The invention relates to marine deployable apparatus, and more particularly to temporary floating breakwaters.
Permanent breakwater structures are offshore concrete or earthen revetments designed to provide coastal defense and mitigate shoreline erosion by absorbing and dissipating sea state intensity and surf conditions. They are often used to extend and enhance protection to harbors and seaports, and may also provide a secondary function as a causeway or travel corridor for land vehicles or foot traffic. The mass, logistics, and labor required to construct a conventional breakwater makes them impractical for remote areas. Temporary, floating breakwater designs have shown some successes. However, such structures typically are intended to attenuate waves with heights not exceeding 4 feet. Practical applications of these temporary structures demand much greater effectiveness in open ocean environments where wave heights up to 12 feet are common during storm conditions. To effectively attenuate sea state conditions of this magnitude, temporary floating structures according to previously disclosed designs would need to be massive, requiring the transport of large volumes of physical structures, mooring lines and anchors to the site being sheltered. This approach is simply not feasible when the quick establishment of a protected area is required.
The US Navy manual for mooring equipment (Mooring Design Physical & Empirical Data Vessel & Ship Characteristics, Mooring Lines & Chain Buoys, Anchors & Riser Type Mooring Systems DESIGN MANUAL 26.6 APRIL 1986, herein incorporated by reference) sets out the basic considerations for keeping a Floating Breakwater (FBW) in place. Any floating structure is dependent on its mooring system to maintain position. A FBW by design is moored to a lee shore, which is an undesirable configuration for a floating object. Under storm conditions, if mooring lines chafe or anchors drag, there is no space or time to respond. A floating breakwater that is driven into the surf zone and pounded between the bottom and breakers will be a total loss.
In general, the design of a robust mooring system is the most important single issue in the design of a breakwater. For a FBW system, mooring loads are generated not just from wave action, but also from wind and current. According to published studies on floating breakwaters and realistic sea state requirements, a rough order of magnitude estimate is that each 25 feet of FBW exposure will require 20,000 lbs of mooring capacity. According to navy ratings for anchors, the mooring capacity of an anchor is approximately 15 times the anchor mass. Further design considerations indicate an anchor specification of 2 tons per 25 ft of breakwater length. Coast Guard data for buoy moorings suggest that these values may not be conservative.
Each shoreline has a unique set of conditions for wind wave and current action, and Floating Breakwater Systems can be designed and configured to address various combinations. The most basic configuration of a FBW concept is shown in
This arrangement has the greatest shore system length, and provides the most direct solution for the most important set of shore wind and wave conditions. This configuration permits sheltered vessels 106 to operate up-wind and down-wind, and to moor with either bow or stern facing into the weather. In addition, any along-shore current 108 does not add significantly to the mooring load, as the projection of the FBW of
An important consideration in the design of the present invention is illustrated in
The configuration of
What is needed, therefore, is an apparatus and method for providing a portable, re-usable, floating breakwater that can be deployed in various configurations as needed, and can withstand realistic sea conditions with waves up to 12 feet in height.
A reusable, temporary Floating Breakwater (FBW) is claimed that includes a plurality of inflated modules enclosed by an encapsulating cover so as to join the inflated modules together, thereby providing redundant buoyancy and in some embodiments also providing support thereupon for a causeway without need of a rigid beam. Various embodiments also include a semi-permeable “sloping beach” section that causes waves to break before reaching the FBW. Some of these embodiments also include a bed of wave-energy-absorbing material that approximates the natural wave-absorbing activity of kelp. And in some embodiments, the kelp and/or synthetic beach include low surface energy fibers and/or films such as olefins and polypropylenes to remove oil from both surface and water columns and the surface zone in the event of an oil spill or accident.
In certain embodiments, the claimed FBW can be temporarily sunk when necessary so as to avoid damage due to hazards such as extremely high seas and/or ice.
Embodiments of the present invention use low-mass inflatable materials. In some embodiments, the base material is a urethane-coated Vectran™ woven with a tensile strength of 2500 lbf/inch.
One general aspect of the present invention is a temporary floating breakwater which includes a plurality of inflatable modules and an encapsulating fabric cover configured for surrounding the inflatable modules when they are inflated, and thereby maintaining the inflatable modules in close proximity to one another. The floating breakwater when deployed is of sufficient size and has suitable characteristics for protecting shorelines and watercraft from waves having heights of more than 10 feet.
Some embodiments further include a semi-permeable sloping beach section which is extendable from the encapsulating fabric cover so as to cause approaching waves to break before reaching the encapsulating fabric cover. In some of these embodiments the sloping beach section includes at least one of low surface energy fibers and films such as olefins and polypropylenes configured to remove oil from both surface and water columns and the surface zone in the event of an oil spill or accident. Other of these embodiments further include a bed of simulated floating kelp material attached to the sloping beach and configured for absorbing energy from waves approaching the encapsulating fabric cover. And in some of these embodiments the bed of simulated floating kelp material includes at least one of low surface energy fibers and films such as olefins and polypropylenes configured to remove oil from both surface and water columns and the surface zone in the event of an oil spill or accident.
Various embodiments further include a rigid top deck of textile cells integral with the encapsulating cover and supportable by the plurality of inflatable modules so as to serve as a causeway. In some embodiments the plurality of inflatable modules can be deflated so as to temporarily sink the floating breakwater and thereby avoid damage due to surface hazards. And in certain embodiments each inflatable module includes a plurality of air-enclosing flotation bladders.
In some embodiments the inflatable floating modules are configured for filling with urethane foam. In certain embodiments the inflatable modules are one of square and rectangular in cross section. And various embodiments further include a floating causeway formed by a plurality of floating modules and a causeway top surface supported thereby.
Certain embodiments further include mooring points suitable for attachment of mooring lines thereto. In some of these embodiments the mooring points are each able to sustain 25 k lbf applied by a mooring line. In other of these embodiments the mooring points include abrasion-resistant sacrificial nylon layers. And still other of these embodiments further include a plurality of mooring lines and a plurality of anchors configured for stabilizing a location of the floating breakwater when deployed on a body of water. In some of these embodiments the plurality of anchors includes at least one vacuum pile anchoring system.
Another general aspect of the present invention is a temporary floating breakwater system which includes a plurality of inflatable floating breakwater support modules, an encapsulating fabric cover configured for surrounding the inflatable floating breakwater support modules when they are inflated, and thereby maintaining the inflatable floating breakwater modules in close proximity to one another, a floating causeway formed by a plurality of floating causeway modules and a causeway top surface which is supportable thereby, and a plurality of mooring lines and anchors configured for stabilizing a location of the floating breakwater and floating causeway when the floating breakwater and floating causeway are deployed on a body of water. The floating breakwater system when deployed is of sufficient size and has suitable characteristics for protecting shorelines and watercraft from waves having heights of more than 10 feet.
In various embodiments the floating breakwater system is configured for packaging in a plurality of containers suitable for simultaneous transport on the deck of vessel having a size and general characteristics comparable to an LCU 1610 class vessel. And in some of these embodiments the temporary floating breakwater system is configured for deployment from the deck of the vessel with the assistance of a utility vessel.
The features and advantages described herein are not all-inclusive and, in particular, many additional features and advantages will be apparent to one of ordinary skill in the art in view of the drawings, specification, and claims. Moreover, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes, and not to limit the scope of the inventive subject matter.
In preferred embodiments, the FBW floats of the present invention include at least one internal bladder for air holding. In some embodiments, each 25 foot float section is fitted with redundant bladders that permit the FBW 500 to be repaired while deployed. In various embodiments, the use of heavy Urethane extruded topcoat layers as part of a two-layer system limits the risk of pack ice damage. Mounting for wear panels can be included at the water line if the system is at risk from large ice flows.
For embodiments that include only inflated elements in the main floats 502 and the upper deck 506, the FWB 500 of the present invention can be sunk if necessary in extreme weather. Both very large ice flows and extreme Sea State 7 conditions would suggest that the safest place for the FBW 500 would be on the bottom. Inflation hoses supported on shore-anchored lines may permit re-floating of the system without divers.
In preferred embodiments, mooring points 508 are separated at 25 foot intervals, and can support a minimum of 25K lbf as the estimated mooring load per 25 foot section when subjected to a 12 foot wave. In preferred embodiments, a design factor of 5 is applied for this type of structure. This requires a load connection to the FBW assembly 500 that is capable of spreading a mooring point load into a 4-5 foot section of FBW cover material 504. As in sail making practice, this is accomplished with doublers and webbing, which are all heat-seal bonded to the base materials. The loads can be addressed with these methods and materials. However, chafing that results from excessive FBW motion in higher sea states 510 is a concern. The first step to address this chafe issue is to limit motion by the pre-tensioning of the mooring lines 512. The second step in various embodiments is the use of synthetic beach 514 and kelp 516 assemblies as stabilizers to reduce motion. Finally in some embodiments the mooring connections include low-friction sliders, combined with abrasion-resistant sacrificial nylon layers.
As can be seen from the full layout of the embodiment of
Reduction of Mooring loads on the FBW 500 will make the system more reliable, lower cost, improve the mean time between repairs (“MTBR”), and system availability. The literature includes the use of a low angle of incidence FBW such as the RIBs system (see
Preferred embodiments of the present invention include a mesh skirt that forms a simulated beach 514 in front of the FBW assembly 500. In some preferred embodiments the beach 504 is between 30 and 40 ft long, and extends at a slope from the main tubes 502. The slope angle is controlled by mooring lines 512 and out-hauls 602 on the beach seaward edge. A Bascom analysis of wave energy distribution puts the majority of the energy at a depth equal to 2/9'ths of the wave length. Realistic sea state design criteria therefore puts the wave length at approximately 90-100 ft. This results in a synthetic beach design depth of approximately 20 ft. The temporary synthetic beach 514 is intended to limit wave height. However, this approach can tend to force the waves to break. While wave breaking is a very effective energy reduction technique, it can have adverse affects on the FBW 500 main structure.
In some embodiments, wave breaking is mitigated by the addition of an artificial kelp bed 516 made of polypropylene textile strips with inherent buoyancy. The strips are long with respect to their mounted depth (see FLOW AND FLEXIBILITY, THE ROLES OF SIZE AND SHAPE IN DETERMINING WAVE FORCES ON THE BULL KELP NEREOCYSTIS LUETKEANA MARK W. DENNY,*, BRIAN P. GAYLORD1 AND EDWIN A. COWEN2, Hopkins Marine Station of Stanford University, Department of Biological Sciences, Pacific Grove, Calif. 93950, USA and 2Civil Engineering Department, Stanford University, Pacific Grove, Calif. 93950, USA Accepted October 1997, herein incorporated by reference) (see also Effect of the kelp Laminaria hyperborea upon sand dune erosion and water particle velocities, Stig Magnar Løvås and Alf Tørum, Department of Coastal and Ocean Engineering, Civil and Environmental Engineering, SINTEF Fisheries and Aquaculture, Klobuveien 153, N-7465 Trondheim, Norway, herein incorporated by reference).
The artificial kelp 516 is designed to reduce wave height in the run up the synthetic beach 514 and reduce the violence of the breaking wave. There are a number of design tools which the beach 514 and kelp 516 assemblies offer. By making the synthetic beach 514 from open mesh material and adjusting its deployed slope, wave behavior can be further controlled. In addition, the use of the kelp 516 permits additional adjustment of the incoming wave height. And in some embodiments, the kelp and/or synthetic beach include low surface energy fibers and/or films such as olefins and polypropylenes to remove oil from both surface and water columns and the surface zone in the event of an oil spill or accident
Various embodiments include a rigid top deck 506 of textile cells. This deck assembly 506 is integral with the outer cover 504 of the main tubes 502. The top deck cells 506 can be simply inflated and/or can be foam filled. Embodiments that use only inflation are very simple to retrieve, and these embodiments can be sunk and refloated for storm and ice protection. However, embodiments in which the top deck cells are filled with urethane provide greater durability. In some of these embodiments, the textiles are coated with urethane. Foam materials soften textile urethane coatings and form a high strength bond to the textile. This 2-part foam is simple to mix and inject into a manifold panel assembly. These foam-cell textile assemblies are very tough, and need only a thin hard surface skin to permit vehicle transport.
The ground tackle required for the claimed FBW system is not low in mass. The total soft goods mass is between ⅓ and ½ of the expected anchor mass required for the system. In the event that a deployment in coral is required, the use of low mass cordage would not be acceptable, and chain would be required, adding significant additional mass to the mooring budget.
The design of self-embedding anchors is not a new area of engineering. For the breakwater alone, the expected requirement is 25-30 long tons of anchor capacity. Novel anchor systems such as jetted or screw type anchors may be able to reduce the required anchor mass. Some embodiments employ vacuum pile anchoring systems for high strength lightweight mooring. Existing Side Load Warping Tug (SLWT) units and other equipment have winch and A-frame gear which may provide a capability to rapidly set such non-traditional anchors.
An M1A tank 700 at 61 long tons has been used as the criteria for causeway flotation and structural design. This load can be supported by embodiments of the present invention having a 5 foot minimum freeboard, and some embodiments include up to 8.5 ft of freeboard with alternative float designs to improve compatibility with INLS units. The top deck and floats of the causeway 600 represents a trade space for selection of various embodiments.
In
With reference to
As illustrated in
A large fairlead assembly 1008 on the bow of the LCU 1000 can feed the soft goods components 1002, 1004, 1006. Beside the soft goods containers 1002, 1004, 1006 the mooring system components 1010 are also on the LCU deck. Three ship anchors 1012 and their rods can be loaded as deck cargo on a RORO rail assembly 1014. The 24 anchors and mooring lines for the breakwater can be transported in two 40′ ISO containers 1016 with integrated RORO rails 1018 that run straight through. Container layout on the LCU deck can thereby be designed to permit full deployment of the claimed invention without re-positioning of container units. The LCU 1000 is large enough to deliver the system containers. In addition, a second vessel such as a LCM-8 or MPF 1020 utility boat is required in support of a deployment mission to manage the static ends during deployment and to support the inflation process.
Deployment of preferred embodiments includes 5 primary steps. With reference to
As illustrated in
Step 4, as shown in
The foregoing description of the embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of this disclosure. It is intended that the scope of the invention include, but not be limited by this detailed description, nor limited by the claims appended hereto.
This application claims the benefit of U.S. Provisional Application No. 61/222,230, filed Jul. 1, 2009, which is herein incorporated by reference in its entirety for all purposes.
Number | Date | Country | |
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61222230 | Jul 2009 | US |