Abstract:
An underwater energy dampening device is disclosed. This device includes a plurality of vertically-spaced bubble producing units. With bubbles produced at various depths, the present invention can effectively attenuate sound and other energy from underwater construction projects in high current or deep water areas.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     This invention relates to devices and methods for attenuating energy that is transmitted underwater.  
         [0003]     2. General Background  
         [0004]     Many underwater engineering projects generate significant amounts of sound and other energy. This energy can have adverse consequences on marine ecology. For instance, the energy generated by a pile driving hammer can be great enough to kill fish that swim nearby. Especially when such noisy underwater projects are undertaken in environmentally sensitive areas, these ecological consequences are unacceptable.  
         [0005]     A number of techniques have been developed to mitigate the adverse biological consequences of underwater construction. The first technique is to stage the project so that noisy phases occur only at times when the biological consequences are minimal. For instance, if the project is in a waterway traveled by anadromous or catadromous fish, noisy phases can be postponed when the fish are migrating. However, this technique is far from ideal, both because it is wasteful to allow labor and equipment to sit idle waiting for fish to migrate, and because most waterways have a residual fish population at all times.  
         [0006]     The second technique is to erect a cofferdam around the project. The cofferdam can be constructed using traditional methods such as sheet piling, or by less traditional methods. For instance, an oversized casing tube can be fitted over a pile casing that is being driven, and then the water can be evacuated from the area between the casings, either partially by injecting air bubbles or fully by dewatering the annular space. The air within the casing or other cofferdam does attenuate the energy from the construction project, but this technique is quite expensive. Indeed, for some underwater projects, it is cost prohibitive to establish a persistent envelope of air around the work area.  
         [0007]     A third technique is to enshroud the underwater construction area with a stream of bubbles. Like a cofferdam, this technique uses air to attenuate the energy, but unlike a cofferdam very little structure is needed. Indeed, this technique only requires bubble-producing units to be placed around and at the bottom of the construction project. The bubbles then travel from the bubble-producing units to the surface, blanketing the project in sound-dampening air.  
         [0008]     While elegant, this technique is ineffective in areas of deep water or strong currents. In these circumstances, the bubbles disperse too far laterally while traveling upward, and cannot completely envelop the project. To contain the bubbles as they ascend, a skirt or blanket of flexible material can be placed around the work area. However, this technique can also be expensive, and is not particularly robust, since the flexible material can be torn or damaged. Also, the flexible material acts like a sail, and therefore this system is not appropriate for areas of high current. A substantial support frame would also be required to implement this system.  
         [0009]     Thus, there is a need for a system that can robustly and inexpensively create a curtain of bubbles around underwater construction sites, even in areas of deep water or strong current.  
       SUMMARY OF THE INVENTION  
       [0010]     The present invention is an underwater energy dampening device that can be used to envelop an underwater construction area in a curtain of bubbles. It comprises a plurality of vertically spaced bubble producing units. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is an environmental perspective view of an underwater energy dampening device according to an embodiment of the present invention, as deployed for use in a pile driving operation.  
         [0012]      FIG. 2  is a top view of an underwater energy dampening device according to an embodiment of the present invention, as deployed for use in a pile driving operation.  
         [0013]      FIG. 3  is an environmental top view of an underwater energy dampening device according to an embodiment of the present invention, as deployed for use in a pile driving operation.  
         [0014]      FIG. 4  is a side view of an underwater energy dampening device according to an embodiment of the present invention.  
         [0015]      FIG. 5  is a front view of an underwater energy dampening device according to an embodiment of the present invention.  
         [0016]      FIG. 6  is is a side view of an underwater energy dampening device according to an embodiment of the present invention, showing the air flow patterns and valve positions within the device.  
         [0017]      FIG. 7  is a sectional view of a bubble producing tube and frame according to an embodiment of the patent invention, taken along line  7 - 7  of  FIG. 5 .  
         [0018]      FIG. 8  is a close-up of the circled area on  FIG. 7 .  
         [0019]      FIG. 9  is a cross-sectional view of a bubble producing tube and frame according to an embodiment of the patent invention, taken along line  9 - 9  of  FIG. 8 .  
         [0020]      FIG. 10  is a close-up end view of a bubble producing tube according to an embodiment of the patent invention, taken along line  10 - 10  of  FIG. 8 .  
         [0021]      FIG. 11  is a cross-sectional view taken along line  11 - 11  of  FIG. 3 .  
         [0022]      FIG. 12  is a top perspective close-up view of a valve that regulates the supply of compressed air to the bubble producing unit, according to an embodiment of the present invention.  
         [0023]      FIG. 13  is a top perspective close-up view of an air supply line at the bottom of a device according to an embodiment of the present invention, as the line branches off to provide air to the bottom bubble-producing tube.  
         [0024]      FIG. 14  is a top view of an alternative bubble producing unit configuration according to an embodiment of the present invention.  
         [0025]      FIG. 15  is a top view of another alternative bubble producing unit configuration according to an embodiment of the present invention.  
         [0026]      FIG. 16  is a top view of another alternative bubble producing unit configuration according to an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0027]     The present invention is an underwater energy dampening device  10  comprising a series of vertically spaced bubble producing units. In one embodiment, the invention comprises a (i) spine  12 , (ii) a series of vertically spaced frames  18  attached to the spine  12 , (iii) a series of tubes  22  on the frames  18 , and (iv) air supply tubing and hardware.  
         [0028]     As shown best in  FIGS. 1, 4 , and  5 , the spine  12  comprises a beam, typically made of steel. Other potential materials include rust resistant materials such as stainless steel. The spine  12  should have a length adequate for the water depth in the area of the underwater project. When installed, its bottom end  14  may be planted into the bed of the waterway, so that the bottom frame  18  is as close to the mudline as practical. See  FIG. 6 .  
         [0029]     A series of vertically-spaced frames  18  are attached to the spine  12 . See  FIGS. 1, 4 ,  5 , and  6 . These frames  18  may be semi-circular, and their purpose is to provide support for the bubble-producing tubes  22 .  
         [0030]     The bubble-producing tubes  22  sit within the frames  18 . See  FIGS. 1 and 9 . These tubes will typically be made of a rust-resistant material like high density polyethylene (HDPE) or stainless steel. The tubes  22  have end plates  20  to seal the ends of the tubes.  
         [0031]     The bubble-producing tubes  22  have a plurality of openings  24  on their top sides for release of bubbles. See  FIGS. 8, 9 , and  12 . The tubes also may have a plurality of openings  26  on their end plates  20  for lateral dispersal of bubbles. See  FIG. 10 . These end openings  26  are useful when there is a gap between one device and the next, as in the embodiments shown in  FIGS. 1, 2 ,  3 ,  14 , and  15 . By releasing bubbles at the end of each tube through the end plate  20 , the curtain of bubbles will be continuous, notwithstanding a gap between the tubes  22 .  
         [0032]     The bubble-producing tubes  22  and frames  18  are just one example of a bubble producing unit. For purposes of this patent, a bubble producing unit is any device or system that delivers bubbles. Such a unit a can be a tube, ring, hose, bubbler, chemical gas generation system, or any other device that can create bubbles.  
         [0033]     The bubble-producing tubes  22  or other bubble producing units are vertically spaced, so that bubbles are being generated at various depths. See FIGS.  1 ,  4 - 6 . Thus, in one embodiment, the bubble-producing tubes  22  are spaced every 3 to 5 meters along the spine  12 . See  FIGS. 1, 4 , and  5 . This distance may vary depending on the conditions within which the invention is operating.  
         [0034]     Air supply tubing and hardware is used to provide and regulate airflow to the bubble-producing tubes  22 . An air supply line  30  supplies air to each of the tubes  22 . See  FIG. 2, 3 , and  13 . Because greater air pressure is needed at the bottom, the air supply line  30  first travels all the way down the spine  12  to the bottom of the device, and then starts distributing air to each bubble-producing unit. See  FIGS. 6 and 13 . This air can be generated by a compressor, pressurized gas, or by other gas generation means such as a chemical reaction. Other gases besides air can be used. The pressure to be generated depends on the depth to which the air is delivered.  
         [0035]     Each tube  22  has a valve  28  to control the flow of air. See  FIGS. 2, 3 ,  6 , and  12 . As shown in  FIG. 6 , the position of the valves can be adjusted to regulate the air flow. Depending on the water current and other conditions within which the device is operated, only certain tubes  22  may be operated at any time. For instance, in certain circumstances, only every other tube needs to be operational at any given time. Also, because greater pressure is needed at lower depths, the position of the valves may vary incrementally from bottom to top. Pressure gauges (not shown) may be installed for each valve, so that operators can more precisely determine the proper position for each valve.  
         [0036]     Although manual valves are shown, the valves may also be pneumatically or hydraulically controlled. Additionally, a more automated version of the present invention could be created, in which acoustic sensors provide data to a processing unit, which in turn control air flow or pressure so that a sufficient but not superfluous quantity of bubbles is produced.  
         [0037]     With the basic structure of the invention now in mind, a particular operational embodiment can be described. In this embodiment, the invention is used in a pile driving operation.  
         [0038]     In this operation, the pile casing  40  is driven deep into the bed of the waterway. A pile driving hammer (not shown) is used, and this hammer has a footprint  80  extending beyond the perimeter of the casing. Thus, the topmost portion of the energy dampening device cannot be inside the hammer&#39;s footprint  80 . See  FIGS. 1, 2 ,  3 ,  14 ,  15 ,  16 . However, the bottom portion of the device can be very close to the casing, and the device can be angled slightly outward so that it is farther away from the casing at the top.  
         [0039]     Typically, a template or deck structure  60  with a deck floor  62  is erected to support the pile driving operations. See  FIGS. 1, 2 , and  3 . The energy dampening device must be installed within the framework provided by the deck structure  60 . This framework may include telescoping struts  64  to secure the casing, and these struts may comprise a wheel  66  on the end of an inner beam  68 , which in turn sits inside of an outer beam  70 . See  FIGS. 1, 3 , and  11 .  
         [0040]     To install an energy dampening device  10  within such a deck structure  60 , a dampening device frame  50  is placed atop the structure  60 , over the opening into which the pile casing  40  is being driven. See  FIGS. 1, 2 ,  3 ,  14 ,  15 , and  16 . The device  10  is then lifted by a crane and then stabbed between the pile casing  40  and the frame  50  into the bed of the waterway. Depending on conditions, the weight of the device  10  may be sufficient to firmly implant the device into the mud. The device should be implanted so that the lowermost bubble producing unit is just above the mudline. To secure or cinch the device  10  to the frame  50 , coupling means  52  such as a chain with a ratcheting device can be used. See  FIGS. 1 and 3 .  
         [0041]     To completely surround the pile casing, it may be necessary to use more than one energy dampening device  10 . Thus, in the embodiment depicted in  FIGS. 1-13 , four devices  10  are used to surround the pile casing  40 . However, fewer or more devices  10  may be appropriate, depending on the particular conditions, including the geometry of the deck structure  60 . Thus,  FIG. 14  shows an alternative embodiment  90  of the device in which two bubble-producing units  92 ,  94  surround the pile casing  40 ,  FIG. 15  shows an embodiment  100  three bubble-producing units  102 ,  104 , and  106  surrounding a pile casing  40 , and  FIG. 16  shows a third embodiment  110  with unitary unit  112  surrounding the pile casing  40 .  
         [0042]     Preferably, the device or devices are installed as close to the energy source as possible. For instance, for pile driving operations, it is preferable to surrounding each pile casing with bubbles, rather than the entire pile group. However, except where limited by express claim language, the present patent covers any version of the present invention, including versions in which the device is placed around the periphery of a large work area.  
         [0043]     The present invention offers a number of advantages over the prior art. First, the present invention can be inexpensively and effectively used in an area of high current and great depth. Before the present invention, the only effective high current/high depth technique was the use of a cofferdam such as an oversized casing, but this technique is quite expensive and difficult to implement at great depths. Second, the present invention can be modular, with the number, shape, and configuration of the energy dampening devices adjusted based on the particular requirements of the project and the available equipment. Third, the present invention is easier to use than the alternatives, since the amount of needed structure is minimal—all that is needed is an array of vertically spaced bubble-producing units.  
         [0044]     One skilled in the art will appreciate that the present invention can be practiced by other than the preferred embodiments, which are presented for purposes of illustration and not of limitation.