Abstract:
The present invention is an apparatus and a method for casting a cementitious or stone pile into the ground. The present invention comprises an exterior driving casing and an interior mandrel acting in cooperation to hold and deliver the pile forming material. A retrievable driving driving shoe is also disclose.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
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   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
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   SEQUENCE LISTING 
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   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to a method and apparatus for placing in-ground piles of either crushed stone or rock, grout or concrete, or some combination thereof. 
   2. Description of Prior Art 
   It has been known in the prior art, to make pilings from concrete by casting them in place in the ground. This is accomplished by driving an elongate mandrel, i.e., a hollow tube of a selected cross-sectional area, into the ground, filling the resultant hole with fluid grout, and then pulling the mandrel back out of the ground leaving the grout in place to cure. The holding ability of such a piling comes from end-bearing and from the friction which is created by the close contact between the pile&#39;s sidewalls and the surrounding soil. It has also become standard practice to place a foot, aka, pile driving shoe, having a larger cross-sectional area than the mandrel, at the bottom of the mandrel before it is driven into the ground. The foot forms an open space around the mandrel. The hole created by the driving of the mandrel is filled with grout, i.e., cementitious fluid, stones, or rock. In the prior art grout may be gravity fed into and/or around the mandrel as it is being driven into the ground. See, e.g., Steding, U.S. Pat. No. 3,851,485 and Poma, U.S. Pat. No. 4,018,056. 
   A significant problem with the gravity feed method is that the grout often cannot flow into the hole fast enough to keep up with its formation, thereby resulting in voids. If soil or objects in the soil fall into these voids, the resultant pile diameter will neck down at the locations of the voids, weakening the pile. Other prior art devices have attempted to overcome this problem by pumping the grout into the mandrel under positive pressure as the mandrel is being driven. See, e.g., Hochstrasser, U.S. Pat. No. 3,084,518 and Federer, U.S. Pat. No. 4,618,289. However, pumping grout is also very problematic due to the inability to maintain a sufficient volumetric flow rate due to grout&#39;s the high viscosity. Accordingly, pumping is sometimes no more effective than gravity filling. 
   A twist on the gravity fed approach is seen in DeWitt, U.S. Pat. No. 4,992,002. In DeWitt, the mandrel is filled with grout prior to driving into the ground. A irretrievable steel foot is placed at the bottom the mandrel, which prevents the premature release of the grout. When the desired depth is reached, the mandrel is lifted out of the ground, leaving the foot behind and the grout flows out the bottom of the mandrel. 
   All of the aforementioned approaches are subject to the problem of necking, because no exterior reinforcing casing is provided. The grout will be still be subject to necking as the mandrel is withdrawn. Without an exterior reinforcing casing there is no reinforcement against side-loading from earth movements, wind and other influences. Accordingly, excess concrete or grout must be pumped at the top of the hole to prevent the collapse of the hole. This adds to the cost of the pile. 
   To provide the necessary reinforcement, the use of a full-length exterior reinforcing casing has been adopted in some circumstances. However, this is also less than ideal because the exterior casing is permanently left in the ground, thereby increasing the costs for each pile. 
   Moreover, the aforementioned prior art devices suffer from lack of durability. All of the prior art devices teach the use of pile driving a single mandrel into the earth. Accordingly, the mandrel must be made of very sturdy material such as heavy steel to withstand the blows of the pile driving hammer and the resultant reactionary forces of the earth. It is not uncommon for such mandrels, despite their sturdiness, to deflect during the driving process, which in turn will lead to inadequate pile formation or lost time. In time, such mandrels may have to be scrapped because they have lost their straightness or because they cannot withstand the blows of the pile driver. This is wasteful and expensive. 
   Additionally, the aforementioned devices do not accommodate the attachment of a vibrator without the need to halt the process. A vibrator is often used to assist in the delivery of pile forming material, such as stone, crushed rock or aggregate, or some combination thereof, into the resultant hole. The vibrator is clamped on to the mandrel and vibrates the mandrel. Prior to initiating the vibrator, the pile driving hammer must be lifted off of the mandrel to prevent damage to the pile driver. This results in additional delay in the pile forming process and consequently results in additional costs for the installation of the pile. 
   Also as can be seen in the above discussion, the foregoing prior art devices are specific for certain types of materials, for example, the DeWitt device can only be utilized for installing piles made of grout, but not stone. Accordingly, a pile forming enterprise must have access to separate apparatuses depending on the requirements of the job. This increases inventory costs, overhead and capital outlay. 
   What is needed is a single apparatus that is more durable when compared with single mandrel embodiments, that eliminates the need for an external casing that is left in the ground, that can be used in multiple piling forming situations, grout, stone, crushed rock, etc., and that can utilize a retrievable foot. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention is an apparatus and a method for either casting a pile in the ground or placing a stone column into the ground. Prior art methods incorporate driving a single mandrel, with a disposable driving boot. The present invention comprises a retrievable exterior driving casing and an interior mandrel and an optional retrievable driving boot as the situation requires. The exterior casing is sized to the desired hole dimensions and the interior mandrel is filled with grout, stone (crushed or un-crushed), sand, cement or some combination thereof. 
   The interior mandrel is sized so as to easily slide along the interior annular space of the exterior casing. The apparatus is driven into the ground using known pile driving methods. During penetration into the soil, depending on the type of soil encountered and the type of pile to be formed, grout, air or water flows into the surrounding earth through aligned apertures on the exterior casing and the interior mandrel; this prevents necking, and provides a temporary frictionless medium to allow easy extraction of the apparatus. When the bottom of the apparatus reaches the desired depth, the interior mandrel is lifted out of phase relative to the exterior casing by raising it a predetermined distance relative to the exterior casing. This allows the pile forming materials to flow out the bottom of the apparatus. After lifting the interior mandrel a certain distances, the exterior casing is caused to be lifted. 
   The exterior casing maintains the integrity of hole as the pile forming material flows into the space created by the apparatus. Accordingly, the tendency to form voids and necks is substantially reduced. Additionally, because the apparatus comprises an exterior casing and an interior mandrel, the tubes may be made of thinner walled material than a conventional single mandrel, with the added advantage that the double tubes will be sturdier than a single mandrel having a thicker wall. This characteristic of double wall construction has been shown in performance and durability of double walled aluminum baseball bats when compared with single walled aluminum baseball bats. 
   Other features and advantages of the present invention will become apparent from the following detailed description taken into conjunction with the accompanying drawings which illustrate by way of example the principles of the invention. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       FIG. 1  is a frontal view of an embodiment according to the invention. 
       FIG. 2  is a cross-sectional view of the embodiment of  FIG. 1  as the invention would appear when being driving into the ground. 
       FIG. 3  is a cross-sectional view of the embodiment of  FIG. 1 , as the invention would appear when being retracted from the ground. 
       FIG. 4  is a partial view emphasizing the lower portion of the embodiment as shown in  FIG. 2 . 
       FIG. 5  is a partial view emphasizing the lower portion of the embodiment as shown in  FIG. 3 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   The invention comprises a pair of tubes with a first tube having a top and bottom. The bottom of the first tube comprises an open bottom and has an interior profile, the preferred profile is frusto-conical. The second tube having a top and bottom. The bottom of the second tube having a preferred exterior profile that is adapted to mate with the interior profile of the first tube, thereby sealing the open bottom of the first tube when the profiles come into contact with each other. Open slots are provided for in the profile of the second tube to allow transfer of material from the interior of the second tube out through the open bottom of the first tube when the profiles disengage. A more specific detail of the preferred embodiment is further discussed below. 
   The preferred embodiment  100  comprises an exterior casing  6  and an interior mandrel  5 . See, e.g,  FIG. 1 . The casing  6  and mandrel  5  may be of any cross section so long as mandrel  5  is able to fit slidably within casing  6 . Each of the tubes have an upper end and a lower end. At the upper end of mandrel  5  is a first pile driver receiving plate  1 , which receives direct blows from a pile driver. Pile driver plate  1  in turn rest on a second plate  2  having an annular opening, whereby mandrel  5  may be inserted there through. Plate  2  is attached to the top end of casing  6 . When the pile driver (not shown) strikes plate  1 , the energy of the strike A is transmitted to plate  2 , which in turns drives casing  6  into the ground. Accordingly, casing  6  bears the majority of the stresses in driving apparatus  100  into the ground. 
   Compound collar assembly  3  provides the means in which device  100  is to be lifted or extracted from the ground. Referring to the  FIGS. 2 and 3 , collar assembly  3  comprises an external lifting collar  14 , which encloses internal collar  4 . External casing  6  fits slidably within and through collar  4 . Although the drawings shows collar  4  as a bolted on structure, collar  4  may also be a structure of a uniform ring. Collar  14  has an annular space  27  (see  FIGS. 2 &amp; 3 ) in which interior collar  4  fits within. Lifting collar  14  is lifted by known lifting means such as cables  13 , which may be attached to a crane (not shown). As collar  14  is lifted by cables  13 , collar  14  engages interior collar  4  at  56 , which lifts mandrel  5 . Internal collar  4  is affixed proximate to an upper portion of mandrel by pin  22 . However, collar  4  may be affixed to mandrel  5  by any number of methods, such as screws or bolts and the like, welding, or mandrel  5  and collar  4  can be casted or machined as a single item. In the preferred embodiment, pin  22  extends through a steel restraining member  40 . Member  40  is restrained and securely affixed within the upper portion of mandrel  5 . Member  40  may be made of any substantial and study material, e.g., a solid steel plug, steel plating, or steel hollow metal cylinder. The ends of pin  22  extends out from opposing sides of the exterior of mandrel  5  and are fixed in a position located proximate to the upper portion of mandrel  5 . The ends of pin  22  interlocked with collar  4 , accordingly, so as pin  22  rides along and is restrained within slot  21  of casing  6  so does collar  4 . Slot  21  is a located proximate the upper portion of casing  6 . Therefore, as collar  4  moves up and down slot  21  so does mandrel  5  in relation to casing  6 . This can be seen when comparing  FIGS. 2 and 3 . Therefore, the interaction between pin  22 , collars  4  and  14 , and the bottom ledge of plate  2 , cause mandrel  5  to be displaced in relation to casing  6  when upward force B is applied. 
   During the driving process, pile driving hammers offer cause pile mandrels to spiral which in turn would cause lifting cables to wind and tangle. This is avoided in collar assembly  3 . In  FIG. 2 , cables  13  exert no lifting force and therefore, interior collar  4  floats within annular space  27 , thus casing  6  may twist and turn with relative freedom within annular void  27 , without affecting cables  13 . 
   Suppressor  20  is located directly above member  40 . Suppressor  20  is made from material possessing an ability to dampen vibrations, such materials can either be a natural material such as rubber or a synthetic elastomer. Suppressor  20  as the drawings show is sandwiched between plate  1  and member  40 . The utility of suppressor  20  is discussed below. 
   At the bottom of apparatus  100  are sealing means to control the release of grout or other pile forming materials. In the preferred embodiment, the sealing means comprise a pair of mating frusto conical profiles which is discussed as follows. At the bottom end of casing  6  is ground contacting member  28 , which comprises an open top end  32  and an open bottom end  31 . See  FIGS. 2 and 3 . Open top  32  end is located at the bottom end of casing  6 , and has an annular cross-sectional area with a downward facing frusto-conical profile. Open top end  32  has a larger cross-sectional area than open bottom end  31 . Ground contacting member  28  may be attached to the bottom of casing  6  either by a variety of means, such as screws, bolts, or by welding. Attached to the bottom end of mandrel  5  is member  11  which has a substantially downward facing frusto-conical profile that is adapted to mate with ground contacting member&#39;s ( 28 ) annular downward facing frusto-conical profile when the profiles come into contact with each other. Member  11  also comprises a plug  8  which seals open bottom end  31 , an upward facing conical member  29 , and a plurality of elongated openings or slots  10  located radially along the upper portion of member  8 . The upper portion of member  11  is hollow, thereby allowing pile forming materials to exit openings  10  and migrate from the interior of mandrel  5  into the surrounding earth when the profiles are disengaged for each other. Conical member  29  facilitates the dispersal of the pile forming materials out through openings  10 . 
   Located proximate to the bottom portion of casing  6  are a plurality of apertures  23 . During the driving of apparatus  100  into the ground, apertures  23  are in flow-through alignment with apertures  9 , which are located proximate the lower portion of mandrel  5 . 
   This flow-through alignment of apertures  9  and  23 , depending on the type of pile being formed, enable cementitious fluid, water, or compressed air to exit from the interior of mandrel  5  and into the surrounding earth. In the case of installing a stone column air may be forced through these openings. This is discussed in further detail below. 
   When it is time to form the pile, cables  13  exert an upward force B. Mandrel  5  is lifted prior to casing  6  being engaged and lifted. See  FIG. 3 . This out of phase lifting of casing  6  and mandrel  5  results in lower plug  8  being lifted and unsealing the open bottom end  31 , which in turn allows the contents within mandrel  5  to be released through elongated slots  10 , out open bottom end  31  and into the hole created by apparatus  100 . As force B continues to lift mandrel  5 , collar  4  will ultimately engage the bottom of plate  2  at  55 , and thereby lift both casing  6  and mandrel  5 . During the entire lifting period, the hole is being filled with the contents of mandrel  5 . 
   Although not shown in the drawings, apparatus  100  may incorporate the use of one or more “O” rings  9   a  to ensure an effective seal against unwanted grout, air, or water seepage when apertures  9  and  23  are out of phase. The “O” rings  9   a  would be mounted on lower portion of mandrel  5  to a position above aperture  9  sealing the annular space between the exterior of mandrel  5  and the interior of casing  6 . The “O” rings  9   a  may be made of any suitable elastomeric material that would be commonly used for the purpose of creating a seal, much like the piston rings of an automotive gasoline engine. 
   Apparatus  100  may also be equipped with an optional foot assembly  7 . Such an assembly would be used when installing a pile formed from grout. As shown in the figures, foot assembly  7  is attached at the bottom of the exterior of casing  6  and encloses member  28 . Foot assembly  7  includes a plate  50 , which is made of a sturdy material such as steel for contacting and penetrating the ground, cylindrical sidewall  72  which extends up over the lower portion of the member  28 , a plurality of removable bolts or screws  26  that are positioned radially proximate the lower portion of foot  7 , and sealing ring  75  with a sealing ring pin  24  which ride along in slot  80 . One end of bolts  26  rides along and is retrained within a channel  25 . Channel  25  is located on the circumferential surface of member  28 . The boot is restrained to member  28  when bolts  26  are screwed in and ride up and down channel  25 . If foot assembly  7  is not desired, bolts  26  are removed and foot assembly  7  may slide off member  28 . 
   Sealing ring  75  comprises an annular ring of a sturdy material such as steel that circumferentially surrounds the a lower portion of the exterior casing  6 . Sealing ring  75  is adapted so that it slideably fits around exterior casing  6 . During the driving process, sealing ring  75  is situated lower than the top edge of cylindrical sidewall  72  and below aligned apertures  9  and  23 . as shown in  FIG. 2 , so as not to hinder the flow of grout, air or water as the case may be, to enter the surrounding earth. When foot assembly is not used, ring  75  may be removed by removing pin  24  and sliding ring  75  off casing  6 ; ground contacting member  28  would also have to be removed. 
   Sealing ring  75  is activated via pin  24 . Pin  24  is rigidly located proximate to the lower end of mandrel  5 , so as mandrel  5  traverse up and down within casing  6 , so does pin  24 . The distal ends of pin  24  extend through casing  6  and are interlocked into ring  75 , therefore, as pin  24  travels so does ring  75 . The travel of pin  24 , however, is confined within the boundaries of lower slot  80 . Lower slot  80  is located on the lower portion of casing  6 . As indicated in the figures, slot  80  is aligned parallel to the length of both casing  6  and mandrel  5 . 
   Accordingly, when force B causes exterior collar  14  to engages interior collar  4  at point  56 , thereby causing mandrel  5  to be upwardly displaced in relation to casing  6 , pin  24  being interlocked to ring  75  causes ring  75  to also be displaced from its first position as seen in  FIG. 4  to a second position, as seen in  FIG. 5 , whereby, ring  75  seals the annular space  85  between the exterior of casing  6  and the interior of sidewall  72 . This sealing of annular space  85  aids in the extraction of device  100  from the earth by preventing debris from the surrounding earth from entering annular space  85  and clogging the extraction process or hanging up the device. 
   Another novel aspect of foot assembly  7  is that it provides a plume forming chamber  30  to facilitate the effective dispersal of grout into the surrounding earth. As shown in  FIGS. 3 ,  4 , and  5  during the extraction process mandrel  5  is displaced first in relation to casing  6 , when the upper portion of collar  14  engages the bottom of plate  2  at  55 , casing  6  begins to lift and is displaced in relation to the surrounding earth, accordingly, ground contacting member  28  lifts as casing  6  lifts, thereby causing the formation of chamber  30 . 
   Grout enters chamber  30  forming a steady state reservoir of grout, i.e., the level within the reservoir will remain steady provided there is sufficient grout be delivered via mandrel  5  as the grout exits out opening  33  of chamber  30 . Opening  33  as the figures show is larger in cross-sectional area than that of opening  31 . As apparatus  100  continues to lift from the ground, ground contacting member  28  engages foot assembly  7  when lifting bolt  26  contacts the bottom of channel  25 . At that point grout flows out of the grout reservoir formed in chamber  30  and into the surrounding earth. The affects of the chamber and the resultant reservoir causes the grout to flow more uniformly and widely into the earth. 
   Another novel aspect of foot assembly  7 , is that the foot is not left in the ground, but retrieved for subsequent and multiple use. This is advantageous as steel is not wasted and thus results in cost savings. The use of optional foot assembly  7  may be used where the desired hole dimensions is larger than can be created with casing  6 . 
   Accordingly, optional foot assembly  7  facilitates the flow, distribution, and placement of the pile forming material and can be adapted to the particular characteristics of pile forming material that is to be placed into the earth. 
   In use, apparatus  100  is driven into the earth using known pile driving techniques and equipment. During the driving process, apertures  9  and  23  are in alignment, thereby allowing grout to flow from the interior of mandrel  5  through the apertures and into the surrounding earth. This provides fluid grout to lubricate the result pile hole to facilitate extraction of the apparatus  100  fills any voids with grout. Pile driving force A maintains the plates  1  and  2  flush against each other and maintains the seal caused by the mating between the annular conical profile of ground contacting member  28  with the conical profile of mandrel end member  11 . 
   When the desired depth is obtained, collar assembly  3  is use to lift the apparatus and extract apparatus  100 . See  FIG. 3 . During the extraction process, casing  6  and mandrel  5  are lifted out of phase, in that, mandrel  5  is first lifted and advances a certain distance prior to casing  6  being also lifted. When casing  6  begins lifting, both tubes are then lifted in unison. 
   As mandrel  5  is displaced in an upwards direction from casing  6 , member  11  unseats from ground contacting member  28 , thereby creating an annular space. See  FIG. 3 . This causes grout to flow out of elongated slots  10 , out the bottom opening  31 , and into the surrounding earth. 
   Apparatus  100  may also be use to place stone column into the ground. When installing a stone pile optional foot  7  assembly would be used. Instead of a grout delivery system as illustrated by  15 , apparatus  100  is equipped with a hopper (not shown), which supplies stone or crushed rock. Mandrel  5  is not prefilled with stone, rocks and the like. Compressed air or water is supplied to the annular space between casing  6  and mandrel  5 . In the placement of stone piles/columns, air or water is used to stabilize the surrounding earth as the device is being driven into the ground. 
   The compressed air or water that is forced into the annual space between exterior casing  6  and mandrel  5  exits casing  6  through apertures  23  and into the surrounding earth. When the desired depth is reached, the hopper fills mandrel  5  with stone/rock, and the lifting procedure as described above begins. In addition, the lifting and depositing of stone may be halted and driving may restart so as to further compact the forming stone column. The water or compressed air that exits through aperture  23  assists in the extraction of the apparatus from the ground. When using apparatus  100  for installing stone or rock pile, optional foot  7  is not required. 
   In addition apparatus  100  easily accommodates the application of vibration equipment. As as shown in the drawings, a suppressor  20 , which is made of an elastomeric material may be inserted within mandrel  5 . It is a common practice when placing stone columns to attached a vibrator to the mandrel. See, for example, the discussions in Goughnour, U.S. Pat. No. 5,279,502. 1  In apparatus  100 , it is anticipated that a driving hammer will be used to drive the apparatus into the earth. Accordingly, after driving, the hammer will rest on plate  1 . If a vibrator is used, suppressor  20  will substantially reduce the vibrations being transmitted to the hammer. Excessive vibrations to the hammer may cause damage to the pile driving equipment. Accordingly, no additional time or procedures will be required to remove the hammer from driving plate  1 . The hammer can ride on top of driving plate  1  during the entire lifting and vibrating process. 1 U.S. Pat. No. 4,397,588, Col. 1. (regarding Vibroflot) 
   A preferred embodiment of the invention has been described and illustrated for purposes of clarity and example, it must be understood that many changes, substitutions and modifications will become apparent to those possessed of ordinary skill in the art without thereby departing from the scope and spirit of the present invention which is defined by the following claims.