inFIGS.2C and2D, facilitating mutual stacking, interlocking and/or positioning of these modules2. This compatibility is also illustrated inFIG.1.

Any embodiment of the underwater modular structure1may further comprise an anti-scour apron24. The anti-scour apron24may be formed from, for example, sheet material and/or a cellular confinement system. The anti-scour apron24may comprise an anchoring25fixed into the seabed6. The anchoring25may be configured to connect to at least one of the plurality of modules2. Alternatively or additionally, the anchoring25may be comprised within the underwater modular structure1without the anti-scour apron24being present. The anchoring25need not be connected to the anti-scour apron24. In any case, as the plurality of modules2are also interlocked by means of the connectors3, the whole of the underwater modular structure1may thus be fixed to the seabed6. Preferably, multiple anchorings25are employed to strongly fix the underwater modular structure1to the seabed6.

The anti-scour apron24may serve two main purposes. First, stabilize surrounding sediments and protect the structure from scour, this is particularly relevant with a sandy seabed6where erosion of sediment can cause the underwater modular structure1to lose stability and fail. Second, the anti-scour apron24may be pre-seeded with vegetation such as seagrass or benthic species that contribute to dissipation of wave energy and to the underwater ecological habitat15while also stabilizing the seabed6.

FIG.2Eillustrates yet another embodiment of a module2. Here, at least one of the modules2comprises a three-dimensional geometric complexity26that further defines the labyrinth4. The three-dimensional geometric complexity26may equally be combined with any other variant of the modules2, such as the examples presented inFIG.2A-2D.

The three-dimensional geometric complexity26may be configured to stimulate development of the underwater ecological habitat15. The underwater ecological habitat15, such as a reef, adds to the three-dimensional geometric complexity26which may already be comprised in some of the modules2and thus further enhances dissipation of wave energy.

Additionally, the three-dimensional geometric complexity26may comprise at least one of a textured surface27, a porous surface28, a plurality of interconnected inlets and outlets29and a cavity30. The porous surface28is preferably configured to be colonised by underwater organisms, thereby promoting additional geometric complexity that dissipates wave energy and/or development of the underwater ecological habitat15. For example, the porous surface28may promote growth of micro-organisms, mollusca and/or anthozoa that produce nutrients for other marine species of the underwater ecological habitat15. The three-dimensional geometric complexity26may vary between modules2and may even vary on a single module2. For example, the module2illustrated inFIG.2Econtains the textured surface27on most of its faces, while another face contains the porous surface28and cavities30are dispersed over all its face. The plurality of interconnected inlets and outlets29in the example ofFIG.2Ecomprise the connector insertion openings11. Another example of the plurality of interconnected inlets and outlets29is illustrated inFIG.2C. Variation within the plurality of modules2and their three-dimensional geometric complexity26allows optimization of the dissipation of wave energy and/or of the underwater ecological habitat15fostered by the underwater modular structure1. The invention thus presents a versatile solution that may be implemented in various circumstances.

The textured surface27may be employed with any of the modules2illustrated inFIG.2A-2Eto promote reef forming organism to establish and thrive on the modules2. The textured surface27may be produced by abrasion, deposition, casting or other known methods. Particularly advantageous is a method of applying a bias voltage on the module2, for example its outer wall20comprising a metallic material, to accumulate calcium carbonate deposited from the water onto the module2in order accumulate surface texturing that is compatible with the marine environment and fosters the underwater ecological habitat15.

The plurality of interconnected inlets and outlets29may differ from the tortuous path14or may at least partly comprise or be at least partly comprised by the tortuous path14.

The underwater modular structure1may be seeded with reef-forming species31to promote development of an underwater ecological habitat15. The reef-forming species31may include anthozoa, such as soft and stony corals, and/or mollusca, such as oysters. The reef-forming species31may encourage growth of a reef as the underwater ecological habitat15, which aids in texturizing contours5defining the labyrinth4. The reef-forming species31thus in particular stimulate the growth of a reef on the underwater modular structure1, which adds a layer of complexity to it and aids in further reducing wave energy.

The seeding of the reef-forming species31may be arranged on any surface of the underwater modular structure, for example on the contours5, on outer contours8and/or inner contours9of the modules2and/or on outer contours12and/or inner contours13of the at least one connector3. Preferably, the reef-forming species31are seeded in specifically prepared cavities on surfaces of the underwater modular structure1such as may be comprised with the three-dimensional geometric complexity26.

The invention may thus also result in a preservation of nature and encouragement of development of the underwater ecological habitat15rather than destroying one as is generally the case with conventional underwater structures.

The reef-forming species31may be selected based on environmental circumstances at the underwater construction site. This may promote growth of the underwater ecological habitat15, in particular a reef habitat, within a reduced period of time.

InFIG.3A, a cross-section of a conventional underwater structure is illustrated near a coast7with an incoming wave10. The conventional underwater structure comprises a dam32. As the wave10approaches this dam32, the wave10results in an upward surge of water along and over the dam32which enlarges the wave10, measured from sea level, as it passes over the dam32and approaches the coast7. In this case, the wave energy is redirected. The wave10continues to propagate past the dam32with high wave energy which has an impact on the coast7.

In contrast to this,FIG.3Billustrates a cross-section of an underwater modular structure1according to the invention near the same coast7with the same incoming wave10. The underwater modular structure1comprises a labyrinth4through which the wave10is forced, in part by its own wave energy. This reduces the upward surge of water along and over the underwater modular structure1compared to the dam32. Yet, the underwater modular structure1retains its structural stability due to the interlocking of the plurality of modules2by the at least one connector3. With the invention, the wave energy of the wave10is effectively dissipated and only a small amount of this wave energy approaches the coast7. This may reduce coastal erosion and achieve other effects described in this application. For example, the invented underwater modular structure1causes lowered wave reflection, thus reducing wave energy and height at the incoming side (usually the off-shore side). This reduces erosion of the seabed6, thus increasing stability of the underwater modular structure1compared to conventional less permeable structures or dams. Further, as the underwater modular structure1allows water circulation, an improved water quality can be achieved which supports development of the underwater ecological habitat15.

The underwater modular structure1of the invention may dissipate wave energy by depth wave breaking as well as by friction-turbulence. Depth wave breaking is induced because the underwater modular structure1makes the water shallower, causing instability to the incoming wave10, making it fall and break. Friction-turbulence is induced by the underwater modular structure1because of its labyrinth4, which creates turbulence in the incoming wave10which through friction dissipates wave energy.

According to the invention, a vast underwater modular structure1may be assembled to provide an underwater structure that mimics natural coral reef, which may dissipate up to 97% of the wave energy, contrary to smaller underwater structures according to the prior art. The invention may provide such underwater modular structure1as an artificial reef that is stable with respect to incoming waves10and promotes development of an underwater ecological habitat15.

InFIG.4, a plan view is shown of the underwater modular structure1ofFIG.3Bin cross-section along the line IV-IV. This view illustrates a possible arrangement of the plurality of modules2for the underwater modular structure2. Here, the plurality of modules2is interlocked and leaves open areas where modules2are absent. This arrangement partially forms the contours5that define the labyrinth4. The wave10may flow through the labyrinth4and thereby wave energy is dissipated. The illustrated underwater modular structure1is further configured to foster an underwater ecological habitat15due to its wave dissipation and/or its labyrinth4. Furthermore, the underwater modular structure1according to the invention may work equally well for the wave10incident from either side. That is, for incoming waves and waves reflected back from the coast7that lies beyond the underwater modular structure1.

The labyrinth4may be defined by any of the features disclosed here and in any combination. In particular, the labyrinth4may be defined by one or more than one of:contours5of at least the plurality of modules2;outer contours8and/or inner contours9of the plurality of modules2;outer contours12and/or inner contours13of the at least one connector3;a tortuous path14of at least one of the modules2;a three-dimensional geometric complexity26of at least one of the modules2; and/oran underwater ecological habitat15in or on the underwater modular structure1.

Any combination of the above features is possible with the invention. The underwater modular structure1of the invention thus has an intrinsic versatility in the design of the labyrinth4which may be adapted to circumstances at the underwater construction site. The underwater modular structure1may also be dismantled and/or adapted as said circumstances change over time.

InFIGS.1,2A-2E,3B and4, several embodiments of modules2of or for an underwater modular structure1according to the invention are shown. Features described for each of these modules2may be combined in any way to form further embodiments of modules2of or for an underwater modular1structure according to the invention. For example, the plurality of modules2may comprise modules2including the tortuous path14, the module parts19with slots22, the chamber16and be seeded with reef-forming species31and other modules2including the three-dimensional complexity26with cavities30and connector insertion openings11with all modules compatibly dimensioned.

InFIG.5, a method according to an embodiment of the invention is shown. This embodiment comprises the step S1of sinking the plurality of modules2to the seabed6and the step S2of interlocking the plurality of modules2with the at least one connector3to form the labyrinth4defined by contours5of at least the plurality of modules2. Though it is preferred that step S2follows step S1, as illustrated inFIG.5, the order may be inverted so that step S1follows step S2. Furthermore, these steps may be taken simultaneously or partly simultaneously. For example, while step S1is performed and yet to be completed, the step S2may be commenced in that a part of the plurality of modules2may be interlocked before being sunk to the seabed6and/or may be interlocked at the seabed6before all of the plurality of modules2have been sunk to the seabed6.

Preferably, the method further comprises the step S3of filling at least part of the underwater modular structure1with the filler17. Step S3may be performed after the steps S1and S2are completed, before any of the steps S1and S2are commenced or at least partly simultaneously with either or both of the steps S1and S2. InFIG.5, step S3is illustrated after performing step S2, which has the advantage that the filler17is yet absent from the underwater structure and therefore may not interfere with interlocking the plurality of modules2with the at least one connector3. An alternative is illustrated inFIG.1, where one of the plurality of modules2is being filled while the underwater modular structure1is being constructed, i.e. steps S1and S2are ongoing.

More preferably, the step S3further comprises the step S3A of pumping the sediment18from the seabed6into the underwater modular structure1. The use of the sediment18from the seabed6to fill the modules2has several advantages, including that the method need not comprise transporting, sinking or producing filler17at or to the construction site. This saves times and effort, especially when compared to pre-filled modules2or solid construction elements that are conventionally made of concrete. Alternatively, the sediment18can be obtained from a shore, preferably nearby the underwater construction site, for example by pumping. Such sediment18may be locally available on said shore or may be imported material.

As illustrated inFIG.1, the sediment18may be pumped from the seabed6into a partially assembled module2, preferably into the chamber16of said module2, by means of a pump, such as a submergible pump or a pump on a ship.

Preferably, the method further comprises the step S4of assembling at least one of the modules2from module parts19. This has the advantage that merely the module parts19, which are preferably prefabricated, rather than whole modules2need transportation to the underwater construction site. Step S4may be performed before S1, as illustrated inFIG.5, though this order is not restrictive. For instance, S4may be performed after S1. In other words, the module parts19may be sunk to the seabed6for assembly at the seabed6into the at least one of the modules2. Alternatively or additionally, step S4may be performed above sea surface, for instance on board a construction vessel, a platform or a nearby coast such as the coast7. Step S4may further be subdivided into constructional steps performed at various locations above and/or under water.

Preferably, the method further comprises the step S5of mounting the anti-scour apron24on the seabed6. As illustrated inFIG.5, step S5is preferably executed before step S1, irrespective of if or when step S4is performed. However, this order is not restrictive. Other sequences may be envisaged, such as performing step S5after step S1with or without performing step S4. The anti-scour apron24may be mounted after some or all of the plurality of modules2has been sunk to the seabed6so that, for example, the anti-scour apron24is only mounted on part of the seabed6surrounding the underwater modular structure1.

Preferably, the method further comprises the step S6of seeding the underwater modular structure1with reef-forming species31. The advantages of the reef-forming species31are described above and equally apply for the method according to the invention. Step S6is preferably performed near or at the end of the method, as is also illustrated inFIG.5. However, the sequence is not restrictive as, for example, step S6may be performed straight after step S1or even before S1. That is, the reef-forming species31may be seeded on the plurality of modules2before and/or after these are sunk to the seabed6. Care should be taken to ensure survival of the seeded reef-forming species31whenever step S6is included in the method. For example, it is preferred that step S3, if included in the method with or without S3A, is performed before S6and waters are left to sufficiently clear before performing step S6.

The method may further include the step S7of shaping the seabed6. This may serve to enhance stability of the underwater modular structure1, facilitate step S5, influence flow of water or may form part of step S3A. As illustrated inFIG.5, step S7is preferably performed before S5, though this order is not restrictive. Step S7may be performed at any time within the method, for example after step S2when step S7may serve to embed the underwater modular structure1in the seabed6or to cover part of the underwater modular structure1with the sediment18and/or the seabed6.

The order in which the steps are illustrated inFIG.5is not intended as restrictive. The steps S3, S3A, S4, S5, S6and/or S7may be left out according to circumstances, though steps S1and S2are preferred in all embodiments of the method according to the invention.

The method performed according to any combination of the above steps may comprise constructing an underwater modular structure1according to the invention. In this particular case, the steps S1and S2are essential.

FIG.6shows a schematic exploded view of an example of an underwater modular structure1according to the invention. This underwater modular structure1comprises four identical modules2and four connectors3arrangeable through connector insertion openings11of the modules2. The connectors3are elongate members, here illustrated as a circular hollow tube, that fit through the connector insertion openings11in order to interlock the modules1. A tight-fitting scheme may be used and/or fastening means such as bolts and nuts may be applied to further secure the coupling between the connectors3and the modules2.

Further, a spacer33is illustrated arranged on two of the connectors3. The spacer33may form a distinct type of module from the plurality of modules2, or may be integrally formed with the connector3. The spacer33here vertically spaces apart two modules2by a distance smaller than the dimensions of these modules2. Spacers33thus further enhance to adaptability of the underwater modular structure1. When the spacer33is a type of module from the plurality of modules3, it preferably comprises connector insertion openings11to readily receive the connector3and/or inward or outward taper11-1,11-2for coupling with further modules, which may be of a different type. The spacer33further prevents blocks from sliding and contributes to reaching a higher height of the underwater modular structure1with less modules2but with a similar wave breaking capability. In addition, it further defines the labyrinth4, increases its complexity as spaces between modules2work as passages and cavities for dissipation of wave energy and/or different marine species to shelter.

As described above, the underwater modular structure1may be an assembly of the plurality of modules2and a connector3interconnecting these modules2. It is however conceivable that a spacer33may provide an offset between two adjacent interconnected modules2. Said spacer33may be a separate element having a through hole for guiding the connector3therethrough, or alternatively, the spacer33may be integrated with the connector3.

Though the invention is described in the context of an underwater modular structure1near the coast7, the nearness of said coast7is not required. For example, the invention may equally be employed in a preferably shallow sea distant from coasts. Alternatively or additionally, the underwater modular structure1may be positioned near a coastal or off-shore structure such as a sandbank, pier, platform, quay, lighthouse and wind turbine.

The invention thus provides an underwater modular structure1of configurable complexity. This complexity may be optimised for particular circumstances at the underwater construction site. The underwater modular structure1may thus be configured to promote a particular underwater ecological habitat15including target species. For example, growth of oysters may be promoted in colder waters while corals may be promoted in warmer waters. As a further example, the underwater modular structure1may provide areas accessible to sunlight and shadow areas, promoting corals and sponges, respectively, each contributing to the underwater ecological habitat15.

Although preferred embodiments of the invention have been described above, these embodiments are intended only to illustrate the invention and not to limit in any way the scope of the invention. Accordingly, it should be understood that where features mentioned in the appended claims are followed by reference signs, such signs are included solely for the purpose of enhancing the intelligibility of the claims and are in no way limiting on the scope of the claims. Furthermore, it is particularly noted that the skilled person can combine technical measures of the different embodiments, such as the module parts19that define the inner wall21of at least one of the plurality of modules2wherein the inner wall21comprises the three-dimensional geometric complexity26. The scope of the invention is therefore defined solely by the following claims.