CA1149183A - Retaining wall system - Google Patents

Abstract

A B S T R A C T
A retaining wall is constructed from concrete slabs laid in horizontal courses, in half-lapped relationship. The slabs are of uniform length and thickness, but of differing widths. The bottom, middle, and top thirds (approximately) of the wall are constructed respectively of relatively wide slabs, of slabs of intermediate width, and of relatively narrow slabs. A course of extra-wide anchoring slabs is provided about half-way up the wall. The front face of the wall defines a substantially planar surface, while the rear face of the wall is stepped, and the extra width of the anchoring slabs projects from the rear face of the wall. The slabs are provided with apertures, so arranged as to be in alignment when the slabs are assembled into a wall structure, forming continuous apertures extending from top to bottom of the wall. Dowell rods of metal or other suitable material, are disposed in these continuous apertures; the rods are of such dimensions as to fit inside the apertures with appreciable clearance. The completed structure is fully interlocked, since all structural slabs are locked into this structure by the dowell rods, and the structure is sufficiently flexible to be capable of substantial deformation, in response to land subsidence, frost heaving, thermal expansion and contraction, and the like, without breakage of structural elements, or loss of structural integrity.

Description

FIE~D OF THE I~VENTION
This invention relates to retaining wall structures formed from concrete slabs, and methods of constructing same.
More particularly, the invention relates to a method of forming such a retaining wall structure, wherein the individual slabs are not rigidly attached -to each other by means of mortar, or the like, but rather form part of an integrated interlocked structure, wherein the individual slabs are restrained from separating from the structure, while at 0 the same time being capable of limited relative movement.
BACKGROUND OF THE INVENTION
Various systems for constructing a retaining wall utilizing a plurality of precast concrete blocks or slabs, are known.
Canadian Patent No. 9~1,626, which issued on 12 February, 1974, to Giuseppe Risi, discloses one such system. In the Rissi system, a wall is constructed from a plurality of blocks, the upper and lower surfaces of which are provided with mating tongues and grooves, for interlocking engagement between vertically adjoining blocks. In one embodiment of the Risi system, as shown in Figure 3 of the Risi patent, the ends of the blocks are also provided with mating tongues and notches, to provide interlocking between hori7ontally adjacent blocks.
The stability of a structure using the Risi system, is entirely dependallt on the engagement between relatively shallow tongues and grooves on adjacent individual blocks, which in turn is dependant upon the blocks remaining in close contact and parallel alignment with each other. The capacity -to withstand deformations resul-ting from the stresses to which a retaining wall is likely to be exposed, without loss of ,;,~

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structural integrity, is therefore very limited. For example, forces exerted against the rear of the wall, by the retained earth, may cause an upper portion of the wall to tilt forward, resulting in disengagement of tongues from grooves, and permitting an upper portion of the wall to topple~ The likelihood of this form of structural failure may be reduced, if the wall, instead of being vertical, is built with a .
substantial rearward slope, as is illustrated in Figure 4 of .
the Risi patent. Sloping walls may be acceptable in some situations, but in many cases, a vertical, or nearly vertical, wall is necessary or desired. Moreover, even if the wall is built with a substantial rearward slope, disengagement of the interlocking means, leading to structural failure, may result when individual blocks, or groups of blocks, are raised, lowered, or tilted, as a consequence of frost heaving, land subsidence, or the like.
Persons skilled in the art will also recognize -that the form of concrete block required for the Risi system will be relatively expensive to manufacture. Moreover, the Risi blocks, particularly if made in accordance with the embodiment of Risi's Figure 3, will be relatively fragile, and likely to suf~er damage when subjected to the type of handling commonly encountered by precast concrete construction materials.
SU~MARY OF TEIE INVENTION

_ _ .
The present invention is directed to providing a retaining wall structure, and method of construction, which avoids the foregoing disadvantages.
A method of constructing a retaining wall according to the present invention comprises the steps of:

a. providing a plurality of generally rectangular concrete slabs of substan~ially the same thickness and length, each slab being provided with a pair of apertures of generally uniform size through the thickness of the slab disposed at locations a pre-specified uniform distance from the front edge of each slab, and a pre-specified uniform distance from each end of each slab, such that the distance between centers of the apertures in an individual slab is not less than, and not greatly in excess of, one-half the slab length;
b. providing a plurality of dowell rods of length not less than the projected height of the wall, and of a size to fit in the apertures with appreciable clearance;
c. assembling the slabs in combination with the rods so as to form a retaining wall of -the desired dimensions, comprising a plurality of horizontal courses of slabs, vertically adjacent slabs being in half-lapped relationship such that the junctions between the ends of slabs in a horizontal course are in alignment with the centers of slabs in each vertically ad~acent horizontal course, the apertures in the slabs co-operating to form continuous apertures extending from top to bottom of the wall; with a dowell rod installed in each continuous aperture extending from top to bottom of the wall, to form a structure which is completely interlocked but which is capable of significant deformation without fracture of any structural elements.
Slabs of different widths may be used, with the lower portion of the wall predominantly formed from slabs having a greater width than the slabs predominantly forming the upper portion of the wall. Preferably, the wall structure is predominantly formed from slabs havlng three different widths; the lowermos-t -third (approximately) of the wall, is predominantly formed from slabs having the greatest of the three widths; the uppermost third (approximately) of the wall is predominantly formed from slabs having the least of the three widths; and the remainder of the wall is predominantly formed from slabs having the intermediate of the three widths.
If the wall is o substantial height, a horizontal course of extra-wide slabs is preferably laid at an intermediate location between the top and bottom of the wall, for example, about half-way up the wall.
The centers of the apertures in each slab may be separated by a distance slightly in excess of one-half the uniform slab length, so that when the slabs are assembled in combination with the dowell rods to form a retaining wall, the adjacent ends of horizontally adjacent slabs are separated by relatively small gaps to permit drainage of water through the assembled re-taining wall.
The slabs and rods may be assembled in combination by:
a. laying a first horizontal course of slabs on a suitably graded bed of particulate material;
b. inserting a dowell rod of suitable length into each aperture in the slabs of the first horizontal course, and driving the rod downwardly into the particulate material to a sufficient extent to support the rod in the upright position; and 9~33 c. laying subsequent horizontal courses of slabs by engaging the apertures of each slab with a pair of upright dowell rods, and lowering the slab into position.
A set of components for assembly into a retaining wall structure, in accordance with the present invention, comprises a plurality of generally rectangular concrete slabs, and a plurality of dowell rods, as described above. The slabs are adapted to be arranged in a plurality of horizontal courses, with vertically adjacent slabs in half-lapped relationship such that the junctions between the ends of slabs are in alignment with th~ centers of slabs in each vertically adjacent horizontal course, the slabs being so posi-tioned that the apertures in the slabs co-operate to form con-tinous apertures extending from top to bo-ttom of the wall, a dowell rod being disposed in each such continuous aperture extending from top to bottom of the wall, whereby the retaining wall structure is completely interlocked but is capable of significant deformation without fracture of any structural elements.
The set of components may comprise slabs of different widths, and may comprise sufficient extra-wide slabs to form a course of extra wide slabs, arranged as described above.
The centers of the apertures in each individual slab may be separated by a distance slightly in excess of one-half the slab length, whereby when the components are assembled into a wall structure, the adjacent ends of horizontally adjacent slabs are separated by relatively small gaps, to permit drainage of water through said retaining wall ~.
structure.
The slabs for forming the uppermost horizontal course of an interlocked retaining wall structure may be all of the same width, and the set of components may comprise a sufficient number of capping slabs having a cross-section in the form of an inverted U, the vertical legs of said inverted U defining an interior space not less than the width of the slabs for the uppermost horizontal course of the interlocked structure, to form a horizontal course of capping slabs laid along the top of the interlocked retaining wall structure, with the uppermost slabs of the interlocked structure being engaged w.ithin the inverted U shaped cross-section of the capping slabs.
The front edge of each slab may comprise upper and lower bevel portions, and a vertical mid-portion, the mid-portion being characterized by the presence of exposed aggregate.
The retaining wall system and method of construction, of the present invention, accordingly provide a structure which is fully interlocked, each individual slab being securely attached to the structure, but which is nevertheless capable of undergoing significant deformation, to accommodate land subsidence, frost heaving, thermal expansion or contraction, and the like, without fracture of any structural elements, and without loss of structural integrity.
Moreover, the individual slabs utilized in a structure in accordance with the present invention, are of simple configuration, easily and inexpensively manufactured, and do not possess any relatively fragile projections or the like, which would be suspectible to accidental damage during normal storage and handling. Vertical retaining walls constructed in accordance wi~h the present invention, have satisfactory stability, even when of substantial height, eight fee-t for example. Retaining wall structures constructed in accordance with the present invention, do not require poured concrete footings, and may be rapidly and easily erected, by unskilled labour, at locations not accessible to heavy equipment.
Further features and advantages of the present invention, will be apparent from the following detailed description of the preferred embodiment of the invention, with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a front elevation of a retaining wall structure in accordance with one embodiment of the invention;
Figure 2 is a cross-sectional view of the retaining wall structure of Figure 1, along the line A-A;
Figure 3 is a perspective view of one embodiment of a slab used in construction of the retaining wall structure of Figures 1 and 2;
Figure 4 is a perspective view of an inslde corner slab, for use in constructing retaining walls in accordance with the present invention; and Figure 5 is a perspective view of a portion of a corner constructed using a plurality of the slabs of Figure 4.
DETAILED DESC~IPTIO~ OF THE PREFERRED EMBODIMENT
In accordance with the presently preferred embodiment of the inven-tion, a retaining wall structure is constructed utilizing a plurality of precast concre-te slabs, each slab being three inches thick, and having a nominal length of twenty-four inches. As shown in E'igure 3, each slab is provided with a pair of apertures 5, of three-quarter inch diameter, running through the thickness of the slab. The apertures are set four inches back ~rom the front edge of the slab, and at equal distances from the respective ends of the slab; the distance between the centers of the apertures is twelve inches. For aesthetic reasons, the front edge of the slab is formed with upper and lower levels 6a and 6b, and a vertical portion 7, the vertical portion 7 showing exposed aggregate. A typical retaining wall structure, as shown in Figures 1 and 2, comprises slabs la, lb, lc and ld, of four different widths, namely eight inches, twelve inches, sixteen inches, and twenty-four inches respectively. As shown in Figure 1, the wall is constructed from a plurality of horizontal courses of these slabs, laid in half-lapped relationship, so that the intersections between individ~al slabs in a given horizontal course, are aligned with the centers of slabs in vertically adjacent horizontal courses.
The slabs are positioned with the apertures 5 in alignment, so that continuous apertures of three-quaxter inch diameter, extend from top to bottom of the structure. Dowell rods 4 of suitable material are positioned in these continuous apertures, extending downward into the material 8 on which the lowermost course of slabs is laid. The dowell rods must be formed from a material which is both strong and durable, and should be so sized that they fit through the apertures in the slabs with appreciable clearance. Half-inch diameter steel rebar (steel reinforcing rod~ has been found to be both suitable and economical for use as dowell rods.
Preferably, the lower portion of the wall, consisting of approximately one-third the total height, is formed using slabs lc, sixteen inches wide; the intermediate portion of the wall, again constituting approximately one-third o~ the total height, is formed from slabs lb, twelve inches wide; and the uppermost portion of the wall is formed from slabs la, eight inches wide. A horizontal course of anchoring slabs ld, twenty-four inches wide, is located at approximately the mid-point in the height of the wall. A
course of capping slabs 3, having a cross-sectional shape in the form of an inverted U, is laid along the top of the wall, embracing the uppermost course of eight inch slabs la.
Half-slabs 2 are provided to complete the horizontal courses, where required. Preferably, precast half-slabs are utilized, although it is of course possible to produce half-slabs at the job site, by cu-tting slabs of standard length, using known concrete-cutting techniques.
The wall shown in Figure 1 of the drawing is laid on a level horizontal surface, but it will be understood that the bottom courses of the wall structure may be stepped, as required, to accommodate the terrain.
It will be seen that the retaining wall structure (apart from the decorative capping slabs) is completely interlocked; that is, each individual slab is securely locked to the entire structure.
Special forms of slab may be provided, to permit the formation of angles or corners in the wall, without interrupting the interlocking structure. Figure 4 illustrates an inside 90 corner block, and Figure 5 illustrates the ~ 10 --manner in which a plurali-ty of blocks of -the type shown in Figure 4, may be assembled to form an inside corner which will interlock with two straight wall segments. Since the upper and lower surfaces of the slabs are in-terchangable, the slabs may be used ei-ther way up; accordingly, only one pattexn of corner block is required, in order to construct a corner in the manner s~nown in Figure 5.
Specialized blocks may also be provided for the construc-tion of Gutside corners, rounded corners, and inside and outside bends of any desired angle, such as 30 or 45.
Such specialized slabs may all be designed on the same principle as the inside corner slabs shown in Figure 4; the appropriate dimensions and configurations will be obvious to persons skilled in the art.
The s-tability of the retaining wall structure arises from two important features of the structure. First, as previously mentioned, the entire structure is completely interlocked; in the absence of fracture of structural elements, individual slabs, or groups of slabs, cannot be separated from the rest of -the structure; the structure will stand or fall as a unit. Secondly, the stepped configuration of -the rear face of the wall, and the presence of a course of twenty-four inch wide anchoring slabs projecting into the backfill, at about the midpoint in the height of the wall, both as shown in Figure 2, mean that a substantial weight of fill rests on the steps of the rear surface, and on the upper surface of the anchoring slabs; the downward force of this weight of backfill, restrains the wall from any tendency to tilt forward.

The presently preferred method of constructing a retaining wall structure, in accordance with the present inventisn, will now be described.
A suitably graded bed of particulate material 8, preferably crushed rock of maxirnum one-inch size, is prepared.
The top sur~ace of the bed should be at least six inches, and preferably more than six inches, below grade level, to prevent forward movemen-t (or "kicking out") of the base of the retaining wall structure. The first course of slabs (of sixteen inch size) is then laid on this prepared foundation.
(A poured concrete footing, or the like, is not required.) After the first course of slabs has been laid, steel dowell rods of a length somewhat greater than the projected height of the completed structure, are inserted vertically downward into the apertures in the first course of slabs, and are driven downwardly into the particulate foundation material 8, to a sufficient extent that they will s-tand upright. The remaining horizontal courses of slabs are -then laid, by fitting each slab over the appropriate pair of upstanding dowell rods, and lowering it into position. Backfill material 10 is conveniently inserted and compacted periodically behind the retaining wall structure, to fill the space between the rear of the retaining wall, and the slope of undisturbed ground 11 behind the retaining wall, as the height of the retaining wall structure increases. In the case of a relatively low retaining wall, it may be satisfactory to complete the entire wall structure, before adding any backfill, but if the wall is of substantial height, it is preferable to ins-tall and compact the backfill material in stages. The backfill material should include at least six inches of crushed stone or yravel 9, 9~

immediately adjacent the rear surEace of the retaining wall structure. When the final course of apertured slabs (of eight inch width) has been laid, the dowell rods are driven further downward, or the ends are cut off, as required, to eliminate any excess projection of dowell rod which might interfere with the laying of the capping slabs. The capping slabs are then installed to complete the structure. Suitable fill is, of course, also added in fron-t of the retaining wall s-tructure, to bring the surface immediately in front of the retaining wall up to grade level.
It has been found that a wall of substantial height, up to about five feet, wil~ have satisfactory stability, if it incorporates a single course of twenty-four inch wide anchoring slabs, located approximately half-way up the wall.
To provide a satisfactorily stable wall of greater height, up to about eight feet, two vertically spaced courses of twenty-four inch anchoring slabs should be utilized, preferably located approximately one-third, and approximately two-thirds, of the way up the wall.
~0 In practice, it has been found advantageous to utilize slabs having an actual length slightly less than their nominal length. That is, a standard slab of nominal length twenty-four inches, will have apertures spaced twelve inches between centers, but the total length of the slab will be slightly less than twenty-four inches, say twenty~three and seven-eighths inches. To put it another way, the spacing of -the apertures is one-half the nominal length of the slab, but is slightly in excess of one-half the actual length of the slab. ~hen such slabs are assembled into a retaining wall structure, with the apertures of the slabs in ver~ical ~ 9~33 aliynment, there will be small spaces or gaps be-tween the ends of horizontally adjacent slabs. This not only contributes to the flexibility of -the retaining wall structure, but also facilitates drainage of water through -the retaining wall.
Drainage is also faciliated by the use of gravel or crushed rock backfill immediately behind the retaining wall, as previously described, which also impedes the washing out of earth through the retaining wall structure. The importance of making adequate provision for drainage in such structures, is of course well-known to persons skilled in the art.
The capabilities of the system of the present invention may be extended to permit the construction of a pair of mutually interlocked spaced parallel retaining walls, by providing "double-edged" extra-wide anchoring slabs, having two pairs of dowell-receiving apertures, each in suitably spaced relationship to ons edge, so that the anchoring slabs may extend transversely between two suitably spaced parallel walls, interlocking with the dowell rods of both walls, to provide an interlocked double wall structure. Various uses of such a double wall structure will be apparent to persons skilled in the art. For example, if the gradient of the earth being retained by a retaining wall represents a relatively steep slope down to the top of the wall, such a double-wall structure may be desired for extra strength. In such a casel the two parallel walls may both be oriented with their stepped faces towards the rear, and the inner of the two walls may be completely buried in the earth mass. As another example, it may be desired to build a structure consisting of two parallel outwardly-facing walls, with earth fill therebetween, to form an elevated path, i.e. a causeway type structure, or the like.
In the manufacturing of concrete slabs for use in the present invention, it has been found convenient to cast the slabs in strips having a width equal to the desired length of the slabs, and traversed by one or more pairs of aligned upper and lower V-grooves, to define the widths of two or more slabs. Separating the strips at the V-grooves produces slabs in which at least the front edge of the slab consists of upper and lower bevels, and a vertical portion showing exposed aggregate, as previously described. A retaining wall formed from such slabs avoids the appearance of a monolithic concrete structure. This manufacturing method is, of course, optional:
the slabs required for the practice of the present invention may be formed by any suitable concrete forming technique, and the front edges of the slabs may be given a wide variety of forms, to produce various decorative effects.
While a specific description of a par-ticular embodiment, including ac-tual dimensions of structural elements, and similar details, has been provided by way of illustration, it will be understood that actual dimensions, and other such details, are arbitrary, at least within reasonable limits, and variations in or departures from the details of this particular embodiment, obvious to persons skilled in the art, may be made without departing from the scope of the present invention, which is defined in the appended claims.

Claims (14)

The embodiments of the present invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method of constructing a retaining wall comprising a plurality of concrete slabs laid in a plurality of horizontal courses, the method comprising the steps of:
a. providing a plurality of generally rectangular concrete slabs, said slabs being of substantially the same thickness and length, each said slab being provided with a pair of apertures of generally uniform size through the thickness of the slab normal to the top and bottom surfaces of the slab, said apertures being disposed at locations a pre-specified uniform distance from the front edge of each slab, and a pre-specified uniform distance from each end of each slab, such that the distance between centers of the apertures in an individual slab is not less than, and not greatly in excess of, one-half the slab length;

b. providing a plurality of dowell rods of length not less than the projected height of the wall being constructed, and of cross-sectional dimensions such that said dowell rods will fit within said apertures with appreciable clearance;

c. assembling said slabs in combination with said rods so as to form a retaining wall of the dasired aimensions, comprising a plurality of horizontal courses of slabs, wherein vertically adjacent slabs are in half-lapped relationship such that the junctions between the ends of - Page 1 of Claims -slabs in a horizontal course are in alignment with the centers of slabs in each vertically adjacent horizontal course, and wherein the apertures in the slabs co-operate to form continuous apertures extending from top to bottom of the wall, and wherein a dowell rod is installed in each said continuous aperture extending from top to bottom of said wall, whereby said slabs and said dowell rods in combination form a structure which is completely interlocked but which is capable of significant deformation without fracture of any structural elements.

2. The method of claim 1, wherein the plurality of slabs includes slabs of different widths, and the lower portion of the wall is predominantly formed from slabs having a greater width than the slabs predominantly forming the upper portion of the wall.

3. The method of claim 1, wherein the plurality of slabs comprises slabs having three different widths; a lowermost portion of the wall, constituting approximately one-third of the total height of the wall, is predominantly formed from slabs having the greatest of said three widths; an uppermost portion of the wall constituting approximately one-third of the total height of the wall is predominantly formed from slabs having the least of said three widths, and the remainder of the wall is predominantly formed from slabs having the intermediate of said three widths.

4. The method of claim 1, 2 or 3, wherein a horizontal course of slabs having a width substantially greater than the - Page 2 of Claims -widths of the slabs from which the wall is predominantly constructed, is laid at an intermediate location between the top and bottom of the wall.

5. The method of claim 1, 2 or 3, wherein a horizontal course of slabs having a width substantially greater than the widths of the slabs from which the wall is predominantly constructed, is laid at a level of approximately half-way between the top and bottom of the wall.

6. The method of claim 1, 2 or 3, wherein the centers of the apertures in each slab are separated by a distance slightly in excess of one-half the uniform slab length, such that when the slabs are assembled in combination with the dowell rods to form a retaining wall, the adjacent ends of horizontally adjacent slabs are separated by relatively small gaps to permit drainage of water through the assembled retaining wall.

7. The method of claim 1, 2 or 3, wherein the slabs and rods are assembled in combination by:
a. laying a first horizontal course of slabs on a suitably graded bed of particulate material;

b. inserting a dowell rod of suitable length into each aperture in the slabs of said first horizontal course, and driving said rod downwardly into said particulate material to a sufficient extent to support said rod in an upright position; and - Page 3 of Claims -c. laying subsequent horizontal courses of slabs by engaging the apertures of each slab with a pair of upright dowell rods, and lowering the slab into position.

8. A set of components operable to be assembled into a retaining wall structure, comprising, in combination:
a plurality of generally rectangular concrete slabs, said slabs being of substantially the same thickness and length, each said slab being provided with a pair of apertures of generally uniform size through the thickness of the slab normal to the top and bottom surfaces of the slab, said apertures being disposed at locations a pre-specified uniform distance from the front edge of each slab, and a pre-specified uniform distance from each end of each slab, such that the distance between centers of apertures in a slab is not less than, and not greatly in excess of, one-half the slab length, and a plurality of dowell rods of length not less than the height of the wall, and of cross-sectional dimensions such that said dowell rods will fit within said apertures with appreciable clearance, said components being adapted to be assembled into a retaining wall structure wherein said slabs are arranged in a plurality of horizontal courses, vertically adjacent slabs being in half-lapped relationship such that the junctions between the ends of slabs in a horizontal course are in alignment with the centers of slabs in each vertically adjacent horizontal course, the slabs being so positioned that the apertures in the slabs co-operate to form continuous - Page 4 of Claims -apertures extending from top to bottom of the wall, a dowell rod being disposed in each such continuous aperture extending from top to bottom of the wall, whereby the retaining wall structure is completely interlocked but is capable of significant deformation without fracture of any structural elements.

9. The set of components of claim 8, wherein the plurality of slabs includes slabs of different widths, such that the lower portion of the retaining wall structure may be predominantly formed from slabs having a greater width than the slabs predominantly forming the upper portion of the wall structure.

10. The set of components of claim 8, wherein the plurality of slabs comprises slabs having three different widths, in such proportions that a lowermost portion of the wall structure, constituting approximately one-third of the total height of the structure, may be predominantly formed from slabs having the greatest of said three widths; an uppermost portion of the structure, constituting approximately one-third of the total height of the structure, may be predominantly formed from slabs having the least of said three widths; and the remainder of the wall structure may be predominantly formed from slabs having the intermediate of said three widths.

11. The set of components of claim 8, 9 or 10, wherein said plurality of slabs comprises a sufficient number of slabs having a width substantially greater than the widths - Page 5 of Claims -of the slabs from which the wall structure is predominantly constructed, to form a horizontal course of such slabs of substantially greater width, at an intermediate location between the top and bottom of said wall structure.

12. The set of components of claim 8, 9 or 10, wherein the centers of the apertures in each individual slab are separated by a distance slightly in excess of one-half the uniform slab length, whereby, when the slabs are assembled into a retaining wall structure, the adjacent ends of horizontally adjacent slabs are separated by relatively small gaps, to permit drainage of water through said retaining wall structure.

13. The set of components of claim 8, 9 or 10, wherein the slabs for forming the uppermost horizontal course of the interlocked retaining wall structure are all of the same width;
the set of components additionally comprising a plurality of capping slabs having a cross-section in the form of an inverted U, the vertical legs of said inverted U
defining an interior space not less than the width of the slabs for the uppermost horizontal course of the interlocked structure;
said capping slabs being adapted to be laid in a single horizontal course along the top of an interlocked retaining wall structure, such that the uppermost slabs of the interlocked structure are engaged within the inverted U shaped cross-section of the capping slabs.

- Page 6 of Claims

14. The set of components of claim 8, 9 or 10, wherein the front edge of each slab comprises upper and lower bevel portions, and a vertical mid-portion, the mid-portion being characterized by the presence of exposed aggregate.

- Page 7 of Claims -