Method And Means For Installing Load Bearing Piles In Situ

Abstract

Method of installing a preformed load-bearing pile in an earth situs, utilizing core of predetermined length and having screw-like ridge means externally along the length thereof. Pile core drilled into earth while supplying fluid jetting medium through said passage means to mix with drilled earth and to facilitate upward movement of earth, until pile cavity of requisite depth formed. Pile core further rotated in place while pumping fluid, self-hardenable, cementitious material through passage means, to urge cementitious material along said screw means, thereby to enlarge girth of pile cavity and form generally tubular body about the pile core. Tubular body sets and hardens with load-bearing pile core anchored therein, as composite pile body of correspondingly increased load-bearing capacity.

Description

BACKGROUND OF THE INVENTION

In the past, numerous methods and means have been devised in which tubular casings were driven into an earth situs to be filled wijh self-hardenable cementitious material and form a load supporting pile. In general, however, the tubular casings were removed from the situs, usually prior to full hardening of the cementitious material. By use of such methods, removal of the casing failed to provide requisite or desired skin friction between the formed piles and the walls of the cavities defined by the driven casings. This condition was to some extent modified by either forming a bulbous concrete body at the inner end of the casing prior to removal of the latter, and/or by jetting water around the casing to enlarge the cavity, and then pouring mortar around the formed pile to fill the resultant space between the pile and the wall of the enlargement, without attaining requisite skin friction for the enlarged pile body.

Lee A. Turzillo U.S. Pat. No. 3,354,657, relates to forming concrete piles in the earth by drilling a hollow cylindrical casing into the situs, while simultaneously pumping pressurized flushing fluid through the casing and an apertured bit on the lower end thereof, until a cavity of predetermined depth was formed, and thereafter pumping cement mortar through the casing to occupy voids around the bit and the casing, as well as to fill the casing. The mortar which forms around the casing, was limited in volume and shape, commensurate with the relatively low fluid pressures attainable in fluid cement mortar by prior art methods in general. Moreover, in order to provide cement-filled casings of the character described by prior methods, the load capacities of the finished piles were quite limited, and the periods required to produce the finished piles in condition for the intended load-bearing uses of the same were considerable, if not impractical for at least some purposes.

SUMMARY OF INVENTION

In use of the method of the invention a preformed load-bearing pile core, having an external helical thread means, is screwed into the earth of a situs while simultaneously jetting water into the drilled earth to define a cavity of predetermined or appropriate depth. During this jetting procedure the thread means is adapted to convey the drilled earth material upwardly to the ground surface. The jetting fluid mixes with the adjacent earth materials to make the same sufficiently fluid to flow upwardly, aided by the lifting action of the helical thread means, while at the same time enlarging the cavity to a substantial extent. Upon discontinuance of the jetting procedure, self-hardenable fluid cement mortar is pumped into the enlarged cavity around the pile core. Continued rotation of the pile core, accompanied with such pumping of the mortar, is effective to increase the depth and/or the girth of the cavity. Rotation of the pile core can be continued with or without increasing the cavity depth, until the enlarged pile cavity around the pile core is completely filled with fluid mortar to desired level in in reference to the top of the cavity. The fluid mortar, upon hardening in the formed cavity, is anchored to the earth and to the pile core, thereby producing a composite, reinforced pile body of high load-bearing capacity.

Objects of the invention will be manifest from the following brief description and the accompanying drawings.

Of the accompanying drawings:

FIG. 1 is vertical cross-section in an earth situs, illustrating an initial step in the method of the invention by which a preformed, reinforced pile core has been screwed to given depth of pile cavity formed thereby in the situs, said pile core being shown broken away and in section to illustrate the internal structure thereof.

FIG. 2 is a view corresponding to FIG. 1, illustrating intermediate fluid jetting step of the method, by which the formed pile cavity has been enlarged in girth around the pile core.

FIG. 3 is a view corresponding to FIG. 2, by which fluid, self-hardening cementitious material has been pumped through the pile core while rotating the core, further to enlarge the cavity and fill the same with cementitious material which hardens to form a sturdy, core-reinforced, concrete pile in the situs.

FIG. 4 is an enlarged cross section taken on the line 4--4 of FIG. 1.

FIG. 5 is an enlarged cross-section taken on the line 5--5 of FIG. 3, to illustrate the resultant formation of a relatively large, hardened concrete pile, which is reinforced by the concrete filled, cavity-forming pile core.

For use in practicing the method of the invention, as for installing a load-bearing pile in an earth situs, a preformed load-bearing core 10 of predetermined length, diameter, and load-supporting capacity is provided as shown in FIGS. 1 and 4 (without reference to the earth situs E). The core 10 may be of any suitable outside diameter and any length and weight, such as 8 5/8 O.D. by 20 feet long, and weighing 1,580 lbs. (or approximately 78 No. per foot in length). The core is shown as including an external pipe or casing 11 of heavy metal with radially outwardly presented, screw-like thread means 12, either formed in the pipe or welded spirally along the length thereof. An axially centered metal conduit 13 is shown extending within the pipe 11 and connected to a drilling bit 14, affixed at the lower end of pipe 11, and a closure cap 15 may be affixed to the upper end of pipe 11. Suitable means 17 may be provided for attaching the core 10 onto a drill rig of known type (not shown). The closed space 18 defined between the pipe 11 and the conduit 13 within the fabricated core 10, is shown completely filled with a concrete mix 20, such as one part cement mortar to one part mason sand, which has been allowed to cure for about 48 hours, for example. Passage means 21, 21 may be suitably provided between the central conduit 13 and the screw-threaded outer casing, for passage of fluid materials fed through said central conduit, in a manner to be described later, but particularly for passage of fluid jetting water and/or air, as well as fluid cement mortar, at points near the lower end of the core 10. The pile core 10 serves as a preformed, reinforced pile body having a very substantial load-bearing capacity.

In practice of the improved pile installing method, the preformed pile core 10, as best shown in FIGS. 1 and 4, is connected to the leads of a drilling rig supporting an auger-type drive means (not shown), and a pump or other source of water under pressure is connected to the central conduit 13 of the pile core. Rotation of the auger drive is started (at 52 RPM for example), simultaneously with operation of the water pump (approximately 20 GPM and 350 PSI), to drill the pile core into the earth situs to predetermined or appropriate depth as shown in FIG. 1, whereby the screw means 12 carries the drilled earth material to the surface S and a cavity 23 is formed. When or if hard earth material is encountered in one way or another, it may be necessary to predrill a cavity of slightly smaller diameter than that to be drilled by the pile core.

In any event, when a said cavity 23 of requisite depth and diameter has been formed by the rotating pile core 10 (see FIG. 1), rotation of the pile core is continued while pumping jetting fluid through the conduit 21, and through jetting passages 21 at least adjacent the lower end of the pile core. This jetting fluid mixes with the adjacent earth materials to make the same sufficiently fluid to flow upwardly, aided by the lifting action of the helical screw threads 12, whereby the formed cavity 23 is substantially enlarged, as indicated at 23a, in FIG. 2. After this jetting procedure is stopped, a concrete mix, including one part fluid cement mortar, one part mason sand, for example, may be pumped into the enlarged cavity 23a, as shown in FIG. 2. In the latter method step continued rotation of the pile core, accompanied with pumping of the mortar, may be utilized to increase the depth of the cavity 23 if desired or necessary. Rotation of the pile core 10 and pumping of the mortar may be continued, with or without increasing the cavity depth, until the enlarged pile cavity around the pile core is completely filled with fluid mortar, as evidenced by the appearance of fluid cement mortar at the top of the cavity. At this point, such rotation of the pile core may be stopped while pumping of fluid mortar is continued for a short time, such as a few minutes, during which time the pile core 10 may be jetted downward a few more inches if desired. In this process of filling the enlarged pile cavity with cement mortar, it has been found that the cavity 23a may be further enlarged, as indicated at 23b in FIGS. 3 and 5, correspondingly to increase the girth and load-bearing capacity of the finished composite, cast-in-place pile P, as shown in FIGS. 3 and 5.

Because the pile core 10 can be completely preformed and conditioned in readiness for use as described above, the improved method is capable of use in a manner which greatly reduces the amount of time normally expended for installing load-bearing piles.

Modifications of the invention may be resorted to without departing from the spirit thereof or the scope of the appended claims.

Claims

What is claimed is:

1. A method of installing a reinforced cast-in-place, load-bearing pile in an earth situs, comprising: the steps of drilling into the earth of the situs with an elongated, rigid core having exterior screw means thereon, while supplying a pressurized fluid medium through passage means in the core to mix with the drilled earth, to facilitate upward discharge of earth along said screw means, until a pile cavity of requisite depth and girth is formed; further rotating said pile core in place within the formed cavity while pumping fluid, self-hardenable, cementitious material through said passage means to force cementitious material along said screw means, thereby to enlarge the girth of the pile cavity, and form a generally tubular body about the rigid core; and allowing said formed generally tubular body to set and harden in the cavity with said rigid pile core anchored therein, as a composite, formed-in-place, pile body of correspondingly increased load-bearing capacity.

2. A method as in claim 1, wherein said rigid core includes a preformed rigid casing containing a filler body of hardened cementitious material adding to the load-bearing capacity of the resultant cast-in-place pile.

3. A method as in claim 1, wherein said rigid core includes a preformed generally tubular, rigid casing and passage means for conducting fluid materials from the exterior to at least the inner end of the rigid core for passage of the fluid materials along said screw means.

4. A method as in claim 1, said upward movement of fluid cementitious material within the formed cavity being facilitated by rotation of the said rigid core forcibly to convey the fluid material upwardly along said screw means toward the top of the cavity.