Patent Publication Number: US-7901159-B2

Title: Apparatus and method for building support piers from one or more successive lifts

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This is a continuation application of Ser. No. 10/728,405 filed Feb. 12, 2004 entitled “Apparatus and Method for Building Support Piers From one or Successive Lifts Formed in a Soil Matrix” which is the utility application derived from and incorporating provisional application Ser. No. 60/513,755 filed Oct. 23, 2003 entitled “Apparatus and Method for Building Support Piers From Successive Lifts Formed in a Soil Matrix” for which priority is claimed. 
    
    
     BACKGROUND OF THE INVENTION 
     In a principal aspect, the present invention relates to an apparatus and a method for constructing a support pier comprised of one or more compacted lifts of aggregate material. The apparatus enables formation or construction of a single or multi-lift pier within a soil matrix while simultaneously reinforcing the soil adjacent the pier. The apparatus thus forms a cavity in the soil matrix by forcing a hollow tube device into the soil matrix followed by raising the tube device, injecting aggregate through the tube device into the cavity section beneath the raised tube device and then driving the tube device downward to compact the aggregate material while simultaneously forcing the aggregate material laterally into the soil matrix. 
     In U.S. Pat. No. 5,249,892, incorporated herewith by reference, a method and apparatus are disclosed for constructing short aggregate piers in situ. The process includes drilling a cavity in a soil matrix and then introducing and compacting successive layers or lifts of aggregate material in the cavity to form a pier that can provide support for a structure. Such piers are made by first drilling a hole or cavity in a soil matrix, then removing the drill, then placing a relatively small, discrete layer of aggregate in the cavity, and then ramming or tamping the layer of aggregate in the cavity with a mechanical tamper. The mechanical tamper is typically removed after each layer is compacted, and additional aggregate is then placed in the cavity for forming the next compacted layer or lift. The lifts or layers of aggregate, which are compacted during the pier forming process, typically have a diameter of 2 to 3 feet and a vertical rise of about 12 inches. 
     This apparatus and process produce a stiff and effective stabilizing column or pier useful for the support of a structure. However this method of pier construction has a limitation in terms of the depth at which the pier forming process can be accomplished economically, and the speed with which the process can be conducted. Another limitation is that in certain types of soils, especially sand soils, cave-ins occur during the cavity drilling or forming process and may require the use of a temporary casing such as a steel pipe casing. Use of a temporary steel casing significantly slows down pier production and therefore increases the cost of producing piers. Thus, typically the process described in U.S. Pat. No. 5,249,892 is limited to forming piers in limited types of soil at depths no greater than approximately 25 feet. 
     As a result, there has developed a need for a pier construction process and associated mechanical apparatus which can be successfully and economically utilized to form or construct piers at greater depths, at greater speeds of installation, and in sands or other soils that are unstable when drilled, without the need for a temporary casing, yet having the attributes and benefits associated with the short aggregate pier method, apparatus, and construction disclosed in U.S. Pat. No. 5,249,892, as well as additional benefits. 
     SUMMARY OF THE INVENTION 
     Briefly, the present invention comprises a method for installation of a pier formed from one or more layers or formed lifts of aggregate material, with or without additives, and includes the steps of positioning or pushing or forcing an elongate hollow tube having a special shaped bottom head element and unique tube configuration into a soil matrix, filling the hollow tube including the bottom head element with an aggregate material, releasing a predetermined volume of aggregate material from the bottom head element as the hollow tube is lifted a predetermined incremental distance in the cavity formed in the soil matrix, and then imparting an axial, static vector force and optional dynamic vector forces onto the hollow tube and its special bottom head element to transfer energy via the lower end of the hollow tube to the top of the lift of released aggregate material thereby compacting the lift of aggregate material and also forcing the aggregate material laterally or transaxially into the sidewalls of the cavity. Lifting of the hollow tube having the special bottom head element followed by pushing down with an applied axial or vertical static vector force and optional dynamic vector forces impacts the aggregate material which is not shielded by the hollow tube from the sidewalls of the cavity at the time of impaction, thereby densifying and compacting the aggregate material as well as forcing the material laterally outward into the soil matrix due to lateral forces on the aggregate material and the soil matrix. The compacted aggregate material thus defines a “lift” which generally has a lateral dimension or diameter greater than that of the cavity formed by the hollow tube and head element resulting in a pier construction formed of one or more lifts. 
     The aggregate material is released from the special bottom head element of the hollow tube as the special bottom head element is lifted, preferably in predetermined incremental steps, first above the bottom of the cavity and then above the top portion of each of the successive pier lifts that has been formed in the cavity and the adjacent soil matrix by the process. The aggregate material released from the hollow tube is compacted by the compacting forces delivered by the hollow tube and special bottom head element after the hollow tube has been lifted to expose a portion of the cavity while releasing aggregate material into that exposed portion. The hollow tube is next forced downward to compact the aggregate and to push it laterally into the soil matrix. The aggregate material is thereby compacted in predetermined, sequential increments, or lifts. The process is continuously repeated along the length or depth of the cavity with the result that an aggregate pier or column of separately compacted lifts or layers is formed within the soil matrix. A pier having a length of forty (40) feet or more can be constructed in this manner in a relatively short period of time without removal of the hollow tube from the soil. The resulting pier also generally has a cross sectional dimension greater than that of the hollow tube. 
     A number of types of aggregate material can be utilized in the practice of the process including crushed stone of many types from quarries, or re-cycled, crushed concrete. Additives may include water, dry cement, or grout such as water-cement sand-grout, fly-ash, hydrated lime or quicklime, or any other additive may be utilized which may improve the load capacity or engineering characteristics of the formed pier. Combinations of these materials may also be utilized in the process. 
     The hollow tube with the special bottom head element may be positioned within the soil matrix by pushing and/or vertically vibrating or vertically ramming the hollow tube having the leading end, special bottom head element into the soil with an applied axial or vertical vector static force and optionally, with accompanying dynamic vector forces. The soil, which is displaced by initial forcing, pushing and/or vibrating the hollow tube with the special bottom head element, is generally moved and compacted laterally into the preexisting soil matrix as well as being compacted downwardly. If a hard or dense layer of soil is encountered, the hard or dense layer may be penetrated by drilling or pre-drilling that layer to form a cavity or passage into which the hollow tube and special bottom head element may be placed and driven. 
     The hollow tube is typically constructed from a uniform diameter tube with a bulbous bottom head element and may include an internal valve mechanism near or within the bottom head element or a valve mechanism at the lower end of the head element. The hollow tube is generally cylindrical with a constant, uniform, lesser diameter along an upper section of the tube. The bulbous or larger external diameter lower end of the hollow tube (i.e. bottom head element) is integral with the hollow tube or may be separately formed and attached to the lower end of a lesser diameter hollow tube. That is, the bottom head element is also generally cylindrical, typically has a greater external diameter or external cross sectional profile than the remainder of the hollow tube and is concentric about the center line axis of the hollow tube. The lead end of the bottom head element is shaped to facilitate penetration into the soil matrix and to transmit desired vector forces to the surrounding soil as well as to the aggregate material released from the hollow tube. The transition from the lesser external diameter hollow tube section to the bottom head element may comprise a frustoconical shape. Similarly, the bottom of the head element may employ a frustoconical or conical shape to facilitate soil penetration and compaction. The leading end of the bottom head element may include a sacrificial cap member which penetrates the soil matrix upon initial placement of the hollow tube into the soil matrix, while preventing soil from entering the hollow tube. The sacrificial cap is then released from the end of the hollow tube to reveal an end passage as the hollow tube is first lifted so that aggregate material may flow into the cavity which results from lifting the hollow tube. 
     Alternatively, or in addition, the leading end bottom head element may include an outlet passage with a mechanical valve that is closed during initial penetration of the soil matrix by the hollow tube and bottom head element, but which may be opened during lifting to release aggregate material. Other types of leading end valve mechanisms and shapes may be utilized to facilitate initial matrix soil penetration, permit release of aggregate material when the hollow tube is lifted and to transmit vector forces in combination with the leading end or bottom head element to compact the successive lifts. 
     Further, the apparatus may include means for positioning an uplift anchor member within the formed pier as well as a tell-tale mechanism for measuring the movement of the bottom of the formed pier upon loading, such as during load testing. Such ancillary features or means are introduced through the hollow tube during formation of the pier. 
     Thus, it is an object of this invention to provide a hollow tube with a special design bottom head element useful to create a compacted aggregate pier, with or without additives, that extends to a greater depth and to provide an improved method for creating a pier which extends to a greater depth than typically enabled or practiced by known short aggregate pier technology. 
     Yet another object of the invention is to provide an improved method and apparatus for forming a pier of compacted aggregate material that does not require the use of temporary steel casing during the pier formation process, particularly in soils susceptible to caving in such as sandy soils. 
     Yet another object of the invention is to provide an improved method and apparatus for forming a pier of compacted aggregate material that may include a multiplicity of optional additives, including a mix of stone, addition of water, addition of dry cement, addition of cementitious grout, addition of water-cement-sand, addition of fly-ash, addition of hydrated lime or quicklime, and addition of other types of additives to improve the engineering properties of the matrix soil, of the aggregate materials and of the formed pier. 
     Yet a further object of the invention is to provide an aggregate material pier construction which is capable of being installed in many types of soil and which is further capable of being formed at greater depths and at greater speeds of construction than known prior aggregate pier constructions. 
     Another object of the invention is to provide a pier forming apparatus useful for quickly and efficiently constructing compacted multi-lift piers and/or piers comprised of as few as a single lift. 
     These and other objects, advantages and features of the invention will be set forth in the detailed description which follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the detailed description which follows, reference will be made to the drawing comprised of the following figures: 
         FIG. 1  is a schematic view of a hollow tube with a bottom head element being pushed, forced or driven into soil by a vertical, static vector force and optional dynamic forces; 
         FIG. 2  is a schematic view of a subsequent step from  FIG. 1  wherein aggregate material is placed into a hopper and fed into the hollow tube; 
         FIG. 3  is a cross sectional view of a hopper that has double isolation dampers and may be used in combination with the hollow tube; 
         FIG. 3A  is a sectional, isometric view of the hopper and hollow tube of  FIG. 3 ; 
         FIG. 3B  is an isometric view of the hopper and hollow tube of  FIG. 3 ; 
         FIG. 4  is a cross sectional schematic view of a hollow tube having an internal pinch or check valve; 
         FIG. 5  is a schematic view depicting the step of optional introduction of water, cementitious grout or other additive material into the hollow tube with recirculation provided to a water or grout reservoir; 
         FIG. 6  is a schematic view depicting a step subsequent to the step of  FIG. 2  wherein the hollow tube with its bottom head element are lifted a predetermined distance to temporarily expose a hollow cavity in the soil matrix to allow aggregate to quickly fill the exposed hollow cavity; 
         FIG. 7  is a schematic view of the process step subsequent to  FIG. 6  wherein a bottom valve in the bottom of the hollow tube is opened releasing aggregate into an unshielded or hollow cavity section; 
         FIGS. 8A and 8B  are schematic cross sectional views of an alternative to the device and step represented or illustrated in  FIG. 7  wherein the bottom head element of the hollow tube includes a sacrificial cap which is released into the bottom of a formed cavity in  FIG. 8B ; 
         FIG. 8C  is a sectional view of the sacrificial cap of  FIG. 8B  taken along the line  8 C- 8 C in  FIG. 8B ; 
         FIG. 9  is a schematic view wherein the hollow tube and its associated special bottom head element provide a vertical, static vector force with optional dynamic forces to move the hollow tube and bottom head element downward a predetermined distance by impacting and compacting the aggregate material released from the hollow tube and by pushing the aggregate material laterally into the soil matrix; 
         FIG. 10  is a schematic view of the hollow tube and its special bottom head element being lifted a predetermined distance to form a second lift; 
         FIG. 11  is a schematic view of the hollow tube and bottom head element operating to provide a vertical vector force to move the hollow tube and bottom head element downward a predetermined distance to form the second compacted lift on the top of a first compacted lift; 
         FIG. 12  is a schematic view of the hollow tube with an optional reinforcing steel rod element or tell-tale element attached to a plate for installation inside of pier; 
         FIG. 13  is a schematic view of the hollow tube wherein optional water or water-cement-sand grout is combined in the hollow tube with aggregate; 
         FIG. 14  is a vertical cross sectional view of the special bottom head element with a trap door-type bottom valve; 
         FIG. 15  is a cross sectional view of the bottom head element of  FIG. 14  taken along the line  15 - 15 ; 
         FIG. 15A  is a cross sectional view of a portion of an alternative bottom head element of the type depicted in  FIG. 14 ; 
         FIG. 16  is a cross sectional view of the special bottom head element including a sacrificial cap at the lower end similar to  FIG. 8A ; 
         FIG. 17  is a cross sectional view of the special bottom head element with an optional uplift anchor member or tell-tale attached to a plate; 
         FIG. 18  is a cross sectional view of a partially formed multiple lift pier formed by the hollow tube and special bottom head element and method of the invention; 
         FIG. 19  is a cross sectional view of a completely formed multiple lift pier formed by hollow tube and special bottom head element and method of the invention; 
         FIG. 20  is a cross sectional view of a formed, multiple lift pier with an optional reinforcing steel rod having an attached plate which enables the formed pier to comprise an uplift anchor pier or to include a tell-tale element for subsequent load testing; 
         FIG. 21  is a cross sectional view of formed pier being preloaded or having an indicator modulus load test being performed on the completed pier; 
         FIG. 22  is a graph illustrating comparative load test plots of the present invention compared with a drilled concrete pile in the same soil matrix formation; 
         FIG. 23  is a schematic, cross sectional view of a method of use of the apparatus of the invention to form a single lift pier or a pier wherein one or more lifts are formed subsequent to raising the apparatus an extended distance from the bottom of a cavity formed by the apparatus initially in a soil matrix; 
         FIG. 24  is a schematic cross sectional view of continuation of the method illustrated by  FIG. 23 ; 
         FIG. 25  is a schematic cross sectional view of further continuation of the step depicted in  FIG. 24 ; and 
         FIG. 26  is a schematic cross sectional view of the further continuation of the method of  FIGS. 22-24 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     General Construction 
       FIGS. 1 ,  2 ,  5 ,  6 ,  7 ,  9 ,  10 ,  11 ,  12 ,  13 ,  18 ,  19 ,  20  and  23 - 25  illustrate the general overall construction of the pier forming device or mechanism and various as well as alternative sequential steps in the performance of the method of the invention that produce the resultant pier construction. Referring to  FIG. 1 , the method is applicable to placement of piers in a soil matrix which requires reinforcement for the soil to become stiffer or stronger. A wide variety of soils may require the practice of this invention including, in particular, sandy and clay soils. With the invention, it is possible to construct piers comprised of one or more lifts, utilizing aggregate materials and optionally utilizing aggregate materials with additive materials such as water-cement-sand grout, which have greater stiffness and strength than many prior art aggregate piers, which can economically be extended to or built to greater depths than many prior art piers, which can be formed without use of temporary steel casing unlike many prior art piers, and which can be installed faster than many prior art piers. 
     As a first step, a hollow tube or hollow shaft  30  having a longitudinal axis  35  including or with a special bottom head element  32 , and an associated top end hopper  34  for aggregate, is pushed by a static, axial vector force driving apparatus  37  in  FIG. 3  and optionally vertically (axially) vibrated or rammed or both, with dynamic vector forces, into a soil matrix  36 . The portion of soil matrix  36 , that comprises the volume of material displaced by pushing a length of the hollow tube  30  including the special bottom head element  32 , is forced primarily laterally thereby compacting the adjacent soil matrix  36 . As shown in  FIG. 1 , the hollow tube  30  may comprise a cylindrical steel tube  30  having a longitudinal axis  35  and an external diameter in the range of 6 to 14 inches, for example. In the event that a layer of hard or dense soil prevents pushing of the hollow tube  30  and special bottom head element  32  into the soil matrix  36 , such hard or dense layer may be drilled or pre-drilled, and the pushing process may then continue utilizing the driving apparatus  37 . 
     Typically, the hollow tube  30  has a uniform cylindrical external shape, although other shapes may be utilized. Though the external diameter of the hollow tube  30  is typically 6 to 14 inches, other diameters may be utilized in the practice of the invention. Also, typically, the hollow tube  30  will be extended or pushed into the soil matrix  36  to the ultimate depth of the pier, for example, up to 40 feet or more. The hollow tube  30  will normally fasten to an upper end drive extension  42  which may be gripped by a drive apparatus or mechanism  37  to push and optionally vibrate or ram, the hollow tube  30  into the soil matrix  36 . The hopper  34 , which contains a reservoir  43  for aggregate materials, will typically be isolated by isolation dampers  46 ,  48  from extension  42 . The vibrating or ramming device  37  which is fastened to extension  42  may be supported from a cable or excavator arm or crane. The weight of the hopper  34 , ramming or vibrating device  37  (with optional additional weight) and the hollow tube  30  may be sufficient to provide a static force vector without requiring a separate static force drive mechanism. The static force vector may optionally be augmented by a vertically vibrating and/or ramming dynamic force mechanism. 
       FIGS. 3 ,  3 A and  3 B illustrate a special feature preferably associated with the hopper  34 . Double isolation dampers  46 ,  48  are affixed to the upper and lower sides of the hopper  34  to reduce the vibration buildup of the hopper  34  and provide a hopper assembly with greater structural integrity. Extension  42  is affixed to tube  30  to impart the static and dynamic forces on the tube  30 . Extension  42  is isolated from hopper  34  and thus is slidable relative to dampers  46 ,  48 . 
       FIG. 4  illustrates an optional feature of the hollow tube  30 . A restrictor, pinch valve, check valve or other type of valve mechanism  38  may be installed within the hollow tube  30  or in the special bottom head element or lower end section  32  of the hollow tube  30  to partially or totally close off the internal passageway of the hollow tube  30  and stop or control the flow or movement of aggregate materials  44  and optional additive materials. This valve  48  may be mechanically or hydraulically opened, partially opened or closed in order to control movement of aggregate materials  44  through the hollow tube  30 . It may also operate by gravity in the manner of a check valve which opens when raised and closes when lowered onto the aggregate material  44 . 
       FIG. 14  illustrates the construction of the special bottom head element or section  32 . The special bottom head element  32  is cylindrical, although other shapes may be utilized. Typically, the external diameter of the special bottom head element  32  is greater than the nominal external diameter of the upper section  33  of the hollow tube  30  and is 10 to 18 inches, although other diameters and/or cross sectional profiles may be utilized in the practice of the invention. That is, the head element  32  may have cross sectional dimensions the same as or less than that of hollow tube  30  though such configuration is generally not preferred. 
       FIGS. 14 ,  15  and  15 A illustrate an embodiment of the invention having a valve mechanism incorporated in the head element  32 . The head element  32  has a frustoconical bottom section or bottom portion  50  with an aggregate material  44  discharge opening  52  that opens and closes as a valve plate  54  exposes or covers the opening  52 . The valve plate  54  is mounted on a rod  56  that slides in a hub  59  held in position by radial struts  58  attached to the inside passage walls of the head element  32  of the hollow tube  30 . The plate  54  slides to a closed position when the hollow tube  30  is forced downward into the soil matrix  36  and slides to an open position when hollow tube  30  is raised, thus allowing aggregate material  44  to flow. The opening of valve  54  is controlled or limited by rod  56  which has a head  56   a  that limits sliding movement of rod  56 . The hollow tube  30  may thus be driven to a desired depth  81  ( FIG. 6 ) with opening  52  closed by plate  54 . Then as the hollow tube  30  is raised (for example, the distance  91  in  FIG. 10 ), the plate  54  extends downwardly due to gravity so that aggregate material  44  will flow through opening  52  into the cavity formed due to the raising of the hollow tube  30 . Thereafter, the tube  30  is impacted or driven downwardly closing valve plate  54  and compacting the released material to form a compacted lift  72 . In the embodiment of  FIGS. 14 ,  15 ,  15 A the valve plate  54  moves in response to gravity. However, rod  56  may alternatively be replaced or assisted in movement by a fluid drive, mechanical or electrical mechanism. Alternatively, as described hereinafter, the plate  54  may be replaced by a sacrificial cap  64  or by the bottom plate of an uplift anchor or a tell-tale mechanism  70  as described hereinafter. Also, the check valve  38  in  FIG. 4  may be utilized in place of the valve mechanism depicted in  FIGS. 14 ,  15 ,  15 A. 
     Typically, the internal diameter of the hollow tube  30  and head element  32  are uniform or equal, though the external diameter of head element  32  is typically greater than that of hollow tube  30 . Alternatively, when a valve mechanism  54  is utilized, the internal diameter of the head element  32  may be greater than the internal diameter of the hollow tube  30 . Head element  32  may be integral with hollow tube  30  or formed separately and bolted or welded onto hollow tube  30 . Typically, the inside diameter of the hollow tube  30  is between 6 to 10 inches and the external diameter of the head element  32  is about 10 to 18 inches. The opening diameter  53  in  FIG. 14  at the extreme lower end or leading end of the head element  32  may be equal to or less than the internal diameter of the head element  32 . For example, referring to  FIG. 14 , the head element  32  may have an internal diameter of 12 inches and the opening diameter  53  may be 6 to 10 inches, while in  FIG. 16 , with the sacrificial cap embodiment described hereinafter, the discharge opening of head element  32  has the same diameter as the internal diameter of the head element  32  and hollow tube  30 . 
     Also the plate or valve  54  may be configured to facilitate closure when the hollow tube  30  is pushed downward into the soil matrix  36  or against aggregate material  44  in the formed cavity. For example, the diameter of member  54  may exceed that of opening  52  as shown in  FIG. 14  or the edge  55  of the valve member may be beveled as depicted in  FIG. 15A  to engage beveled edge  59  of opening  52 . Then when applying a static or other downward force to the hollow tube  30 , the valve plate  54  will be held in a closed position in opening  52 . 
     The bulbous lower head element  32  of hollow tube  30  typically has a length in the range of one to three times its diameter or maximum lateral dimension. The head element  32  provides enhanced lateral compaction forces on the soil matrix  36  as tube  30  penetrates or is forced into the soil and thus renders easier the subsequent passage of the lesser diameter section  33  of the hollow tube  30 . The frustoconical or inclined leading and trailing edges  50 ,  63  of the head element  32  facilitate lowering or driving penetration and lateral compaction of the soil  36  because of their profile design. The trailing inclined edge  63  in  FIG. 14  facilitates the raising of the hollow tube  30  and head element  32  and lateral compaction of soil matrix  36  during the raising step of the method. Again, the shape or inclined configuration of head element  32  enables this to occur. Typically the leading and trailing edges  50 ,  63  form a 45°±15° angle with the longitudinal axis  35  of the hollow tube  30 . 
       FIG. 5  illustrates another feature of the hollow tube  30 . Inlet port  60  and outlet port  62  are provided at the lower portion of the hopper  34  or the upper end of hollow tube  30  to allow addition of water or of grout, such as water-cement-sand grout, as an additive to the aggregate for special pier constructions. A purpose of the outlet port  62  is to maintain the water or additive level where it will be effective to facilitate flow of aggregate and also to allow recirculation of the grout from a reservoir back into the reservoir to facilitate mixing and to keep the water head or grout head (pressure) relatively constant. The inlet port  60  and outlet port  62  may lead directly into the hopper  34  or into the hollow tube  30  (see  FIG. 13 ), or may connect with separate channels or conduits to the head element  32 . Note, grout discharge openings  31  may be provided through hollow tube  30  above head element  32  as shown in  FIG. 2  to supplement discharge of grout into the annular space about hollow tube  30  and prevent cavity fill in by soil from the matrix  36 . 
       FIGS. 8A ,  8 B,  8 C and  16  illustrate another alternate feature of the bottom head element  32 . A sacrificial cap  64  may be utilized in lieu of the bottom or lower end sliding valve  54  to protect the head element  32  from clogging when the head element  32  is pushed down through soil matrix  36 . The cap  64  may be configured in any of a number of ways. For example, it may be flat, pointed or beveled. It may be arcuate. When beveled, it may form an angle of 45±25° with respect to horizontal axis  35 . Cap  64  may include a number of outwardly biased legs  87  positioned to fit in the central opening  89  of the bottom head element  32  and hold cap  64  in place until hollow tube  30  is first raised and aggregate  44  caused to flow out the opening  52  into an exposed cavity section. 
       FIG. 17  illustrates another alternate feature of the special bottom head element  32 . The sliding plate  54  and rod  68  for support of plate  54  may include a passage or axial tube  57  that allows the placement of a reinforcing element or rod  68  attached to a bottom plate  70 . The rod  68  and plate  70  will be released at the bottom of a formed cavity and used to provide an uplift anchor or a tell-tale for measuring bottom movement of a pier during a load test. The sliding rod  68  attached to a bottom plate  70  may be substituted for the sacrificial cap  64  closing the opening of the special head element  32  during pushing into the soil matrix  36 , and perform as a platform for the uplift anchor or tell-tale being installed. The bottom valve plate  54  may thus be omitted or may be kept in place while the uplift anchor or tell-tale elements are being utilized.  FIG. 20  illustrates the uplift anchor  68 ,  70  or tell-tale in place upon the forming of a pier by the invention wherein the plate or valve  54  is omitted. 
     Method of Operation: 
       FIG. 1  illustrates the typical first step of the operation of the described device or apparatus. The hollow tube  30  with special head element  32  and attached upper extension  42  and connected hopper assembly  34 , are pushed with a vertical or axial static vector force, typically augmented by dynamic vector forces, into the soil matrix  36  by drive apparatus  37  or by the weight of the component parts. In practice, utilizing a tube  30  with special bottom head element  32  having the dimensions and configuration described, a vector force of 5 to 20 tons applied thereto is typical throughout.  FIG. 2  illustrates placing of aggregate  44  into the hopper  34  when the hollow tube  30  and attachments reach the planned depth  81  of pier into the soil matrix  36 .  FIG. 6  illustrates subsequent upward or lifting movement of the hollow tube  30  by a predetermined lifting distance  91 , typically 24 to 48 inches to reveal a portion of cavity  102  below the lower section head element  32  in the soil matrix  36 . 
       FIG. 7  illustrates opening of the bottom valve  54  to allow aggregate  44  and optional additives to fill the space or portion  85  of cavity  102  below the special head element  32  while the hollow tube  30  and attachments are being raised. The valve  54  may open as the hollow tube  30  is lifted due to weight of aggregate  44  on the top side of valve  54 . Alternatively, valve  54  may be actuated by a hydraulic mechanism for example, or the hollow tube  30  may be raised and aggregate then added to flow through valve opening  53  by operation of valve  54 . Alternatively, internal valve  38  may be opened during lifting or after lifting. Alternatively, if there is no valve  54 , the sacrificial cap  64  will be released from the end of the head element  32 , generally by force exerted by the weight of aggregate material  44  directed through the hollow tube  30  when the special head element  32  is raised from the bottom  81  of the formed pier cavity  102 . 
       FIG. 9  illustrates the subsequent pushing downward of the hollow tube  30  and attachments and closing of the bottom valve  54  to compact the aggregate  44  in the cavity portion  85  thereby forcing the aggregate  44  and optional additives laterally as well as vertically downward, into the soil matrix  36 . The predetermined movement distance for pushing downward is typically equal to the lifting distance  91  minus one foot, in order to produce a completed lift  72  thickness of one foot following the predetermined lifting distance  91  of hollow tube  30 . The designed thickness of lift  72  may be different than one foot depending on the specific formed pier requirements and the engineering characteristics of the soil matrix  36  and aggregate  44 . Compacting the aggregate material  44  released into the vacated cavity portion  85  in  FIG. 7  to effect lateral movement of the aggregate material  44  horizontally as well as compaction vertically is important in the practice of the invention. 
       FIG. 10  illustrates the next or second lift formation effected by lifting of the hollow tube  30  and attachments another predetermined distance  91 A, typically 24 to 48 inches to allow opening of the bottom valve  54  (in the event of utilization of the embodiment using valve  54 ) and passage or movement of aggregate  44  and optional additives into the portion of the cavity  85 A that has been opened or exposed by raising tube  30 . 
     Raising of the hollow tube in the range of two (2) to four (4) feet is typical followed by lowering (as described below) to form a pier lift  72 , having a one (1) foot vertical dimension is typical for pier forming materials as described herein. The axial dimension of the lift  72  may thus be in the range of ¾ to ⅕ of the distance  91  the hollow tube  30  is raised. However, the embodiment depicted in  FIGS. 23-26  constitutes an alternate compaction protocol. 
       FIG. 11  illustrates pushing down of the hollow tube  30  and attachments and closing of the bottom valve  54  to compact the aggregate  44  in the newly exposed cavity portion  85 A of  FIG. 10  and forcing of aggregate  44  and optional additives laterally into the soil matrix  36 . The distance of pushing will be equal to the distance of lifting minus the designed lift thickness. When the sacrificial cap  64  method is utilized, the bottom opening  50  may remain open while compacting the aggregate  44 . 
       FIG. 18  illustrates a partially formed pier by the process described wherein multiple lifts  72  have been formed sequentially by compaction and the hollow tube  30  is rising as aggregate  44  is filling cavity portion  85 X.  FIG. 19  illustrates a completely formed pier  76  by the process described.  FIG. 20  illustrates a formed pier  76  with uplift anchor  68 ,  70  or tell-tale installed.  FIG. 21  illustrates an optional preloading step on a formed pier  76  by placement of a weight  75 , for example, on the formed pier and an optional indicator modulus test being performed on the formed pier  76  comprised of multiple compacted lifts  78 . 
       FIGS. 23 through 26  illustrate an alternative protocol for the formation of a pier using the described apparatus. The hollow tube  30  is initially forced or driven into a soil matrix  36  to a desired depth  100 . The extreme bottom end of the head element  32  includes a valve mechanism  54 , sacrificial cap  64  or the like. Forcing the hollow tube  30  vertically downward in the soil forms a cavity  102  ( FIG. 23 ). Assuming the special bottom head element  32  is generally cylindrical, cavity  102  is generally cylindrical, and may or may not maintain the full diameter configuration associated with the shape and diameter of special bottom head element  32 . 
     Upon reaching the desired penetration into the matrix soil  36  ( FIG. 23 ), the hollow tube  30  is raised to the top of the formed cavity ( FIG. 24 ). As it is raised, aggregate material  44  and optional additive materials are discharged below the bottom end of the special bottom head element  32 . 
     Optionally, additive materials are discharged into the annular space  104  defined between the upper section  33  of hollow tube  30  and the interior walls of the formed cavity  102 . Note the additive materials may flow through ancillary lateral passages  108  or supplemental conduits  110  in the hollow tube  30 . As the hollow tube  30  is raised, the cavity  102  is filled. Also, additive materials in the annular space  104  may be forced outwardly into the soil matrix  36  by and due to the configuration of the special bottom head element  32  as it is raised. 
     The hollow tube  30  is thus typically raised substantially the full length of the initially formed cavity  102  and then, as depicted by  FIG. 25 , again forced downward causing the material in the cavity  102  to be compacted and to be forced laterally into the soil matrix  36  ( FIG. 25 ). The extent of downward movement of the hollow tube  30  is dependent on various factors including the size and shape of the cavity  102 , the composition and mix of aggregate materials and additives, the forces imparted on the hollow tube  30 , and the characteristics of the soil matrix  36 . Typically, the downward movement is continued until the lower end or bottom of the special bottom head element  32  is at or close to the bottom  81  of the previously formed cavity  102 . 
     After completion of the second downward movement, the hollow tube  30  is raised typically the full length of the cavity  102 , again discharging aggregate and optionally additive materials during the raising, and again filling, the newly created cavity  102 A ( FIG. 26 ). The cycle of fully lowering and fully raising is completed at least two times and optionally three or more times, to force more aggregate  44  and optionally additive materials, laterally into the matrix soil  36 . Further, the cycling may be adjusted in various patterns such as fully raising and lowering followed by fully raising and partially lowering, or partially raising and fully lowering, and combinations thereof. 
     Summary Considerations: 
     Water or grout or other liquid may be utilized to facilitate flow and feeding of aggregate material  44  through hollow tube  30 . The water may be fed directly into the hollow tube  30  or through the hopper  34 . It may be under pressure or a head may be provided by using the hopper  34  as a reservoir. The water, grout or other liquid thus enables efficient flow of aggregate, particularly in the small diameter hollow tube  30 , i.e. 5 to 10 inches tube  30  diameter. Note typically the size of the tube  30  internal passage and/or discharge opening is at least 4.0 times the maximum aggregate size for all the described embodiments. With each lift  72  being about 12 inches in vertical height and the internal diameter of tube  30  being about 6 to 10 inches, use of water as a lubricant is especially desirable. 
     It is noted that the diameter of the cavity  102  formed in the matrix soil  36  is relatively less than many alternative pier forming techniques. The method of utilizing a relatively small diameter cavity  102  or a small dimension opening into the soil matrix  36 , however, enables forcing or driving a tube  30  to a significant depth and subsequent formation of a pier having horizontal dimensions adequately greater than the external dimensions of the tube  30 . Utilization of aggregate  44  with or without additives including fluid materials to form one or more lifts by compaction and horizontal displacement is thus enabled by the hollow tube  30  and special bottom head element  32  as described. Lifts  72  are compacted vertically and aggregate  44  forced transaxially with the result of a highly coherent pier construction. 
     Test Results: 
       FIG. 22  illustrates the results of testing of piers of the present invention as contrasted with a drilled concrete pier. The graph illustrates the movements of three piers constructed in accordance with the invention (curves A, B, C) with a prior art drilled concrete pier (curve D), as the piers are loaded with increasing loads to maximum loads and then decreasing loads to zero load. The tests were conducted using the following test conditions and using a steel-reinforced, drilled concrete pier as the control test pier. 
     A hole or cavity of approximately 8-inches in diameter was drilled to a depth of 20 feet and filled with concrete to form a drilled concrete pier (test D). A steel reinforcing bar was placed in the center of the drilled concrete pier to provide structural integrity. A cardboard cylindrical form 12 inches in diameter was placed in the upper portion of the pier to facilitate subsequent compressive load testing. The matrix soil for all four tests was a fine to medium sand of medium density with standard Penetration Blow Counts (SPT&#39;s) ranging from 3 to 17 blows per foot. Groundwater was located at a depth of approximately 10 feet below the ground surface. 
     The aggregate piers of the invention, reported as in tests A, B, and C, were made with a hollow tube  30 , six (6) inches in external diameter and with a special bottom head element  32  with an external diameter of 10 inches. Tests A and B utilized aggregate only. Test C utilized aggregate and cementitious grout. Test A utilized predetermined lifting movements of two feet and predetermined downward pushing movements of one foot resulting in a plurality of one foot lifts. Test B utilized predetermined upward movements of three feet and predetermined downward pushing movements of two feet, again resulting in one foot lifts. Test C utilized predetermined upward movements of two feet and predetermined downward pushing movements of one foot, and included addition of cementitious grout. 
     Analyses of the data can be related to stiffness or modulus of the piers constructed. At a deflection of 0.5 inches, test A corresponded to a load of 27 tons, test B corresponded to a load of 35 tons, test C corresponded to a load of 47 tons and test D corresponded to a load of 16 tons. Thus at this amount of deflection (0.5 inches) and using test B as the standard test and basis for comparison, ratios of relative stiffness for test B is 1.0, test A is 0.77, Test C is 1.34, and Test D is 0.46. The standard, Test B, is 2.19 times stiffer than the control test pier, Test D. The standard Test B is 1.30 times stiffer than Test A, whereas the Test C with grout additive is 2.94 times stiffer than the prior art concrete pier (Test D). This illustrates that the modulus of the piers formed by the invention are substantially superior to the modulus of the drilled, steel-reinforced concrete pier (Test D). These tests also illustrate that the process of three feet lifting movement with two feet downward pushing movement was superior to the process of two feet lifting movement and one foot downward pushing movement. The tests also illustrate that use of cementitious grout additive substantially improved the stiffness of the formed pier for deflections less than about 0.75 inches, but did not substantially improve the stiffness of the formed pier compared with Test B for deflections greater than about 0.9 inches. 
     In the preferred embodiment, because the bottom head element  32  of the hollow tube or hollow shaft  30  has a greater cross sectional area, various advantages result. First the configuration of the apparatus, when using a bottom valve mechanism  54 , reduces the chance that aggregate material will become clogged in the apparatus during the formation of the cavity  102  in the soil matrix  36  as well as when the hollow tube  30  is withdrawn partially from the soil matrix  36  to expose or form a cavity  85  within the soil matrix  36 . Further, the configuration allows additional energy from static force vectors and dynamic force vectors to be imparted through the bottom head element  32  of the apparatus and impinge upon aggregate  44  in the cavity  70 . Another advantage is that the friction of the hollow tube  30  on the side of the formed cavity  102  in the ground is reduced due to the effective diameter of the hollow tube  30  being less than the effective diameter of the bottom head element  32 . That is, the cross section area of the remainder of the hollow tube  30  is reduced. This permits quicker pushing into the soil and allows pushing through formations that might be considered to be more firm or rigid. The larger cross sectional area head element  32  also enhances the ability to provide a cavity section  102  sized for receipt of aggregate  44  which has a larger volume than would be associated with the remainder of the hollow shaft  30  thus providing for additional material for receipt of both longitudinal (or axial) and transverse (or transaxial) forces when forming the lift  72 . The reduced friction of the hollow tube  30  on the side of the formed cavity  102  in the soil  36  also provides the advantage of more easily raising the hollow tube  30  during pier formation. 
     In the process of the invention, the lowest lift  72  may be a larger effective diameter and have a different amount of aggregate provided therein. Thus the lower lift  72  or lowest lift in the pier  76  may be configured to have a larger transverse cross section as well as a greater depth when forming a base for the pier  76 . In other words, by way of example the lowest portion or lowest lift  72  may be created by lifting of the hollow shaft  30  three feet and then reducing the height of the lift  72  to one foot, whereas subsequent lifts  72  may be created by raising the hollow shaft  30  two feet and reducing the thickness of the lift  72  to one foot. 
     The completed pier  76  may, as mentioned heretofore, be preloaded after it has been formed by applying a static load or a dynamic load  75  at the top of the pier  76  for a set period of time (see  FIG. 21 ). Thus a load  75  may be applied to the top of the pier  76  for a period of time from 30 seconds to 15 minutes, or longer. This application of force may also provide a “modulus indicator test” inasmuch as a static load  75  applied to the top of the pier  76  can be accompanied by measurement of the deflection accruing under the static load  75 . The modulus indicator test may be incorporated into the preload of each pier to accomplish two purposes with one activity; namely, (1) applying a preload; and (2) performing a modulus indicator test. 
     The aggregate material  44  which is utilized in the making of the pier  76  may be varied. That is, clean aggregate stone may be placed into a cavity  85 . Such stone may have a nominal size of 40 mm diameter with fewer than 5% having a nominal diameter of less than 2 mm. Subsequently a grout may be introduced into the formed material as described above. The grout may be introduced simultaneous with the introduction of the aggregate  44  or prior or subsequent thereto. 
     When a vibration frequency is utilized to impart the dynamic force, the vibration frequency of the force imparted upon the hollow shaft or hollow tube  30  is preferably in a range between 300 and 3000 cycles per minute. The ratio of the various diameters of the hollow tube or shaft  30  to the head element  32  is typically in the range of 0.92 to 0.50. As previously mentioned, the angle of the bottom bevel may be between 30° and 60° relative to a longitudinal axis  35 . 
     As a further feature of the invention, the method for forming a pier may be performed by inserting the hollow tube  30  with the special bottom head element  32  to the total depth  81  of the intended pier. Subsequently, the hollow tube  30  and special bottom head element  32  will be raised the full length of the intended pier in a continuous motion as aggregate and/or grout or other liquid are being injected into the cavity as the hollow tube  30  and special bottom head element  32  are lifted. Subsequently, upon reaching the top of the intended pier, the hollow tube  30  and special bottom head element  32  can again be statically pushed and optionally augmented by vertically vibrating and/or ramming dynamic force mechanism downward toward or to the bottom of the pier in formation. The aggregate  44  and/or grout or other material filling the cavity as previously discharged will be moved transaxially into the soil matrix as it is displaced by the downwardly moving hollow tube  30  and head element  32 . The process may then be repeated with the hollow tube  30  and head element  32  raised either to the remaining length or depth of the intended pier or a lesser length in each instance with aggregate and/or liquid material filling in the newly created cavity as the hollow tube  30  is lifted. In this manner, the material forming the pier may comprise one lift or a series of lifts with extra aggregate material and optional grout and/or other additives transferred laterally to the sides of the hollow cavity into the soil matrix. 
     It is noted that the mechanism for implementing the aforesaid procedures and methods may operate in an accelerated manner. Driving the hollow tube  30  and head element  32  downwardly may be effected rather quickly, for example, in a matter of two minutes or less. Raising the hollow tube  30  and head element  32  incrementally a partial or full distance within the formed cavity may take even less time, depending upon the distance of the lifting movement and rate of lifting. Thus, the pier is formed from the soil matrix  36  within a few minutes. The rate of production associated with the methodology and the apparatus of the invention is therefore significantly faster. 
     Various modifications and alterations may thus be made to the methodology as well as the apparatus to be within the scope of the invention. Thus, it is possible to vary the construction and method of operation of the invention without departing form the spirit and scope thereof. Alternative hollow tube configurations, sizes, cross sectional profiles and lengths of tube may be utilized. The special head element  32  may be varied in its configuration and use. The bottom valve  54  may be varied in its configuration and use, or may be eliminated by use of a sacrificial cap. The leading end of the bottom head element  32  may have any suitable shape. For example, it may be pointed, cone shaped, blunt, angled, screw shaped, or any shape that will facilitate penetration of a matrix soil and compaction of aggregate material. The enlarged or bulbous head element  32  may be utilized in combination with one or more increased external diameter sections of the hollow tube  30  having various shapes or configurations. Therefore the invention is to be limited only by the following claims and equivalents thereof.