BACKGROUND OF THE INVENTION U. S. Patent No. 4,668,129 (Babcock et al) discloses a modular precast concrete retaining wall system that utilizes rigid counterfort elements that interact with the surrounding backfill or bulk material to redistribute stresses within the retained soil mass.

Although the wall configurations disclosed in the above referenced patent are capable of providing high stable retaining walls, none of the walls provide a smooth visually unbroken face. This is because the concrete retaining wall panels are supported at each end by bearing directly upon the vertical columns of each adjacent precast concrete counterfort. These column portions must be of sufficient thickness and strength to withstand the transmitted earth loads from the wall panels retaining the earth mass. The wall configurations of U. S. Patent 4,668,129 typically result in substantial protruding vertical columns that are regularly spaced vertically or horizontally along the length of the retaining wall. Many situations preclude the use of such a retaining wall configuration. For example, if directly next to a roadway the protruding vertical concrete columns may be deemed to be a dangerous obstruction or if columns are incompatible with architectural aspects of the facing.

U. S. Patent No. 4,655,646 (Babcock et al), attempts to overcome the problem of exposed vertical counterfort columns by providing configurations that hold prestressed wall panels with horizontal continuous precast concrete beams placed at the base and top of the precast concrete counterforts. While the configurations provided by U. S. Patent 4,655,646 eliminate the vertical counterfort columns the disclosed configurations still do not provide a smooth unbroken architectural face.

Also, the wall configurations of U. S. Patent 4,655,646 require additional precast beam components which are expensive and difficult to transport and handle.

Erection proves most difficult and construction tolerances are greatly reduced.

There are also some prior art retaining wall systems that provide a smooth faced retaining wall structure but none afford the geotechnical engineering benefits of the systems disclosed by U. S. Patents No.

4,668,129 and 4,655,646.

For example, U. S. Patent No. 4,884,921 discloses a modular"T"unit that can be stacked in multiple configurations to create a smooth faced retaining wall system. However, the stacking of these "T"units creates a brick bonded system from the top to the bottom of the wall system. This direct stacking of the modular units without backfill between adjacent vertical units precludes soil arching and provides none of the desired geotechnical benefits disclosed by U. S.

Patent No. 4,668,129.

It would, therefore, be desirable to provide a modular precast retaining wall system that simply and economically provides a smooth faced retaining wall but

maintains the geotechnical design advantages of the wall system of U. S. Patent No. 4,668,129.

SUMMARY OF THE INVENTION _ According to the invention there is provided a retaining wall module comprising a wall panel member having a front and a rear and a footing member mechanically connected to the rear of the panel member by means of mutually engaging members provided on the panel member and the footing member, respectively.

Also according to the invention there is provided a modular wall retaining system comprising a plurality of the retaining wall modules arranged in a row along the ground with the wall panel members in abutting relationship with one another. The modular retaining wall system may comprise a plurality of the rows arranged in tiers.

Further according to the invention there is provided a retaining wall module comprising a pair of opposing wall panel members, each having a front and a rear and provided with a connection member at its rear and a footing member extending between the rears of the wall panel members and being mechanically connected to each wall panel member by means of the connection members.

Further objects and advantages of the invention will become apparent from the description of preferred embodiments of the invention below.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an isometric view, from within a soil mass, of an assembled precast concrete module of the present invention, comprising a panel and a footing member.

Figure 2 is an isometric view showing the footing member of the module of Figure 1.

Figure 3 is an isometric view showing the panel of the module of Figure 1.

Figure 4 is a cross-sectional view of an assembled three tier wall system of one embodiment of the present invention.

Figure 5 is a cross-sectional view of a six tier wall system illustrating the use of tie-backs, anchors, geogrid elements, soil nails and rock anchors in conjunction with the present invention.

Figure 6 is a plan view of one row of the modules of Figure 1.

Figure 7 is an isometric view showing a two- headed fence footing member for use in the implementation of the present invention as a free standing fence or sound wall.

Figure 8 is a cross-sectional view of a tapered three tier wall constructed according to one embodiment of the invention, using the footing member of Figure 7.

Figures 9A, B and C are fractional plan views, respectively showing the orientation of the footing member at different levels of the wall of Figure 8.

Figure 10 is a cross-sectional view of a vertical four tier wall according to another embodiment of the invention, using the footing member of Figure 7.

Figure 11 is an isometric view showing the implementation of the present invention as a free standing single tier fence or sound wall.

Figures 12 through 15 illustrate the assembly sequence for the wall panel and footing member of Figure 1.

Figure 16 is a schematic illustration of resultant load vectors on a typical modular unit of the present invention.

Figure 17 is a perspective view of an implementation of a multi-tier retaining wall using the present invention.

Figure 18 is an isometric view of a panel according to another embodiment of the invention having a connection loop which is not integral therewith.

Figure 19 is another isometric view showing the panel of Figure 18 before attachment of the loop.

Figure 20 is an isometric view of a loop suitable for attachment to the panel of Figure 19.

Figure 21 is an isometric view of a footing member according to another embodiment of the invention.

Figure 22 is another isometric view showing the footing member of Figure 21 being connected to the panel of Figure 19.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Figure 1 shows an assembled retaining wall module 1 of the present invention. The assembled components depicted in Figure 1 comprise a precast concrete wall panel member 2 and a precast concrete footing member 4. Panel 2 is mechanically attached to the footing member 4 by a connecting loop 10 that is an integral component of panel 2. Connecting loop 10 fits into a matching connecting loop groove 20 (Figure 2) that is a manufactured component of footing member 4.

Connecting loop 10 may be made of any structurally suitable material, such as a steel rod or cable, and be incorporated into panel 2 by any conventional method.

Also shown in Figure 1 are compacted backfill material 6 and extension clip 12. Extension clip 12 is a continuous tie-back element which is preferably in the form of a rigid steel rod. It is attached to footing member 4 by looping it into a connecting groove 22 (Figure 2) that is part of footing head 8. Once attached to the footing member 4, extension clip 12 may be used to strengthen and stabilize backfill material 6 or may be connected to a deadman anchor 36, as shown in Figure 5. Footing member 4 is also manufactured with a raised formation 14 to securely lock the retaining wall module 1 into the material backfill 6.

Multiple retaining wall modules 1 can be used to construct numerous retaining wall configurations to meet design requirements. More specific design methods and the geotechnical engineering advantages are

described in U. S. Patent No. 4,668,129 the contents of which has been incorporated herein.

Figure 2 more fully illustrates the footing member 4 of the retaining wall module 1 of Figure 1.

Footing member 4 is of a general rectangular shape with the head portion 8 having an assembly facet 26 and connecting grooves 20 and 22. Footing member 4 is typically manufactured having a flat bottom to facilitate alignment on a graded surface and backfill interaction, respectively. Footing member 4 includes a panel bearing area 24. Head 8 must be of sufficient size and strength to withstand the shear forces imparted by connecting loop 10 (Figure 1) and the shear forces generated by extension clip 12 when used. Panel bearing area 24 is used to effect the final alignment of panel 2 with footing member 4.

Figure 3 more fully discloses panel member 2 of the retaining wall module 1 depicted in Figure 1.

Panel 2 is of general rectangular shape having connecting loop 10 laterally centered on the rear of the panel 2. Panel 2 must be of sufficient thickness and strength to transmit the retained earth loads from panel 2 through the moment connection between connecting loop 10 and panel bearing area 24 to the coupled footing member 4 (Figure 1). The edge cross section of panel 2 may be varied as dictated by design or architectural requirements.

Figure 4 shows a cross section of a typical three tier retaining wall using the retaining wall modules 1 of the present invention. Tier one components 29 are erected on a base excavation 32 and backfill 6 is placed to the level of the base of the next higher tier 31. Tier two components 31 are then erected and

backfill placed up to the base level of the top tier components 33. Finally, backfill 6 is placed for the tier three retaining wall components 33 and compacted to the final grade line 27. Multiple retaining wall r modules as described in Figure 1, comprising panels 2 connected to footing members 4 by connecting loops 10 are used to construct the three tier wall. A clearance 34 is provided between adjacent tiers to allow for vertical movement between the vertically adjacent tiers and is maintained during the construction sequence so that the footing member 4 can react with the backfill 6 to produce the stable retention structure.

Figure 5 illustrates the use of a vertical tiered configuration of the retaining wall modules of Figure 1 in conjunction with additional stabilization devices that may be required by specific retaining wall designs. Again, the retaining wall modules comprise panels 2 connected to footing member 4 by means of connecting loops 10 (Figure 1). In this case, tier 29 is placed at the base of excavation 32 and is anchored to bedrock 41 by rock anchor 42. After the backfill is placed and compacted to a grade at the top of tier 29 the second tier 31 modules are placed and erected. The tier 31 footing members are in this case anchored by soil nails 40 before backfill 6 is placed and compacted for tier 31. Similarly, third tier 33 footing members are anchored by soil nails 40 after being erected. The footing members 4 used as components for tier 29 through tier 33 are designed and manufactured to accept the rock anchors or soil nails and may be field modified as required. Once the backfill 6 is placed to a grade at the top of tier 33, the fourth tier 35 components are erected. The tier 35 retaining wall modules are used in conjunction with a geogrid 38 stabilizing element

attached by placing the footing member 4 over the geogrid 38.

The fifth tier 37, of the retaining wall system, illustrated in Figure 5, incorporates extension clips 12 attached as depicted in Figure 1 to the retaining wall modules to increase stability in the lateral direction. In this case, the lateral resistance provided by the extension clip 12 embedded in backfill 6 is sufficient to provide a required additional lateral resistance.

Finally, for tier six of the wall system, the extension clip 12 attached to the tier six retaining wall modules 39 is also connected to a deadman anchor 36 to generate an additional required lateral resistance after backfill 6 is placed to plan and grade.

A plan view more fully illustrating the use and attachment of an extension clip 12 in conjunction with the retaining wall modules 1 of the present invention is presented in Figure 6 and will be described in more detail below.

Deadman anchors 36 would typically be necessary on the top tiers of walls constructed in high seismic zones or in cases where a wall supports a significant active surcharge load such as a railroad.

The wall system depicted in Figure 5 is a hybrid system specifically chosen to illustrate the use of known techniques and components of the earth retention art with the precast concrete retaining wall module 1 of the present invention.

The use of a geogrid 38 in conjunction with the precast concrete modules 1 of this invention. The required geogrid material 38 is placed on a graded surface and footing members 4 placed on geogrid 38.

Once the footing member 4 has been placed on geogrid 38, the panels 2 are coupled to the footing members 4 by connecting loops 10. The coupling sequence between panel and dart 4 is fully illustrated in Figures 12 through 15 and will be described more fully below.

Figure 7 illustrates a specific variation of the footing member 4 of the present invention. In this embodiment, the footing member is precast having two heads 8, one on each opposing end, to create a fence footing member 46. Both heads 8 of the footing member 46 have associated connecting grooves 20.

The footing member 46 has a pair of opposed longitudinal sides 46.1 and a pair of opposed transverse sides 46.2. The footing member 46 has a third pair of sides 46.3 which are located diagonally opposite each other. In the present embodiment, the sides 46.1,46.2 and 46.3 are slanted, as shown in Figure 7.

The footing member 46 is also provided with a lip 47 extending around its lower periphery. This lip 47 can be removed by knocking it off with a mason hammer, depending on the type of application, as will be described below.

The utility of the fence footing member 46 is that it allows the creation of free standing precast concrete wall structures which may be utilized as fences, median dividers, and sound walls, for material segregation etc.

The outer face of the lip 47 provides a bearing surface 24 for contact with a wall panel member, such as the wall panel member 49, a number of which are shown in Figure 8.

A free standing wall is formed by attaching a pair of opposed panel members 49 at a pair of opposed sides of the footing member 47, as shown in Figure 8.

Each panel member 49 has a connecting loop 10 which is engaged with the groove 20 on the head 8 of the footing member 46. The one panel member 49 is connected to the one head 8 and the opposing panel member 49 is connected to the other head 8.

As can be seen each panel member 49 has a front side 49.1 which is inclined relative to its rear side 49.2 so that when the rear sides 49.2 of a pair of opposed panel members 49 are in a vertical position, the front sides of the panel members 49 are tapered upwardly.

The wall shown in Figure 8 is a three tier tapered wall. In the lowest tier, the footing member 46 is located transversely relative to the panel members 49, so that the lips 47 on the opposed sides 46.2 are in contact with the panel members 49, as shown in Figure 9A.

In the narrower middle tier, the footing member 46 is located diagonally between the panel members 49, so that it is the lips 47 on the diagonally opposed sides 46.3 which are in contact with the panel members 49, as shown in Figure 9B.

In the top tier, which is the narrowest, the footing member 46 is located longitudinally between the

panel members 49 so that it is the lips 47 on the opposed longitudinal sides 46.1 which are in contact with the panel members 49. (For the sake of simplicity, the lip 47 and loops 10 are not shown in Figures 9A, B and C).

As each tier is constructed, backfill 6 is introduced between the wall panels 49 so that the tiers are stacked vertically.

By removing the lip 47, a free standing wall with vertical outside faces can be constructed, as shown in Figure 10. In this case, a bearing surface 24 is provided at the face where the lip 47 has been removed.

The removal of the lip 47 results in the distance between two opposed sides of the footing member 46 to be shortened, resulting in the upper ends of the panel members 49 being spaced further apart, as the panel members 49 are secured in position by means of the backfill 6 which is introduced into the space between them. The effect of this is that the inner sides of the panel members 49 are now diverging outwardly, resulting in the outer sides of the panels being located vertically, as shown in Figure 10. Thus, as one tier after another is added, a wall with a vertical outer face is formed, such as the four tier wall in Figure 10.

In the wall of Figure 10, the opposed transverse sides 46.2 are in contact with the panel members 49 so that the footing member 46 is located transversely, but walls of different thickness can be constructed by orienting the footing member 46 diagonally or longitudinally, as shown in Figures 9B and 9C, respectively.

Figure 11 shows an isometric cut-away drawing of a single tier free standing wall construction using a differently shaped footing member 51. Panels 2 (or 49) are coupled to both ends of the footing member 51 by the connecting loops 10 that are hooked over each head 8.

The panels 2 bear on the panel bearing area 24.

Backfill 6 is placed, to a design elevation, between panels 2 for added mass and increased stability. A fence cap 48 covers and joins the two opposing panels 2.

In the fence or free standing wall configuration horizontal earth loads are substantially decreased by the reduced volume of backfill 6. This allows significantly taller panels to be supported in the fence configurations. The design width of fence footing member 51 and/or the batter angle of panel bearing surface 24 can be varied as desired and provide the degree of versatility necessary to create structures of varied geometries. For example, a structure having a trapezoidal cross section may be built by stacking fence footing members 46 of decreasing width.

Although not shown, a cap 48 may also be used to cover the opposing panels 49 in the top most tier of the walls of Figures 8 and 10.

Figures 12 and 15 are a series of sequential illustrations detailing the assembly method for the retaining wall module 1. The panel 2 is mechanically coupled, at its lateral center point, to footing member 4 by connecting loop 10. A necessary requirement to create a secure rigid coupling of panel 2 with footing member 4 is that connecting loop 10 be firmly fixed into connecting loop groove 20. Figure 12 depicts the two components prior to assembly. The footing member 4 is positioned to line and grade and any required extensions clips are connected to footing member 4 at

connecting groove 22. The panel 2 is then supported above and at an angle to the footing member head 8 with a hand truck, a crane, or manually, depending upon the size and weight of panel 2. The panel positioning r depicted in Figure 12 facilitates hooking connecting loop 10 in connecting groove 20 on the head 8 of footing member 4 as illustrated in Figure 13. Figures 13 and 14 also illustrate the utility of assembly facet 26 which allows panel 2 to rotate to a vertical position without impinging upon footing member head 8 while keeping connecting loop 10 securely seated in connecting groove 20.

Figure 15 illustrates a completely assembled retaining wall module 1 of the present invention. Loads from panel 2 are transferred to footing member 4 at the panel bearing area 24. When required by design, an extension clip may be attached to footing member 4 at connecting groove 22 during assembly of the retaining wall module 1.

Figure 16 is a schematic cross-section of a single tier retaining wall, using the retaining wall module 1 of this invention, that illustrates the resultant force vectors generated by earth loads upon the assembled and backfilled module. Backfill 6 is placed in excavation 32 covering footing member 4 and is retained by panel 2. Backfill 6 having specific design characteristics exerts lateral force 50 on panel 2 which is transferred to footing member 4 through connecting loop 10 and vertical force 51 on footing member 4. The lateral force 50 is opposed by friction force 54 that is generated as a result of material reactions to loading from backfill 6. Geotechnical design insures that satisfactory design factors of safety are maintained for each specific retaining wall installation. A detailed

description of geotechnical design procedures is disclosed by U. S. Patent No. 4,668,129.

Figure 17 is a perspective view of a completed retaining wall of retaining wall modules 1 of the present invention and illustrates the smooth unbroken architectural wall face 58 that is achieved with the invention.

Figure 18 shows an isometric view of a panel 60, similar to the panel 2 of Figure 3, but with a connecting loop 62 which is not integral with the panel 60.

The panel 60 is provided with a pair of recesses 64 in its rear, each recess 64 being provided with a connection pin 66, as shown in Figure 17. The loop 62 is configured into a hook 68 at each end (see Figure 20) for engagement with the connection pins 66.

The loop 62 may therefore be attached to the panel 60 at the construction site, thereby facilitating transportation of the panel 60.

In another embodiment, a footing member 70 is provided which has hooks 72 which are integral therewith, as shown in Figure 21.

The footing member 70 is attached to the panel 60 by engaging the hooks 72 with the connecting pins 66.

This is achieved by initially locating the footing member 70 in an inclined position relative to the panel 60, as shown in Figure 22, engaging the hooks 72 with the pins 66 and then lowering the footing member 70 to lock it in position.

The present invention provides a novel and unique method and apparatus for building precast concrete retaining walls having architecturally uniform wall faces while using a geotechnically preferred design procedure. The necessary precast concrete components (footing member and panel) assemble to make a standardized retaining wall module that can be used to create many and varied retention structures. A special fence footing member component allows the invention to be used to build free standing median dividers, fences, and sound walls. Unlike prior retaining walls of this type the present invention allows the coupling of the panel to the footing member (counterfort) to be made at the lateral mid-point of the panel. The structural forces are therefore concentrated toward the center of the precast panel where it is most desirable structurally. Previous walls of this type effected the load transfer between panel and counterfort at the panel edges where it is difficult and expensive to provide the necessary structural reinforcement.

The foregoing description of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and other modifications may be possible in light of the above teachings. The embodiment was chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and various modifications as are suited to the particular use contemplated. It is intended that the appended claims be construed to include other alternative embodiments of the invention, except insofar as limited by the prior art.