Abstract:
A retaining-wall block has a set of liquid impervious walls defining a completely bounded cavity having a sealable opening for filling the cavity with a fill material to add weight, and a seal element for sealing the sealable opening. In some cases the block has a second cavity with openings for collecting liquid and for passing collected liquid out of the second cavity to adjacent blocks in an assembly.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to block retaining walls, and pertains more particularly to wall blocks, systems for assembly, and drainage systems utilized for construction of such retaining walls.  
       BACKGROUND OF THE INVENTION  
       [0002]     Many known systems and methods have been developed in the construction industry for forming block retaining walls constructed for such purposes as hillside erosion control, substantial ground elevation changes in landscaping, and so on. In conventional art such retaining walls are constructed with blocks usually formed of heavy, high-density material, typically concrete. In some applications the blocks may be formed of solid stone material cut from a base stone material.  
         [0003]     A disadvantage common to conventional retaining wall blocks is that, due to the dense properties of the concrete or stone materials forming the block, a single conventional retaining wall block is a heavy object in itself, often 70-100 pounds or more for a commonly sized block, difficult for many to lift and handle conveniently. Another inherent disadvantage in such heavy blocks is that, since transportation costs of such materials is directly affected by the weight of the transported materials from the store outlet or manufacturing site of the new blocks to a final destination, transportation is often cost prohibitive, particularly when the work site is located in a substantially distant geographic location from the source of the heavy blocks.  
         [0004]     Construction of most larger retaining walls, such as those designed for retaining hillsides, particularly ones which may, at times, have substantial water drainage needs, usually involves a substantial amount of ground excavation and preparation along and behind the proposed line of the wall, and then layering successive layers of back fill and drain fill materials, and often other supplemental drainage systems which may be required for proper drainage behind the retaining wall, along with successive rows of retaining wall blocks. A drainage pipe, or “tile” as it is commonly known in the industry, is commonly utilized for displacement of water which has drained down to the lower row of the retaining wall blocks, channeling the water draining into the drainage tile from above, along the base of the retaining wall, usually behind the retaining wall base layer, and eventually outside of the retaining wall area. In some extreme water situations such as when retaining walls are located near and below bodies of water or above-ground or below-ground streams, or in geographic areas with high annual rainfall, where sudden and intense rainfall may greatly increase the water saturation of the ground being retained in a short period of time, additional vertical drainage columns are employed to add increased drainage capability to the system.  
         [0005]     Retaining wall block designs known in the art have addressed the problem of the heavy weight of individual concrete or stone building blocks by the development in the industry of lighter-weight, modular building blocks, some also adapted for receiving heavy fill material into a hollow cavity within the block. A block of this sort is taught in U.S. Pat. No. 5,658,098, issued to inventor Mark A. Woolbright on Aug. 19, 1997. The surface area behind a finished retaining wall utilizing such waterproof blocks forms a waterproof wall, through which water draining down from the ground and fill materials, and possibly accumulating behind the retaining wall, cannot pass. In some instances extreme drainage flow may cause water to drain through the soil and drain fill and backfill materials at a rate that is greater than that of the drainage capacity of the entire system, which may cause an elevated water level behind the retaining wall, particularly if the undisturbed soil behind the wall has been previously saturated. In such instances when drainage capacity is suddenly exceeded, the sudden excess water flow has nowhere else to accumulate but upward from the bottom of the retaining wall as the fill material fields continue to fill with drainage overflow water.  
         [0006]     What is clearly needed is a retaining wall block and drainage system having the advantages of the individual block being of a substantially lighter weight compared to conventional concrete or stone retaining wall blocks, thereby greatly increasing the cost-effectiveness of transportation and handling of the blocks between the source and the work site, while also providing means for increasing the drainage capability of the retaining wall drainage system. Such an improved system also incorporates both additional drainage capacity into the individual building blocks, and additional drainage capacity for water draining through the drain fill and back fill materials behind the wall that when combined, provide far greater drainage capacity than systems of conventional art as described above. The individual, lightweight, drainage-capable building blocks of the system of the invention are adapted for receiving heavy fill material at the work site, causing each individual block to be of sufficient weight for construction of a retaining wall according to industry standards.  
         [0007]     The additional drainage capability provided in such a retaining wall block and drainage system provides advantages over conventional systems by enabling one to economically increase the overall drainage capacity of the system so as to accommodate much greater fluctuations in drainage flow due to heavy rains, and so forth, thereby also greatly reducing the amount of ground excavation and preparation necessary prior to wall construction, because much shallower drain fill and free-draining back fill fields are required behind the retaining wall due to the increased drainage capacity incorporated into the blocks of the retaining wall. Such a system therefore greatly increases the cost-effectiveness of overall construction of the retaining wall and draining system, and also that of transporting and handling the retaining wall blocks and back fill and drain fill materials, by reducing the needed amount of such materials, which are typically provided from outside of the work site, and also by eliminating the need for various separate horizontal or vertical drain conduit systems which are required in many applications utilizing conventional retaining wall blocks.  
         [0008]     The wall block and drainage system of the present invention addresses all of the above-described problems in the prior art by providing means for increasing drainage capacity in a retaining wall drainage system utilizing for the first time new and novel drain-capable lightweight retaining wall blocks and drainage systems in embodiments which are described below in enabling detail.  
       SUMMARY OF THE INVENTION  
       [0009]     In a preferred embodiment of the present invention a retaining-wall block is provided, comprising a set of liquid impervious walls defining a completely bounded cavity having a sealable opening for filling the cavity with a fill material to add weight, and a seal element for sealing the sealable opening. In some embodiments the blocks are formed of polymer material by injection molding. It is known to the inventor that the blocks can be made of any other waterproof material. It is also known to the inventor that the blocks can be made of any non-waterproof material incorporating a waterproof insert. In some embodiments the block has a curved (or any other shaped) front simulating a stone material, concrete, wood or any other material. There may also be engagement elements for engaging adjacent blocks in an assembly to limit movement between the adjacent blocks.  
         [0010]     In an alternative preferred embodiment the completely bounded cavity is a first cavity, and there is further a second cavity adjacent the first cavity, separated from the first cavity by at least one of the liquid-impervious walls, the second cavity having through-openings to the outside of the block for accepting drainage liquids, and for passing said liquids out of said second cavity into the blocks below or a drainage system.  
         [0011]     In a preferred embodiment the block is formed of polymer material by injection molding. In an alternative embodiment the through-openings include openings on an upper surface to accept liquid from a second block above in an assembly of blocks, openings in a rearward-facing surface to accept liquid from a drain field, and openings in a lower surface for passing liquids to a third block below in an assembly of blocks. There may further be an engagement interface for engaging a drain grid comprising both a mesh material and conduits for liquid, wherein individual ones of the through-openings are positioned to engage individual ones of the conduits.  
         [0012]     In some cases the through-openings include openings on an upper surface to accept liquid from a second block above in an assembly of blocks, openings in a rearward-facing surface to accept liquid from a drain field, at least one opening in a first side to accept liquid from an adjacent block in the assembly of blocks, and at least one opening in a second side opposite the first side to pass collected liquid to an adjacent block in the assembly.  
         [0013]     In another aspect of the invention a retaining wall assembly of blocks is provided, comprising a plurality of individual hollow blocks, individual ones of said blocks comprising a set of liquid impervious walls defining a completely bounded cavity except for a fill opening and filled with a fill material to add weight. In preferred embodiments individual ones of the blocks in the assembly are formed of polymer material by injection molding. Also in preferred embodiments individual blocks have engagement elements used for engaging adjacent blocks in the assembly to limit movement between the adjacent blocks.  
         [0014]     In an alternative preferred embodiment, in individual ones of the blocks, the completely bounded cavity is a first cavity, and there is further a second cavity adjacent the first cavity, separated from the first cavity by at least one of the liquid-impervious walls, the second cavity having through-openings to the outside of the block for accepting drainage liquids, and for passing said liquids out of said second cavity. In some embodiments the two-cavity blocks are formed of polymer material by injection molding. Also in some embodiments, in individual blocks, the through-openings include openings on an upper surface to accept liquid from a second block above in an assembly of blocks, openings in a rearward-facing surface to accept liquid from a drain field, and openings in a lower surface for passing liquids to a third block below in an assembly of blocks.  
         [0015]     In some embodiments of the assembly, on individual ones of the blocks, there is an engagement interface for engaging a drain grid comprising both a mesh material and conduits for liquid, wherein individual ones of the through-openings are positioned to engage individual ones of the conduits. Also in some embodiments, in individual ones of the blocks, the through-openings include openings on an upper surface to accept liquid from a second block above in the assembly of blocks, openings in a rearward-facing surface to accept liquid from a drain field, at least one opening in a first side to accept liquid from an adjacent block in the assembly of blocks, and at least one opening in a second side opposite the first side to pass collected liquid to an adjacent block in the assembly.  
         [0016]     In yet another aspect of the invention a drain grid for a retaining wall is provided, comprising a mesh material, and conduits for liquid, the conduits integrated with the mesh material. The drain grid is further characterized in that the conduits have openings for receiving liquid from surrounding volume.  
         [0017]     In embodiments of the invention described in enabling detail below, for the first time blocks are provided for building retaining walls, wherein the blocks are of very light weight for transport, and can be made heavy at point-of-application, and wherein the weight cavities are fully enclosed. Such blocks may also have second cavities adapted for collecting and passing water. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES  
       [0018]      FIG. 1  is a side elevation view of a retaining wall and drainage system according to conventional art.  
         [0019]      FIG. 2A  is a top view of a retaining wall block according to an embodiment of the present invention.  
         [0020]      FIG. 2B  is a section view of the retaining wall block of  FIG. 2A , taken along section line  2 B- 2 B.  
         [0021]      FIG. 2C  is a rear view of the retaining wall block of  FIG. 2A .  
         [0022]      FIG. 2D  is a bottom view of the retaining wall block of  FIG. 2A .  
         [0023]      FIG. 3A  is a top view of a section of drain grid according to an embodiment of the present invention.  
         [0024]      FIG. 3B  is a section view of the drain grid of  FIG. 3A  taken along section line  3 B- 3 B.  
         [0025]      FIG. 4A  is a top view of a section of the drain grid of  FIG. 3A  secured to retaining wall blocks of  FIG. 2A  according to an embodiment of the present invention.  
         [0026]      FIG. 4B  is a section view of the drain grid and retaining wall blocks of  FIG. 4A , taken along section line  4 B- 4 B of  FIG. 4A .  
         [0027]      FIG. 5A  is a rear view of a bottom-row retaining wall block according to an embodiment of the present invention.  
         [0028]      FIG. 5B  is a bottom view of the retaining wall block of  FIG. 5A .  
         [0029]      FIG. 6  is an elevation view the retaining wall blocks and drain grid of  FIG. 4A  and bottom-row retaining wall blocks of  FIG. 5A  assembled according to an embodiment of the present invention.  
         [0030]      FIG. 7A  is an elevation view of the retaining wall blocks and drain grid of  FIG. 4A , and bottom-row retaining wall blocks of  FIG. 5A  forming a section of retaining wall according to an embodiment of the present invention.  
         [0031]      FIG. 7B  is a side elevation view of the retaining wall and drain grids of  FIG. 7A , retaining drain fill and back fill material and undisturbed soil according to an embodiment of the present invention.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0032]      FIG. 1  is a cutaway side elevation view of a retaining wall and drainage system  11  according to prior art. Retaining wall and drainage system  11  comprises a conventional retaining wall  14  formed by individual retaining wall blocks  13 , drainage fill  23  and free-draining back fill  19 , mesh anchoring material  17 , and additional drainage and water disbursement provided by drain tile  21 . Retaining wall  14  is constructed according to conventional methods well-known in the art for the purpose of retaining soil  15  undisturbed. Retaining wall blocks  13  forming retaining wall  14  are typically formed of high-density concrete or other solid stone material, as is most common in the industry, and are adapted to stack one upon the other such that retaining wall  14  is formed by arranging, side-by-side, a plurality of stacks of retaining wall blocks  13 , which may also engage one another.  
         [0033]     Blocks  13  represent conventional concrete or stone building blocks, which are provided in a wide choice of sizes, shapes and designs, and which may also be adapted for receiving various different designs of decorative facings, caps and so on. Blocks  13  are generally adapted to seat securely one upon the other utilizing various known means such as raised lip edges, such as shown in the present example, or may incorporate protrusions in one block to seat within sockets or notches in another block to secure one upper block from sliding on the top surface of a block below. The various means for preventing forward and backward movement of one block on another also typically allows for a setback angle to be achieved in the retaining wall, by securing an upper block to a lower block with the face surface of the upper block being slightly set back from flush with the face of the lower block, which is also shown in the example of  FIG. 1 .  
         [0034]     Undisturbed soil  15  is shown in the prior art example of  FIG. 1  to have an upward slope extending behind retaining wall  14 . Undisturbed soil  15  also has a drainage requirement so as to avoid water accumulation behind retaining wall  14 . Drainage back fill  19  and drainage fill  23  are typically employed as shown behind the retaining wall to provide such drainage, wherein some water draining from above or near the draining fill materials eventually drains through a portion of drainage fill  23  and is then channeled along the base of retaining wall  14  through drain tile  21 , towards one end of the retaining wall, and eventually away from the retaining wall. Drain tile  21  is typically a tubular conduit which allows water to pass from above into the interior utilizing such as perforations, or the like, and runs parallel to the retaining wall, typically behind the retaining wall as shown in the example, having a slight descending grade as it continues to the discharge end of the conduit.  
         [0035]     In most conventional applications the setback angle of the retaining wall such as wall  14  is determined, in part, by the desired finished height of the retaining wall. The angle is determined according to the slope and amount of pressure which will be placed above and behind the retaining wall by the undisturbed soil and drainage fill materials, as well as any additional surcharge or adverse soil conditions, and so on. In addition to the angle incorporated into retaining wall  14  such as shown in  FIG. 1 , retaining wall  14  is also typically anchored to the fill materials behind retaining wall  14  by utilizing sections of reinforced geogrid  17 , used as previously described for conventional retaining wall systems in the background section. Geogrid  17  is typically a reinforced mesh material generally supplied in rolls of a predetermined width, and is cut to length according to the engineering pre-determination of the extent to which geogrid  17  is to extend into the fill material or soil behind wall  14 . The number of layers and intervals at which the geogrid layers are placed is also determined by all of the previously described variables of wall height, soil conditions, drainage requirements, and so on. Water draining from undisturbed soil  15  and down through back fill  19  and drain fill  23  passes directly through the geogrid layers  17  embedded in the fill material, as the mesh material utilized in geogrid  17  is conventionally designed for such unimpeded water passage.  
         [0036]     Dimensions A and B of  FIG. 1  represent the depth of the fields of drain fill  23 , and back fill  19 , and combine also represent in the example the length of geogrid  17  extending behind retaining wall  14 . Prior to construction of a retaining wall such as shown in  FIG. 1 , the combined dimensions of A and B also represent the minimal amount of excavation that must take place behind the proposed line of the retaining wall, in addition to that of the immediate area of the wall. For very high drainage requirements, such as in temperate geographic areas with heavy annual rainfall, or nearby bodies of water or small streams flowing aboveground or underground behind the retaining wall, and so on, the field depth of drain fill  23  and back fill  19  may be much deeper, requiring much more excavation and fill material than would be normally needed.  
         [0037]     In the conventional example shown in  FIG. 1 , water drains from soil  15  into and through back fill  19  and drain fill  23 , and through geogrid layers  17 , down towards the bottom of retaining wall  14 . If water drain flow is especially pronounced or prolonged, such as during or shortly after a sudden heavy rainfall, for example, the water seepage requiring drainage from behind retaining wall  14  may exceed the drainage capacity of the fill materials and lower soil  15 , and the ability of drain tile  21  to carry the draining water away. In such an instance, particularly if the surrounding soil  15  is previously saturated prior to the increased drainage flow, the draining water will begin to accumulate in the fill material towards the bottom of retaining wall  14 , and if the heavy drainage flows continue for a period of time at a rate exceeding the drainage capacity of the system, the water level will increase behind wall  14  as the fill and drainage materials continue to fill with drainage overflow, because the upwardly accumulating water overflow, which exceeds the drainage capacity of the system, has nowhere else to accumulate. The water is prevented from passing through the rear surface of retaining wall  14 , due to the nature of the construction of the wall and individual blocks  13  utilized, and the surrounding soil  15  may be saturated and unable to absorb additional water. Undue pressure on retaining wall  14  and possible collapse of the system is the possible result in such an occurrence.  
         [0038]     Referring now to  FIG. 2A  and  FIG. 2B , a new and novel retaining wall block  31  is presented according to an embodiment of the present invention, which block provides several advantages over conventional blocks.  FIG. 2A  is a top view of a retaining wall block  31  according to an embodiment of the present invention.  FIG. 2B  is a section view of retaining wall block  31  of  FIG. 2A  taken along section line  2 B- 2 B of  FIG. 2A . An exemplary representation of the embodiment is best given in the following description with reference to both  FIGS. 2A and 2B  alternatively, and therefore is further described in such a manner.  
         [0039]     Retaining wall block  31  it is preferably formed of high-density, extremely durable plasticized material, such as polyurethane or some other such polymer compound, which is lightweight, resistant to UV damage, erosion, impact, and is waterproof. The material used for forming block  31  is suitable for an injection molding process, which is the preferred method of manufacture for forming block  31 . Other known methods, however, may be utilized in alternative embodiments for forming block  31 . Block  31  can also be made of any other waterproof material or non-waterproof material with the incorporation a waterproof insert.  
         [0040]     Another advantage of the innovative retaining block system is that the blocks can be made quite larger that the conventional retaining block whose size is restricted by shipping weight. An increased size would allow additional fill material to be added to the inside of the block thereby increasing the weight and effectiveness of the block. The fill material can be a combination of gravel and anti-freezing liquid.  
         [0041]     Block  31  may be provided in a variety of shapes and sizes suitable for forming a retaining wall, and is shown in  FIGS. 2A and 2B  to be of a conventional height, width and depth commonly used in the industry. Referring again to  FIGS. 2B and 2B , block  31  comprises a base  45 , face wall  50 , rear wall  36 , side walls  33   a  and  33   b , and a cap wall  54 , all of which together define the shape and outside dimensions of block  31 . Face wall  50  extends upwardly from base  45 , and is better shown in  FIG. 2A . Face wall  50  has a raised side lip  44  near the intersection of side wall  33   a , and a groove  42  recess into the edge near the intersection of the opposite edge of face wall  50  and side wall  33   b . Raised side lip  44  and groove recess  42  provide a means for aligning blocks  31  side-by-side such that a raised side lip  44  of a first block fits securely into a width recess  42  of a second adjacent block, thereby preventing forward movement of a side of the second block  31  against a side of a first block  31 , and also obscuring from view any gap formed by space between the side walls of pair of adjacent blocks  31 .  
         [0042]     Referring again to  FIG. 2A , the upper surface shown in the top view of cap wall  54  has a plurality of set back holes  35   a  and  35   b  near the intersection of face wall  50  and side walls  33   a  and  33   b , aligned generally along the length of walls  33   a  and  b . Individual ones of setback holes  35   a  and  35   b  are equally-spaced between adjacent holes in each set, and extend slightly into, but not completely through the thickness of cap wall  54 .  
         [0043]     As is better illustrated in  FIG. 2B , block  31  also provides protrusions  49  extending slightly downward from the underside of base  45 , located on base  45  relative to setback holes  35  on cap wall  54 . Only one of protrusions  49 , namely  49   b , is shown in the sectional view of  FIG. 2B , a second protrusion  49   a , as will be shown in further illustrations, is hidden from view. Protrusions  49   a  and  b  and setback holes  35  of block  31  are for the purpose of engaging adjacent blocks and for preventing one block  31  stacked on top of another from sliding in any direction relative to the lower block. When stacking one block  31  on another, protrusions  49 , which are slightly smaller in diameter than setback holes  35 , seat snugly within setback holes  35 , allowing the underside of base  45  of the upper block  31  to be generally flush and in substantial contact with the upper surface of the cap wall  54  of the lower block  31 , the upper surface of lower block  31  thereby forming a smooth foundation for the upper block. An upper block  31  may be securely stacked on a lower block, the upper block slightly set back from the lower block by inserting protrusions  49   a  and  49   b  of the upper block into either the forward, middle or rearward sets of setback holes  35   a  and  35   b  when stacking one block upon another. The plurality of holes  35   a  and  35   b  thus provide a choice of position for stacking upper blocks on lower blocks. This choice of setback dimension allows a variation in the angle from vertical for a completed wall made from blocks  31 . It will be apparent that the holes and protrusions need not be circular, but could be in any one of a variety of shapes.  
         [0044]     Block  31  also has a pair of protrusions  43   a  and  43   b  in this embodiment located on either side of cap wall  54 , located near the rear of cap wall  54 , extending slightly upward from the upper surface, as better seen in  FIG. 2B . Sets of holes  51   a  and  51   b , each of which are slightly larger in depth and dimension than protrusions  43   a  and  43   b  of cap wall  54 , are located on the underside of block  31 , also towards the rear, and extend partially into the thickness of base  45 . Recessions  51   a  and  51   b  are arranged linearly, similar to the arrangement for setback holes  35  of cap wall  54 , and the distance between the centers of each recession  51   a  or  b  to that of adjacent recession  51   a  or  b  is the same distance as the center of one setback hole  35  to the center of an adjacent setback hole  35 . Although only one set of recessions are shown in the sectional view of  FIG. 2A , namely recessions  51   b , an additional and identical set of recessions  51   a  are present in block  31 , located on the opposite side of block  31  from recessions  51   b  shown, but are not shown in  FIG. 2B . Protrusions  54   a  and  54   b  and recessions  51   a  and  51   b  have the purpose of securing a portion of anchoring mesh material to blocks  31  in a retaining wall, as will be detailed further below.  
         [0045]     It will be apparent that setback holes and protrusions, raised lip extensions and recesses, and the like, for securing one block on top of or next to another, and for securing a portion of anchoring mesh material, such as described above in the embodiment presented in  FIGS. 2A and 2B , are known and commonly utilized in the art, and a variety of different interlocking and mesh-securing apparatus and methods may be utilized in systems in which the present invention may be practiced, without departing from the scope and spirit of the invention.  
         [0046]     Side walls  33   a  and  33   b  extend upright from base  45  on either side of, and behind face wall  50 . Rear wall  36  extends upwardly from the rear edge of base  45 , each side edge of rear wall  36  meeting a side edge of a side wall  33   a  or  33   b . Rear wall  36  has a slightly smaller width dimension than that of face wall  50 , such that blocks  31  arranged side-by-side may be slightly angled so that outside curves in the retaining wall may be achieved without affecting the appearance of the front seam between face walls of individual blocks  31 . Cap wall  54 , generally equal in width and length to base  45 , covers the upper edges of face wall  50 , side walls  33  and rear wall  36  to form an enclosure.  
         [0047]     The height of building block  31  is defined by distance between the outside bottom surface of base  45  and the outside upper surface of cap wall  54 , and the width dimension of block  31  is defined by the distance between the outer surfaces of side walls  33   a  and  33   b , and the length dimension of block  31  is defined by the distance between the outer surface of face wall  50  and that of wall  36 . In alternative embodiments different from that shown in  FIG. 1  face wall  50  may be of different height or width than that of the outer dimensions of block  31  itself, for decorative purposes, or for providing overlap for seams between blocks, and so on.  
         [0048]     Referring again to  FIG. 2B , block  31  comprises a unique cavity wall  38  which also extends upwardly from base  45  parallel to, and in between the inner surfaces of face wall  50  and rear wall  36 , positioned substantially rearward to the center of the length dimension of block  31 , such that, in this embodiment, two separate cavities  39  and  40  are formed within the enclosure of block  31 , the rearward smaller cavity  40 , in a preferred embodiment, being of substantially smaller volume than the forward cavity  39 .  
         [0049]     Cavities  39  and  40  are formed by cavity wall  38  between face wall  50  and rear wall  36 . Cavities  39  and  40  are shown by hidden lines (dotted) in  FIG. 2A , and are more clearly illustrated in the sectional view of  FIG. 2B . The volume of cavity  39  is defined by the distance between the inner surfaces of face wall  50  and the opposing surface of cavity wall  38 , the inner surfaces of side walls  35  and the upper surface of base  45  and bottom surface of cap wall  54 . The volume of cavity  40  is defined by the distance between the inner surfaces of rear wall  36  and the opposing inner surface of cavity wall  38 , the inner surfaces of side walls  35  and the upper surface of base  45  and bottom surface of cap wall  54 . Cavity  40  is separate from cavity  39 , in that fluid or fill material cannot pass between one cavity and the other.  
         [0050]     The purpose of the larger cavity  39  is for receiving fill material, such as water or other fluid, or other heavy fill materials which may include water, such as a water/gravel mixture, in geographic areas where freezing is not an issue, for example, or a mixture of anti-freeze solution and water, or a combination of any of the above. Ideally, all or a large portion of the fill material for filling cavity  39  of block  31  is obtained from the construction site during construction of the retaining wall, in the case of using earth or gravel or fill material, or, in the case of water or liquid mixture fill, may be delivered to the construction site by such means as pumping the fill material through a delivery hose to blocks  31  and filling blocks  31  as each is positioned during retaining wall construction, by pumping the fill from a local source or from an onsite container delivered to the construction site, for example.  
         [0051]     Fill cavity  39  in an embodiment of the invention has a fill volume preferably of 80 percent or more of the total volume of cavities  39  and  40  within block  31 , which is deemed by the inventor to be more than sufficient for containing an amount of fill material which would allow block  31 , upon filling cavity  39  to capacity with whatever fill material described above is used, to have sufficient weight for a retaining wall block. Block  31 , being formed primarily of polymeric material or other similar high-density material, is relatively lightweight in its unfilled state, allowing for ease of lifting and transporting, but also has sufficient weight in its filled state to provide necessary stability to act as a module for a retaining wall constructed according to industry standards.  
         [0052]     Face wall  50 , rear wall  36 , side walls  33   a  and  33   b , base  45  and cap wall  54  in the embodiment shown each have a mean thickness sufficient for providing support and stability for block  31  in an unfilled condition so as to minimize damage during transportation of blocks  31  to the construction site, while also allowing for sufficient volume in cavity  39  for containing an amount of fill material sufficient for block  31  to achieve desired weight when filled. Structural integrity of block  31  sufficient for enabling block  31  to be used as a module in a retaining wall is provided by the fact of the mean thickness of all of the walls of block  31  as mentioned above, combined with that of the fill volume itself within cavity  39 .  
         [0053]     Block  31  is provided with an opening  37  extending through cap wall  54  allowing access to cavity  39  for the purpose of filling cavity  39  with filling material. A fill cap  52  is provided adapted to tightly seal opening  37 , such that the upper surface of fill cap  52  is flush with or recessed from the upper surface of cap wall  54 , when fill cap  52  is inserted into opening  37 , as is clearly shown in  FIG. 2B . Fill cap  52  provides a water-tight seal preventing water or fill material within block  31 , or outside materials surrounding block  31  in a construction wall, from passing through opening  37 . In this embodiment recesses  69 , being a pair of half-circle indications extending slightly into the surface of fill cap  52 , are provided to allow for a person to easily remove fill cap  52  by grasping the cap vie recesses  69  with the fingers and removing fill cap  52  up from opening  37 . In other embodiments the opening may be circular and threaded, and cap  52  may be circular with a matching thread, so the opening is sealed by rotating the cap into the opening in the manner of a pipe plug.  
         [0054]     Cavity  40  provides block  31  with a drainage capability which is integrated into the design of block  31 . Drain cavity  40  is separate from fill cavity  39 , thereby preventing fill material from escaping cavity  39  into cavity  40 , or any drainage material from entering fill cavity  39  from drainage cavity  40 . As is further described below in subsequent illustrations and description, block  31 , utilizing drain cavity  40 , is adapted for draining water into and out of cavity  40  from above block  31 , and also from behind block  31  through rear wall  36 .  
         [0055]      FIG. 2A  illustrates a plurality of drain holes  32  arranged near the rear of block  31  towards rear wall  36 . Drain holes  32  extend completely through the thickness of cap wall  54 , and open into drain cavity  40 , shown directly below in the hidden view. Drain holes  32  have a purpose of allowing water to drain from directly above drain holes  32  down into drain cavity  40 . An arrangement of drain holes  46 , similar to drain holes  32 , extend completely through base  45  at the bottom of cavity  40 , better illustrated in  FIG. 2B . Drain holes  46  have the purpose of allowing water to drain from cavity  40  down through drain holes  46  and out directly below cavity  40 . A plurality of drain holes  53  is also provided to allow additional drainage capability through rear wall  36  into drain cavity  40 . Drain holes  53  extend completely through the thickness of rear wall  36 , as better seen in  FIG. 2B , and enable water to drain from behind block  31 , through rear wall  36 , into drain cavity  40 .  
         [0056]     Also shown are a plurality of passages  47  extending into and completely through rear wall  36 . Passages  47  are half-circular in shape in this embodiment, and are located at the intersection of the upper edge of rear wall  36 , and rearward edge of cap wall  54 , better illustrated in  FIG. 2B . Passages  47  open into cavity  40  as shown in  FIG. 2B , and also provide additional drainage capacity into drain cavity  40 , when utilized with an additional drainage grid system as will be shown in further illustrations and description.  
         [0057]     Recesses  48  are shown in  FIG. 2B  extending into rear wall  36 , but not completely through rear wall  36 , as do passages  47 . Recesses  48  are of the same shape and size as passages  47 , and are located at the intersection of the lower edge of rear wall  36  and the rear edge of base  45 , relative to the locations of passages  47  along the upper edge of rear wall  36 . The relevance of the locations of passages  47  and recessions  48  relative to each other is also made clear in subsequent illustrations and description.  
         [0058]      FIG. 2C  is a rear view of retaining wall block  31  of  FIG. 2A . A face-on view of the outer surface of rear wall  36  is provided, clearly illustrating the plurality of drain holes  53  described above which extend completely through to internal drain cavity  40 . Drain passages  47  are also clearly shown along the upper edge of rear wall  36 , passages  47  also passing completely through rear wall  36  into drain cavity  40 . Recesses  48  are shown in their location along the lower edge of rear wall  36 , relative to the location of drain passages  47  along the upper edge of rear wall  36 , being of similar size and dimensions as drain passages  47 . Protrusions  43   a , and  43   b , extending upward from cap wall  54  near side walls  33 , are also clearly seen in this view, and recessions  51   a  and  51   b  are shown extending slightly into the underside of base  45 , recessions  51  located relative to the location of protrusions  43  of cap wall  54 . Protrusions  49   a  and  49   b  are also shown in this view extending slightly down from the underside of base  45  near side walls  33 , and setback holes  35 , located in cap wall  54  relative to the location of protrusions  49 , are shown extending slightly down into the surface of cap wall  54 .  
         [0059]     Drain holes  32  are shown extending completely through cap wall  54 , providing drainage from above block  31  into drain cavity  40 , and drain holes  46  are shown extending completely through base  45  providing drainage from within drain cavity  40 , through base  45  and out the underside of base  45 . Drain holes  53  are shown in this view substantially covering the area of rear wall  36 , providing a substantial increase in drainage capability from behind block  31 , drain holes  53  passing completely through rear wall  36  into drain cavity  40 .  
         [0060]      FIG. 2D  is a bottom view of the retaining wall block of  FIG. 2A . A face-on view of the bottom surface of base  45  is given in the illustration, clearly showing the location of protrusions  49   a  and  49   b , near the intersections of the side edges of face wall  50  and side walls  33 , as well as the location of recessions  51   a  and  51   b  near the intersections base  45  and rearward edges of side walls  33 . Recessions  48  can also be clearly seen along the rear edge of base  45 , recessions  48  extending partially into the intersection of rear wall  36  and base  45 . Drain holes  46 , which extend completely through base  45 , as shown in  FIG. 2C , are arranged towards the rear of base  45 , relative to the internal drain cavity  40 , such that the entire plurality of drain holes  46  open into drain cavity  40 , allowing water to drain directly below and out from drain cavity  40  unimpeded.  
         [0061]     As described in the background section and portions of the description relative to the conventional example of the retaining wall and drainage system  11  of  FIG. 1 , in addition to the angle incorporated into a retaining wall for added stability for restraining the soil and drain fill material behind the retaining wall, the retaining wall is also anchored to the drain fill materials and soil behind the retaining wall by utilizing sections of reinforced mesh material, known in the industry has geogrid, as previously described for conventional retaining wall systems. The number of layers and intervals at which the geogrid layers are placed is also determined by all of the previously described factors of wall height, soil conditions, drainage requirements, and so on.  
         [0062]     Individual retaining blocks  31  in some embodiments of the present invention also utilize such an anchoring system, except that the mesh anchoring system of the present invention also uniquely incorporates additional drainage capability into the anchoring mesh system, thereby providing a distinct advantage over conventional systems which do not incorporate such additional drainage capability, which is described below in enabling detail.  
         [0063]      FIG. 3A  is a top view of a section of drain grid  61  according to an embodiment of the present invention. Drain grid  61  comprises a reinforced mesh  63 , similar to that of geogrid material commonly known in the industry, modified with a plurality of drain channels  65  which are integrated with the mesh material for providing substantial additional water drainage and disbursement per cubic yard of drain fill and back fill behind a retaining wall, as compared to conventional systems utilizing conventional geogrid material.  
         [0064]     Each drain channel  65  in the embodiment shown is essentially a tubular water disbursement conduit, having perforations  62  along substantially the entire length of drain channel  65 , extending completely through at least an upper portion of each drain channel  65 , so as to allow water to drain freely from directly above and around the area of drain channel  65 , into the interior of drain channel  65 , and then to be channeled by drain channel  65  away from the points of entry, towards output ends  66 . Perforations  62  are adapted and designed to keep solid material in and allow only liquid in. Perforations can be of any shape. Drain grid  61  is designed to allow unfettered water passage through mesh  63 , while mesh  63  also firmly anchors the retaining wall utilizing blocks  31  to the drain fill and back fill material behind the retaining wall, as in conventional geogrid mesh materials. In an alternative embodiment (not shown) drain conduits  65  may be glued into pre-formed holes into the rear of block  31  to provide additional anchoring characteristics for the grid material to block connection.  
         [0065]     Near output ends  66  of drain channels  65 , is a header portion  67  of mesh  63 , allowing enough mesh  63  material to extend beyond output ends  66  of drain channels  65 , to allow for attaching drain grid  61  by header portion  67  between two stacked rows of reinforcing wall blocks  31  of  FIG. 2A , as is described further below. The length of a section of drain grid  61  is represented by dimension A, and the width by dimension B, as shown in  FIG. 3A . Drain grid  61  is preferably provided in a number of pre-cut lengths differing in length in increments according to lengths typically used in the industry for common applications, considering various slopes, soil conditions, additional surcharges and water drainage requirements behind the retaining wall, as described in the background section. In such a manner, if the engineering analysis of the conditions behind a retaining wall necessitate a length of drain grid somewhat different than the pre-cut length as provided, drain grid  61  may be trimmed to the exact desired length at the end opposite of mesh header portion  67 , with minimal scrap. Also, drain grid  61  may be rolled up along its length, and supplied to the construction site in a length equaling the proposed length of the retaining wall, or may be unrolled over a layer of previously laid down retaining wall blocks and compacted material during construction of the retaining wall, and then trimmed to size at the end of the layer, by cutting along the length of mesh  63  of drain grid  61 .  
         [0066]     In alternative embodiments of the present invention, drain channels  65  may be provided for drain grid  61  which may be collapsible channels woven into mesh  63 , with a collapsible perforated top portion allowing drainage into the collapsible channel, such that when drain grid  61  is rolled up, drain channels  65  collapse to provide compactness of storage, and then upon installation, a collapsible drain grid  61  may secured down by the starting end at a starting point of the retaining wall layer, unrolled along the entire length of the retaining wall layer, and then cut flush with the ending point of the retaining wall. Drain grid  61  may then be anchored to a row of retaining wall blocks  31  utilizing mesh header portion  67 , extended back from the row of retaining blocks, and then secured into position by tacking the end of drain grid  61  opposite mesh header portion  67  into the ground behind the retaining wall. Upon stretching drain grid  61  and applying slight tension before securing into the ground, the collapsible drain channels  65  would also stretch out and form drain channels capable of carrying drain water away from the drainage area, and the passages within drain channel  65  would remain open when the next layer of drain fill material is layered upon it.  
         [0067]      FIG. 3B  is a section view of drain grid  61  of  FIG. 3A  taken along section line  3 B- 3 B of  FIG. 3A . Drain channels  65  are shown in the illustration to be of a tubular shape, but it is noted that whether drain channels  65  are round or some other shape is not particularly important in practicing the present invention, as long as drain channels  65  allow drain water to drain along the length of drain channel  65 . In the embodiment shown, drain channels  65  are integrated into mesh  63 , and arranged in three groups of three, and are spaced from each other within each group when drain grid  61  is laid flat as shown in  FIG. 3B , such that when the portion of drain grid  61  shown, is stretched across and attached to a row of three retaining wall blocks  31  of  FIG. 2A , each output end  66  of drain channels  65  is aligned with each passage  47  of the three retaining wall blocks  31 . The distance between the center points of one drain channel  65  and that that of an adjacent drain channel  65  within the same group of three, is the same as the distance between the center points of one of passages  47 , and that of an adjacent passage  47  in a retaining wall block  31 . The relevance of the spacing between drain channels  65  of drain grid  61 , and that of passages  47  of retaining wall block  31 , is made readily apparent in description below.  
         [0068]      FIG. 4A  is a top view of a section of drain grid  61  of  FIG. 3A  secured to adjacent and joined retaining wall blocks  31  according to an embodiment of the present invention.  FIG. 4A  illustrates a manner in which drain grid  61  is laid over and attached to upper surfaces above a row of three retaining wall blocks  31 . In practice, there will typically be many more retaining wall blocks  31  arranged in their installed position than are shown in  FIG. 4A , and only a portion of drain grid  61 , generally equal in width to the combined width of the three blocks  31 , is shown for simplicity. The purpose of  FIG. 4A  is to illustrate attaching drain grid  61  to a plurality of retaining wall blocks  31 .  
         [0069]     In this example retaining wall blocks  31  have been placed in their proper position during construction of a retaining wall, and may be assumed to be securely resting upon a layer of retaining wall blocks below, acting as a foundation, or on another foundation surface. Header portion  67  of mesh  63  is positioned over the rearward portion of the row of blocks  31 , such that each of the output ends  66  of drain channels  65  are positioned near passages  47  of blocks  31 . Output ends  66  of drain channels  65  are then seated within passages  47  as far forward as they will fit, and mesh header portion  67  is then stretched over protrusions  43 , which extend slightly upward from the top surface of blocks  31 , and a single opening of mesh  63  is then pulled over each of protrusions  43 , protrusions  43  being slightly less in dimensions than each opening of mesh  63 , thereby securing mesh  63  by header portion  67  to the row of blocks  31 , which also holds the output ends of each drain channel  65  of drain grid  61  into each passage  47  of blocks  31 .  
         [0070]     Although it is not explicitly shown in  FIG. 4A , it can be assumed that retaining wall blocks  31  have been positioned and a layer of drain fill and back fill has also been applied behind the row of blocks  31  and compacted such that the upper level of the drain and back fill material is generally flush with the upper surface of blocks  31 , in accordance with construction of a retaining wall utilizing known methods. Drain grid  61  is attached to the row of retaining wall blocks  31 , as shown, and is then laid out over the drain and back fill materials behind blocks  31 , such that a slight downward grade toward blocks  31  is incorporated along the length of drain grid  61 , so that drain channels  65  follow a gentle slope downward towards retaining wall blocks  31 . In such a manner, water draining into drain channels  65  flows, urged by gravity, towards blocks  31 , and then enters blocks  31 , into the internal drainage cavities  40  (not shown), as previously described, through passages  47  of blocks  31 . Header portion  67  of mesh  63  is sufficiently flexible such that if a light curvature is desired in the retaining wall, individual blocks  31  may be slightly angled to accommodate such a curvature, without affecting the attachment of header portion  67  to protrusions  43  of blocks  31 , and securing of output ends  66  of drain channels  65  into passages  47  of blocks  31 .  
         [0071]      FIG. 4B  is a section view of drain grid  61  and retaining wall blocks  31  of  FIG. 4A , taken along section line C-C. In this view, three blocks  31  are arranged in their installed position, as in  FIG. 4B . Drain grid  61  is layered directly atop the upper surfaces of blocks  31 , and attached at the header portion  67  to blocks  31  as illustrated in the previous figure. Protrusions  43  can be seen protruding up from the upper surfaces of blocks  31 , and extending up through mesh  63  of drain grid  61 , as previously described. Drain channels  65  of drain grid  61  are now clearly shown seated into passages  47 , each of which open into drain cavity  40 . Recessions  48  are shown along the bottom of each block  31 , positioned relative to passages  47  along the top of block  31 .  
         [0072]     A plurality of drain holes  32  are shown extending completely through cap wall  54  of blocks  31  and opening into drain cavity  40 , and a plurality of drain holes  46  are also shown extending completely through base  45 , also with an opening into drain cavity  40 , as described previously. As described earlier, drainage water is allowed to drain into drain cavity  40  from drain holes  32  extending through cap wall  54 , as well as passages  47  from the output ends a drain channels  65 , and then is allowed to drain out of drain cavity  40  down through drain holes  46  extending through base  45 . In practice, if drain flow from drain channels  65  of drain grid  61 , and that of drain holes  32  through cap wall  54 , momentarily exceeds the drainage capacity of drain holes  46 , the volume of drain cavity  40  may provide reservoir volume for any required accumulation of drain water until the incoming drain flow recedes to a point equal to or less than the capacity of drain holes  46 .  
         [0073]     A bottom-row retaining wall block, used in conjunction with blocks  31  and drain grid  61  is illustrated in  FIGS. 5A and 5B .  FIG. 5A  is a rear view of a bottom-row retaining wall block  41  according to an embodiment of the present invention.  FIG. 5B  is a bottom view of retaining wall block  41  of  FIG. 5A . Drain block  41  is a polymeric retaining wall block adapted for filling a cavity within block  41  with fill material, and has drainage capability integrated within block  41  allowing for drainage to enter block  41  similarly to the drainage capability as illustrated for block  31  previously described. Referring now to  FIGS. 5A and 5B , drain block  41  comprises a face wall  87 , a pair of side walls  90 , a base  96 , a cap wall  85  and a rear wall  94 , which combine to form an enclosure, generally equal in outside dimensions and shape to those of block  31  of  FIG. 2A . Block  41  also has an internal cavity wall  97 , similar to that of block  31 , situated between face wall  87  and rear wall  94 , forming a pair of separate internal cavities in block  41 , cavity  99  being the larger of the two, for filling with fill material similar to fill cavity  39  of block  31 , and a smaller cavity  86  located to their rear of fill cavity  99 , which accommodates drainage into block  41 , also similarly to block  31 . Water is enabled to drain into drain cavity  86  through drain holes  92  extending completely through cap wall  85 , equivalent to drain holes  46  of block  31 , and passages  103 , which are equivalent to passages  47  of block  31 , also opening into drain cavity  86 . Also similar to block  31 , as shown in their rear view of  FIG. 5A , a plurality of drain holes  101 , equivalent to drain holes  53  of rear wall  36  of block  31 , allow additional drainage from the area behind rear wall  94  of drain block  41 , through rear wall  94  into drain cavity  86 . It is noted, however, that base  96  of block  41 , differs from base  45  of block  31 , in that there are no protrusions extending from, or recessions extending into base  96 , as used in block  31  for aligning and securing an upper block  31  to a lower block  31 , because block  41  is designed to be the bottom-row block in practice of the present invention. Notably, block  41  also lacks drainage holes extending through base  96 , such as drainage holes  46  of block  31 , because there is intended to be no drainage from drain cavity  86  through base  96 .  
         [0074]     Block  41  also has a pair of protrusions  83  for attaching a header portion  67  of a drain grid  61 , and a set of setback holes  89 , equivalent to set back holes  35  of block  31 , extending partially into the upper surface both cap wall  85 , for inserting protrusions  49  of a block  31 , which is stacked atop block  41  in practice of the invention, as detailed further below.  
         [0075]     Bottom-row retaining wall block  41  differs significantly from retaining wall block  31 , in that a drainage base wall  105  is provided between cap wall  85  and base  96 , and a drainage conduit  91  is provided below base wall  105  for channeling drainage water away from block  41 . Drainage conduit  91  is positioned directly below drain cavity  86 , and extends along the width of block  41  from the outer surface of one side wall  90  to the outer surface of the opposite side wall  90 . Drain conduit  91  has an intake opening  93  on one end, and an output nozzle  95  on the other end, intake opening  93  having an inside diameter slightly greater than the outside diameter of output nozzle  95 . Output nozzle  95  is adapted to fit neatly and snugly into intake opening  93 .  
         [0076]     Drain holes  97  are provided to allow drainage from drain cavity  86  into drain conduit  91 , drain holes  97  passing completely through drain wall  105  into drain conduit  91 . Drainage water enters block  41  through drain holes  92  of cap wall  85 , drain passages  103 , and drain holes  101  of rear  94 , in the same fashion that water enters block  31  as previously described. However, instead of drain water exiting block  41  through base  96 , similarly to that of block  31 , drain water exits drain cavity  86  down through drainage holes  97 , into drain conduit  91 , and then is channeled out of block  41  via drain conduit  91 .  
         [0077]      FIG. 6  is an elevation view of an assembly of retaining wall blocks  31  and drain grid  61  of  FIG. 4A , and bottom-row retaining wall blocks  41  of  FIG. 5A , assembled according to an embodiment of the present invention. The upper row, comprising three retaining wall blocks  31 , has a drain grid  61  layered on top of the surfaces of blocks  31 , and is attached by the header portion utilizing protrusions  43 , the output ends of drain channels  65  securely seating within passages  47 , as previously described for blocks  31 . Three drainage blocks  41  form the lowermost row. Between the upper row of blocks  31  and the lower row of blocks  41 , is another drain grid  61 , which is attached to the upper surfaces of blocks  41 , utilizing the protrusions similarly to that for the upper row of blocks  31 . The output ends of channels  65  seat within drain passages  103  of blocks  41 , also similarly as described for passages  47  of blocks  31 , and drain into drain cavities  86  within blocks  41 .  
         [0078]     A shown in the illustration, each block  31  in the upper row is stacked upon a drainage block  41  in the lower row, the underside surface of blocks  31  substantially flush and in contact with the upper surfaces of blocks  41 . Recesses  48  of blocks  31  seat securely over the output ends of drain channels  65  which are also securely seated within passages  103  of blocks  41 . Blocks  31  are prevented from sliding back and forth or laterally by protrusions  49  of blocks  31  fitting snugly into recessions  89  of blocks  41 , aided by extensions  83  of blocks  41  for securing mesh  63  of drain grid  61 , also fitting snugly into recessions  51  of blocks  31 , extending up into the bottom surface of blocks  31 .  
         [0079]     Drainage blocks  41  are the first and bottom row of blocks to be layered in construction of a drainage retaining wall in accordance with the present invention. A first block  41  is first positioned to begin the row, and a second block  41  is positioned next to the first block  41  such that the intake opening of drain conduit  91  of the second block  41  fits snugly over the output nozzle of drain conduit  91  of the first block  41 . The second block  41  is then urged toward the first block  41  until the end of the second block  41  meets that of the first block, and a continuous drain conduit is thereby formed between drain conduit  91  of the first block and drain conduit  91  of the second block. A third block  41  is then positioned and urged against the other end of the second block, as in the second block  41  to the first block  41 , thereby extending the retaining wall bottom layer, and also the drain conduit formed by conduits  91 . The stepwise procedure is repeated for subsequent blocks  41  until the entire first bottom layer comprising blocks  41  is complete for the retaining wall being constructed. Once the first bottom row comprising blocks  41  is completed as described above, the drain grid  61  is attached by the header portion  67  (not shown) to the upper surface of blocks  41  as described above with drain channels  65  seating within passages  103  of blocks  41 .  
         [0080]     A second row comprising blocks  31  is then layered upon blocks  41 , one block  31  at a time, utilizing the protrusions and extensions of blocks  31  and  41  as described above for aligning each upper block  31  to each lower block  41 . Recessions  48  of blocks  31  in the upper row seat snugly over drain channels  65 , and the bottom surface of each block  31  comes into substantial contact with the upper surface of each of  41 , and is prevented from sliding in any direction, by way of the protrusions of one block fitting into the recessions of another, and drain grid  61  is securely anchored between the upper row of blocks  31  and the lower bottom row of blocks  41 .  
         [0081]     In the exemplary example shown in  FIG. 6 , water may drain into drain cavities  40  of blocks  31  from above through drain holes  32 , drain channels  65  of drain grid  61 , or through drain holes  53  of rear wall  36  (not shown). Water then drains from cavity  40  of block  31  out through the bottom of blocks  31  via drainage holes  46  of blocks  31 , through drainage holes  92  extending through the upper surface of blocks  41 , and into drain cavities  86  of blocks  41 . Additional drainage may enter drain cavity  86  of block  41  via drain channels  65  of drain grid  61  secured between blocks  31  and  41 , or also through drainage holes  101  (not shown) extending through the rear wall of blocks  41 , as previously described. Water then drains from cavities  86  of blocks  41  down through drainage holes  97  at the bottom of drain cavity  86 , and enters drain conduits  91 , which then channel the water away.  
         [0082]      FIG. 7A  is an elevation view of retaining wall blocks  31  and drain grids  61  of  FIG. 4A , and bottom-row drainage blocks  41  of  FIG. 5A , forming a section of retaining wall according to an embodiment of the present invention.  FIG. 7A  is an example of a drainage-capable retaining wall constructed utilizing drain blocks  31 , drain grids  61  and bottom-row drain blocks  41  in embodiments of the invention described above.  
         [0083]     Retaining wall  71  as shown in the illustration comprises a first bottom row of drain blocks with an additional seven rows of blocks  31  layered upon the bottom row of drain blocks  41   a - n . A section of drain grid  61  is layered upon the upper surface of the second row of retaining wall  71 , which comprises blocks  31 , and is secured between the upper surface of blocks  31  in the second row and the lower surface of the row of blocks  31  directly above in the third row. Additional sections of drain grid  61  are layered and secured between the surfaces of blocks in row  4  and  5 , and again between rows  6  and  7 , all of which comprise blocks  31 . It is noted that the relevance of the intervals at which drain grids  61  are layered is not particularly important in describing the present invention as illustrated in  FIG. 7A . In practice of the present invention, more, fewer or no layers of drain grid  61  may be utilized, depending on the drainage and anchoring requirements behind retaining wall  71 . It is also noted that retaining wall  71  is an example only. In practice of the present invention there may be many more stacks of blocks  41  and  31 , and each stack may comprise a much greater number of blocks  31 , than are shown in the illustration.  
         [0084]     As is well-known in the art, it is generally desirable to construct a retaining wall wherein, where practical, the upper surface of the top row of blocks utilized in the retaining wall is horizontally level. Line D 1  represents a level line along which the upper surface of the top row of blocks  31  follows, in a preferred embodiment. It is also well-known that drain water which has drained to the bottom of the retaining wall from above, must be carried away from the retaining wall and be drained elsewhere, to avoid accumulation of drain water at the base of the retaining wall. A known preferable method for such disbursement is a gravity-fed flow of drainage water following a slight descending slope towards the drainage end of the retaining wall.  
         [0085]     Such a gradual downward slope for carrying away is represented by line E, which begins at the bottom surface of the first lower drain block  41   a , and follows a gradual downward slope along subsequent blocks  41   b ,  41   c , and so on. Line D 2  represents a horizontally level line parallel with top level line D 1 , beginning also at the bottom surface of the first lower drain block  41   a.    
         [0086]     In order to accommodate a gradual descent of the flow of drainage water passing through drain conduits  91  of blocks  41 , blocks  41  are manufactured having slightly varying heights differing in small increments. In one example, if one wishes to build a retaining wall according to present invention, that is approximately 40 feet long, a total of 32 blocks  41  would be required in the first bottom row of the retaining wall. By knowing the standard rate of slope for a given number of feet of retaining wall for effectively dispersing drainage water, for example, a user may be able to provide the proposed length of the wall to the manufacturer of blocks  41 , and the manufacturer may calculate the exact required size for each of the number of blocks  41  required for the project, beginning with a starting height of block  41   a , as shown in  FIG. 7A , for example, and incrementing the height of subsequent blocks  41  ( 41   b, c, d  and so on) such that the last block  41  in the row of 32 blocks is of the proper height such that, when all of the rows of blocks  31  are completed, the upper surface of the top row of blocks  31  is level, as represented by line D 1 .  
         [0087]     Since all of the drainage conduits  91  in the bottom row of retaining blocks  41  must align with each other, in a preferred embodiment of the invention the small increments in height between one block  41  and another are increased above the level of drain conduit  91 . For example the small increment in overall height may be incorporated into the upper cap wall  85  of block  41 , resulting in a cap wall  85  having a slightly larger mean thickness than that of another block  41 , or the additional increment in overall height may be achieved by adding height to the rear, side and face walls of block  41 . It is noted that the method for incrementally increasing the height between one block  41  and another is not particularly important in describing the present invention, as long as each drain conduit  91  of each block  41 , regardless of the differing overall heights of blocks  41 , are elevated at the same distance from the bottom surface of each block  41 , and all of drain conduits  91  are at the same level when all of the retaining blocks  41  are positioned side-by-side in forming the first bottom row of the retaining wall.  
         [0088]     As shown in  FIG. 7A , retaining wall  71  incorporates such a gradual downward slope in the bottom row of drain blocks  41 , while all of the rows comprising blocks  31  are level with line D 1 . Drainage water may drain down from the top row of blocks  31  in the example shown, and drain down through subsequent rows of blocks  31 , through drain cavities  40  and drainage passages in the top and bottom surfaces of blocks  31 , as previously described, until reaching the lower row of drain blocks  41 , at which point the drain water enters drain cavities  86  of blocks  41  through the drain holes in the upper surface of blocks  41 . The water then drains from cavities  86  down through drainage holes into drain conduits  91 , which carry the drain water away from retaining wall  71  along slope line E.  
         [0089]      FIG. 7B  is a side elevation view of retaining wall  71  with drain grids  61  of  FIG. 7A , retaining drain fill and back fill material and undisturbed soil according to an embodiment of the present invention. In this view retaining wall  71  is shown at a slight setback angle, as is commonly used for retaining walls over a certain height, or for retaining soil with certain conditions and so on, as described previously. A field of drain fill material  107 , the field depth of which is represented by dimension C, extends directly behind retaining wall  71 , and a field of free-draining back fill material  109 , the field depth represented by dimension D, are utilized for drainage in the example illustrated, similar to those of retaining wall  14  of the prior art example of  FIG. 1 . However, in this example, by virtue of the substantial additional drainage capacity incorporated into blocks  31  and  41  of retaining wall  71 , drain fill field depth C, and free-draining back fill field depth D are substantially shallower than drain field A and back fill field B of  FIG. 1 . A substantially smaller amount of drain fill  107  and back fill  109  is therefore required in construction of the retaining wall of the present invention, and, thus, a smaller excavation field is required prior to construction of the wall. It is noted that a drain pipe or “tile”, as it is known, as shown in  FIG. 1  for carrying away drainage water which accumulates through seepage towards the bottom and behind retaining wall  14 , is also not required in a construction wall according to the present invention because the function of draining the lower drain flow and carrying the water away from the bottom of the retaining wall has been incorporated into drain conduits  91  of blocks  41  of the lower row.  
         [0090]     Drain grids  61  are shown extending from in-between rows of blocks  31 , and are attached to blocks  31  utilizing the mesh header portions  67  (not shown) of drain grids  61 , as previously described with reference to  FIG. 4A . Drain grid  61  extends behind retaining wall  71 , at a slight upward angle, through the fields of drain fill  107  and back fill  109 , generally extending entirely through the fields, and are securely anchored within the drain fill material by the weight of the compacted drain material itself, as well as the downward pressure from undisturbed soil  111  above. Retaining wall  71  is thereby securely anchored to the compacted fill material and soil behind retaining wall  71 .  
         [0091]     In the conventional system described with reference to  FIG. 1 , water drains through the undisturbed soil, and down through the drain fill and back fill material, passing unimpeded through the conventional geogrid mesh anchoring material  17 , and finally down towards the bottom of the retaining wall towards a drain pipe system which carries the water away. In prior art, however, the water drain flow may exceed the drainage capacity of the drain and back fill materials, and the ability of a drain tile to carry the water away. In such an instance, particularly if the surrounding soil is previously saturated, the draining water will begin to accumulate in the fill material towards the bottom of retaining wall, and if the heavy drainage flows continue for a period of time at a rate exceeding the drainage capacity of the system, the water level will increase behind the retaining wall as the drain fill and back fill fields continue to fill with drainage overflow, because the upwardly accumulating water overflow exceeding the drainage capacity of the system, has nowhere else to accumulate but upward, because the water is prevented from passing through the rear surface created by the retaining wall, due to the water resistant or waterproof nature of the construction of the wall and conventional individual blocks utilized, and the undisturbed soil behind the drain fill and back fill fields may be saturated and unable to absorb additional drainage water. Accumulating drain water and an undue surcharge on the back of the retaining wall, and flooding or possible collapse of the system is the possible result in such an occurrence.  
         [0092]     In the present invention, however, such accumulation of water drain flow behind the retaining wall is avoided because of the substantial additional drainage capability incorporated into the new and novel retaining wall building blocks as detailed above, and also the additional drainage capacity of drain grids  61 , which reduces the amount of drainage water that would otherwise seep down through the drain fill and back fill fields through conventional geogrid material, to the bottom of the retaining wall.  
         [0093]     Referring now again to  FIG. 7B , drain grids  61 , extending back into the fields of drain fill  107  and  109 , capture a substantial amount of the drainage flowing down through the fields, and because of the slight angle incorporated into the placement of drain grids  61 , sloping down towards the back of retaining wall  71 , the drainage water captured by drain channels  65  of drain grid  61  is channeled away from the back fill and drainage fill fields towards the rear walls of individual blocks  31 , wherein the water passes from drain channels  65  into drain cavities  40  of blocks  31  through the drain channel passages, as described previously, and is then drained down through the drain cavities  40  of successive blocks  31 , until reaching the lower drain blocks  41 , wherein the drainage water is carried away by drain conduits  91  of drain blocks  41 . If a substantial and sustained rainfall occurs, such as described above, and the water drain flow temporarily exceeds the drainage capacity of the undisturbed soil and supplemental draining provided by drain fill  107  and back fill  109 , any water that may begin to accumulate at the bottom of retaining wall  71  will drain into the perforated rear walls of blocks  41  and  31 , into the internal drain cavities of the individual blocks, and will then drain down through the drain cavities of the blocks as described above. The accumulation of excess water drainage flow at the bottom of retaining wall  71 , in such an instance, it is therefore largely prevented due to the increased drainage capability incorporated into the individual retaining wall blocks.  
         [0094]     It will be apparent to one skilled in the art that many variations of the embodiments described above may be incorporated into the retaining wall blocks and drainage system described above, without departing from the scope and spirit of invention. For example, drain-capable retaining wall blocks  31  and  41  may be of a variety of different sizes, shapes and styles, and the internal fill cavities, drain cavities, and water passages for draining water into and out of the drain cavities may vary significantly in form from embodiments described herein, while retaining the unique drainage functionality incorporated. Furthermore, drain grid  61  may utilize a variety of different types and shapes of drain channels for channeling drain water from the drain fill and back fill fields. For example the drain channels incorporated into the drain grid mesh may be collapsible such that the drain grid with drain channels may be compactably stored and transported, and an upon unrolling and stretching out the drain grid, for example, the drain channels will expand enabling the water channeling functionality of the system.  
         [0095]     Therefore, the present invention described above in terms of the preferred embodiments is defined only by the claims that follow, and not limited by the particular embodiments herein described in detail.