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CROSS-REFERENCE TO RELATED APPLICATIONS 
   Priority of U.S. Provisional Patent Application Ser. No. 60/277,573, filed 21 Mar. 2001, incorporated herein by reference, is hereby claimed. 

   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not applicable 
   REFERENCE TO A “MICROFICHE APPENDIX” 
   Not applicable 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to the repair of building foundations by underpinning. More specifically, the present invention relates to an interlocking slab leveling system using longitudinally reinforced segmented underpinning pilings. 
   2. General Background of the Invention 
   Most conventionally available leveling systems use segmented underpinning pilings comprised of vertically stacked, unconnected, precast concrete segments. These segments are pressed or driven vertically into the soil one at a time until an adequate load capacity is obtained. Segmented underpinning pilings are useful because they can be installed with minimal clearance underneath an existing foundation which is to be leveled. 
   Although serviceable, these segmented underpinning pilings have various disadvantages, which include, but are not limited to: (a) pile segments being not aligned, other than being stacked one on top of each other allowing for problematic misalignments and (b) completed underpinning pilings being unreinforced stacks of precast concrete segments. Misalignment of segments during installation can produce several problematic conditions related to pile stability. 
   Non-interlocked segmented underpinning pilings can separate at segment joints or fail at segment midpoints where dynamic soil conditions create transient longitudinal or tensile stresses, such as in clay soils having high shrink-swell potentials. Separation of segments can occur when clay soils swell after an increase in moisture content where the soil swell exposes the segmented pile to tension forces in a longitudinal direction. 
   These transient longitudinal stresses are detrimental to non-interlocked segmented underpinning pilings because they can create gaps between the piling segments. Even a slight gap between two segments allows for soil intrusion between the two segments and prevents closing of the gap when soil moisture decreases. Each time a new swell cycle is found the gap can be increased allowing for additional soil intrusion. Each joint between the various segments can experience this phenomenon. Over a period of years, cyclical shrink-swell effect can lift the upper portion of the segmented underpinning pile and the supported structure creating a new non-leveled condition. 
   A second type of segmented piling system is described in U.S. Pat. No. 5,288,175 which describes a segmental precast concrete underpinning pile using a continuous high strength strand for longitudinally reinforcing the various the precast segments which strand is bonded or anchored upon completion. This type of piling is more labor intensive to install then the present invention in requiring monitoring of the placement of the individual segments, threading of the strand, and placement of the bonding agent. Areas with high water tables can circumvent the use of a bonding agent as the water comes in contact with the agent. Furthermore, the steel strand can relax over time reducing the amount of longitudinal reinforcement. Additionally, if the strand fails due to corrosion or for some other reason the entire pile becomes an unreinforced segmented pile with the above described disadvantages. 
   The following U.S. patents are incorporated herein by reference: U.S. Pat. No. 5,288,175. 
   While certain novel features of this invention shown and described below are pointed out in the annexed claims, the invention is not intended to be limited to the details specified, since a person of ordinary skill in the relevant art will understand that various omissions, modifications, substitutions and changes in the forms and details of the device illustrated and in its operation may be made without departing in any way from the spirit of the present invention. No feature of the invention is critical or essential unless it is expressly stated as being “critical” or “essential.” 
   BRIEF SUMMARY OF THE INVENTION 
   The apparatus of the present invention solves the problems confronted in the art in a simple and straightforward manner. What is provided is a method and apparatus for repairing building foundations by segmented underpinning. More specifically, the present invention provides a method and apparatus for repairing building foundations using interlocking segmented underpinning piles which are reinforced in a longitudinal direction. 
   In a preferred embodiment, the invention incorporates a precast starter segment with a coil embedded in one end of the segment, and a coil rod protruding from the other end. This starter segment is driven into the soil with its protruding rod end facing downwards. A second segment is next interlocked with the first by threading the second segment&#39;s rod end into the coil end of the starter segment. The second segment is screwed into the first until the two lock. The segmented underpinning piling is then further driven into the ground with the second segment. 
   The above procedure is repeated for third, fourth, and additional segments until sufficient load capacity and depth are obtained for the underpinning piling. The process ultimately creates an interlocked segmented underpinning piling reinforced in the longitudinal direction. 
   In a preferred embodiment, the method and apparatus of a preferred embodiment of the present invention provides a longitudinally aligned, interlocked, and longitudinally reinforced, segmented underpinning piling. The segmented underpinning piling can be installed with minimal clearance underneath an existing structure. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     For a further understanding of the nature, objects, and advantages of the present invention, reference should be had to the following detailed description, read in conjunction with the following drawings, wherein like reference numerals denote like elements and wherein: 
       FIG. 1  is sectional view of a pile section in a preferred embodiment of the apparatus of the present invention; 
       FIG. 2  is a section view of a upper coil, bars, and rod in a preferred embodiment of the apparatus of the present invention; 
       FIG. 3  shows an excavated area under a building slab which is supported by a wooden piling; 
       FIG. 4  shows the upper portion of the wooden piling being removed; 
       FIG. 5  shows the top of the lower portion of the wooden piling being drilled; 
       FIG. 6  shows a starter pile segment being attached to the top of the lower portion of the wooden piling; 
       FIG. 7  is a sectional view of  FIG. 6  showing the starter pile segment attached to the top of the lower portion of the wooden piling; 
       FIG. 8  shows a jack being used to push the starter pile segment and wooden piling into the soil; 
       FIG. 9  shows the jack of  FIG. 8  after the starter pile segment and wooden piling have been pushed down into the soil; 
       FIG. 10  shows a second pile segment being attached to the starter pile segment; 
       FIG. 11  shows the jack supporting the slab after several pile segments have been pushed into the soil; 
       FIG. 12  shows a block being placed on top of the piling cap while thejack is supporting the building slab after several pile segments have been pushed into the soil; 
       FIG. 13  shows two blocks supporting the building slab after several pile segments have been pushed into the soil; 
       FIG. 14  shows backfill filling the excavated space under the slab; 
       FIG. 15  shows a sectional and perspective view of a preferred embodiment of the apparatus of the present invention after several pile segments and the wooden piling have been pushed into the soil; 
       FIG. 16  shows a perspective view of a control system for simultaneously operating a series of hydraulic jacks for controlling the lift of a defined area of the building slab; 
       FIG. 17  is sectional view of an alternative embodiment for a pile section in a preferred embodiment of the apparatus of the present invention; 
       FIG. 18  is sectional view of a second alternative embodiment for a pile section in a preferred embodiment of the apparatus of the present invention; 
       FIG. 19  shows two pile sections interlocked in a second alternative embodiment; 
       FIG. 20  shows an exploded view of a second alternative embodiment. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  is sectional view of a pile section  10  in a preferred embodiment of the apparatus of the present invention. The segment body  20  can be made of concrete or other structural material having good compressive strength. It preferably has a circular cross section of approximately 6 to 14 inches in diameter and is 6 to 14 inches in height. However, its cross-section can be of different or varying shapes without substantially impacting the effectiveness of each segment&#39;s bearing capacity. As shown in  FIG. 2 , the segment body  20  includes two bars  30 , coil  40 , and rod  50 . The two bars  30  can be attached to the coil  40  and rod  50  by various conventionally means such as welding. The pitch of the threads for the coil  40  and rod  50  should match and should be course enough to avoid seizure even if particles of soil become lodged inside said threads. One thread which has worked is adapted (as shown in  FIGS. 1 ,  2 , and  10 ) from the coil rod, coil hangers, and/or screed chairs manufactured by Meadow Burke (www.meadowburke.com). The two bars  30 , coil  40 , and rod  50  form interlocking unit  55 . Interlocking unit  55  can be prefabricated and then integrally cast with segment body  20 . Preferably interlocking unit  55  is placed in the center of the cross section of segment body  20  along the body&#39;s longitudinal axis. Placing interlocking unit  55  in the center facilitates easy installation of various pile segments along a single longitudinal axis. 
     FIGS. 3 through 15  show various steps for installing a segmented piling on top of an existing wooden piling. As shown in  FIG. 3  an excavated area  90  under the building slab  60  and around the upper portion  80  of the wooden piling is made.  FIG. 4  shows the upper portion  80  of the wooden piling being removed by a saw  120 . The lower portion  110  of the wooden piling remains in the subsoil  105 .  FIG. 5  shows the top  115  of the lower portion  110  of the wooden piling being drilled by drill  130  to form bore  116 . 
     FIG. 6  shows a starter pile segment  10  being attached to the top  115  of the lower portion of the wooden piling. The starter pile segment  10  is turned in the direction of arrow  135  while downward pressured is placed. Rod  50  will threadably lock with the lower section  110  of wooden piling through bore  116 .  FIG. 7  is a sectional view of  FIG. 6  showing the starter pile segment  10  attached to the top of lower portion  110  of the wooden piling. The threads of rod  50  are interlocked with the wooden piling and the bottom surface  15  of segment  10  is touching the top surface  16  of wooden piling. Thus, the segment  10  and wooden piling can become interlocked. 
     FIG. 8  shows jack  150  being used to push starter pile segment  10  and wooden piling into soil  105  in the direction of arrow  140 . The downward pushing force is created by the weight of the building slab  60  as jack arm  151  is raised.  FIG. 9  shows jack  120  having been pushed down into soil  105  (in the direction of arrow  140 ) both starter pile segment  10  and wooden piling where jack arm  151  is in a raised condition. Downward movement is achieved where the reactionary force from the building slab  60  transferred through jack arm  151  exceeds the combined frictional forces created by soil  105  against the lower portion  110  of the wooden piling. Jack  150  is now removed so that another segmented piling  10  can be installed. 
     FIG. 10  shows a second pile segment  10 A being attached to the starter pile segment  10 . Rod  50 A of pile segment  10 A threadably engages coil  40  of pile segment  10 . Pile segment  10 A is turned until its lower surface engages the upper surface of pile segment  10 . Thus, pile segment  10 A and pile segment  10  become interlocked with each other. Jack  150  is placed on top of pile segment  10 A and the previously described process of jacking and pushing down is repeated until pile segment  10 A, pile segment  10 , and wooden piling have been pushed down into soil  105  in the direction of arrow  140 . Jack  150  is then again removed.  FIG. 15  shows a perspective view of a preferred embodiment of the apparatus of the present invention after several pile segments  10  and the lower portion  110  of the wooden piling have been pushed into soil  105 . Building slab  60  is supported by jack  150  which is supported on the uppermost pile segment  10 . 
   Additional pile segments can be installed using similar procedures until the frictional forces from the soil  105  on the lower section  110  of the wooden piling until all segmented pile sections  10  reach a point where jack  150  can actually lift building slab  60  instead of further pushing down the segmented piling. Piling cap  170  is then installed on top of the uppermost segmented pile  10 . This point is shown in  FIG. 11  where jack  150  is supporting slab  60  after several pile segments  10  have been pushed into soil  105 . The lower portion  110  of the wooden piling is below the numerous segmented pile sections  10 . 
     FIG. 12  shows a block  180  and shims  181 ,  182  placed on top of piling cap  170  while the jack  150  is supporting the building slab  60  after several pile segments  10  have been pushed into the soil  105 . Ultimately, building slab  60  will rest on block  180  and shims  181 ,  182 . Shims  181 ,  182  should be selected to ensure proper height of the bottom  70  of building slab  60 .  FIG. 13  shows two blocks supporting building slab  60  after several pile segments  10  have been pushed into soil  105 . A second block  185  and second set of shims  186 ,  187  are inserted between pile cap  170  and building slab  60 . 
     FIG. 14  shows backfill  190  filling the excavated space  90  under building slab  60 . The backfill  190  can be sand or other fill compatible with soil  105 . Preferably, the backfill should be self-compacting to minimize possible subsidence. 
   The above described process has included a wooden piling. However, the segmented piling blocks  10  can be used by themselves without wooden pilings. 
     FIG. 16  shows a perspective view of a conventionally available control system  320  for simultaneously operating a series of hydraulic jacks  300  for controlling lift of a defined area of building slab  60 . Use of control system  320  minimizes the risk that slab  60  will crack due to differential forces created by the set of jacks  300 . Using individual jacks risks differentially raising the slab and creating stress cracks. Using control system  320  allows numerous segmented piles to be simultaneously pushed into soil  105 . 
     FIG. 17  is sectional view of an alternative embodiment for a pile section  11  in a preferred embodiment of the apparatus of the present invention. The segment body  20  can be made of concrete or other structural material having good compressive strength. It preferably has a circular cross section of approximately 6 to 14 inches in diameter and is 6 to 14 inches in height. However, its cross-section can be of different and varying shapes without substantially impacting the effectiveness of each segment&#39;s bearing capacity. The segment body  20  includes two bars  31  which substantially extend throughout the height of block  20 . Also included are upper coil  40  and lower coil  41 . Rod  50  is threadably attached by lower coil  41  and can be permanently welded or attached by some other conventional means. 
     FIGS. 18 and 20  show sectional views of a second alternative embodiment for a pile section  12  in a preferred embodiment of the apparatus of the present invention. The segment body  20  can be made of concrete or other structural material having good compressive strength. It preferably has a circular cross section of approximately 6 to 14 inches in diameter and is 6 to 14 inches in height. However, its cross-section can be of different and varying shapes without substantially impacting the effectiveness of each segment&#39;s bearing capacity. The segment body  20  includes a recessed space  400  and longitudinal bore  470 . A threaded rod  430  is placed in longitudinal bore  470 . Upper washer  420  is placed in recessed spaced  400  over threaded rod  430 . Nut  410  is threaded onto the top portion of threaded rod  430  in recessed space  400 . Lower washer  440  is placed over the lower portion of threaded rod  430  and nut  450  used to secure threaded rod  430  into block  20 . Nut  410  is installed on rod  430  such that it has adequate threads above the top of rod  430  to accept a second rod. The bottom of rod  460  has adequate threads protruding through nut  450  so that it can threadably engage a nut  410  on a second block  12 . Nuts  410  and  450  can be torqued down on block  20  to prevent rotational slippage of rod  430 .  FIG. 19  shows two pile sections  12  and  12 A interlocked in a second alternative embodiment. The portion of rod  430 A protruding through nut  450  threadably engages nut  410 . Thus sections  12  and  12 A become interlocked. 
   PARTS LIST 
   The following is a list of parts and materials suitable for use in the present invention: 
   Reference Numeral Description 
   
       
       
         
             10  pile segment of a preferred embodiment of the present invention 
             10 A second pile segment 
             11  pile segment for an alternative embodiment 
             12  pile segment for a second alternative embodiment 
             12 A second pile segment for second alternative embodiment 
             15  bottom surface of pile section 
             16  top surface of wooden piling 
             20  segment body (concrete or other structural material) 
             30  bar (steel, copper, aluminum or other structural material) 
             31  bar (steel, copper, aluminum or other structural material) 
             40  upper coil 
             40 A upper coil in second pile segment 
             41  lower coil 
             50  rod 
             50 A rod in second pile segment 
             55  interlocking unit 
             60  building slab 
             70  bottom of slab 
             80  upper portion of wood piling 
             85  cut portion of wood piling 
             90  excavated space under building slab 
             100  top of soil 
             105  soil 
             110  lower portion of wood piling 
             115  top portion 
             116  longitudinal bore 
             120  saw 
             130  drill 
             135  arrow 
             140  arrow 
             150  jack 
             151  raised portion of jack 
             160  arrows 
             170  pile cap 
             180  block 
             181  shim 
             182  small shim 
             185  block 
             186  shim 
             187  small shim 
             190  backfill 
             300  hydraulic jacks 
             310  control panel for hydraulic jacks 
             320  hydraulic lifting system 
             400  recessed space 
             410  upper nut 
             420  upper washer 
             430  rod 
             430 A rod 
             440  lower washer 
             450  lower nut 
             450 A lower nut 
             460  lower tip of rod 
             470  longitudinal space through pile segment 
         
       
     
  
   All measurements disclosed herein are at standard temperature and pressure, at sea level on Earth, unless indicated otherwise. All materials used or intended to be used in a human being are biocompatible, unless indicated otherwise. 
   Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention set forth in the appended claims. 
   The foregoing embodiments are presented by way of example only; the scope of the present invention is to be limited only by the following claims.

Summary:
A method and apparatus for repairing building foundations by segmented underpinning. More specifically, a method and apparatus is provided for repairing building foundations using interlocking segmented underpinning piles which are reinforced in a longitudinal direction.