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FIELD OF THE INVENTION 
       [0001]    The present invention pertains generally to retaining walls. Specifically, the invention relates to an apparatus and method of installation for a completely precast concrete retaining wall of the type typically used alongside highways and railways. 
       BACKGROUND OF THE INVENTION 
       [0002]    Various retaining wall systems have been developed for use in retaining soil on an embankment. In a conventional retaining wall design, one of the major design criteria that must be considered is the pressure exerted on the foundation at the front of the base (toe) of the retaining wall system. This becomes particularly limiting in tall vertical walls with sloping backfill. Conventionally designed cantilevered walls reduce the pressure at the toe by providing a lever arm perpendicular to and behind the wall face upon which the vertical load of the backfill acts, creating a moment opposite in direction to the moment due to the horizontal force of the backfill material on the wall face. This moment is increased for design purposes by increasing the area of the cantilever arm subject to the vertical loads by increasing the size or length of the moment arm until a suitable toe pressure is reached and a suitable factor of safety against overturning is reached. 
         [0003]    Many different schemes for increasing the opposing moment force, i.e., the vertical force on the lever arm, have been employed and are well known in the art. Some ways that the industry has tried to oppose the moment force are through using a gravity wall, piling wall, mechanically stabilized earth wall, cantilever wall or an anchored wall.  FIGS. 1 and 2  show examples of a prior art retaining wall. 
         [0004]    A major disadvantage of the prior art is that many of the tieback elements, including straps, anchors, and/or stems, must extend too far behind the face to engage the wall panels in order to produce a margin of safety which is sufficient to overcome the overturning moment. In these situations, there is frequently insufficient room to introduce stabilizing members of adequate length between the front of the wall and the stable earth or rock mass created by excavation. Consequently, a considerable cut must be made into the soil behind the retaining wall in comparison to the height of the soil retained for conventional static, leverage retaining wall systems in order to meet suitable margins of safety. This design constraint effectively limits the height of a wall to single tiers 10 to 12 feet high. 
         [0005]    Cast-in-place cantilever retaining walls are a proven method of retaining earth. These retaining walls typically consist of a vertical wall on top of a horizontal base. These walls work by utilizing the same soil they are retaining at the face of the wall to also anchor the base below. The walls are very commonly designed for up to approximately twenty feet tall retained earth, which is the height difference from the high elevation to the low elevation. For walls over twenty feet, one way to keep the sections from getting too massive is to utilize counterforts. Counterforts are also vertical but perpendicular to the face extending at an angle from the top of face to the base. 
         [0006]    While counterforts have been a great innovation to the industry, a disadvantage of prior art counterforts is that they can require special forming and labor which can be expensive when performed on site. Inside a plant, the sections can be pre-manufactured in a controlled environment at less cost. There is prior art that consists of a face with counterforts, but it still relies on a final pour on-site to fill a base shell which is substantially open. This cast-in-place base can take a significant amount of time to cure and can be costly to form and place the rebar in situ. These prior art retaining walls also require labor intensive temporary shoring to hold the face upright until the cast-in-place base has cured. 
         [0007]    Another prior art product has a precast base and precast wall, but fails to include a counterfort for support. This is disadvantageous as the wall heights grow, since the lever arm to resist the overturning moment is confined within the planes of the base and face. Not only does this lead to unpractical, inefficient reinforcement design and panel thickness, but it requires a large number of expensive and labor intensive mechanical splice sleeve connections at the critical juncture between the face and base. Another disadvantage to not having a counterfort is that the wall needs to be temporarily braced during installation, which adds both cost and time. 
         [0008]    There is also prior art of pre-manufactured upside-down, T-shaped retaining walls with small scale counterfort ribs. The disadvantage of these walls is that they require specific foams and therefore are not customizable. Also their installation allows for less flexibility due to the fixed connection between the base and face of these T-shaped retaining walls. Further, due to how this system needs to be formed, it makes it difficult to add textured aesthetics to the face of the wall. This system is also limited in retained height due to the challenge of handling such a large, one-piece unit. At a certain height, these retaining walls are also limited in size due to shipping limitations. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention provides an apparatus and method for constructing a retaining wall which allows for taller walls and shorter bases by pre-manufacturing parts of the wall to be transported to and assembled at the site. Using pre-manufactured assembly components will save both on installation and transportation costs. Generally, a precast, substantially solid, rectangular or trapezoidal base is set on grade at the job site, and a face panel with an integral counterfort is set upright on the base with a connection joining them together. Temporary shoring is not required with this assembly. As soon as the face panel and counterfort are set on the base, it can withstand temporary wind loads immediately. The invention is also flexible in that the height or width of any of the individual components can vary over a wide range. All of the pieces of the assembly can easily be made to custom sizes. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    In describing the prior art and preferred or illustrative embodiments, reference is made to the accompanying drawings. It should be understood, however, that the application is not limited to the precise arrangements and instrumentalities shown therein: 
           [0011]      FIG. 1  represents a perspective view of a prior art retaining wall. 
           [0012]      FIG. 2  represents a perspective view of a prior art retaining wall. 
           [0013]      FIG. 3  represents a perspective view of a retaining wall comprising a first embodiment of the present invention. 
           [0014]      FIG. 4  represents a plan view of the embodiment of  FIG. 3 . 
           [0015]      FIG. 5  represents a front elevation view of the embodiment of  FIG. 3 . 
           [0016]      FIG. 6  represents a right elevation view of the embodiment of  FIG. 3 . 
           [0017]      FIG. 7  represents a close-up view of a connection between a base and face panel with an exposed end of rebar fixed into an opening in a base with grout. 
           [0018]      FIG. 8   a  represents a plan view of a retaining wall comprising a second embodiment of the present invention using H-Piles beneath the base. 
           [0019]      FIG. 8   b  represents a front view of a retaining wall comprising a second embodiment of the present invention using H-Piles beneath the base. 
           [0020]      FIG. 8   c  represents a right side view of a retaining wall comprising a second embodiment of the present invention using H-Piles beneath the base. 
           [0021]      FIG. 8   d  represents a perspective view of a retaining wall comprising a second embodiment of the present invention using H-Piles beneath the base. 
           [0022]      FIG. 9   a  represents a plan view of a retaining wall comprising a third embodiment of the present invention using H-Piles beneath a pocket in the base. 
           [0023]      FIG. 9   b  represents a front view of a retaining wall comprising a third embodiment of the present invention using H-Piles beneath a pocket in the base. 
           [0024]      FIG. 9   c  represents a right side view of a retaining wall comprising a third embodiment of the present invention using H-Piles beneath a pocket in the base. 
           [0025]      FIG. 9   d  represents a perspective view of a retaining wall comprising a third embodiment of the present invention using H-Piles beneath a pocket in the base. 
           [0026]      FIG. 10   a  represents a plan view of a retaining wall comprising a fourth embodiment of the present invention using a barrier located on top of the face panel. 
           [0027]      FIG. 10   b  represents a front view of a retaining wall comprising a fourth embodiment of the present invention using a barrier located on top of the face panel. 
           [0028]      FIG. 10   c  represents a right side view of a retaining wall comprising a fourth embodiment of the present invention using a barrier located on top of the face panel. 
           [0029]      FIG. 10   d  represents a perspective view of a retaining wall comprising a fourth embodiment of the present invention using a barrier located on top of the face panel. 
           [0030]      FIG. 11   a  represents a plan view of a retaining wall comprising a fifth embodiment of the present invention using a barrier located on the rear side of the face panel. 
           [0031]      FIG. 11   b  represents a front view of a retaining wall comprising a fifth embodiment of the present invention using a barrier located on the rear side of the face panel. 
           [0032]      FIG. 11   c  represents a right side view of a retaining wall comprising a fifth embodiment of the present invention using a barrier located on the rear side of the face panel. 
           [0033]      FIG. 11   d  represents a perspective view of a retaining wall comprising a fifth embodiment of the present invention using a barrier located on the rear side of the face panel. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0034]    While embodiments of this invention can take many different forms, specific embodiments thereof are shown in the drawings and will be described herein in detail with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention, and is not intended to limit the invention to the specific embodiment illustrated. 
         [0035]    Referring to the drawings in detail, wherein like numerals indicate like elements throughout, there is shown in  FIGS. 3-7  a preferred embodiment of a retaining wall in accordance with the various aspects of present invention. While retaining wall systems are commonly used in retaining soil, it should be understood that the present invention can be used in many different applications including retaining other materials such as sand, pebbles or rocks. 
         [0036]      FIG. 3  illustrates a perspective view of an embodiment of wall  10  embodying principles of the present invention. The retaining wall  10  of the present invention is made of precast concrete in two discrete, modular parts. 
         [0037]    Wall  10  comprises a precast concrete face panel  12  with an integral counterfort piece  14  and a precast base piece  16 . A first precast modular part  11  is a generally flat front face panel  12  with an integral counterfort  14  extending from the rear side of the panel  18 . The face panel is typically not completely “flat” because it has surface ornamentation so that for example it appears to be a stone or brick or other ornamentation wall. The panel  12  can have a common height of twenty feet. The counterfort  14  which extends from the rear side of the panel  18  is unitary with the face panel  12 . The face panel  12  will preferably have at least two counterforts  14  spaced apart evenly from ends of the face  12 . The counterfort  14  has a flat bottom, so that in side view, the counterfort  14  is generally a right triangle. However, it should be understood that many different embodiments of the shape of the counterfort have been envisioned. For instance, when viewed from the side, the counterfort  14  could be a generally rectangular shape or be made of a shape that is generally rectangular and then transitions to a triangular shape. Many different combinations are claimed and disclosed herein. A side view of an embodiment of the retaining wall  10  is shown in  FIG. 6 . 
         [0038]    Unless the wall is designed to retain water, it is important to have proper drainage behind the wall in order to limit the pressure to the wall&#39;s design value. Therefore an opening for drainage is preferably provided or the wall can be constructed using the dry stone building method so that the wall can be self-draining. Drainage materials will reduce or eliminate the hydrostatic pressure and improve the stability of the material behind the wall. Therefore, as seen in  FIG. 6 , the counterfort  14  may also have an opening  20  for drainage near the bottom front corner of the counterfort  14 . Face panel  12  may also have a weep hole for drainage towards the bottom. 
         [0039]    The front face panel  12  may have more than one counterfort  14  providing support. The counterfort  14  extends perpendicularly from the face panel  12 , and its base extends rearward (illustratively thirteen feet). The top of the “triangle” may be squared off to have a horizontal top ledge (illustratively of six inches), with a bottom edge (illustratively of ten feet). The bottom edge may also be squared off. 
         [0040]    Reinforcing bars (rebar)  22  can be cast within the counterfort  14 . Preferably, there will be more longitudinal, approximately vertical steel reinforcements incorporated in the lower part of the counterfort securing that part of the wall  10  where overturning forces are greatest. Furthermore, such rebars  22  are preferably in greater concentration at the rear of the counterfort  14  where they can best resist tensile forces, although reinforcements will normally also run approximately vertically at intermediate positions nearer the facing panel  12 . Rebars can also be added within the base  16  for additional strength. 
         [0041]    These rebars  22  act as a tensioning device within the concrete helping to meet design loads. In one embodiment, the rebars  22  extend through the bottom of the counterfort  14 . The rebars  22  can also terminate in an “L” or “backwards L” configuration. This helps the exposed portions of the rebars  22  act as anchors. Another option is to utilize a forged foot  24  at the free end, where the bar (illustratively one inch diameter) terminates in a horizontal disk (illustratively two and a half inch diameter). However, it should be understood that the rebar  22  can terminate in a number of differing configurations. 
         [0042]    A second precast modular part  15  comprises a base  16  which is illustratively one foot thick. The base  16  is generally a rectangular or trapezoidal shaped platform and typically is set on grade. Because the base  16  is a platform, it is generally solid with no substantial openings other than small openings for grout fill. The base  16  is precast concrete and therefore does not require that the base  16  be cast in-situ at the construction site. 
         [0043]    In one embodiment, a shear key  26  can be made between the face  12  or counterforts  14  and the base  16 . This shear key can be a depression in the base  16  and sized to accept the bottom  30  of the front face panel  12 . Once the bottom  30  of the face  12  is set into place, the voids between the shear key  26  and bottom  30  of the face panel  12  can be filled with grout to solidify the connection. 
         [0044]    A shear key  26  can also extend down from the base  16  into the ground. This could be a pre-manufactured shear key or there can be exposed rebar extending down from the base  16  to be later poured with concrete in the field. In another embodiment, the base  16  can be precast with a front lip which protrudes from the end of the base  16  near the face panel  12 . 
         [0045]    In one embodiment, the base  16  has at least one opening  32  sized to accept the downward-extending rebar  22  ends from the counterfort  14 . This opening  32  can be sized to accept more than one rebar  22  end. In a preferred embodiment, the base has a single row or multiple rows of openings  32 , illustratively four and a half inches in diameter, to receive multiple downward-extending rebar  22  ends from the counterfort  14 . This connection point between the counterfort  14  and base  16  is shown more closely in  FIG. 5 . As shown in this Figure, rebar  22  can terminate in forged foot anchor  24 . 
         [0046]    The connection between the first module  11  and second module  15  is made by inserting an end of a piece of rebar of one module into an opening in the other module and then sealing the connection with grout. For the purposes of this disclosure, a method of connecting the modules will be described where the first module has protruding rebar and the second module has openings. However, it should be understood to one of ordinary skill in the art that the connection described herein can be reversed with the second module  15  having rebar extending from its top surface and connecting with openings within the bottom surface of the first module  11 . 
         [0047]    To connect the first module  11  and second module  15 , an installer would place the second module  15  into a substantially horizontal position. The installer would then raise the first module  11  above the second module  15  and align the exposed ends of the rebars  22  of the first module  11  with the openings  32  on the second module  15 . The installer would then lower the first module  11  on top of the second module  15  such that the exposed ends of the rebar  22  of the selected first module are placed within the openings in the second module. One advantage of this arrangement is that once the first module  11  is placed on the second module  15 , no temporary shoring is required to hold the face upright until the grout connection between the first module  11  and second module  15  has cured. 
         [0048]    By lowering the first module  11  onto the second module  15 , the anchor  24  is simultaneously lowered into an opening  32  in the base  16 . This opening  32  can be a straight cylindrical shape, tapered or formed using a corrugated pipe. It can extend partially or all the way through the base  16 . It shall be understood that those of ordinary skill in the art can use a number of different sizes and shapes for the opening  32 . Before the first module  11  is completely set on the second module  15 , an installer can use one or more shims  36  to make the front face panel  12  plumb in both the vertical and horizontal directions. An installer can also use shims  36  to rotate the face  12  to any desired angle. 
         [0049]    Once the installer has installed the shims  36  and is satisfied with the placement of the first  11  and second modules  15 , the anchor  24  can finally be set into the opening  32 . The shims  36  elevate the first module  11  above the second module  15  enough so that an installer can pump a high strength grout  34  into the opening  32 . This high strength grout  34  fills the void remaining in the opening  32  and bonds itself to the concrete base  16  and the anchor  24 . This results in a shear cone in the base to resist the pullout of the rebar  22 , ultimately connecting the two precast modular pieces  11 ,  15 . Once the face  12  and counterfort  14  are connected to the base  16  with grout  34 , the connection is complete. An installer can then backfill the area behind the retaining wall  10 . 
         [0050]    In a typical installation, multiple retaining walls  10  are placed adjacent to one another to form a continuous wall. To allow for flexibility between adjacent walls  10 , an installer can place a shear key or use ship laps between adjacent modules. This interface between adjacent walls can either be grouted or not grouted. A product such as butyl mastic joint sealant or wrap can also be used to seal the vertical joint between adjacent faces  12 . 
         [0051]    If circumstances require extra precautions to keep the base  16  from sliding once it is backfilled and any surcharge loads are applied, several measures can be taken. One option is that the bottom of the base  16  can be textured or roughened to increase friction between the base  16  and subsurface ground beneath the base. An alternative is that the base  16  can be set on shims and have various holes or ports  38  in the base  16  so that flow-able grout can be pumped through the base  16  and into the void created by the shims underneath. This grout will serve to increase the frictional force between the base  16  and subsurface. 
         [0052]    If there are poor soil conditions under the base, then H-piles  40  can be driven into the ground and the base  16  set on top of these piles  40  for added stability.  FIG. 8  shows an embodiment of the present invention with piles  40  driven into the earth underneath the base  16 . If desired, a pocket  42  can be created in the base  16  to allow the pile  40  to extend up into the base  16  and then the connection can be filled with grout.  FIG. 9  shows images of pocket  42  formed in base  16 . Alternatively, the piles  40  could extend up into the grouted area between the subsurface and the base  16  and then this void would be filled with grout. Still a fourth alternative method would be to utilize a cast-in-place pile cap which can be poured prior to setting the base  16 . This pile cap is typically a thick concrete mat that rests on concrete, steel or timber piles that are driven into the unstable ground to provide a suitable stable foundation. 
         [0053]    In another embodiment, a vehicle impact barrier  44  can be formed and cast-in-place on top of the wall  10  or behind the wall  10 .  FIG. 10  shows an embodiment of the retaining wall  10  with a vehicle impact barrier  44  attached on top of the wall  10 .  FIG. 11  shows an alternative embodiment of the retaining wall  10  with a vehicle impact barrier  44  attached to the rear side of the panel  18 . To create a cast-in-place impact barrier, will use a face panel  12  that has exposed rebar extending out of the face  12 . This rebar will extend vertically out of the top surface of the face panel  12  if a user wishes to have the impact barrier  44  formed on top of the face  12 . However if a user prefers that the impact barrier  44  be formed on a rear surface  18  of the face  12 , then the rebar will extend horizontally out of the rear surface  18 . In either scenario, an installer can cast an impact barrier  44  around the exposed rebar to form the cast-in-place barrier  44  at the desired location. Another embodiment of this impact barrier eliminates the need for in situ casting because a pre-manufactured, pre-cast barrier can also be formed integrally with the face  12  at the factory. The pre-cast concrete barrier can be precast in a number of different desired locations. However, in a preferred embodiment, the pre-cast concrete barrier is located on top of the face  12 . 
         [0054]    All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. 
         [0055]    Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features. 
         [0056]    The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Summary:
A retaining wall comprises a precast concrete face panel with integral counterfort connected to the rear of the facing and a precast concrete base supporting the facing and the counterfort. The counterfort comprises a reinforced concrete slab having a substantially vertical front portion at a substantially right angle to a base portion, and a rear portion running from substantially the top of the counterfort to the rear of the base portion thereof. The face and counterfort module is connected to the base module through the use of rebar and openings which are fixedly attached together using a high strength group.