US3859803A

US3859803A - Anti-scour means for submarine structures

Info

Publication number: US3859803A
Application number: US425229A
Authority: US
Inventors: Kristen I Pedersen; William F Cavanaugh
Original assignee: Sofec Inc
Current assignee: Sofec Inc
Priority date: 1973-12-17
Filing date: 1973-12-17
Publication date: 1975-01-14
Anticipated expiration: 1992-01-14

Abstract

An anti-scour skirt is pivotally secured to a structure installed on the sea floor or a water bottom so as normally to extend outwardly from the structure and rest on the sea or stream bottom for preventing scouring or washing by water action of sand and other bottom material from around and beneath the structure. The skirt structure is circumferentially deformable so that it can be pivoted upwardly to a compact position adjacent the structure to facilitate transport through the water.

Description

United States Patent [191 Pedersen et al.

[ ANTl-SCOUR MEANS FOR SUBMARINE STRUCTURES [75] Inventors: Kristen I. Pedersen, Scarsdale;

William F. Cavanaugh, Rockville Center, both of NY.

[73] Assignee: Soiec Inc., Houston, Tex.

[22] Filed: Dec. 17, 1973 [21] Appl. No.: 425,229

[52] US. Cl. .1 61/46, 61/1 R [51] Int. Cl E02d 29/00 [58] Field of Search 61/1 R, 46, 46.5, 48, 52,

[56] References Cited UNITED STATES PATENTS 954,973 4/1910 Koetitz 61/54 3,091,249 5/1963 ONeil.... 135/16 3,456,448 7/1969 Luque 61/46.5

[111 3,859,803 [451 Jan. 14,1975

9/1970 Titman .1 61/46 12/1971 Friedberg 155/5 R X Primary Examiner-Paul R. Gilliam Assistant Examiner-David H. Corbin Attorney, Agent, or Firm-Bertram H. Mann; Frank B.

Pugsley [57] ABSTRACT An anti-scour skirt is pivotally secured to a structure installed on the sea floor or a water bottom so as normally to extend outwardly from the structure and rest on the sea or stream bottom for preventing scouring or washing by water action of sand and other bottom material from around and beneath the structure. The skirt structure is circumferentially deformable so that it can be pivoted upwardly to a compact position adjacent the structure to facilitate transport through the water.

10 Claims, 6 Drawing Figures ANTI-SCOUR MEANS FOR SUBMARINE STRUCTURES BACKGROUND OF THE INVENTION This invention relates to anti-scour means for resisting scouring or washing of sand other discrete or soft materials by water action from around a structure mounted on the sea or stream bottom.

Where a structure of some kind, for instance, a mooring base for a single anchor leg mooring and product transfer device, which may have lateral dimensions of fifty to a hundred feet or more, tests on or is secured to an unprotected seabed or stream bottom, the interruption of free flow along the sea bed or bottom will cause highly increased flow velocities and violent action of the water around the edges of the structure and may cause scouring or washing of sand and other fine material from around and beneath the foundation of such structure, thus permitting the structure to slip sidewardly and/or tilt in an unacceptable manner. Riprap revetment can be installed around the structure to prevent such water flow scrouring, but effective placing of such riprap revetment is difficult or impossible in deep water.

SUMMARY OF THE INVENTION Accordingly, an object of the invention is to provide relatively simple scour protecting skirt means which may be applied to a structure of any kind supported on a sea or stream bottom to protect the surrounding bottom material from scouring action by the water.

Another object is to provide such means which may be maintained in a compact position during transport of the structure on or through the water and may be easily and quickly shifted to its deployed position without diver assistance.

In accordance with the invention, the anti-scour device comprises a pliableband which snugly fits around the structure just above the sea or stream bed and a protective skirt pivotally secured to the pliable band. The skirt is circumferentially deformable to permit swinging to a compact position extending along the structure, to facilitate transport of the structure through the water, and may be readily dropped to its dployed or outwardly extending position for resting on the bottom material aroundthe structure to'shield the same from water scour action.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings which illustrate the invention,

FIG. 1 is a vertical transverse section of portions of the foundation of a single point mooring facility with the novel anti-scour means applied thereto.

FIG. 2 is a plan view of the structure in FIG. 1.

FIG. 3 is an enlarged detail vertical transverse section indicating different positions of the novel skirt means.

FIG. 4 is a detail section on line 4-4 of FIG. 2.

FIG. 5 is a one-quarter view similar to FIG. 2 illustrating a modification.

FIG. 5A is a view similar to FIG. 5 and showing the protective apron in deployed position.

DETAILED DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2 illustrate a foundation for a single point mooring and product transfer facility, as illustrated, for instance, in Flory et al. U.S. Pat. No.

3,641,602. The foundation comprises a large panshaped body having an annular bottom 8 and a cylindrical outer side wall 9. Centrally there is provided a cylindrical column 10 having attachment elements'll on its top wall 12 for attachment of the mooring facility components. The body is providedinternally'with a cartwheelarranged multiplicity of buoyancy tanks 13 with suitable bracing (not shown), but is otherwise generally hollow about central part l0, 12. In use, the hollow body rests upon the seabed or harbor bottom 14 and is filled with heavy material such as sand and/or rock, as at 15.

An annular ridge 16 depends from the lower periphery of the foundation structure for penetration of the water bottom to stabilize the same. However, water currents may so scour or wash the water bottom material around the foundation structure as to expose'this ridge 16 and even subject the foundation to undesirable settling or tilting. In order to prevent such scouring action by the water, the anti-scour means shown in detail in FIG. 3 is applied to the structure. This means comprises a band 20 of pliable material which snugly envelops the lower part of the foundation. Band 20 is secured along its upper edge 'to' the: foundation structure by stripping 21 and/or bolts 22, the lower portion of the band hanging normally against the side wall 9 but not being secured thereto. There are secured to the lower edge of band 20 a plurality of hinging tubes or pipes 23 by means of stripping or washers 24 and bolts 25. Also secured to each of the hinge elements 23 is a flat plate or panel 26 of form-sustaining material and generally rectangular shape and with radial reinforcing ribs 27. These plates are annularly arranged edge to edge and connectedby gussets 28 of pliable material bolted to the plates as at 29. Accordingly, plates 26 and gussets 28 form a circumferentially continuous and deformable skirt which may pivot from between the compact position shown at 26a in dotted lines in FIG. 3, in which plates 26 extend upwardly along the outer side wall 9 of the foundation, and the outwardly deployed positions shown in solid lines in FIG. 3, in which the apron rests upon the water bottom. Band 20 and this apron construction shield the foundation structure and the water bottom therearound from water currents. The radial width of the skirt structure, of course, must be adequate for this puspose. In one exemplary embodiment, this apron structure was approximately ten feet in radial dimension.

The apron structure may be secured in the compact position of FIG. 3, as by circumferential cords 30, enveloping the entire foundation structure and received in notches 31 in ribs 27 on the outer sides of plates or panels 26. In the compact position, the weight of the skirt structure is supported on the pliable band as at 2%. When the foundation structure is lowered to the sea floor and the skirt is deployed, the skirt will rest snugly on the sea bottom and adapt itself to a possible uneven bottom surface. The pliable band will allow the skirt to assume any vertical position within its designed range causing the band to bulge as indicated in 20a. However, the skirt and band assembly will remain sand tight.

In FIGS. 5 and 5A, the skirt is formed by continuous pliable annular band having an inner flange 33 snugly enveloping and bolted or otherwise secured to the lower, outer foundation wall 9a and a continuous outer portion 34 normally deployed into the outwardly extending position of FIG. 5A. T-shaped reinforcing

members

35, 36 are suitably secured to the upper face of the banding portion 34, as illustrated in FIG. 5A. In the deployed position, band portion 34 lies flat against the sea or stream bottom 34, with reinforcement stem parts 36 extending radially outwardly and resting on band part 34. Crossbar parts 35 form the pivot pieces about which the skirt forming band portion 34 may swing upwardly to the compact position of FIG. 5 in which portion 34 is circumferentially contracted to scalloped or crimped shape. The skirt structure will be detachably secured in the compact position by any suitable means, for instance, cords as at 30 in FIG. 3. In both forms, the securing means may be released by various means, for instance, by a diver, or remotely by any of the cutting devices available on the market utilizing, for instance, explosives or hydraulic or electrical action, and the signal may be transmitted from the remote position, as is well-known, by hydraulic or pneumatic, electrical, or sonic impulse means.

OPERATION It is believed the operation will be clear from the above description. In transporting the skirt-equipped structure-in this case, the mooring facility foundation-through the water, the skirt structure will be held in its circumferentially and radially compacted position of FIGS. 3 and S and will be retained in this position until the structure is properly planted on the sea or stream bottom. The holding cords or other devices will then be released or severed, permitting the skirt structure to swing outwardly and downwardly so as to lie flat against the water bottom all around the structure. Thus, the entire water bottom around the structure will be shielded from destructive water currents so that scouring action thereof will be prevented and the water bottom about and beneath the structure will remain firm.

Of course, the invention may be applied to other sea or stream bed supported structures, whether they rest upon the bottom, as herein illustrated, or are driven thereinto, or are otherwise secured to the sea or stream bed as by means of piles. Various features may be modified as will occur to those skilled in the art and the exclusive use of all modifications as come within the scope of the appended claims is contemplated.

We claim:

1. The combination with a structure projecting upwardly from a sea or stream bed of skirt means encompassing said structure and pivotally attached thereto, said skirt means being circumferentially yieldable to facilitate pivoting thereof between a compact position extending along the structure and an extended position for resting on the bottom material surrounding the structure to shield the same from scouring action of the water.

2. The combination described in claim 1 further including detachable means for securing said skirt means in said compact position.

3. The combination described in claim 2 in which said detachable means comprises a cord for encircling said skirt means to hold the same in said compact position.

4. The combination described in claim 1 in which said skirt means comprises circumferentially arranged reinforcing members and pliable sheeting interconnecting said members.

5. The combination described in claim 4 in which said reinforcing members are plates disposed annularly and edge-to-edge.

6. The combination described in claim 4 in which said skirt means is a continuous band of pliable material shaped normally to extend outwardly from the structure and crimpable to permit pivoting to said compact position, said reinforcing members being T-shaped including parts extending, respectively, across said skirt means and along an edge thereof as means for pivotal attachment of said skirt means to the structure.

7. The combination described in claim 1 further including a band for snug reception about the structure and for pivotally connecting said skirt means to the structure.

' 8. The combination described in claim 7 in which said skirt means is made of pliable material and is adapted to be secured at its inner portion to the structure.

9. The combination with a sea or stream bed supported of anti-scour means comprising a pliable band extending around the structure and secured along its upper edge thereto, a plurality of annularly arranged hinge elements secured to the lower portion of said band, circumferentially yieldable skirt means projecting from said hinge elements in a manner to facilitate pivoting between a compact position around said structure and an extended position resting on the surrounding bottom, and reinforcing elements projecting from said hinge elements along said skirt means.

10. The combination described in claim 8 in which said rigid elements are annularly arranged plates arranged edge to edge with pliable gussets interconnecting the same.

v TJNTTED STATES PATENT oTTTcE QERHWCATE 0F QQRREQTWN 'Patent No. 3,859,863 Dated 3Q 1215 ln n fl Kristen I. Pedersen and William F. Cavanaugh It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 6, after "sand the word. and should appear; line 22, "scrouring" should read scouring line 45, "dployed" should be deployed Column 2, line 7, a space should appear between "wheel" and "arranged".

Column 3, line 44, a comma should appear after the word Ii art" Column 4, line 37, before "of anti-scour means" (claim 9) the word structure should be inserted.

Signed and sealed this 11th day of March 1975.

(SEAL) Attest:

C, MARSHALL DANN RUTH C. MASGN Commissioner of Patents Attesting Officer v and Trademarks FORM P0-1050 (10-69) USCOMM-DC 50376-P69 Y U,S. GOVERNMENT PRINTING OFFICE: [969 0-366-334

Claims

8. The combination described in claim 7 in which said skirt means is made of pliable material and is adapted to be secured at its inner portion to the structure.