Abstract:
A modular earth retaining wall system comprising a plurality of similarly configured wall blocks that have lock channels and lock flanges that provide a locking mechanism for resisting leaning or toppling of the blocks. A positive retaining mechanism is also provided for attaching reinforcement fabrics to the retaining wall in between mating courses of wall blocks. This mechanism secures the reinforcement fabrics in place and permits the fabrics to extend along the entire contact area between adjacent stacked wall blocks to avoid an aggregate leaning effect. The retaining mechanism includes a retaining bar that is placed on top of the reinforcement fabric within the lock channel. The retaining bar holds the fabric against a wall of the lock channel in response to tensile loads applied to the fabric to prevent it from being pulled out of the retaining wall.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a continuation of U.S. patent application Ser. No. 09/049,627, filed Mar. 27, 1998, now U.S. Pat. No. 6,338,597 which is hereby incorporated by reference in its entirety into the present disclosure. 
    
    
     FIELD OF THE INVENTION 
     The invention relates generally to earth retaining walls. More particularly, the invention relates to a modular retaining wall system composed of a plurality of wall blocks that are provided with locking means for precluding forward leaning or tipping of the blocks. Further, the invention pertains to retaining means for attaching reinforcement members to the retaining wall in between mating courses of wall blocks formed in the retaining wall. 
     BACKGROUND OF THE INVENTION 
     Modular earth retaining walls are commonly used for architectural and site development applications. Such walls are subjected to very high pressures exerted by lateral movements of the soil, temperature and shrinkage effects, and seismic loads. Therefore, the backfill soil typically must be braced with tensile reinforcement members. Usually, elongated structures, commonly referred to as geogrids or reinforcement fabrics, are used to provide this reinforcement. Geogrids are often configured in a lattice arrangement and are constructed of a metal or polymer while, reinforcement fabrics are constructed of a woven or nonwoven polymer fiber. These reinforcement members typically extend rearwardly from the wall and into the soil to stabilize the soil against movement and thereby create a more stable soil mass which results in a more structurally secure retaining wall. 
     Although several different forms of reinforcement members have been developed, difficulties remain with respect to attachment of the members to retaining walls. In particular, the reinforcement members can shift out of position and be pulled out from the retaining wall due to movement of the soil. This difficulty can be especially problematic in areas of high seismic activity. In response to this problem, several current retaining wall systems have been developed to retain geogrid reinforcement members. Rake shaped connector bars are transversely positioned in the center of the contact area between adjacent stacked blocks with the prongs of the connector bar extending through elongated apertures provided in the geogrid to retain it in place. Despite adequately holding the geogrid in position under normal conditions, this system of attachment provides a substantial drawback. Specifically, the geogrids of the system only extend along the back halves of the contact areas between the blocks. Although the geogrids are relatively thin, this partial insertion of the geogrids can cause the retaining wall to bow outwardly due to the aggregate thickness of the geogrids. As can be appreciated, this outward bowing can be substantial with tall retaining walls that require a multiplicity of geogrids. Aside from creating the impression of instability, this condition increases the likelihood of wall failure, particularly in response to seismic activity. 
     Another problem associated with the construction of modular retaining walls is securement of the blocks to each other within the wall. Various connection methods are currently used in retaining wall construction to interlock the blocks. In one known system, blocks having bores inwardly extending within their top and bottom surfaces are provided for the receipt of dowels or pins. In addition to limiting shifting of the blocks, these pins are used to retain geogrids. Where a geogrid is to be inserted between two courses of stacked blocks, the pins are inserted into the bores with the pins extending through the apertures of the geogrid. Although providing some resistance against block shifting, the actual strength of the block-to-block connection is generated by the friction between the block surfaces. Therefore, shifting can occur. Moreover, the pins do not lock the upper blocks to the lower blocks. Accordingly, severe seismic activity can cause the upper blocks to jump from their foundations and topple downward. Additionally, when the pins are made of metal, they will corrode over time due to the infiltration of moisture from the surrounding environment. 
     In another known retaining wall, an upper surface of the blocks includes a projection and a lower surface of the blocks includes a cavity into which the projection can extend. Although the provision of these projections and cavities avoids the corrosion problem associated with the pins of the previously described system, similar to that system, no positive locking mechanism is provided to retain the upper blocks on top of the lower blocks. Therefore, this system is susceptible to toppling in response to strong seismic activity. In addition, construction of the walls is complicated by the fact that the top course of blocks must be held in place when the backfill soil is poured to prevent the blocks from being pushed over the edge of the wall. 
     It can therefore be appreciated that there exists a need for a mechanically stabilized wall system having secure retaining means for maintaining reinforcement members in their proper positions within the wall. Accordingly, it is to the provision of such an improved mechanically stabilized retaining wall system that the present invention is directed. 
     SUMMARY OF THE INVENTION 
     The present invention provides a mechanically stabilized wall system having secure retaining means for maintaining reinforcement members in their proper positions within the retaining wall. Retaining walls constructed in accordance with the invention comprise a plurality of wall blocks that are stacked on top of each other in a plurality of ascending courses. Generally, each of the wall blocks is substantially identical in size and shape to simplify block fabrication and wall construction. Therefore, each of the blocks comprises an exterior face, an interior face, a top surface, a bottom surface, and opposed sides. The exterior faces of the blocks form the exterior surface of the retaining wall and typically are provided with an ornamental facing. In addition, the exterior face of each block normally slopes inwardly from the bottom surface to the top surface of each block. 
     The top and bottom surfaces of the blocks are typically parallel to each other such that the blocks can be stacked atop each other to form an upright wall. Similarly, the opposed sides of the blocks are normally parallel to each other such that a straight wall will be formed. The top and bottom surfaces of each block are provided with a lock channel and lock flange, respectively. The lock channel is defined by a front wall, a rear wall, and a channel bottom surface and the channel typically extends transversely across the top surface of each wall block. The front wall of this channel forms a frontal lip that extends obliquely toward the exterior face of the wall block. The frontal lip is normally curved such that a first substantially arcuate edge of the channel is formed. Positioned opposite the front wall, the rear wall of the lock channel extends obliquely toward the interior face of the wall block. Like the front wall, an upper extent of the rear wall is typically curved so as to form a second substantially arcuate edge of the lock channel. Provided in the channel bottom surface is a longitudinal notch that usually extends the full length of the lock channel. 
     The lock flange is defined by a front surface, a rear surface, and a top surface and typically extends transversely across the bottom surface of the wall block. Each of the front and rear surfaces extend obliquely toward the exterior face of the wall block such that the lock flange itself extends obliquely towards the exterior face. The front surface of the flange is specifically sized and shaped for mating engagement with the front wall and frontal lip of the lock channel. 
     Positioned between at least one pair of mating courses of wall blocks is a reinforcement member. This reinforcement member is of known construction and typically extends from the exterior surface of the retaining wall, into the lock channel, and past the interior surface of the retaining wall to extend into the soil. Placed on top of the reinforcement member in the lock channel is a retaining bar which secures the reinforcement member in place between the courses of the wall. The retaining bar is sized and shaped for easy insertion into the lock channel. In a preferred arrangement, the retaining bar has a top surface, a bottom surface, a first upright surface, a second upright surface, a first oblique surface, and a second oblique surface. Normally, the top and bottom surfaces are parallel to each other as are the first and second oblique surfaces. Configured in this manner, the retaining bar fits closely between the front and rear walls of the channel so that the first upright surface and the second oblique surface of the retaining bar hold the reinforcement member against the front and rear walls of the channel, respectively. So disposed, the retaining bar prevents the reinforcement member from being removed from the retaining wall. 
     In constructing a retaining wall according to the present invention, a plurality of starting blocks are usually aligned along the length of a leveling pad formed on the construction site. Each of the starting blocks is provided with a lock channel in its top surface just as the above described wall blocks. However, since the starting blocks form the first course of the wall, they need not be provided with lock flanges. 
     After the starting course has been formed, the first course of wall blocks is constructed. Each of the wall blocks is placed on top of one or more starting blocks with the lock flanges of each wall block extending into the lock channels of the lower blocks. The upper blocks are then slid forward along the starter blocks until the lock flanges of the upper blocks engage the front walls of the lock channels provided in the starter blocks. Specifically, the front surface of the lock flanges and frontal lip of the lock channels mate such that the lock flanges extend underneath the frontal lips. This mating relationship holds the wall blocks in place atop the starter blocks and prevents them from tipping forward, thereby providing an integral locking means for the blocks. After the first course of wall blocks has been formed, the backfill soil can be poured into place behind the blocks. In that the blocks are locked into place with the mating relationship of the frontal lips and lock flanges, the pouring of the soil can be accomplished without having to provide additional stabilization to the blocks to prevent them from toppling forward. 
     Once the proper amount of soil has been poured, additional courses are laid in the manner described above. Typically, a reinforcement member is laid between every other course of blocks, although it will be appreciated that greater or fewer reinforcement members can be provided depending upon the particular reinforcement needs of the construction site. As noted above, the reinforcement member is positioned so that it extends from the exterior surface of the wall and into the lock channel before extending into the backfill soil. To lock the reinforcement member between the courses, a retaining bar is placed on top of the reinforcement member in the lock channel. When the next course of blocks is laid, the lock flange of the upper blocks extend into the lock channels so that they are positioned adjacent the retaining bar. When a tensile force is applied to the reinforcement member from the soil side of the retaining wall, the retaining bar is urged towards the interior surface of the retaining wall, causing the second oblique surface to press the reinforcement member against the rear wall of the channel, locking it in place. 
     The objects, features, and advantages of this invention will become apparent upon reading the following specification, when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a retaining wall formed in accordance with the present invention. 
     FIG. 2 is a perspective front view of a wall block used in the present system. 
     FIG. 3 is a perspective rear view of the wall block shown in FIG.  2 . 
     FIG. 4 is a detail view of a lock channel provided in a top surface of the wall blocks. 
     FIG. 5 is a detail view of a lock flange provided on a bottom surface of the wall blocks. 
     FIG. 6 is a side view of a reinforcement member retaining bar used in the present system. 
     FIG. 7 is a partial side view of a wall block depicting insertion of a retaining bar over a reinforcement member within a lock channel of the wall block. 
     FIG. 8 is a cross-sectional view of an example retaining wall constructed in accordance with the present invention. 
     FIG. 9 is a detail view showing the retention of a reinforcement member between adjacent stacked wall blocks. 
    
    
     DETAILED DESCRIPTION 
     Referring now in more detail to the drawings, in which like numerals indicate like parts throughout the several views, FIG. 1 illustrates the general concept of a modular retaining wall  10  constructed in accordance with the present invention. As depicted in this figure, the retaining wall comprises a plurality of wall blocks  12  that are stacked atop each other in ascending courses  14 . When stacked in this manner, the wall blocks together form an exterior surface  15  which faces outwardly away from the soil, and an interior surface  17  which faces inwardly toward the soil. 
     Generally speaking, the blocks  12  are substantially identical in size and shape for ease of block fabrication and wall construction. Accordingly, each block is provided with a lock channel  16  and a lock flange  18  that are configured so as to mate with each other when the blocks are stacked atop one another to form the retaining wall  10 . When the blocks are aligned side-by-side within each course as shown in FIG. 1, the lock channels  16  form a continuous lock channel that extends the length of the lower of the mating courses. Similarly, the lock flanges form a continuous lock flange that extends the length of the upper of the mating courses. Accordingly, the blocks can be stacked in a staggered arrangement as shown in FIG. 1 to provide greater stability to the wall. In addition to providing for correct alignment of the blocks of each course, the lock channels and lock flanges preclude forward leaning or toppling of the blocks. Therefore, the lock channels and lock flanges serve as integral locking means for positively locking the blocks together. 
     Positioned between two mating courses of wall blocks is a reinforcement member  20 . The reinforcement member is of known construction and typically extends from the exterior surface  15  of the retaining wall  10  and into the backfill soil S. Specifically, the reinforcement member extends from the exterior surface  15 , into the lock channel  16 , and past the interior surface  17  of the retaining wall to extend into the soil. Placed on top of the reinforcement member in the lock channel  16  is a retaining bar  22 . This retaining bar secures the reinforcement member in place between the courses of the retaining wall and therefore forms part of retaining means for securing the reinforcement member in place with respect to the retaining wall. In that a continuous lock channel is formed by the blocks, a single elongated retaining bar can be used. However, it will be understood that several shorter retaining bars could be used if desired. 
     Having generally described type of retaining wall that can be constructed in accordance with the present disclosure, a detailed description of the wall blocks will now be provided. Referring to FIGS. 2 and 3, each wall block  12  comprises an exterior face  24 , an opposed interior face  26 , a top surface  28 , a bottom surface  30 , and two opposed sides  32 . As briefly identified above, the exterior faces of the blocks form the exterior surface of the retaining wall. Accordingly, the exterior faces are typically provided with an ornamental facing to create a visually pleasing facade. Also, the exterior face  24  of each wall block usually is sloped inwardly from the bottom surface  30  to the top surface  28  in an incline ratio of approximately 30 to 1. This inward slope creates an aggregate inward slope effect over the entire retaining wall which counteracts the outward leaning impression commonly created by such walls when viewed by the observer. Contrary to the exterior face, the interior faces  26  of the wall blocks are configured in an upright orientation and, therefore, form the upright interior surface of the retaining wall. Normally, the blocks are approximately 15 inches tall and 8 inches wide, although it will be appreciated that almost any size block can be formed in accordance with this disclosure. 
     The top and bottom surfaces  28  and  30  of each block are typically parallel to each other so that, when stacked on top of one another, an upright wall is formed. Similar to the interior faces  26 , the opposed sides  32  are typically parallel to each other. However, the opposed sides can be inwardly tapered from the exterior face of the block to the interior face of the block to form curved walls of nearly any shape. Further provided in the wall blocks are interior openings  34 . These openings reduce the amount of materials needed to fabricate the blocks and reduces the weight of the blocks to simplify wall construction. 
     As described above, the top and bottom surfaces of each block are provided with a lock channel  16  and lock flange  18 , respectively. Illustrated in FIG. 4, the lock channel  16  is defined by a front wall  36 , a rear wall  38 , and a channel bottom surface  40  and extends transversely across the top surface  28  of each wall block. The front wall forms a frontal lip  42  that extends obliquely toward the interior face  26  of the wall block  12 . As indicated in the figure, the oblique extension of the frontal lip begins at a point approximately halfway along the height of the front wall  36 . The lip is normally curved such that a first substantially arcuate edge  44  of the channel is formed. Positioned opposite the front wall, the rear wall  38  of the lock channel  16  extends obliquely toward the exterior face  24  of the wall block  12 . Like the front wall, an upper extent of the rear wall is curved so as to form a second substantially arcuate edge  46  of the lock channel. Provided the channel bottom surface  40  is a longitudinal notch  47 . This notch typically extends the full length of the lock channel and, as will be described below, facilitates insertion of a reinforcement member retaining bar. 
     Illustrated in FIG. 5 is the lock flange  18 . As indicated in this figure, the lock flange is defined by a front surface  48 , a rear surface  50 , and a top surface  52  and the flange extends transversely across the bottom surface  30  of the wall block. Similar to the rear wall  38  of the lock channel, both the front surface  48  and the rear surface  50  extend obliquely toward the exterior face  24  of the wall block  12  such that the lock flange  18  itself extends obliquely towards the exterior face  24  of the block. To provide for the locking function noted above, the front surface  48  of the block is specifically sized and shaped for mating engagement to the front wall  36  of the lock channel  16 . Accordingly, during wall construction, the wall blocks can be placed on top of lower wall blocks such that the lock flanges extend into the lock channels. Once so situated, the upper wall blocks can be slid forward along the lower blocks so that the front surfaces  48  of the lock flanges  18  abut the front walls  36  of the lock channels. As will be described below, it is this abutment that prevents the block from leaning forward or toppling. 
     Although capable of alternative construction, the wall blocks  12  are preferably formed of pre-cast concrete. As is known in the art, the blocks are commonly mixed in a hatching plant in a high-speed process. Cement, aggregate, and water are mixed in a hopper to form a concrete mixture which is poured into a mold box to form the blocks. To increase block output of this process and simplify the block forming process, typically a multiple block mold is used. In particular, the mold is configured to form one continuous piece from which several blocks will be made. Once the piece is formed, the individual blocks are separated from the extended piece with a splitter that slices through the piece. In this manner, the number of mold fillings and compactions per block is reduced, increasing fabrication productivity. This splitter also typically gives the exterior face of the block a rough split-stone appearance. 
     The reinforcement member retaining bar  22 , shown most clearly in FIG. 6, is specifically shaped and configured to fit within the lock channel  16 . In a preferred arrangement, the retaining bar  22  has six different surfaces: a top surface  54 , a bottom surface  56 , a first upright surface  58 , a second upright surface  60 , a first oblique surface  62 , and a second oblique surface  64 . Normally, the top surface and the bottom surface are parallel to each other as are the first oblique surface and the second oblique surface. Similarly, the first upright surface and the second upright surface are typically parallel to each other such that the first upright surface extends perpendicularly from the upper surface and the second upright surface extends perpendicularly from the bottom surface. Configured in this manner, the retaining bar can be positioned on top of a reinforcement member  20  in the lock channels  16  by inserting the retaining bar into the channels with the second upright surface  60  forward, and twisting the bar downward into place as depicted in FIG.  7 . In that the bar is designed to fit closely between the front and rear walls of the channels when in place, the longitudinal notch  46  provides a void that accommodates the second upright surface to facilitate the twisting and downward insertion of the bar. 
     Once correctly inserted within the lock channel, the first upright surface  58  and the second oblique surface  64  of the retaining bar hold the reinforcement member  20  against the front and rear walls of the channel, respectively, as shown in FIG.  7 . So disposed, the retaining bar prevents the reinforcement member from being pulled out from the retaining wall. Specifically, when a tensile force is applied to the reinforcement member from the soil side of the retaining wall, the retaining bar is urged towards the interior surface of the retaining wall, causing the second oblique surface  64  to press the reinforcement member against the rear wall  38  of the channel, locking it in place. In that the amount of pressure that must be applied by the retaining bar is not large, the retaining bar can be constructed of a polymeric material such as nylon  66  or high density polyethylene. Usage of such polymers provides the additional advantages of being lightweight and therefore easy to manipulate, and chemically inert and therefore resistant to corrosion. 
     Several different types of reinforcement members are currently available. For example, both metal and polymeric geogrids are in manufacture. In the present system, however, the selected reinforcement member must be adequately flexible to permit insertion of the reinforcement member into the lock channel and subsequent insertion of the retaining bar. Furthermore, the selected reinforcement member, like the retaining bar, should be constructed of an inert material which will resist rusting or other corrosion. Accordingly, it is preferred that the reinforcement member comprise a flexible fabric composed of a polymeric material such as polypropylene or high tenacity polyester. 
     The system of the present invention can be used to construct any number of different configurations of modular retaining walls. FIG. 8 illustrates one example of such a retaining wall  64 . To construct such a wall, a leveling pad  66  is laid to provide a foundation upon which to build the wall. Typically, this leveling pad comprises a layer of compacted crushed stone that is embedded under the soil to protect the wall foundation. Once the leveling pad is laid and compacted, a plurality of starting blocks  68  are aligned along the length of the pad. Each of the starting blocks is provided with a locking channel in its top surface. However, since there are no lower courses with which to engage, the starter blocks are not provided with lock flanges. Additionally, the starting blocks are only approximately half as tall as the wall blocks and are therefore approximately 7.5 inches in height. Although such starting blocks are typically used in the starting course of the retaining wall, it is to be noted that the standard wall blocks  12  could be used to form this course if a groove is provided in the leveling pad to accommodate the lock flanges of the blocks. As is evident from FIG. 8, the starting course of the wall is normally embedded underground along with the leveling pad. 
     After the starting course has been formed with either the starting blocks  68  or wall blocks  12 , the next course of blocks can be laid. The wall blocks are placed on top of the blocks of the starting course with the lock flanges  18  of each block extending into the lock channels  16  of the lower blocks. Once so positioned, the upper blocks are slid forward along the lower blocks until the lock flanges engage the front walls  36  of the lock channels  16  provided in the lower blocks. As can be appreciated from FIG.  8  and with reference to FIGS. 4 and 5, the front surfaces  48  of the lock flanges mate with the frontal lips  42  of the lock channels such that each lock flange  18  extends underneath the frontal lips. This mating relationship holds the wall block in place atop the lower block and prevents it from tipping forward, thereby providing integral locking means for the block. 
     Once the first wall course has been formed atop the starting course, backfill soil S can be poured into place behind the blocks. Typically, a non-woven filter fabric  70  is provided between the wall and the backfill soil to prevent the introduction of particulate matter between the courses of blocks due to water migration within the soil. Alternatively, a layer of gravel aggregate can be provided between the wall and the soil to serve the same function. 
     Additional ascending courses are thereafter laid in the manner described above. Although alternative configurations are possible, a reinforcement member is typically laid between every other course of blocks as indicated in FIG.  8 . It will be appreciated, however, that more or fewer reinforcement members can be provided depending upon the particular reinforcement needs of the construction site. Preferably, these reinforcement members  20  are composed of a flexible polymeric fabric. As described above, the reinforcement member is positioned so that it will extend from the exterior surface  15  of the retaining wall, into the lock channel  16 , and past the exterior surface  17  of the retaining wall to extend into the soil. As shown most clearly in FIG. 9, a reinforcement member retaining bar  22  is placed on top of the reinforcement member  20  in the lock channel  16 . When the next course of blocks  12  is laid on top of the lower course, the lock flange  18  of the upper blocks will extend into the lock channel  16  and will be positioned adjacent the retaining bar. 
     Construction of the retaining wall  65  continues until the desired height is attained. As indicated in FIG. 8, the inward slope of the wall blocks creates a net inward slope of the retaining wall. Additionally, the configuration the blocks creates an aesthetically pleasing stepped appearance for the exterior surface of the wall. Where the full height of a wall block  12  is unnecessary or not desired, short wall blocks  74  can be used to form the top course. Typically, these short wall blocks are approximately 7.5 inches in height, one half the height of the standard wall blocks  12 . Once the retaining wall has been raised to the required height, cap blocks  72  can be used to complete the wall. As shown in FIG. 8, these cap blocks  74  are provided with a lock flange, but do not have an upper lock channel in that further construction will not be conducted. Normally, the cap blocks are fixed in position with concrete adhesive and the top surface of the cap blocks are provided with an ornamental pattern similar to the exterior faces of the blocks. The cap block is designed to extend out over the lower block to provide a lip for aesthetics. Additionally, a subsurface collector drain  76  can be provided within the backfill soil to remove excess water collected therein. 
     While preferred embodiments of the invention have been disclosed in detail in the foregoing description and drawings, it will be understood by those skilled in the art that variations and modifications thereof can be made without departing from the spirit and scope of the invention as set forth in the following claims. For instance, as briefly referenced above, the sides of the blocks can be tapered inwardly to form a curved wall. As will be appreciated by those having skill in the art, when such a curved wall is constructed, the reinforcement member retaining bar will likewise need to be curved or angled if the builder wishes to extend reinforcement members from the blocks of the curved portions of the wall.