US3894397A

US3894397A - Beach erosion control structure

Info

Publication number: US3894397A
Application number: US494845A
Authority: US
Inventors: Samuel S Fair
Original assignee: Individual
Current assignee: Individual
Priority date: 1974-08-05
Filing date: 1974-08-05
Publication date: 1975-07-15
Anticipated expiration: 1992-07-15
Also published as: NL182330C; DK354075A; JPS5143835A; NL7509306A; BR7504993A; CA1007874A; GB1487646A; DK147488B; DK147488C; SE409342B; FR2281462B1; SE7508825L; NL182330B; FR2281462A1; JPS5334427B2; AU8352375A

Abstract

Beach erosion control structures comprising a perforate wall designed to combat erosion of a beach shoreline by wave action. The wall includes multiple courses of cored concrete blocks laid on their side so that the core holes provide horizontal passageways through the wall for the flow of water and entrained sand in incoming waves. The wall also includes multiple rows of such blocks arranged in such manner that the core holes of adjacent rows of blocks are staggered. A beach erosion structure according to the invention comprises a wall composed of individual, cored concrete blocks arranged in multiple rows and courses. The blocks of each row are arranged end-to-end and parallel to the adjacent row or rows, but the blocks of each row are longitudinally offset so that the core holes of adjacent rows of blocks are out of register. In some instances the blocks are preassembled by securing individual blocks into like block units, each block unit having a plurality of blocks (three blocks in the usual case) assembled in a longitudinally staggered side-by-side relationship such that the core holes in adjacent block are offset. By offsetting a central block longitudinally of the outer blocks, tongue and groove interlocks between adjacent block units within the wall can be achieved. Such a wall may be laid up without the use of mortar. Instead, mechanical fastening means, such as crimped straps, may be employed to couple adjacent courses to each other. Some or all of the block openings may be provided with reed or flapper-type valves which are swung open by an incoming wave, and then move to a partially closed position to resist or restrict the flow of water in ebbing waves. A sheet metal footing may be employed to provide and maintain a general horizontal alignment between adjacent block units in the lowermost course.

Description

United States Patent 1191 Fair [ l BEACH EROSION CONTROL STRUCTURE [22] Filed: Aug. 5, 1974 [211 App]. No.: 494,845

[76] lnventor:

[52} US. Cl. 61/4; 52/584; 52/593; 61/37 [51] Int. Cl E02b 3/06 [58] Field of Search 52/227, 582, 584, 592, 52/593; 61/3, 4, 5, 37

l 56] References Cited UNITED STATES PATENTS 2.474.786 6/1949 Humphrey 1. 61/4 2.755.631 7/1956 Hayden...... 61/4 3.011.316 12/1961 Wilson 61/4 3.176.468 4/1965 Nagai et a1. 61/4 3.252.287 5/1966 Suzuki 61/5 3.3 86252 6/1968 Nelson 61/37 3.344.125 10/1974 Williams 61/3 FOREIGN PATENTS OR APPLICATIONS 730.189 8/1932 France .6 61/4 769,861 3/1957 United Kingdom 61/4 Primary E.raminer-Robert L. Wolfe Assistant Examiner-David H. Corbin Attorney. Agenl, or Firm-Learman & McCulloch [5 7] ABSTRACT Beach erosion control structures comprising a perforate wall designed to combat erosion of a beach shoreline by wave action. The wall includes multiple [4 1 July 15, 1975 courses of cored concrete blocks laid on their side so that the core holes provide horizontal passageways through the wall for the flow of water and entrained sand in incoming waves. The wall also includes multiple rows of such blocks arranged in such manner that the core holes of adjacent rows of blocks are staggered.

A beach erosion structure according to the invention comprises a wall composed of individual, cored concrete blocks arranged in multiple rows and courses. The blocks of each row are arranged end-to-end and parallel to the adjacent row or rows, but the blocks of each row are longitudinally offset so that the core holes of adjacent rows of blocks are out of register. In some instances the blocks are preassembled by securing individual blocks into like block units. each block unit having a plurality of blocks (three blocks in the usual case) assembled in a longitudinally staggered side-by-side relationship such that the core holes in adjacent block are offset. By offsetting a central block longitudinally of the outer blocks, tongue and groove interlocks between adjacent block units within the wall can be achieved. Such a wall may be laid up without the use of mortar. Instead, mechanical fastening means, such as crimped straps, may be employed to couple adjacent courses to each other. Some or all of the block openings may be provided with reed or flapper-type valves which are swung open by an incoming wave, and then move to a partially closed position to resist or restrict the flow of water in ebbing waves. A sheet metal footing may be employed to provide and maintain a general horizontal alignment between adjacent block units in the lowermost course.

15 Claims, 9 Drawing Figures FIG! FIGB

FIGSG F|G.5

BEACH EROSION CONTROL STRUCTURE BACKGROUND OF THE INVENTION Erosion of beaches by wave action is a problem most frequently encountered along the shores of large bodies of water where large and persistent wave action is exerted on beaches of sand or fine shingle. A detailed discussion of the problem is found in .larlan US. Pat. No. 3,387,458 in which it is pointed out that the most commonly employed erosion control expedient, namely, a solid seawall, is often self-defeating in that the wall itself produces a scouring or erosive action concentrated at the base of the wall.

The present invention is especially designed for use on beaches of sand and/or shingle where a substantial amount of the beach material is entrained in incoming and outgoing waves. The present invention is especially designed to provide a perforate wall structure which acts in a manner such that the flow of water and entrained beach material inwardly through the structure is easier than outward flow so that a greater quantity of entrained sand or shingle settles in or near the wall so that the process of erosion is minimized and in some instances actually reversed.

SUMMARY OF THE INVENTION A wall of the present invention may be constructed from standard concrete blocks of rectangular parallelepiped overall configuration having a pair of relatively large core holes extending through the block. When employed in the present invention, each block is laid on its side so that the core holes extend horizontally through the block. Individual blocks may be preassembled into block units in which three, or more or less, blocks are secured together side-by-side in a longitudinally staggered relationship such that the core holes of adjacent blocks communicate with each other, but are longitudinally staggered so that water flowing into the core holes of an outermost block is impeded and divided as it flows into the holes of the next adjacent block. The central block of each such unit is longitudinally offset in one direction relative to both of the two outermost blocks so that the three-block unit can be laid up in an end-to-end tongue and groove interlock construction.

In the laying up of a wall, a footing element in the form of a relatively light-weight, sheetmetal member is laid on the beach surface to receive the first course of the wall and maintain adjacent ends of adjacent block units at substantially the same level. Additional courses are laid up on top of the first course to the desired height, which is determined by the wave action normally expected to be encountered. Adjacent courses and rows need not be mortared or bonded to each other, but instead may be mechanically coupled to each other by passing a metal strap or other anchor device through openings in one course and crimping or bending the projecting ends of the strap inwardly into the openings in the next course.

In general, the lower part of the wall is wider than the upper part so as to provide stability and minimize the risk of toppling of the upper part of the wall due to excessively high waves.

In some instances, some or all of the openings in the wall may be provided with a flexible metal flapper or reed valve of sheet metal or plastic material which is oriented to be opened by an incoming wave to accommodate inward flow through the wall and to move to a substantially closed position to exert a throttling action on waves ebbing outwardly through the wall. The wall normally is constructed at or slightly outwardly from the normal or calm water shoreline.

Other features and objects of the invention will become apparent by reference to the following specification and to the drawings, wherein:

FIG. 1 is a top plan view, partially broken away, of a section of a wall embodying the present invention;

FIG. 2 is a front elevational view of a portion of the wall of FIG. I;

FIG. 3 is a cross-sectional view taken on the line 33 of FIG. 2;

FIG. 4 is a perspective view of a pair of individual block units prior to assembly;

FIG. 5 is a front elevational view of an individual block having flapper or reed valves;

FIG. 6 is a cross-sectional view taken on the line 6-6 of FIG. 5:

FIG. 7 is a view similar to FIG. 1, but illustrating a modified construction; and

FIGS. 8 and 9 are respectively top and end views of variant forms of walls.

Referring first to FIG. 4, a seawall W embodying the present invention is constructed from a plurality of concrete blocks designated generally 10 of standard construction and having a nominal length I of 16 inches, a nominal height h of 12 inches, and a nominal width w of 8 inches. In practice, each block is laid on its side so that the normal width dimension represents the height of the block.

Each block 10, when laid on its side, consists basically of top and

bottom panels

12 and 14 which are integrally interconnected to each other by transverse webs or partitions 16 which are longitudinally spaced from each other to provide longitudinally spaced core openings 18 which extend transversely entirely through the block. The two openings 18 represent approximately 50 percent of the total side area of the block.

In FIG. 4, three blocks 10 are bonded or otherwise prearranged side-by-side to form a three-block unit designated generally 20 with the central block of each unit longitudinally offset relative to the two outer blocks so that a tongue and groove interlock can be achieved between adjacent block units 20 when the block units are moved into abutting end-to-end relationship with each other.

The longitudinal offsetting of the individual blocks in each block unit locates the transversely extending vertical partitions 16 out of alignment with each other as best seen in the broken-away portion of FIG. I. As a consequence, water can flow easily through an assembled wall via passageways provided by the openings 18, but such passageways are successively subdivided so that the flow of a wave through a wall is impeded by the partitions with the result that the force of the wave is successively broken up as it traverses each row of blocks in the completed wall.

In FIGS. 1 and 2 the two outermost blocks of a block unit 20 are shown as being transversely aligned with each other. However, transverse alignment is not required. Rather, longitudinal offsetting of each row of blocks is preferred, as is shown in FIG. 7, since such an arrangement provides a more tortuous path through the wall. A three-block unit having the two outer blocks transversely aligned is somewhat more convenient to handle, however. because it can be laid up in the tongue and groove interlock with either side up.

in laying up the wall, a flanged footing element 22 in the form of a strip of sheet metal. such as aluminum, is laid down along the line to be followed by the wall. Footing element 22 serves primarily to maintain an approximate general level between adjacent blocks 20 and to serve as a guide for the laying down of the first course. It is not particularly critical if the wall sinks somewhat into the surface upon which it is laid. Footing element 22 functions primarily to assure that if the wall does sink somewhat, it sinks fairly evenly.

The first course is laid up on top of footing element 22 simply by laying individual blocks or block units on the footing element in abutting end-to-end relationship with the core holes 18 substantially horizontal and facing seaward. Additional rows and courses are then laid up in succession, thereby providing multiple courses and multiple rows of blocks. As each row is laid up, the blocks are longitudinally staggered relatively to the adjacent row so that the core openings in adjacent rows of blocks communicate, but are out of register with one another.

Adjacent rows and courses are mechanically locked to each other by mechanical fastener or anchor elements. The specific mechanical fastening elements may comprise any of a number of different devices such as chains, cables, and the like. It is preferred, however, to utilize a fastener element 24 comprising an elongate metal rod or strap which is passed through some or all of the core openings of one block or block unit and reversely bent as at 26 into the openings of the block of the next underlying course. Fastening elements 24 function primarily to prevent horizontal shifting of one course relative to the other. It is preferred that fastening elements 24 also be utilized to secure the footing 22 to the lowermost course.

In some instances it may be desirable to employ a flapper or reed valve, designated generally 28 (FIGS. and 6) in some or all of the block openings. Valve 28 can be constructed from resiliently flexible sheet metal or sheet plastic. As best seen in FIG. 5, the transverse width of the flapper or reed portion 30 of the valve is somewhat less than that of a block opening 18, but the length of flapper 30 is somewhat greater than the height of the block opening. The flapper merges at its upper end with a mounting tab portion 32 which is bent to overlie the upper surface of the block. The valves normally are not employed in the top course and are held in position by the weight of the next overlying course resting on the top of mounting tab portion 32.

The flapper portion 30 is capable of hinging or flexing about the upper edge of the opening in which it is mounted and is oriented so that the valve is on the seaward side of the block upon which it is mounted. The valve can thus be deflected upwardly from the full-line position shown in FIG. 6 in response to the incoming waves to afford a relatively wide open passage to the incoming wave and entrained sand to permit such ma terial to pass relatively freely inwardly from the sow ward to the landward side of the wall. As the wave gins to ebb, the flapper 30 is returned to the full-line position shown in FIG. 6 in which the flapper impos a substantial restriction to outward flow of water and entrained sand, thus assuring that a substantial amount of the entrained sand will be restrained against outward flow through the wall.

The assembled wall, while permitting the flow therethrough of a substantial portion of water and entrained sand in incoming waves, exerts a restriction or throttling effect on the incoming wave and the longitudinally offset and staggered partitions of the successive rows of blocks successively break up the force of the incoming wave so that the force and velocity of the wave are greatly reduced by the time the wave has passed through the wall. The throttling action thus imposed on the incoming wave promotes the settling or depositing of entrained sand or shingle on the landward side of the wall and the wall in turn induces a second throttling action on the ebbing wave to promote further settlement of entrained sand from the water as the wave passes outwardly through the wall. A substantially augmented throttling action to the ebbing wave may be achieved by the employment of flapper valves 28.

The wall W normally is constructed so as generally to parallel the shoreline. The number of rows and courses of blocks is determined generally by the height of waves encountered during storms. It is important, however, that the wall be capable of withstanding the force of storm-generated waves occurring shortly after installation of the wall. Wall stability during this critical period can be achieved in a number of ways. For example, the wall can be of substantially pyramid configuration in cross-section, as indicated in FIG. 9. Such a wall is wider at its lower part than at its upper part, thereby providing substantial resistance to toppling. Further, since such a wall has fewer blocks at its upper part than at its lower part, there are fewer core openings and fewer partitions to exert a throttling effect on a wave. Thus, the greater forces exerted on the wall are along its lower part.

It is not necessary to construct a wall with fewer rows of blocks at its upper part than at its lower part to provide for an unequal distribution of forces over the height of the wall. Lessening of the forces exerted at the upper part of the wall may be effected by changing the extent to which the blocks in adjacent rows are staggered. Thus, the blocks in adjacent rows at the upper part of the wall may be less staggered than those at the lower part of the wall so that the core openings of the upper blades are more nearly in register.

As indicated in FIG. 8, the wall in some instances may be provided with flanking wings extending generally perpendicular to the seawall W and constructed in the same manner except that the openin gs in the blocks extend substantially parallel to the shore. The wings function in the same manner as the wall W and are of particular advantage in those instances in which the direction of incoming waves is not perpendicular to the wall W. The wings also function to reinforce the ends of the wall.

A particularly significant characteristic of a wall constructed according to the invention is that a considerable quantity of sand entrained in the water which passes through the wall in either direction is deposited adjacent the opposite sides of the wall, as well as in the "min gs of the blocks. The deposited sand thus will ac- -..mulate at both the landward and seaward sides of the wall and provide a barrier to erosion of the beach. After a period of time the deposited sand will bury the wall, thereby providing an unblemished waterfront. Should a particularly severe storm subsequently generate wave action violent enough to erode the deposited sand from the area of the wall, the latter will be capable of functioning to effect a reaccumulation of sand following subsiding of the violent wave action.

Although only two embodiments of the invention have been described in detail, it will be apparent to those skilled in the art that the disclosed embodiments may be modified. Therefore, the foregoing description is to be considered exemplary rather than limiting. and the true scope of the invention is that defined in the following claims.

What is claimed is:

l. A beach erosion control structure comprising a plurality of courses of parallel rows of blocks arranged end-to-end and forming a wall extending along a shoreline and substantially parallel thereto, the blocks of each row abutting the blocks of each adjacent row, each of said blocks having top and bottom panels integrally interconnected by a plurality of transversely extending vertical partitions longitudinally spaced from each other to define openings facing seaward and extending horizontally entirely through the blocks, the openings of the blocks of adjacent rows being in communication with each other but being longitudinally staggered so that water flowing into an opening of an outermost block of said wall is impeded and divided by a partition in a block of the next adjacent row as it flows into an opening in a block of the next adjacent row, said wall being so positioned that it imposes a first throttling action on the water of incoming waves to promote depositing of entrained sand on the landward side of the wall and a second throttling action on the water of ebbing waves to promote depositing of entrained sand.

2. A structure as defined in claim 1 including means for securing adjacent rows to each other.

3. A structure as defined in claim 1 including means for fastening adjacent courses to each other.

4. A structure as defined in claim 3 wherein said fastening means comprises an elongate bar passing through openings in adjacent rows of blocks of one course and having opposite ends reversely bent into the openings of the blocks in an adjacent course.

5. A structure as defined in claim 1 wherein there are at least three of said rows.

6. A structure as defined in claim 1 including an elongate, footing member underlying the lowermost course of said wall.

7. A structure as defined in claim 1 including a resiliently flexible flapper member mounted within an opening in a block, said flapper member being swingable about a horizontal axis extending longitudinally of the block along the upper edge of the opening at the seaward side of the block and inclined from said axis downwardly and inwardly of the block.

8. A structure according to claim 7 wherein said flapper member is of such length as to engage the bottom of the opening within which it is mounted.

9. A structure according to claim 1 including at least one wing at one end of said wall and extending substantially nonnal to said wall, said wing having a plurality of courses and parallel rows of blocks arranged like the blocks of said wall.

10. A shore erosion control structure comprising a wall extending along a shoreline and substantially parallel thereto, said wall being composed of a plurality of parallel rows of block members arranged end-to-end with the block members of each row abutting the block members of each adjacent row, each of said block members comprising top and bottom panels joined by vertical partitions spaced from one another to form horizontal openings between said panels, each opening extending entirely through the block member and facing seaward, the partitions of each block member of a row being staggered with respect to the partitions of the block members of the adjacent row, whereby the openings of the block members in adjacent rows communicate with each other but are longitudinally staggered so that water flowing into an opening of an outermost block member of said wall is impeded and divided by a partition in a block of the next adjacent row as it flows into an opening in a block member of the next adjacent row, said wall being so positioned that it imposes a first throttling action on the water of incoming waves to promote depositing of entrained sand on the landward side of the wall and a second throttling action on the water of ebbing waves to promote depositing of entrained sand.

11. A structure as defined in claim 10 wherein there are at least three side-by-side rows of said block members.

12. A structure as defined in claim 11 wherein adjacent block members of adjacent rows are secured to one another to form a unit of three of said block members.

13. A structure as defined in claim 12 wherein each of said units has a center block member sandwiched between two outer block members, the center block member being staggered with respect to the outer block members, whereby each of said block units has a groove at one end thereof and a tongue at the opposite end thereof.

14. A structure as defined in claim 13 wherein said outer block members are transversely aligned.

15. A structure as defined in claim 13 wherein said outer block members are staggered with respect to each other.

Claims

1. A beach erosion control structure comprising a plurality of courses of parallel rows of blocks arranged end-to-end and forming a wall extending along a shoreline and substantially parallel thereto, the blocks of each row abutting the blocks of each adjacent row, each of said blocks having top and bottom panels integrally interconnected by a plurality of transversely extending vertical partitions longitudinally spaced from each other to define openings facing seaward and extending horizontally entirely through the blocks, the openings of the blocks of adjacent rows being in communication with each other but being longitudinally staggered so that water flowing into an opening of an outermost block of said wall is impeded and divided by a partition in a block of the next adjacent row as it flows into an opening in a block of the next adjacent row, said wall being so positioned that it imposes a first throttling action on the water of incoming waves to promote depositing of entrained sand on the landward side of the wall and a second throttling action on the water of ebbing waves to promote depositing of entrained sand.

9. A structure according to claim 1 including at least one wing at one end of said wall and extending substantially normal to said wall, said wing having a plurality of courses and parallel rows of blocks arranged like the blocks of said wall.