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CROSS-REFERENCE TO RELATED APPLICATION 
   This application claims the benefit of U.S. provisional patent application Ser. No. 60/401,596 filed Aug. 7, 2002. 

   BACKGROUND OF THE INVENTION 
   The present invention relates generally to a screw anchor apparatus for use in underpinning and tiebacks and, in particular, to a modular helical anchor. 
   Helical anchors are well known. Helical anchors are utilized in the geotechnical industry to anchor building foundations in unstable soil and to stabilize and/or repair the integrity of existing foundations and the like. A typical helical anchor is part of an assembly that consists of at least one elongated shaft member having at least one helical plate member attached thereto and extending therearound. The helical plate member is fixedly attached to the shaft member and the assembly is mounted in the ground for securing to a foundation or the like. Typically, the helical plate member is placed in the ground and the helical anchor assembly is rotated about the longitudinal axis of the shaft member, which enables the helical plate member to engage with the ground material, drawing the entire assembly into the ground to form, typically with a plurality of other anchor assemblies, a firm anchor point for the foundation. The anchor assemblies can be utilized under compression, known in the art as underpinning, wherein the anchor assembly supports a body by absorbing a compression load between opposed ends, one of which is attached to the ground and the other of which is attached to the body. The anchor assemblies can also be utilized under tension, known in the art as a tieback, wherein the anchor assembly retains the body to the foundation by applying a tension load to the opposed ends thereof. 
   It is common for the helical anchor assembly to vary in length, depending on the different requirements of the particular installation. Typically, the length of the helical anchor is varied by attaching a plurality of shaft members end to end, with each of the shaft members having at least one helical member attached thereto, to form an elongated anchor assembly. The shaft members are typically required to be attached by welding at the job site when the helical anchor assembly is installed, which is disadvantageously time-consuming and expensive. In addition, the helical anchor assemblies are often installed in tight quarters, which makes welding the shaft members particularly difficult. 
   It is desirable, therefore, to provide a helical anchor assembly that is modular in design for modifying the length of the assembly for the requirements of each installation. It is also desirable to provide a helical anchor that may be assembled, utilized, and installed in tight quarters. 
   SUMMARY OF THE INVENTION 
   The present invention concerns a modular helical anchor apparatus for use in underpinning and tiebacks. The modular helical anchor assembly includes: at least two shaft sections; at least one anchor section having a helical plate attached thereto; and fastening means releasably attaching said shaft sections to opposite ends of said at least one anchor section. 
   The modular helical anchor in accordance with the present invention is advantageously suitable for use as an underpinning (under compression) or as a tieback (under tension). The shaft sections and anchor sections are modular and, therefore, may be prefabricated and used as a kit together with a plurality of other shaft sections and anchor sections to tailor the helical anchor assembly to the requirements of the particular installation, allowing field personnel at the construction site to select the size and quantity of helices without field welding. 
   The present invention advantageously provides a modular helical anchor assembly that is modifiable in length by fastening shaft portions with the anchor portions without requiring the portions to be welded together. Furthermore, the fasteners of the present invention allow the anchor assembly to be assembled and mounted in tight quarters. 

   
     DESCRIPTION OF THE DRAWINGS 
     The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment when considered in the light of the accompanying drawings in which: 
       FIG. 1  is an exploded elevation view of a modular helical anchor apparatus in accordance with the present invention; 
       FIGS. 1A and 1B  are end views of the first shaft section and the tube of the first anchor section shown in  FIG. 1 ; 
       FIGS. 1C and 1D  are end views of alternate embodiments of the first shaft section and the tube of the first anchor section shown in  FIG. 1 ; 
       FIG. 2  is an exploded perspective view of the modular helical anchor apparatus shown in  FIG. 1 ; 
       FIG. 3  is an exploded perspective view of an alternate embodiment of the modular helical anchor apparatus according to the present invention; and 
       FIG. 4  is an exploded perspective view of another alternate embodiment of the modular helical anchor apparatus according to the present invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   A modular helical anchor apparatus  10  is shown in  FIGS. 1 and 2  for use in underpinning and tieback installations. A first or upper shaft section  11  can be formed of a square cross section metal bar stock of any suitable length having an upper end  11   a  and a lower end  11   b . A second or middle shaft section  12  can be constructed the same as the first shaft section  11  having an upper end  12   a  and a lower end  12   b . A third or lower shaft section  13  can be formed of the same material with the same cross section as the sections  11  and  12  having an upper end  13   a  and a lower end  13   b . A first anchor section  14  is formed of a square cross section tube  15  having an open upper end  15   a  sized to receive the lower end lib and an open lower end  15   b  sized to receive the upper end  12   a . The tube  15  has a helical plate  16  attached thereto and extending thereabout. Preferably, the helical plate  16  is welded to the tube  15 . A second anchor section  17  is formed of a square cross section tube  18  having an open upper end  18   a  sized to receive the lower end  12   b  and an open lower end  18   b  sized to receive the upper end  13   a . The tube  18  has a helical plate  19  attached thereto and extending thereabout. Preferably, the helical plate  19  is welded to the tube  18 . The lower end  13   b  is pointed or tapered to assist in installing the anchor apparatus  10  in the ground. 
     FIGS. 1A and 1B  are end views of the first shaft section  11  and the tube  15  of the first anchor section  14  respectively showing the square cross section.  FIGS. 1C and 1D  are end views of alternate embodiment first shaft section  11 ′ and tube  15 ′ of the first anchor section  14  respectively showing a round or circular cross section. 
   The length, cross section, and number of the sections  11  and  12  and the diameter of each of the helical plates  16  and  19  can be selected to correspond to the requirements of the installation. Thus, the modular design of the helical anchor  10  according to the present invention permits an anchor system to be custom built to the installation requirements. The upper end  13   a  is provided with a through aperture  13   c  that can be aligned with a through aperture  18   d  formed in the lower end  18   b  when the third shaft section  13  is inserted into the second anchor section  17 . A suitable fastener such as a bolt  20  is inserted through the apertures  18   d  and  13   c  and threadably engaged with a nut  21 . Alternatively, another suitable type of fastener, such as a rivet or the like (not shown) is used to fasten the shaft sections  11  and  12  to the tube  18 . The second shaft section  12  is attached to the second anchor section  17  in a similar manner with the lower end  12   b  being inserted into the upper end  18   a  and a through aperture  12   d  aligned with a through aperture  18   c  to receive the bolt  20  and the nut  21 . The first anchor section  14  and the first shaft section  11  are attached in a similar manner. The first shaft section  11  has a through aperture  11   c  formed in the upper end  11   a  to enable additional anchor sections and shaft sections to be attached as desired. 
   The modular helical anchor apparatus  10  is suitable for use as an underpinning (under compression) or as a tieback (under tension). The modular design permits assembly in the field whereby the diameter and number of the helical plates to be used can be selected on the job without resorting to welding as was required by the prior art anchoring systems. Also the modular helical anchor apparatus  10  is suitable for use in tight quarters (e.g., under a foundation) whereby subsequent shaft sections and anchor sections can be added as the anchor is being screwed into place. 
   An alternate embodiment modular helical anchor apparatus  30  is shown in  FIG. 3  for use in underpinning and tieback installations. A first or upper shaft section  31  can be formed of a square cross section metal tubular stock of any suitable length as can a second or middle shaft section  32  and a third or lower shaft section  33 . A first anchor section  34  is formed of a square cross section bar stock  35  having a helical plate  36  attached thereto and extending thereabout. Preferably, the helical plate  36  is welded to the bar stock  35 . A second anchor section  37  is formed of a square cross section bar stock  38  having a helical plate  39  attached thereto and extending thereabout. Preferably, the helical plate  39  is welded to the bar stock  38 . The anchor sections  35  and  37  each have ends that are sized to slide into the interiors of the shaft sections  31 ,  32  and  33  to form the anchor apparatus  30 . The shaft sections and the anchor sections are each provided with through apertures, similar to the through apertures  11   c ,  11   d ,  15   a ,  15   b ,  12   c ,  12   d ,  18   c ,  18   d ,  13   a , and  13   c  shown in  FIG. 1 , and can be releasably attached using the bolt  20  and nut  21  fasteners shown in  FIG. 1 . 
   Another alternate embodiment modular helical anchor apparatus  40  is shown in  FIG. 4  for use in underpinning and tieback installations. A first or upper shaft section  41  can be formed of a square cross bar stock of any suitable length as can a second or middle shaft section  42  and a third or lower shaft section  43 . A first anchor section  44  is formed of a square cross section bar stock  45  having a helical plate  46  attached thereto and extending thereabout. Preferably, the helical plate  46  is welded to the bar stock  45 . A second anchor section  47  is formed of a square cross section bar stock  48  having a helical plate  49  attached thereto and extending thereabout. Preferably, the helical plate  49  is welded to the bar stock  48 . A lower end  41   b  of the shaft section  41  is formed with an open end or upset that accepts an upper end  45   a  of the bar stock  45 . Similar open ends or upsets are formed on the ends  42   a ,  42   b  and  43   a  to receive the corresponding ends  45   b ,  47   a  and  47   b . Thus, the anchor sections  45  and  47  are sized to slide into the interiors of the upsets of the shaft sections  41 ,  42  and  43  to form the anchor apparatus  40 . The upsets of the shaft sections and the anchor sections are each provided with through apertures, similar to the through apertures  11   c ,  11   d ,  15   a ,  15   b ,  12   c ,  12   d ,  18   c ,  18   d ,  13   a , and  13   c  shown in  FIG. 1 , and can be releasably attached using the bolt  20  and nut  21  fasteners shown in  FIG. 1 . 
   Alternatively, the shaft sections  11 ,  12 ,  13 ,  31 ,  32 ,  33 ,  41 ,  42 , and  43  and the anchor sections  15 ,  17 ,  35 ,  37 ,  45 , and  47  are each formed of tube or stock that is circular in cross section or any other type of shape that is advantageous for transmitting torque to the ground for attachment thereto. 
   The apparatus  10  in accordance with the present invention advantageously provides a helical anchor assembly that is modular, cost-effective, and timesaving for installation of the helical anchor assembly. The present invention advantageously provides a modular helical anchor assembly that is customizable in length by fastening shaft portions with the anchor portions without requiring the portions to be welded. Furthermore, the fasteners of the present invention allow the anchor assembly to be assembled and mounted in tight quarters. 
   In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.

Summary:
A modular helical anchor apparatus includes at least two shaft sections connected by an anchor section. An end of each of the shaft sections is releasably connected to opposite ends of the anchor sections by fasteners. The anchor section includes a helical member.