Abstract:
A method for installing a pre-cast/pre-stressed concrete and steel pile used in the construction of pile foundations and the resulting installed pile that has its distal end anchored to bedrock is disclosed. After the pile is located on bedrock, a first hole is drilled into bedrock that is of sufficient depth to accommodate a lower portion of the steel pipe that extends below the concrete pile and contains a plurality of orifices. A second hole is drilled into bedrock that is below and concentric to the first hole and has a diameter than that is usually less than that of the first hole. The second hole forms an anchoring socket to accommodate an anchoring anchor. Grout is injected into the steel pile and anchoring socket until the grout fills the voids in the interior of the steel pipe. Grout also seeps through the orifices in the lower end of said steel pipe and fills the second hole, and an annular space between the outer circumference of the steel pipe and the walls of the first hole.

Description:
FIELD OF THE INVENTION 
   The present invention relates to concrete piles used in the construction of pile foundations into bedrock and methods of installing such piles. More particularly the present invention relates to pre-cast, pre-stressed concrete and steel piles that are anchored to bedrock. 
   BACKGROUND OF THE INVENTION 
   Various methods are known for using steel tubes or pipes as part of a pier support system in a soil matrix and removing the soil matrix with drills or augers placed within the steel tubes; see, e.g., U.S. Pat. Nos. 6,425,713 and 6,688,815. It is also known to use steel tubes in pier support systems for modular residential or commercial buildings using rock anchors to anchor the pier support systems to solid bedrock; see, e.g., U.S. Pat. No. 6,094,873. 
   U.S. Pat. No. 5,771,518 is directed to a steel-reinforced, pre-cast concrete pier structure in which a uniform diameter hole is drilled to a sufficient depth into the earth and at a sufficient diameter to more than accommodate the outer diameter of each of the main pier elements. The main pier elements are defined by a central steel pipe around which is formed a tubular, steel-reinforced, pre-cast concrete section. After the pier element is lowered into the earth-drilled hole, loose aggregate material is dumped into the annular space between the outer surface of the pier element and in the central steel pipe interior. A quick-setting grout is injected through this central pipe down through the aggregate to the bottom of the pipe and up through the aggregate and fills the entire annular space occupied by the aggregate. 
   While it may be practical to drill a uniform diameter hole into the earth to a depth to accommodate the outer diameter of the pre-cast concrete pile as described in the &#39;518 patent, there is a need for an improved method of installation of a pile in cases where drilling is done into bedrock usually at the bottom of a body of water, e.g., under a seabed or an ocean floor. 
   SUMMARY OF THE INVENTION 
   The present invention solves the above-identified problem of installing a pre-cast, pre-stressed concrete and steel pile in bedrock. During the pre-casting operation, the concrete pile is reinforced with a central steel pipe, which has a lower portion extending below the concrete pile. A plurality of orifices is distributed over the entire cylindrical area of the portion of the steel pipe that extends below the distal end of the concrete pile. 
   In the first step of one embodiment of method of the present invention, the pre-cast, pre-stressed concrete pile is located on bedrock. A drilling tool is lowered through the entire length of the steel pipe and a first hole is drilled into the bedrock during the next step of the method. The first hole is of sufficient depth to accommodate the lower portion of the steel pipe. The diameter of the first hole is greater than the outer circumference of the steel pipe to allow the steel pipe to move down as the first hole is being drilled from within the pipe during this drilling step. The diameter of the first hole is drilled not only to have a diameter slightly greater than the diameter of the steel pipe, but also to form a substantially uniform annular space between the outer circumference of the lower portion of the steel pipe and the drilled wall of the first hole in the bedrock. 
   The drilling tool while still within the steel pipe is then used to drill a second hole that is below and concentric with the first hole and has a smaller diameter than that of the first hole to form an anchoring socket to accommodate an anchor. The drilling tool is removed from the steel pipe and the anchor is extended through substantially the entire length of the steel pipe and into the anchoring socket. A grout injection pipe is lowered into the steel pipe and grout is injected under pressure until the grout fills the interior of the second hole and interior of the steel pipe. In addition, the grout seeps through the orifices in the lower end of the steel pipe to fill this uniform annular space. The grout injection pipe is removed from the steel pipe and the grout is allowed to harden. 
   In another embodiment of the method of the present invention, the foregoing steps are carried out except that after the anchor has been lowered so that its distal end is adjacent the bottom of the second hole, an inflatable bladder, preferably having a shape similar to that of a doughnut, is lowered along the anchor within the steel pipe. The doughnut-shaped bladder is positioned so that it is part way between the proximate and distal ends of the steel pipe. The grout injection pipe is then lowered through the “doughnut hole” of the bladder and the bladder is inflated to provide stability of the injection pipe and to allow the grout to be injected under pressure during the step of injecting grout into the pipe. 
   In still another embodiment of the method of the present invention, the anchor is a rock anchor comprising a high strength rod extending through the entire length of the steel pipe and through its distal ends to a position adjacent the bottom of the second hole of the anchoring socket. Preferably, a bearing plate is attached to the distal end of the anchoring rod. 
   The steel pipe-reinforced concrete pile of the present invention that is installed in accordance with the method of the present invention includes: 
   a) the pre-stressed concrete pile that has its distal end located on bedrock; 
   b) the steel pipe pre-cast along the same longitudinal axis as the concrete pile that has a lower portion containing a plurality of orifices and extending below the distal end of the concrete pile and into the first hole drilled into bedrock to leave an annular space between the outer circumference of the steel pipe and the walls of first hole in the bedrock; 
   c) the anchor that extends through the entire length of the steel pipe, through its distal end and into the second hole drilled into the bedrock and has a diameter less than the diameter of the first hole; and 
   d) grout that fills the annular spaces between the rock anchor and the interior walls of the steel pipe, the rock anchor and the walls of the second hole, and the outer circumference of the steel pipe and the bedrock. 
   One of the advantages of the present invention is to provide an improved pile structure to support foundation structures and the like. 
   A further understanding of the invention can be had from the detailed discussion of the specific embodiments below. For purposes of clarity, this discussion refers to specific equipment and method steps. However, other equipment and variations of these specific method steps may be used. It is therefore intended that the invention not be limited by the following discussion of specific embodiments. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing aspects and the attendant advantages of the present invention will become more readily appreciated by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
       FIG. 1  is a schematic cross-sectional view of the lower section of a steel pipe-reinforced concrete pile after a pile locating step of an embodiment of the method of the present invention; 
       FIG. 2  is a schematic cross-sectional view of the lower section of a steel pipe-reinforced concrete pile during a first drilling step of an embodiment of the method of the present invention; 
       FIG. 3  is a schematic cross-sectional view of the lower section of the steel pipe-reinforced concrete pile after the first drilling step of an embodiment of the method of the present invention; 
       FIG. 4  is a schematic cross-sectional view after a second drilling step of an embodiment of the method of the present invention; 
       FIG. 5  shows a schematic cross-sectional view of the lower section of the steel pipe-reinforced concrete pile after an anchor placement step of an embodiment of the method of the present invention; 
       FIGS. 6 and 7  show schematic cross-sectional views of the lower section of the steel pipe-reinforced concrete pile during the grout injecting step of another embodiment of the method of the present invention; 
       FIG. 8  is a schematic cross-sectional view showing an installed steel pipe-reinforced concrete pile according to one embodiment of the present invention; 
       FIG. 9A  is a longitudinal view, partially in cross-section, to reveal the contents of the internal structure of the installed steel pipe-reinforced concrete pile according to another embodiment of the present invention; 
       FIG. 9B  is a cross-sectional end view of the installed steel pipe reinforced concrete pile shown in  FIG. 9A  taken along line  9 B- 9 B; 
       FIG. 10  is an isometric view of the upper portion of a tremie cap high pressure grout injection system used during the grout injecting step of another embodiment of the method of the present invention 
       FIG. 11  is a top view of the tremie cap high pressure grout injection system shown in  FIG. 10 ; and 
       FIG. 12  is a top view of the tremie cap high pressure grout injection system shown in  FIG. 10 . 
   

   Reference symbols or names are used in the figures to indicate certain components, aspects or features shown therein, with reference symbols common to more than one figure indicating like components, aspects or features shown therein. 
   DETAILED DESCRIPTION OF THE INVENTION 
   To facilitate its description, the invention is described below in terms of specific embodiments, and with reference to the figures. 
     FIGS. 1-5  are illustrative of the sequential steps of the one embodiment of the method of the present invention described in detail below. The product resulting from the method of the present invention is an installed steel pipe-reinforced concrete pile  10  having air or water jet tubes  12  extending therethrough and reinforced with internal steel pipe  20  positioned along longitudinal axis  22  (shown in  FIG. 9A ) and is partially shown in  FIG. 8 . The lower portion  30  of steel pipe  20  extends below pile  10  and has a plurality of grout holes  34  that are preferably uniformly drilled around the lower approximately one-third of the cylindrical area of lower portion  30  of pipe  20 . 
     FIGS. 1-8  only show the lower section  38  of concrete pile  10  to illustrate the steps of various embodiments of the method of the present invention of firmly cementing lower portion  30  of pipe  20  in bedrock  40 . 
     FIG. 1  shows lower section  38  after special lifting apparatus such as a crane, or other piece of construction equipment is used to lower concrete pile  10  through a body of water  41  until lower portion  30  of steel pipe  20  is embedded in sand, soil or other composition  42  to complete the first step. Usually the combined weight of steel-pipe reinforced pile  10  is sufficient to cause steel pipe  20  to sink into composition  42  and to have the lower end  39  of pipe  20  come to rest on bedrock  40  after this pile locating step of the present method. Pressurized air is passed through air jet tubes  12  to loosen composition  42  and assist in lowering pipe  10  as shown in  FIGS. 1-3 . In some installations, lower end  39  of portion  30  is above bedrock  40  after the concrete pile is lowered through water  41  as shown in  FIG. 1 . In either case, after rotary drilling equipment  50  is lowered through pipe  20  so that hammer  52  and drill bit  54  having wings  55  are adjacent bedrock  40 , the drilling step begins in either bedrock  40  or composition  42  above bedrock  40 . 
     FIG. 2  shows lower section  38  during the first hole drilling step in which air driven drilling equipment  50  is used to drill first hole  60  into bedrock  40  using retractable drill bit  54  with wings  55  at the end of drill stem  56 . The diameter of first hole  60  is slightly greater than the outside diameter of pipe  20  to form annular space  64  (shown in  FIGS. 3-4 ) between the outer circumference of pipe  20  and the bedrock walls of first hole  60  that is later filled in with grout. Preferably the diameter of first hole  60  is at least about 6 inches and more preferably in the range of about 6 to 30 inches. The preferred length of first hole  60  is at least about 5 feet and more preferably in the range of about 5 to about 25 feet. 
   A suitable type of drilling equipment  50  for the drilling operations of the present invention is one that has the feature that when drill bit  54  is lowered in place adjacent bedrock  40 , wings  55  furl out from drill bit  54  as shown in  FIGS. 1-3  to permit the drilling of first hole  60  with the desired diameter slightly greater than the outer diameter of pipe  20 . Hammer  52  is pneumatically operated at air pressures in the range of about 100 to about 300 psi. The drilling operation can also be done by using steerable drilling equipment  50  positioning drill bit  54  in various offset positions to drill holes larger than the inner diameter of pipe  20  by techniques well known in the prior art; see, e.g., U.S. Pat. No. 6,595,303 for a description of this type of drilling operation. 
     FIG. 3  shows lower section  38  of steel-pipe reinforced concrete pile  10  after first hole  60  has been drilled to the desired depth at the completion of the first drilling step. After this step, wings  65  can be retracted back into bit  54 . If desired, this will allow hammer  52  and bit  54  to be pulled back up via drill stem  56  after the drilling of first hole  60  to change the drill bit for the next step. 
     FIG. 4  shows shoulder  66  of concrete pile  10  resting on surface of bedrock  40  and end  39  is shown adjacent the bottom of first hole  60 . During the second hole drilling step, drilling equipment  50  is replaced with drilling equipment  70  of drilling stem  76  and drill bit  75  to drill second hole  80  having a smaller diameter than that of the first hole. Preferably the diameter of second hole  80  is at least about 3 inches and more preferably in the range of about 3 to 24 inches. Second hole  80  is preferably drilled to a depth of at least about 5 feet, and still more preferably to a depth within a range of about 5 to about 25 feet. 
   Referring to  FIG. 5 , an anchoring means  90  has been lowered into place within concrete pile  10  so that the anchor is positioned along the entire length of pipe  20  and through the combined depths of first hole  60  and second hole  80 .  FIG. 5  shows section  30  after the completion of the next step of the preferred embodiment. In this example, a suitable anchoring means is a rock anchor having a reinforcing steel tension rod  96  and a bearing plate  100  held in place by anchoring nuts  98 ,  101  and  102 . The U.S. Army Corps of Engineers&#39; Unified Facilities Guide Specifications, dated December 2001, contains details of the installation of rock anchors. 
     FIG. 6  shows lower section  38  during the initial phase of the injection step according to one embodiment of the present method. In this embodiment, grout injection pipe  104  has been lowered within pipe  20  so that its injection pipe outlet  106  is adjacent bearing plate  100 . An inflatable pneumatic bladder  110  is installed in lower portion  30  as shown. Bladder  110  is then inflated to place grout  120  under pressure during the injection step. A suitable injection pipe is a standard tremie pipe having a  2  inch nominal diameter. Prior to the injection of grout  120 , compressed air is used to flush any loose drilling materials from hole  80  and annular space  64 . Grout  120  is preferably injected at a pressure in the range of about 80 to about 120 psi, and more preferably at a pressure of about 100 psi. Additional details well known in the art regarding installing pneumatic bladders prior to injection of grout can be found in Britannia Mine Remediation 4100 Level Plug Safety Investigation Plan, dated December, 2001. At the end of the initial phase of the injection step, grout  120  has filled anchoring socket  80 , the annular spaces between tensioning rod  96  and the inner wall of pipe  20  in lower section  30 , and annular space  64 , as shown in  FIG. 6 . 
     FIGS. 5-6  also show an upper section of rod  96  encased in a plastic pipe  130 , preferably polyvinyl chloride pipe to prevent the outer surface of rod  96  from contacting grout  120  during the grout injection step. In addition, a plastic centering element  140  is tightened around the lower section of rod.  96  within first hole  60  and is attached by nut  142  to the section of rod  96  within second hole  80 . The portion of plastic centralizer  140  between first hole  60  and second hole  80  is bulged to fill the opening of hole  80  to provide centering of rod  96  during the grout injection step. 
     FIG. 7  shows lower section  38  during the next phase of the injection step in which pneumatic bladder  110  and the end of injection pipe  104  have been moved above lower section  30 . Grout  120  is then injected into the void spaces in the interior of steel pipe  20  below bladder  110 . The foregoing is repeated until all of the void spaces in the entire interior of steel pipe  20  are filled with grout  120  and bladder  110  and injection pipe  104  are removed. 
     FIG. 8  shows lower portion  30  of the installed steel pipe-reinforced concrete pile  10  of the present invention after grout  120  has hardened with plastic pipe  130  and centering element  140  remaining in place. 
   An example of the preferred embodiment of the present invention that follows illustrates that after a concrete pile had been installed using the method of the present invention, the pipe was stress tested to a high percentage of its rated capacity. The example is for illustrative purposes only and is not meant to limit the scope of the claims in any way. 
   EXAMPLE 
     FIGS. 9A and 9B  show an octagonal concrete pile after installation in accordance with this Example. Octagonal concrete piles were found to be preferred for the pile foundations subjected to the environmental conditions of this Example. Specifically, a 24 inch octagonal pre-stressed concrete pile  200  having a 12 inch nominal diameter carbon steel pipe  20  was first pre-cast along longitudinal axis  22 . Steel prestressed strand  240  was wrapped with epoxy coated steel rebar  230  before being pre-cast with steel pipe  20  in concrete. Approximately 65 grout holes  34  were uniformly drilled over the entire cylindrical area of lower portion  30  of pipe  20  that extends below shoulder  246  of concrete pile  200 . The holes were about ⅛ inch in diameter to allow the grout to flow therethrough. 
   The remaining description of this Example refers to the steps of the method of the present invention generally as shown in  FIGS. 1-7 . Octagonal concrete pipe  200  was lowered through about 8 to about 10 feet of moist sand and sand overburden of seabed  42  with the assistance of pressurized air that was passed through air jets  12  until distal end  39  of steel pipe  20  struck bedrock  40 . 
   A super Jaws® Under Reaming Bit  65 , Number VT 315, and a Challenger hammer  52 , both of which are manufactured by Numa Corporation, were lowered through pipe  20  and were used to drill an approximately 13-⅜ inch diameter pile rock first socket  60  to a depth of 16 feet into bedrock  40 . Annular space  64  had a thickness of about ⅜ inch. Bit  54  was removed from the 0.75 inch drill string  56  and replaced with a drill equipment  70  having a 10 inch bit  75 . Drill bit  75  was used to drill a 10 inch diameter rock anchor socket  80  to a depth of 10 feet. Pile  200  continued to be lowered into pile rock socket  60  during the entire first hole drilling operation until shoulder  246  was in place on the top surface of bedrock  40  at the completion of the second hole drilling step. During these drilling operations, air was continuously passed through air jet  12  to blow the sand away from the outer surface of pipe  200 . Drill equipment  50  was then removed and rock anchor socket  80  was prepared to receive a Dywidag-System Grade  150  Bar Rock Anchor  90  having a 1-¾ inch steel rod  96  and an 8 inch diameter bearing plate  100  attached at its distal end in the manner described above in the Detailed Description of the Invention section. 
   During the initial grout injection step, a 2 inch tremie grout injection pipe  104  was lowered into pipe  20  so that outlet  106  was adjacent bearing plate  100  and grout  120  was injected until the grout had filled the interior of second hole and interior of the steel pipe  20 . Grout injection pipe  104  was then removed. During the final grout injection step, a tremie cap assembly  300  including tremie cap chamber  310  having a 1 inch vent nipple  312  shown in  FIGS. 10-12  was affixed to the top of steel pipe  20  using a 12 inch diameter Type {dot over (9)}9 Roust-a-bout Victaulic pipe coupling  315 . For this project, a grout nipple connection  340  as shown in  FIG. 12  was not used since steel pipe  20  was completely filled with grout before the tremie cap assembly  300  was coupled to the top of pipe  20 . 
   Another modification for this Example was that Dywidag rod  96  was extended approximately 12 inches above the top of steel pipe  20  and did not extend up through the Dywidag nipple sleeve  320 . Instead, a Dywidag coupling nut, not shown in  FIGS. 10-12 , was threaded onto the end of the threaded Dywidag rod  96  and a Dywidag rod extension piece was threaded onto the coupling nut to provide the necessary length of rod  96  above the steel pipe  20  as shown in  FIGS. 10 and 12 . The Dywidag nipple connection  320 , although not used for this project, was designed so that the Dywidag rod  96  could extend several feet above the top of steel pipe  20  without the need for a coupling nut and a rod extension piece. The Dywidag nipple connection  320  was designed so that the distal end of a 3 inch diameter Dywidag nipple sleeve  320  for rod  96  was welded to the center of top of chamber  310 . A urethane gasket  322  and a ½ inch steel plate  326  were mounted over Dywidag rod  96 . Dywidag nut  330  was threaded onto rod  96  and tightened so that steel plate and gasket  322  were brought to bear against top of nipple  320  providing a sealed connection. Another ½ inch plate  328  encircled the extension of rod  96  and mounted onto the top of nut  330 . A washer and a nut was tightened onto each of a pair of ½ inch threaded rods  336  to secure rod assembly  96 . The grout nipple connection, although not used for this project, was designed so that the distal end of a 2-½ inch grout nipple  340  was welded to the outer circumference of the top of chamber  310 . A Smith-Blair steel pipe coupling  350  was used to connect the proximate end of nipple  340  to grout pipe  360  that was connected to the source of grout (not shown). A washer and a nut were tightened onto each of a pair of ⅝ inch threaded rods  356  to secure coupling  350  in place. 
   Once the tremie cap assembly  300  was secured onto steel pipe  20 , an air hose was attached to the vent nipple  312  to feed compressed air into the tremie cap assembly  300 . The tremie cap chamber  310  was pressurized to 125 psi for 5 minutes to force the fluid grout through the orifices  34  into the lower portion  30  of steel pipe  20  and into the annular space  64  between the steel pipe and the area of the first hole  60 . The tremie cap assembly  300  was removed and the change in the level of grout at the top of steel pipe  20  was measured after pressurizing to determine the volume of grout placed into annular space  64  and to assure that space had been filled with grout. After the grout injection step, the grout was allowed to hardened. The resulting installation was then tested in situ by stressing the rock anchor to 70% of its rated capacity or approximately 285 kips. 
   Without departing from the spirit and scope of this invention, one of ordinary skill in the art can make various changes and modifications to the method and resulting installed pile of the present invention to adapt it to various usages and conditions. As such, these changes and modifications are properly, equitably, and intended to be, within the full range of equivalents of the following claims.