US 3347048 A
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Description (OCR text may contain errors)
1967 R. A. BROWN ETAL 3,3
REVETMENT BLOCK 2 Sheets-Sheet 1 Filed Sept. 27, 1965 INVENTOR Richard 14. Brown James D. Brown ATTOR 0" Oct. 17, 1967 BROWN ETAL. 3,347,048
REVETMENT BLOCK Filed Sept. 27, 1965 2 Sheets-Sheet 2 INVENTORS Richard A]. Brown James D. Brown ATTORN Y6 United States Patent 3,347,048 REVETMENT BLOCK Richard A. Brown and James D. Brown, Glen Burnie, Md., assignors to Coastal Research Corporation, Glen Burnie, Md., a corporation of Maryland Filed Sept. 27, 1965, Ser. No. 490,203 8 Claims. (Cl. 61-37) ABSTRACT OF THE DISCLOSURE Tongue and groove revetment blocks are loosely joined and have recesses between adjacent blocks. This permits the release of the hydrostatic pressure of the water beneath the blocks. Lightweight blocks are used which can move under the pressure without breaking the joints.
This invention relates to a revetment block and to a revetment composed of the blocks.
Heretofore, revetments have been usually constructed of heavy slabs or blocks which are joined to each other, such as by tongue and groove joints, and to the ground as shown in the patent to Schlueter No. 1,205,810. The weight of the block, together with the fastening to the ground, was presumed to be able to resist the pressure of the water produced by waves striking the revetment. Although floor tiles having drainage openings therein have been known, as shown by Landers No. 572,762, nevertheless, heretofore lightweight revetment blocks have not been constructed so as not to prevent hydrostatic pressure of ground water to build up beneath the blocks, and then to relieve such pressure before it causes a breakage in the joints between the blocks, dislocation of the blocks, and resumption of bank erosion.
The object of this invention is to produce a lightweight revetment block and a revetment composed of such blocks by means of which the hydrostatic water pressure beneath the blocks first rises and then is relieved, and to produce loosely interlocked blocks so as to allow relative tilting movement between adjacent blocks both longitudinally and transversely of the joint.
In this invention, the concrete blocks used are flat and rectangular and joined together by a loose tongue and groove joint so designed that the blocks may tilt slightly with respect to each other so that the upper surface of the revetment remains relatively smooth despite the slight displacement of adjacent blocks. This reduces the frictional force of the water rushing up and down the surface of the blocks. Water is permitted to flow through recesses or openings between adjacent blocks to beneath the blocks and then allowed to escape through the recesses so as to relieve hydrostatic pressure beneath the blocks. Consequently, the wave pressure on the blocks may force water behind the blocks and this is relieved as the wave recedes by means of the recesses. Ground water in the earth behind the blocks also escapes through the recesses. Because the blocks are flexibly interlocked, the joints give rather than break. At the same time, the blocks, through such flexible joints, are able to adapt themselves to an uneven grade. Consequently, the eflFects of the three forces; namely, the wave pressure, water friction, and bydrostatic pressure, are minimized so that a revetement composed of these blocks is durable despite its lightweight and severe wave action.
The means by which the objects of the invention are obtained are described more fully with reference to the accompanying drawings in which:
FIGURE 1 is a perspective view of the block;
FIGURE 2 is a side view of the tongue and groove joint between adjacent blocks;
FIGURE 3 is a view similar to FIGURE 2 with the blocks tilted in one direction with respect to each other;
FIGURE 4 is a view similar to FIGURE 2 with the blocks moved relative to each other; and
FIGURE 5 is a perspective view of a plurality of blocks laid as a revetment on a slope having a fiat subgrade.
The revetment block is composed of a flat rectangular concrete body 10 of such minimum size and weight as will resist movement under normal wave conditions and permit a limited amount of movement during more severe conditions. Each body has a fiat top surface 12, a grooved bottom surface 14, a fiat side 16-, and an opposite side 18 containing a recess 20. At one end of the block is a tongue 22 and at the opposite end of the block a groove 24 As shown in FIGURES 2 and 3, the tongue 22 and the groove 24 are constructed so that a flexible tongue and groove joint is formed between adjacent blocks while permitting relative movement between the blocks so that one block may be tilted with respect to an adjacent block a limited distance so as to maintain a relatively smooth upper surface on a revetment built of the blocks. The upper side 30 of the tongue is slightly downwardly inclined from the end portion 32 of the block, while the lower side 34 of the tongue is longer than the upper side as it extends from a cut back end portion 36 in the bottom 14 of the .block to leave an opening 38 between the lower ends of adjacent blocks. The lower side 34 of the tongue has an upwardly inclined end portion 40. When the blocks are laid on a flat grade, the edges 41a and 41b of adjoining blocks abut.
Groove 24 extends inwardly from the straight-sided end of the block with an upper wall 42 downwardly inclined at substantially the same angle as the upper side 30 of the tongue. The bottom wall of the groove has a horizontal portion 44 and an upwardly inclined inner end portion 46 at an angle less than the inclination of the inclined outer end portion 40 of the tongue. Inclined portion 46 also forms a fillet which reinforces the bottom of groove 24. The tongue 22 is of less size than the groove 24 to leave a space 47 between side 30' and wall 42, and does not extend into contact with the bottom of the groove 24 as the upper side 30 of the tongue is of less length than the upper wall 42 of the groove.
As shown in FIGURE 3, spaces 38 and 47 permit the blocks to be tiltable with respect to one another. Edge 50 of the tongue contacts the upper wall 42. This limits the movement of the tongue in the groove while permitting fiexibility between adjacent blocks. A further contact is made between the edge 52 of the groove with the lower side 34 of the tongue. When the blocks are tilted in the opposite direction, the lower side end portion 40 of the tongue will become in contact with the inclined wall portion 46 of the groove. Such a tilting movement is possible because in practice it is not possible to lay hundreds of blocks with all edges 41a tightly abutting edges 4112. In addition to this movement transversely of the joint, it is apparent that space 47 will permit relative movement longitudinally of the joint.
FIGURE 4 shows that while edge 41a can drop below edge 4112, it can never rise above edge 41b because of the contact which will occur between horizontal portion 44 with lower side 34.
Recess 20 terminates short of the tongue and groove sections, respectively, of the block. The grooves 54 in the bottom of the block extend parallel to the tongue 22 and communicate with recess 20. When assembled, the grooves of adjacent blocks are aligned. This is for the purpose of permitting water in the ground beneath the blocks to run both beneath the block and adjacent blocks and escape to the surface of the revetment through recess 20.
As shown in FIGURE 5, the blocks are adapted to be laid together on a sloping bank to form a revetment. In so doing, it is preferred to have the tongue directed up slope. There is therefore the tendency of the uppermost of the blocks in a row of blocks to settle down over the tongue 22 of the block in a lower row of blocks. As shown, the blocks are preferably laid with staggered joints;
The blocks are laid on a graded gravel filter having a particle size in contact with the block greater than the Width of the recess 20, or if gravel is not available, the blocks are preferably laid on a so-called filter cloth, which is commercially available for this purpose, in order to prevent particles of sand or dirt from escaping between adjacent blocks.
As heretofore indicated, the blocks are designed to minimize the effects of the three forces resulting from wave pressure, water friction on the upper surface of the revetment, and hydrostatic pressure produced by the water in the ground beneath the blocks. When the blocks are laid, the flexible tongue and groove joints enable the blocks to adjust themselves to any unevenness in grade.
Any block that will tend to settle with respect to the next lower block will do so because of space 47 so that the lower edge 41a of a block will drop slightly beneath the upper edge 41b of the adjacent block. Atthe same time, the joint is flexible along the length of each tongue 22 by rea-son of the space 47. It is preferred that the blocks be laid with the tongues extending parallel to the longitudinal length of the slope as shown in FIGURE 5. The recesses 20 will consequently extend upwardly and downwardly of the slope. When a wave strikes the uppersurface of the revetment and rushes upwardly thereon, such surface is relatively smooth, and any unevenness of the joint between the blocks does not resist the upward movement of the water so that water friction is minimized and a wave spends energy by climbing the slope. The impact force of the wave is transmitted directly through the block to the subsoil. The following downward movement of the water is insignificant as far as pressure and friction forces are concerned.
The rising water against the revetment causes the water to. flow through the recesses into contact with the subsoil, thus resulting in a hydrostatic pressure beneath the blocks when the water recedes. Since the grooves 54 of adjacent blocks are aligned, and as the advancing front of a wave is not a straight line, the wave water entering recesses 20 will be distributed through grooves 54 to beneath adjacent blocks, thus distributing the hydrostatic pressure beneath adjacent blocks along the slope. This gives maximum use of recesses 20. This hydrostatic pressure is immediately relieved; first, because the loose joint permits the upward lifting movement of the blocks, while at the same time,
water will drain through the grooves 54 and escape through the recesses 20. Water and small particles of soil or sand cannot enter the tongue and groove joint because the recesses20 terminate short of the joint. Also water flowing through space 38 helps to remove sand and dirt. Thus the joint is kept clean so that relative movement can take place between joined blocks. The grooves 54 tend to be self-cleaning as they extend in the direction and the length of the slope and are in free communication with the recesses 20. As the water recedes, the blocks settle down and in so doing pump water upwardly through the grooves 54 and recesses 20.
Heretofore used revetment blocks were constructed to resist water from entering the subsoil so as to prevent the creation of hydrostatic pressure beneath the blocks. As contrasted thereto, the block of the instant invention per mits water to reach the subsoil beneath the block, and because the hydrostatic pressure is immediately relieved both by drainage and relative movement of the blocks, the blocks themselves can be made much lighter than heretofore possible. Thus washing of the soil from beneath the blocks is prevented by the underlying filter so that wave pressure is transmitted through the blocks directly 4 to the ground. Water draining in the earth beneath the blocks passes out through grooves 54 and recesses 20 without disturbing the blocks.
In the preferred from of the invention, each block is composed of concrete and has the proportions of being 24.875 inches long including tongue 22, 8.625 inches wide, and 5.625 inches thick, and weighs about pounds. The tongue and groove are dimensioned so that the space 47 between them is about 0.125 inch wide. Recess 20 is about 0.250 inch deep and space 38 about 1.0 inch wide.
Having now described the means by which the objects of the invention are obtained, we claim:
1. A revetment block comprising a flat rectangular body, a tongue on one end of said body, a groove in theopposite end of said body for making a tongue and groove joint with an adjacent block, and said tongue being smaller than said groove and being loosely fittable in the groove of an adjacent block and having an upper side and a relatively longer lower side for forming a space between bottim faces of adjacent joined blocks and for permitting relative tilting movement in two directions between adjacent joined blocks.
2. A revetment block as in claim 1, further comprising a recessed side wall adapted to adjoin an adjacent block in said body extending from the top surface to, the bottom surface ofsaid block and with the recess terminating short of the tongue and the groove, respectively.
3. A revetment block as in claim 2, further comprising grooves in the bottom of said block extending parallel to said tongue and communicating with said recessed said wall.
4. A revetment block as in claim 1, said tongue having a downwardly inclined upper side and a relatively longer horizontal lower side ending in an upwardly inclined outer end portion; and said groove having an upper Wall'downwardly inclined at substantially the same angle as the upper side of said tongue and a lower wall having a horizontal portion and an inner end portion upwardly inclined at a less angle than that of the upwardly inclined outer end portion of said tongue.
5. A revetment block as in claim 4, said tongue having a length less than the depth of said groove.
6. A revetment comprising a plurality of blocks laid side by side in rows along the length and up the slope of a sloping ground, tongue and groove joint means extending parallel to the length of the slope for loosely interconnecting the blocks in one row with the blocks of an adjacent row while permitting relative tilting movement. in both directions between adjacent blocks and recess,
means between adjacent blocks and extending at right angles to said tongueand groove means for relieving hy-' drostatic pressure produced beneath the blocks by water beneath the blocks.
7. A revetment as in claim 6, further comprising grooves in the bottoms of the blocks aligned with adjacent blocks and extending parallel to the length of the slope and communicating with said recesses for relieving hydrostatic pressure from beneath the blocks.
8. A revetment block as in claim 7, said tongue and groove joint means further including means for permitting.
relative movement between a block in an upper row with a block in the adjacent lower row so that the top surface edge in the upper row block can drop below the top surface edge of the lower row block but can never rise above the top surface adge of said lower row block.
References Cited UNITED STATES PATENTS 1,164,708 12/1915 Edinger 61-38 1,378,735 5/1921 Talbot 52-595 3,200,553 8/1965 Frashour et al. 52-595 DAVID J. WILLIAMOWSKY, Primary Examiner.
P. M. CAUN, Examiner.