US3113436A - Bulb pile - Google Patents

Description

Dec. 10, 1963 J. L. NALEN 3,113,436

BULB PILE Filed April l, 1960 2 Sheets-Sheet l INVENTOR. LfosEPH LEO [WM5/V.

Dec. 10, 1963 J. L.. NALENl 3,113,436

BULB PILE Filed April 1, 1960 2 Sheets-Sheet 2 wwwmwmm United States Patent O M 3,113,436 BULB PILE Joseph Leo Nalen, Kinderboek, N.Y., asslgnor to Raymond International Inc., New York, NX., a corporation of New Jersey Filed Apr. l, 1960, Ser. No. 19,287 3 Claims. (Cl. A51-$3.6)

This invention relates to the installation and formation of piles, and, more particularly, to the formation of cast in place concrete piles having an enlarged or bulbous lower end.

In order to improve the load bearing ability of concrete piles generally, various methods have been proposed for enlarging their lower ends. Thus, -it is known to position a charge of concrete at the bottom of a. hole 1n the earth and then to expand that charge by exerting continuous pressure or a series of impacts thereon as by transmitting driving blows to a core or to a core and casing so as to drive the same at least partially into the charge of concrete for expanding the latter. It has been proposed to use a water jet, explosive charge or a bag of water under pressure to form an enlarged hole below the lower end of a casing and thereafter to attempt to till the enlarged hole with concrete. None of these methods has proven entirely satisfactory due to the likelihood that soft earth, mud or water will tumble or ilow into the enlarged part of the hole, thus to exclude variable amounts of the concrete or to mix with and weaken the concrete. Additionally, it is now known that it is often diiilcult to prevent some eccentricity from developing in the direction of delivery of the ramming forces relatively to the pile axis; and that this will in turn cause the development of an eccentric bulb where the concrete is merely positioned at the bottom of a hole and rammed.

Because these disadvantages have long been recognized, it has been proposed for particularly soft soils to enlarge the bottom of a hole, as by water jet for example to form a preliminary footing excavation and then to lower an empty or collapsed bag to the bottom of the hole and to fill the same with grout under pressure to inilate the bag and form a footing. The pile is completed by lling the hole with concrete and the bag of grout remains at the bottom of the pile. This expedient of course fails completely to offer a solution to the problem of forming an enlarged footing where the earth is rm or comprised of sand or gravel, and even in the particularly soft soils for which it is intended, the grout so used forms a relatively weak footing and is subject to breaking away from the concrete above it, should the pile be subjected to lateral stresses. With all such prior methods or proposals, diiiculties and uncertainties arise in securing an enlarged concrete footing for the pile which will be symmetrical with the pile axis and uniformly strong.

Accordingly, the present invention contemplates a method of forming a pile with an enlarged or bulbous lower end which method is not subject to any of the foregoing diculties or disadvantages. That is to say, the present method is advantageous to form a strong and symmetrical bulb pile regardless of the degree of firmness or water content of the soil.

According to the invention a method is provided for forming a bulb pile by utilization of an expansible bag which is expanded in situ by the pressure of heavily rammed concrete.

As a feature or" the invention, an expansible bag is secured to the lower end of a hollow pile shell and is positioned within the lower end of a casing which may then be partially withdrawn. Actually, the casing may be dispensed with in some cases as where the hole has 3,113,436 Patented Dec. l0, 1h63 been angered or otherwise excavated. A charge of concrete is positioned in the bag at the lower end of the shell, `and rammed as by the use of a heavy ram driven by a powerful pile driving hammer to expand the bag thus compressing the surrounding earth and forming a bulbous configuration beneath the pile shell. The bag is preferably formed of rubber or other expansible material so that it will stretch under the influence of the rammed concrete, but it will be appreciated that any material may be used which will permit the bag to expand and which will protect the bulb against contamination by soil and water and in fact, the bag may be formed of a suitable fabric which may be folded and taped or otherwise constrained in a collapsed disposition until ramming breaks the tape and permits the bag to expand to its full volume.

The entire charge necessary to expand the bag to its desired nal volume may be positioned in the bag at one time or separate partial charges may be rammed sequentially with the casing being raised `in increments between each ramming operation. Actually, it has been found that the impact forces delivered by a hammer capable of delivering large energies, for example, one capable of delivering 24,000 foot pounds or more of work per blow depending upon the soil, job conditions and the size of the bulb desired, provides very desirable results even in firm earth, as the concrete is in effect partially liqueed and caused to flow as a liquid to effect expansion of the bag and compression of the earth. Because of the partial liquefication of the concrete, the bag will tend to expand uniformly in all directions (in accordance with Boyles law), thus resulting in a symmetrical bulb; and since the force backing up the bag against the earth is exerted through a liquid medium, the bag will tend to mold itself around, and possibly even to largely enclose obstacles such as stones which might be encountered. Thus, a bulb having a diameter of ve feet or more can be formed beneath a pile one foot in diameter. It is important to note that inasmuch as all of the hammer energy is expended directly against the bulb and shaft concrete, and is not dissipated in creating a heterogeneous mixture of soil, concrete and ground water, it is possible to measure the amount of work done by the bulb on the soil by equating the amount of work produced by the pile hammer energy. Furthermore, it is possible to predict the size of the bulb since none of the concrete is dissipated. It will be appreciated too, that multiple bulbs around the pile shaft can be produced above the lowermost bulb by utilizing expandable sections in the pile shafe at various points thereon.

After the bag has been fully expanded, the ram is withdrawn and the shell filled with concrete.` The casing may also be fully withdrawn and grout injected into the space thus vacated.

As another feature of the invention, the pile shell may have an extension or other portion projecting beyond its usual lower end, that is, beyond the region thereof to wlhich the neck of the bag is iaxed so that when the bag is filled with concrete, the extension or other portion will be embedded in and `surrounded by the bulb. The pile shell extension portion may be formed with several apertures therein to enable the concrete to flow outwardly through the extension and to expand the bag even in that portion thereof which eneloses the extension. These apertures also provide positive locking between the extension and the cement, while the extension serves also to reinforce the bulb iat its neck which is inherently its region of greatest weakness. The pile shell extension serves `also to transmit, at least in part, the load from the shell-l tothe bulb by providing a good bond between it and the concrete.

There has thus been outlined certain important features of the present invention in order that the detailed description thereof that follows may be better understood, and in order that the contribution to the rar-t may be better appreciated. Additional features of the invention will be described hereinafter and will also form the subject of claims appended hereto. Those skilled in the art will appreciate that the conception upon which the present disclosure is based may readily be utilized as a basis for the formulation of other steps for carrying out the several purposes of the invention. it is important, therefore, that the claims be regarded as including such equivalent steps as do not `depart from the spirit and scope of the invention.

A specic embodiment of the invention has been chosen for purposes of illustration and description, and is shown in the accompanying drawings, forming a part of the speciiication, wherein:

FIG. l is ra vertical `sectional view through a drive casing and closure mandrel disposed in a hole driven in the earth;

FIG. 2 is a similar view but showing the mandrel withdrawn and a pile shell with a bag attached inserted in its place; and if desired, containing a small charge ot" concrete which will partially extend the bag.

lFIG. 3 is a is similar to rFIG. 2 but showing the drive casing partially withdrawn;

FIG. 4 is a view similar to FIG. 3 but showing concrete being poured into the pile shell and bag;

FIG. 5 illustrates a mandrel ramming the concrete;

FIG. 6 is similar Ito FIG. 5, but shows the mandrel withdrawn and the idr-ive casing partially withdrawn;

FIG. 7 shows additional concrete being poured into Ithe shell;

FIG. 8 shows the mandrel `again ramming the concrete;

FiIG. 9 shows the mandrel and drive casing withdrawing, the shell filled with concrete and the space between the shell and the earth lied with grout; and

FIG. 10 is a fragmentary view illustrating an enlarged portion of the structure of FIG. 9.

Referring now to the drawings, and particularly to FIG. 1, there is shown a drive casing 1d and a mandrel 11 having a boot 12 at the bottom thereof which serves to close the lower end of the casing. In the drawing, these ele-ments are shown occupying a position in the earth to which they have been driven by a suitable pile driver (not shown).

,In accordance with the method of the present invention, andas shown in FlG. 2, the mandrel has been withdrawn and la pile shell 14 is lowered inside the casing i0. This shell may comprise sheet metal tubing yor pipe of suitable size or in fact may have any convenient shape, but for the purpose of the present disclosure, it is shown as a corrugated tubing. The lower end of the shell has an extension 15 to which an expansible bag 16 is suitably con- :nected at its neck yas by embracing with a wire or strap 17. -It will be observed that the shell 14 is lowered to a point at which the bottom of the bag 16 contacts the earth, but the bottom of the extension 15 is spaced thereabove.

As shown in FIG. 3, the drive casing 1.0 is then partially withdrawn, preferably to a level yapproximating that of the bottom of the pile shell extension 15, although it is to be understood that the casing may be raised before insertion of the shell or even during pouring of the concrete. The assembly is now prepared to receive a quantity of concrete.

Thus, as shown in FIG. 4, a quantity of concrete is poured into the bag 16 and the pile shell extension. This quantity may be suicient to expand the bag to its desired nal volume when rammed, or it may be only a portion thereof, or a partial charge, las in the case illustrated.

in FIG. 5 there is shown a ram 19 extending down into the pile shell to ram the partial charge of concrete. This ramming is accomplished by the delivery to the r-am 19 of a series of blows by a conventional, powerful pile driving hammer (not shown). As mentioned, such a hammer may be one capable of delivering 24,000 foot pounds or more of work per blow. Because of the high impact forces thus delivered, the concrete is in effect liquefied and causes the bag to tend -to expand uniformly in all directions to compress the surrounding earth. Where a partial charge has been inserted into the bag, ramming continues until the bag has been expanded against the surrounding earth to a proportional fraction of its desired final volume, as indicated by the 'extent of drop of the upper end of the ram.

As illustrated in FIGS. 6 and 7, respectively, the casing .10 is then further withdrawn to a level at least as high as that at which the neck of the bag is attached to the shell and additional concrete is poured into the shell, preferably enouglh to tcornplete a full charge thereof.

FIG. 8 illustrates a further ramming operation in which the additional concrete is rammed into the bag thus further expanding it against the surrounding earth. This ramming is continued until the bag reaches its full desired final volume, as shown, which point will be indicated by the final level of the top of the ram. As shown, the respective sizes of the ram 19 and casing 10 may be so related to the extent of withdrawal of the casing 10 that expansion and therefore ramming, is completed when the ram head 20 reaches the upper end of the casing.

As shown in FIG. 9, the ram and casing have been withdrawn, and the pile shell 14 is lilled with concrete, and the space vacated by the casing 10 may be lled with grout. If desired, a collar 21 may be inserted into the ground surrounding the top of the pile and filled along with the space vacated by the casing. The pile may, of course, be terminated at this level or not, as required.

It is to be understood that, depending upon job conditions and requirements, a single full charge of concrete may be used to expand the bag or a series of partial chargers, with ramming after each, may be utilized. Additionally, the casing and ram may be removed together or individually after final ramming, and grouting may take place as the casing is removed or thereafter.

As shown in FIGS. 2, 3, 6 and l0, the pile shell extension 15 may have several apertures` 22 thus enabling the concrete to flow through the extension to more readily position itself within the neck portion of the bag outside of the extension. However, the apertures may not be necessary for certain purposes, and when used, two or four are usually suiiicient.

lt is sometimes desirable that the bulbbe formed with a flat bottom, as when the pile is bottomed on rock or hardpan. in this case, the pile shell extension 15 is lengthened and extends further down into the bag while the number of apertures is limited, say to two, or the apertures are eliminated altogether. The length of the extension may also vary dependent upon the load to be supported and the pile diameter, as it serves to transmit, at least in part, the load from fthe shell to the bulb and also to reinforce the bulb.

The bag 16 is` preferably formed of rubber although any strong expansible sheet material is feasible since resilience is not essential. Thus, a fabric bag may be attached by its neck to the bottom of the pile shell and then folded and taped below it. As the concrete is rammed, it will break the tape and expand the bag against the surrounding earth.

From the foregoing description, `it will be Seen that the present novel concept contributes `a method for forming a bulb at the lower end of a pile which bulb is strong and compact, is free of water, mud or earth, and is strongly bonded to the pile itself. `In fact, at all stages of the operation, the bulb and pile shaft are protected against contamination by soil land water. Itis important to note that the bulb so formed is substantially symmetrical about the pile axis and actually increases the bearing value of the surrounding earth by compressing it. A further advantage resides in the lfact that the bulb may be formed relatively quickly before any of the concrete has had an opportunity to become set.

It will be appreciated by those persons skilled in the ant that soil or sand may be used in place of grout in the space vacated by the casing land that this iilling may not be necessary if the ground comes back naturally against the pile shaft. lt will also be appreciated that the present method permits visual inspection at each stage of the operation. i

What is claimed and desired to be secured by Letters Patent is:

1. A method for forming an integrally constructed bulb pile of a given diameter comprising, forming in the ground a cylindrical -hole slightly larger than said given diameter, providing `a hollow pile shell having said given diameter and further having `a uid impervious expansible bag attached securely about and depending from its lower end, lowering said pile shell with said bag attached into said hole until said bag is positioned at the lower end thereof, positioning concrete in said bag to a level in the vicinity of the lower end of said pile shell, ramming said concrete to expand said bag to a bulbous configuration, and filling said shell with concrete.

2. A method for forming an integrally constructed bulb pile or" a given diameter comprising, positioning `a hollow cylindrical casing slightly Alarger than said given diameter in the ground to `a predetermined depth, providing a hollow pile shell having said given diameter `and further having a iluid impervious expansible bag attached securely about and depending from its lower end, lowering said hollow pile shell into said casing until said bag is positioned adjacent the bottom of said casing, partially withdrawing said casing, positioning concrete in said bag to a level in the vicinity of the lower end of said pile shell, ramming said concrete to expand said bag to a bulbous conguration, and filling said shell with concrete.

3. A method for forming an integrally constructed bulb pile of a given diameter comprising, positioning a hollow cylindrical casing slightly larger than said given diameter in the ground to a predetermined depth, providing a hollow pile shell having said given diameter and further having a iluid impervious expansible bag `attached securely about `and depending from its lower end, lower-ing said hollow pile shell into `said casing until said brag is positioned adjacent the bottom of said casing', partially withdrawing said casing, positioning within said bag -a charge of yconcrete equal in volume to a fraction of the desired volume of the fully expanded bag, ramming said charge to partially expand said bag against the surrounding earth, further partially withdrawing said casing, adding a further charge of concrete equal in volume to the remaining fraction of the desired Volume of the fully expanded bag, ramming the concrete to fully expand said bag, and filling said shell with concrete.

References Cited in the tile of this patent UNITED STATES PATENTS 951,668 Welsh Mar. 8, 1910 961,492 Goldsborough June 14, 1910 1,255,164 Barry May 7, 1918 1,421,857 Store Iuly 4, 1922 1,794,892 Goldsborough Mar. 3, 1931 2,007,668 Watt July 9, 1935 2,326,155 McCook Aug. 10, 1943 2,497,377 Swann Feb. 14, 1950 FOREIGN PATENTS 33,250 Norway of 1921 400,283 Great Britain of 1933 1,215,827 France Nov. 23, 1959 880,736 Great Britain Oct. 25, 1961

Claims (1)

1. A METHOD FOR FORMING AN INTEGRALLY CONSTRUCTED BULB PILE OF A GIVEN DIAMETER COMPRISING, FORMING IN THE GROUND A CYLINDRICAL HOLE SLIGHTLY LARGER THAN SAID GIVEN DIAMETER, PROVIDING A HOLLOW PILE SHELL HAVING SAID GIVEN DIAMETER AND FURTHER HAVING A FLUID IMPERVIOUS EXPANSIBLE BAG ATTACHED SECURELY ABOUT AND DEPENDING FROM ITS LOWER END, LOWERING SAID PILE SHELL WITH SAID BAG ATTACHED INTO SAID HOLE UNTIL SAID BAG IS POSITIONED AT THE LOWER END THEREOF, POSITIONING CONCRETE IN SAID BAG TO A LEVEL IN THE VICINITY OF THE LOWER END OF SAID PILE SHELL, RAMMING SAID CONCRETE TO EXPAND SAID BAG TO A BULBOUS CONFIGURATION, AND FILLING SAID SHELL WITH CONCRETE.

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