Method for forming cast-in-place reinforced concrete pile

BACKGROUND OF INVENTION

This is a divisional application of U.S. application Ser. No. 696,21.2 filed Jan. 8, 1968.

Heretofore; reinforced concrete piles have been provided in an earth situs by drilling or otherwise providing a cavity in the situs, filling the cavity with fluid cement mortar, and manually forcing an elongated, steel rod downwardly through the formed, still fluid pile body. It has however, been found virtually impossible to center the rods axially within such fluid pile bodies, because of the strong tendency for such rods to drift from the intended axial courses thereof. In fact, test piles have shown a high incidence of cases in which the rods projected angularly of the axes of the piles to extend outwardly of the peripheral walls of the piles at points intermediate the ends thereof. This problem was multiplied as the lengths of the pile bodies increased.

U.S. Pat. No. 3,363,422, discloses a method in which a hollow-shafted auger is used to drill a hole in an earth situs. In that method, however, anchoring rods were affixed to a driving bit and both the rod and bit were released into the drilled hole as a unit. The rod, therefore, had to be in place within the auger shaft before earth drilling operations commenced, and only one rod could be installed.

SUMMARY OF INVENTION

In the present invention, a hollow-shafted auger is screwed into an earth situs to define a hole of predetermined depth and location, and thereafter an elongated reinforcing rod is released down the auger shaft, to disengage a driving bit from the inner end of the same into the bottom of the hole. As the auger is withdrawn from the hole, fluid hydraulic cement mortar is pumped down the auger shaft, first to surround the lower end of the rod and hold it centered in the hole, and then progressively to surround the upper portions of the rod. The hollow shaft, being smaller in diameter than the drilled hole, serves as guide means to maintain the rod substantially centered in the resultantly formed pile body.

An object of the invention is to provide an improved method and means of the character described, by which one or more rods of requisite lengths may be positioned within the hole after it is drilled, and by which such rods are effectively maintained substantially in axially centered relation by the auger shaft while mortar is progressively pumped through the auger shaft, into the drilled hole.

Other objects of the invention may be resorted to with25 out departing from the spirit thereof or the scope of the appended claims.

Of the accompanying drawings:

FIG. 1 is a vertical cross-section, partly broken away, through a rod-reinforced concrete pile, formed in an earth situs by the method of the invention.

FIG. 2 is a similar vertical cross-section, showing a preliminary step in the method, in which a hollow-shafted continuous-flight auger has been screwed into an earth situs to drill a hole of requisite depth and location in the situs by displacement of earth therein, and wherein is illustrated a driving bit releasably affixed on the lower end of the auger shaft.

FIG. 3 is an enlarged fragmentary cross-section of the lower portion of a drilled situs, showing a step of partially withdrawing the auger to present the lower end of the auger, with the releasable bit thereon, freely in lower portion of the hole or cavity formed by displacement of earth.

FIG. 4 is a view corresponding to FIG. 3, in which by operation of valve means shown at the upper portion of FIG. 2, a pile-reinforcing rod is fed down the auger shaft to release the releasable driving bit from the lower end of the auger shaft.

FIG. 5 is a view corresponding to FIG. 4, in which the reinforcing rod has come to rest in axially centered relation, and hardenable, fluid mortar has been pumped down the auger shaft to surround and anchor the rod in the hole in substantially axially centered position, to facilitate effective completion of the pile as shown in FIG. 1.

FIG. 6 is a fragmentary view corresponding to FIG. 5, but illustrating use of the method to provide a concrete pile or column with a plurality of reinforcing rods embedded therein.

FIG. 7 is a fragmentary cross-section, corresponding to the upper portion of FIG. 2, and on the same scale, illustrating a modified means for feeding a pile-reinforcing rod down the auger shaft.

FIG. 8 is a fragmentary cross-section, corresponding to the lower portion of FIG. 2, and on the same scale, illustrating a modified means for releasably retaining the auger bit on the lower end of the auger shaft.

Referring to FIG. 2 of the drawings, there is illustrated apparatus suitable to practice the method of the invention to produce a reinforced concrete pile or like column P in an earth situs E, as shown in FIG. 1. Such apparatus may include a continuous flight, hollow-shafted auger 10, interchangeably affixed on a chambered adapter 10α, rotatably mounted on a carriage 11 which is vertically movable on a crane or like rig 12 by suitable power means (not shown). A reversible hydraulic motor 13 on carriage 11 is operable through a chain drive 14, selectively to rotate the auger 10 in either of opposite directions.

The adapter 10α, to which auger 10 is removably affixed, may be rotatably mounted on carriage 11, to connect with a fixed housing 13 on the carriage 11 having a chamber 14 communicating at its upper end with a normally closed flapper valve 14, and at its lower end with the axial passage 10c of auger shaft 10b, through the fixed adapter 10α. The flapper valve 15 may have a top access opening 16, adapted to be opened by a manually rotatable arcuate valve plate 17, for inward reception of a reinforcing rod 18, to the interior of auger shaft 10b, as shown in chain-dotted lines in FIG. 2, and for purposes to be described later.

When the valve plate 17 has been rotated to close the valve access opening 16, pressurized hydraulic cement mortar from a suitable source (not shown), may be supplied through a conduit 19, to chamber 14 and the auger 10b.

The lower end of the hollow auger shaft 10b may be

3,512, provided with a reduced irregular-shaped orifice 21, defining a seat for releasable non-rotative reception of a driving bit 22 serving as a closure member. Spring-pressed detent means 23 may be provided for releasably retaining the bit non-rotatably seated in the orifice 21. ₅

Referring to FIG. 2 in particular, the above-described auger-drilling apparatus may be used in the method of invention to form a reinforced column or pile P in an earth situs E, as shown in FIG. 1. To this end, the auger 10 with the driving bit 22 releasably closing the lower end of auger ₁₀shaft 10b is, by operation of motor 13, screwed vertically into the situs E to define a pile cavity or hole 25 of predeterminate depth and location. When this has been accomplished, as shown in FIG. 2, the motor 13 may be reversed to rotate the auger 10 while the carriage 11 is ele- j ₅vated as necessary to withdraw the auger and thereby lift or displace the loose earth S from the cavity 25.

In an initial stage of such withdrawal of the auger 10, an elongated rigid element, such as a steel reinforcing rod 18, may be dropped or otherwise fed through the top 20 opening 16 in the open flapper valve 15 (see FIG. 2), through chamber 14 in the relatively fixed housing 13, and down the inside of the auger shaft 10b (whether moving or stationary). The rod 18 may be of easily predetermined length (as shown in FIG. 1), and controlled in its descent 25 to engage the lower end of the same with the driving bit 22, and thereby release the bit into the bottom of the pile cavity 25, which is now partially vacated by displacement of earth, as illustrated in FIGS. 3 and 4.

At about the time the rod 18 releases the bit 22 from the 30 auger, as described, the handle H on valve 15 is operated to close valve opening 16, as previously described, and with continued progressive upward movement and requisite rotation of the auger to continue displacement of earth from the formed cavity, fluid hydraulic cement mortar M ₃₅is pumped under pressure through conduit 19, chamber 14, and through the orifice 21 of auger shaft 10b. Thus, fluid mortar fills the space vacated by the progressively displaced earth, initially to embrace the lower end of the positioned rod, to anchor the same substantially axially 40 centered with reference to the cavity 25, somewhat as shown in FIG. 5. For this purpose, the inner end of the bit 22 may have provided therein a tapered recess 26, designed to be loosely centeringly engaged by the lower end of the downwardly injected rod, to keep the rod generally centered with reference to the auger shaft 10α and, 45 therefore, the cavity 25.

With continued progressive withdrawal of the rotating auger to displace all earth S from the defined cavity 25, the fluid mortar is progressively formed upwardly in the cavity and around the centered rod, until the auger is 50 completely retracted and the pile P is fully formed, as shown in FIG. 1. The formed concrete body P is then allowed to set or harden with the rod 18 centeringly embedded therein.

FIG. 6, corresponding substantially to FIG. 4, illus- 55 trates use of the method described to install a pile P in a cavity 25, with a plurality of reinforcing rods 18α, 18α incorporated therein.

In any event, the method of the invention may be utilized to produce partial pile bodies or columns P, deep 60 in an earth situs, to have one or more reinforcing rods anchored therein, with or without extensions thereof projected outwardly for use as anchoring bars of known type. In some instances, it may be desirable to leave earth S in an upper extent of the cavity above the anchoring con- 65 crete pile or body, as by turning the auger in screwing direction while withdrawing it from the defined cavity.

It is also readily apparent that the present method and means also makes it possible to stop movement of the drill, as well as stop inward passage of fluid mortar, pe- 70 riodically and momentarily, to allow reinforcing rods or similar means of varying lengths and proportions to be placed through the valve opening 16 as before, and then to resume the progressive pumping and auger withdrawing operations as before. Thus, the finished pile may be vari- 75

366 ously reinforced at different levels in the pile body as needed.

Referring to FIG. 7, there is illustrated a modified mortar-supply means at the upper end of the auger 10α, adapted for feeding reinforcing rods 18 down an auger shaft having an extension lOe which rotates freely above the carriage 11 with rotation of the adapter 10α. For this purpose a quick-release coupling C may have an outer part 30 releasably rotatably connected to an inner coupling part 31 threaded or otherwise attached to the extension 10c, to be rotatable therewith. A swivel connector 32 on mortar supply line or conduit 19 may be rotatably attached to upper end of the outer coupling part 30 to permit the connector 32 and conduit 19 to be held affixed while the extension lOe, adapter 10α, and auger 10 are rotated, in the manner previously described. Accordingly, upon removal of quick-release coupling C from extension 10c a reinforcing rod 18 may be fed or dropped down the auger shaft, as indicated in chain-dotted lines in FIG. 7, while the auger is either rotating or stationary.

FIG. 8 illustrates a modification of the invention wherein the drill bit 22 may be generally the same as before, except that it is releasably affixed in the lower end of the auger shaft 106 by a shear pin 23α, adapted to be sheared by forcible engagement of the bit 22 by rod 18, to eject the bit from the end of the auger shaft, as best shown in FIG. 5.

Other modifications of the invention may be resorted to without departing from the sprit thereof or the scope of the appended claims.