Abstract:
A durable, quickly deployable temporary floating breakwater (FBW) can protect areas in austere locations. A plurality of inflatable modules is encapsulated within a common cover, which holds the modules together and in some embodiments supports a causeway thereupon. A separate floating causeway can be included. Embodiments include a semi-permeable “sloping beach” section which causes waves to break before reaching the FBW. A bed of wave-energy-absorbing synthetic kelp can be attached to the sloping beach. The beach and/or kelp can include low-surface-energy fibers and films, such as olefins and polypropylenes, to remove oil from the water in case of an oil spill or accident. In embodiments, the FBW can be temporarily sunk to avoid extremely high seas, ice, and/or other surface hazards. The FBW is lightweight, can be quickly and compactly stowed, and in some embodiments can be transported and deployed from the deck of an LCU 1610.

Description:
RELATED APPLICATIONS 
       [0001]    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. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to marine deployable apparatus, and more particularly to temporary floating breakwaters. 
       BACKGROUND OF THE INVENTION 
       [0003]    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. 
       Mooring Forces 
       [0004]    The US Navy manual for mooring equipment (Mooring Design Physical &amp; Empirical Data Vessel &amp; Ship Characteristics, Mooring Lines &amp; Chain Buoys, Anchors &amp; 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. 
         [0005]    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. 
       Floating Breakwater Configurations: 
       [0006]    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  FIG. 1 . The unit  100  is moored parallel to the shore  102  and facing the prevailing wind and wave direction  104 . This configuration has been well studied, and provides 60-80% reduction of wave energy in flume testing (see MOORING FORCES AND MOTION RESPONSES OF PONTOON-TYPE FLOATING BREAKWATERS, S. A. Sannasiraj, V. Sundar and R. Sundaravadivelu, Ocean Engineering Centre, Indian Institute of Technology, Madras 600 036, India, Received 1 May 1996, herein incorporated by reference). 
         [0007]    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  FIG. 1  is favorable in the along-shore direction. In contrast, the configuration of  FIG. 4  has twice the system length and will be subject to very large mooring forces if there is significant along-shore current. However the Army RIBs configuration reflects a large proportion of the wave energy and therefore reduces its mooring load. 
         [0008]    An important consideration in the design of the present invention is illustrated in  FIG. 2 , where the shoreline and the wind-wave direction are at 45 degrees. This configuration shows the difficulty of satisfying all the current and wind preferences in a non-orthogonal situation of wind, shore, and current. In the design shown, the FBW is in a good alignment to the weather—it will reflect some of the wave energy and absorb the rest to keep the wave action in the anchorage low. However the wind action on the moored ships is far from optimal. 
         [0009]    The configuration of  FIG. 3  provides for a partial solution in which the wind and anchorage directions are aligned, and some reflection and absorption of wave actions results from the angle of the FBW. However, the current adds to the mooring loads on the FBW. It should be pointed out that the configurations of  FIGS. 2 and 3  have the advantage of permitting the use of a decked FBW to double as a causeway for vehicle transport directly to shore. The potential elimination of a separate causeway requirement may compensate for the other drawbacks of these non-orthogonal case. The configuration of  FIG. 1  has the most flexibility and the best logistics. 
         [0010]    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. 
       SUMMARY OF THE INVENTION 
       [0011]    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. 
         [0012]    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. 
       Component Level Design of the Floating Breakwater 
       [0013]    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. 
         [0014]    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. 
         [0015]    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. 
         [0016]    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. 
         [0017]    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. 
         [0018]    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. 
         [0019]    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. 
         [0020]    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. 
         [0021]    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. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  is a simplified top view illustrating a typical configuration of a FBW where the direction of the prevailing waves and wind is perpendicular to the shore; 
           [0023]      FIG. 2  is a simplified top view illustrating a typical configuration of a FBW where the direction of the prevailing waves and wind is oblique to the shore; 
           [0024]      FIG. 3  is a simplified top view illustrating a typical configuration of a FBW where the direction of the prevailing waves and wind is parallel to the shore; 
           [0025]      FIG. 4  is a simplified top view illustrating an alternate configuration of a FBW where the direction of the prevailing waves and wind is perpendicular to the shore; 
           [0026]      FIG. 5  is a cross-sectional view of a preferred embodiment of the present invention which includes a sloping beach section with artificial kelp; 
           [0027]      FIG. 6  is a simplified top view of a layout of a preferred embodiment including a 300 foot breakwater and a 600 foot causeway; 
           [0028]      FIG. 7  is a simplified, close-up top, front, and side view of an embodiment with a causeway supported by separated round floats; 
           [0029]      FIG. 8  is a simplified, close-up top, front, and side view of an embodiment supported by adjacent round floats having a causeway supported by top deck beams; 
           [0030]      FIG. 9A  is a simplified, close-up top and side view of an embodiment supported by adjacent round floats having a causeway which does not require top deck beams; 
           [0031]      FIG. 9B  is a close-up cross-sectional view of the floats of  FIG. 9A ; 
           [0032]      FIG. 10  is a simplified top view illustrating transportation of a preferred embodiment on an LCU vessel; 
           [0033]      FIG. 11  is a simplified top view illustrating the first step in deployment of the embodiment of  FIG. 10  from the LCU vessel; 
           [0034]      FIG. 12  is a simplified top view illustrating the second step in deployment of the embodiment of  FIG. 10  from the LCU vessel; 
           [0035]      FIG. 13  is a simplified top view illustrating the third step in deployment of the embodiment of  FIG. 10  from the LCU vessel; 
           [0036]      FIG. 14  is a simplified top view illustrating the fourth step in deployment of the embodiment of  FIG. 10  from the LCU vessel; and 
           [0037]      FIG. 15  is a simplified top view illustrating the fifth step in deployment of the embodiment of  FIG. 10  from the LCU vessel; 
       
    
    
     DETAILED DESCRIPTION 
     Main Tube and FBW Floats 
       [0038]      FIG. 5  is a cross sectional view of an embodiment of the present invention in which an inflatable floating breakwater (“FBW”)  500  is deployed at 300 feet. The total packed volume of the inflatable portion of this 300′ system as shown in the cross section of  FIG. 5  can be packed in a single 20′ ISO container. The elimination of mechanical joints between inflated sections is a major feature of this approach, since hinges with solid pivot points are large, heavy, and prone to failure from wave action on a FBW. The embodiment of  FIG. 5  also provides redundant flotation chambers  502  by enclosing a plurality of standard 10×25 ft floats  502  within a continuous cover layer  504 . The cover layer  504  protects the inflated floats  502  and forms a textile flex point in the structure. This arrangement permits buckling of the assembly under extreme loads without damage. By staggering the float elements  502  in a second tube assembly  504  (i.e. the continuous cover layer), this double-tube system provides for a stable platform for service, and operation as a causeway if required. Antifouling coatings can be applied to the topcoat of the embodiment of  FIG. 5 , if required for example to prevent large accumulations of marine growth. 
         [0039]    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. 
         [0040]    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. 
       FBW Mooring 
       [0041]    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. 
         [0042]    As can be seen from the full layout of the embodiment of  FIG. 6 , the moorings  512  for the breakwater  500 , the causeway  600  and the ships  106  can all be separate, thereby providing good redundancy in the design. As wave and wind storm loads increase, larger vessels (3000 ton)  106  will need to move off shore and get clear. This will free up these large moorings for use as a safety on the FBW  500  and causeway  600 . Lighterage and small craft will have to stay behind the protection of the FBW  500  and will also need added mooring capacity to prevent dragging. 
         [0043]    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  FIG. 4 ). Based on the problems associated with along-shore currents  108  and the very large system length of the RIBs design, embodiments of the present invention include a FBW  500  that is moored parallel to the wave line  104 . Wave reflection in this configuration is limited. 
       Beach and Kelp Assemblies 
       [0044]    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&#39;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. 
         [0045]    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). 
         [0046]    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 
       Top Deck Assembly 
       [0047]    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. 
       Ground Tackle and Mooring Lines 
       [0048]    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. 
         [0049]    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. 
       Causeway 
       [0050]    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. 
         [0051]    In  FIGS. 6-7 , embodiments are illustrated with a common 10′×25′ round float  702  shown at 20 foot centers. These embodiments minimize the number of floats  702  but maximize demands on the structural performance of the top deck. As illustrated in  FIG. 8 , the common round floats  702  can be moved together to provide greater support and stability, at the expense of requiring more floats  702 . The same tradeoffs for inflation and foam filling systems apply in this case as for the breakwater. 
         [0052]    With reference to  FIGS. 9A and 9B , other embodiments include floats with a square or rectangular form. The square design provides full support to the upper deck and allows a simple belt design for the Deck layer without any inflated beams. Even though the M1A  700  has a high mass, the contact pressures for the treads are approximately 12 psi. Of the M1A  700 , the full vehicle area distributed load is as low as 3 psi. These are modest design loads for the Causeway hard surface and can be supported with a single thin hard surface panel that bears directly on square main floats. 
       Logistics 
       [0053]    As illustrated in  FIG. 10 , in preferred embodiments an LCU 1610 class vessel  1000  can be used as the primary transport and deployment vessel. For example, forward on the LCU deck, a 40′ ISO container  1002  can be used to contain the breakwater cover  514  and beach kelp  516  assemblies. The breakwater main float tubes  502 , which are in a 20′ ISO container  1004 , can be transported in a second position on the deck of the LCU  1000 , and the causeway floats  702  and top deck  600  can be contained in a 30′ ISO and transported in a third position  1006  on the LCU deck. 
         [0054]    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 
       [0055]    Deployment of preferred embodiments includes 5 primary steps. With reference to  FIG. 11 , first the ship  1000  and causeway anchors  1012  and mooring lines  512  are set from the roll-off rails on the LCU  1000 . As illustrated in  FIG. 12 , the seaward breakwater anchors  1016  and the cover/beach/kelp assembly  516  are then set along the outer mooring line with the aid of the second vessel  1020 . The second vessel  1020  also provides the inflation air to float the system. The baseline process has the tube floats  502 ,  702  drawn through a messenger tube in the forward container  1002 . This permits packing of the cover  504  and the main floats  502  in separate containers positioned in line on the deck. The seaward anchors  1012  are placed as the FBW  500  is deployed. 
         [0056]    As illustrated in  FIG. 13 , step  3  is backhaul of the breakwater to leeward. 
         [0057]    Step  4 , as shown in  FIG. 14 , consists of setting the leeside moorings for the FBW  500  from the LCU  1000 , using the utility boat  1020  to ferry the mooring lines  512  to personnel on the breakwater top deck  600 . Step  5 , as shown in  FIG. 15 , is deployment of the causeway unit from the third soft goods container  1006  on the LCU deck. The utility boat  1020  will draw out the uninflated units and inflate the system as it proceeds to shore. 
         [0058]    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.