US3543524A - Thin-walled pile with closure plug - Google Patents

Description

I 0 w H A 2 Sheets-Sheet l lNVENTOR/S II I. W II '1 E H E A n. U H PIU L y iillllkll i NM F C [MI W IIL 1 a HW/ u 5 F 2%, ATTOR NEYS 1970 w. c. CLEMENTS THIN'WALLED FILE WITH CLOSURE PLUG Filed June 20, 1969 1970 -w. c. CLEMENTS THIN'WALLED FILE WITH CLOSURE PLUG Filed June 20, 1969 2 Sheets-Sheet 2 FIG. I5

FIG. I6

FIG l7 lNVENTOR/S WILLIAM C. CLEMENTS M yam, @9 42 0424 ATTORN EYS 3,543,524 THIN-WALLED PllLE WITH CLOSURE PLUG William C. Clements, Middletown, Ohio, assignor to Armco Steel Corporation, Middletown, Ohio, a corporation of Ohio Continuation-impart of application Ser. No. 650,018,

June 29, 1967. This application June 20, 1969,

Ser. No. 835,048

Int. Cl. E02d 5/28, 5/72 US. CI. 61-53 14 Claims ABSTRACT OF THE DISCLOSURE Thin-walled shell piles, each comprising a thin-walled shell of a length suitable to form a pile, and one of a variety of tapered closure plugs to expand or compress the lower end of the shell within a specified range. Additionally, the thin-walled shell piles may be of a steppeddown diameter, in which case a tapered, drive fit, stepped diameter transition ring joins the varying diameters of the shells.

CROSS-REFERENCES TO RELATED APPLICATIONS This application is a continuation-in-part of application Ser. No. 650,018, filed June 29, 1967 now United States Letters Patent No. 3,482,409 dated Dec. 9, 1969, in the name of William C. Clements, and titled Thin-Walled Piled With Method of Driving the Same.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to achieving stable building foundations, and in particular to piles which are formed by driving a steel shell into the ground and then filling the shell with concrete.

Description of the prior art In considering the selection of a pile section, the most economical pile section that will meet the following criteria should be chosen:

(1) The pile must develop the required structural column strength within permissible allowable stresses;

(2) The pile must develop the required resistance or reaction in the soil formation either by friction and/or end hearing within the limits of permissible settlement;

(3) The pile itseself or in combination with a mandrel or drive core must be capable of being driven into the soil formation Without damage to the pile.

With allowable stresses permitted by regulations, codes and accepted engineering criteria, a pile comprising relatively thin smooth walled shell, filled with concrete in place, will meet requirement number (1). However, generally when the required energy for driving a shell is imparted to the top or butt of a shell having a diameter and thickness selected to fulfill requirement number (1), the completed pile, in most cases, will not fulfill requirement number (2), because it will either structurally fail under the imparted energy, or it will not transmit sufiicient effective energy to the pile tip to accomplish driving to the required end bearing and/or desired penetration. Thus, when the diameter and thickness of a smooth walled shell is selected using stress levels permissible in modern codes and criteria (12,000 to 20,000 p.s.i. for steel, and up to 0.45% of concrete compressive strength), the permissible wall thickness usually dictates that a mandrel or drive core device be employed to drive the shell to the required bearing and/or desired penetration to avoid structural failure of the shell during driving.

ited States Patent O Driving devices for installing smooth walled shell piles utilizing economical closure plugs and appurtenances with relation to the cost of heavier walled shells have not been available to the engineer and contractor. Accordingly, engineers and contractors have been forced into using shells having thicker walls to accomplish driving to required bearing and/or desired penetration, resulting in an uneconomical utilization of this pile type. Since handling and driving hazards are the main obstacles to the use of pile shells having thinner walls, the most logical approach toward development of such piles was found to be along the lines disclosed by I. H. Thornley in US. Pat. No. 2,465,557, including further development of improved closure plugs, drive cores and methods of making the piles.

Briefly, Mr. Thornley discloses in his patent an improved pile shell core plug and method for driving a pile shell, known as the swage method. A tapered. concrete plug is disposed in the ground at a location where the pile shell is to be driven. The open end of a thin-Walled shell is then placed over the plug and pressed down to drive the plug into the ground. The resistance of the plug to driving causes the lower end of the shell to telescope over the tapered plug to a predetermined distance, expanding the lower end of the shell, and then drive pressure is applied to the shell and to the plug. The concrete plug of Thornley comprises a precast body of concrete having an upwardly tapered shank with a flat driving face at the top and a downwardly convex working face for penetrating the soil. The tapered plug for 11 inch inside diameter pipe is generally about 18 inches long, with the top diameter 11 inches or less, and the maximum diameter 12 /2 inches. The included angle is one inch per foot, the cone having a 4 degree and 46 minute included angle. Generally, the only requirement of Thornley is that the taper of the plug be less than the critical angle, whereby the plug and the pile shell are held together by friction between them.

While the disclosure of Thornley has proven to be sat isfactory in some respects, in other respects it has proven to be most unsatisfactory. For example, the closure plug of Thornley has been found to excessively expand pile shell ends, and thus pile tips, which may split the shells, permitting the entry of water, or enlarge the pile tip to such magnitude that frictional or shearing forces between the shell and soil interface are destroyed or substantially reduced. Additionally, the Thornley closure plugs very often sustain defects during the driving thereof.

SUMMARY OF THE INVENTION are of a nature as not to substantially reduce the column strength of the pile. The novel drive core and method described and claimed in the aforementioned application may be used for driving a thin-walled shell, provided with a novel closure plug, so as to form the improved thinwalled pile of this invention.

The improved thin-walled hollow pile of the instant invention comprises a thin-walled steel shell of a length suitable to form a pile, and a variety of closure plugs which have bodies with tapered sides. The lower end of the steel shell telescopes with the tapered sides of a closure plug such that the change in circumferential length of the lower end of the steel shell is, as stated in the aforementioned Clements application, within the range of 0.5% to 10%, and, as shown by further development, preferably within the range of 0.2% to 4%. In one embodiment of the invention the sides of the closure plugs are externally tapered inwardly and upwardly and the lower end of the steel shell is forced over the tapered sides, the circumferential length thereof being elongated within the aforementioned ranges. In a further embodiment the sides of the closure plug are internally tapered outwardly and upwardly and the lower end of the steel shell is forced inside the plug, the circumferential length thereof being compressed Within the aforementioned range. A change in the circumferential length of the lower end of the steel shell within the aforementioned ranges is not known in the prior art and has been found to alleviate the problems caused by excessive expansion of the pile tips which may split the shell, permit entry of water, or enlarge the pile tip to such a magnitude that frictional or shearing forces between the shell and soil interface are destroyed or substantially reduced. Additionally, if the thin-walled shell is of a stepped-down diameter, a tapered, drive fit, stepped diameter transition ring joins the varying diameters of the shell.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a broken-away side elevation showing the thin-walled shell and a tapered closure plug which form the parts of the pile to be driven.

FIG. 2 is a broken-away side elevation showing the pile to be driven after the drive core has been placed therein.

FIG. 3 is a broken-away side elevation of the pile of the instant invention after it has been partially driven so that the plug is embedded within the lower end of the thin-walled shell.

FIG. 4 is a broken-away side elevation showing the pile of the instant invention driven to the desired depth and filled with concrete.

FIG. 5 is a cross-sectional view through the shell and an internally tapered closure plug according to the instant invention.

'FIG. 6 is a perspective view of a closure plug according to the instant invention, the tip of which has been reinforced by an embedded fabricated cross.

FIG. 7 is a perspective view of a closure plug according to the instant invention which has been reinforced with a shield.

FIG. 8 is a perspective view of the closure plug of FIG. 7, the tip of which has been further reinforced with a fabricated steel cross.

FIG. 9 is a perspective view of the closure plug according to the instant invention which has been reinforced at its lower end with another type of shield.

FIG. 10 is a perspective view of a closure plug according to the instant invention wherein a plate having a fabricated steel cross depending therefrom is embedded in the plug.

'FIG. 11 is a perspective view of a closure plug according to the instant invention which is provided with at least two holding tabs extending from the periphery of its lower base.

-FIG. 12 is a cross-sectional view of a closure plug which comprises a precast concrete pile section.

FIG. 13 is a side elevational view showing a previously driven shell having a tapered butt which acts as a plug for the next shell to be driven.

FIG. 14 is a cross-sectional view of a pedestal closure plug according to the instant invention.

FIG. 15 is a perspective view of another closure plug according to the instant invention and a cross sectional view of the shell.

FIG. 16 is a perspective view of another closure plug according to the instant invention and a cross-sectional view of the shell.

FIG. 17 is a perspective view of another closure plug according to the instant invention and a cross-sectional view of the shell.

4 DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention provides an improved construction for placing thin-walled shell in the ground to form a pile. It will be understood that after the shell has been placed in the ground, it will be filled with concrete to complete the formation of the pile.

FIG. 1 discloses the elements of the pile according to the instant invention. A shell 10 of a length sufficient to form the desired pile is disposed over a tapered closure plug 11. The plug 11 is preferably of precast concrete, but, as will be more fully expained hereinafter, it may be of metal or other suitable material so long as its sides, either externally or internally tapered, provide a change in the circumferential length of the lower end of the shell within the range of 0.5% to 10%, and preferably within the range of 0.2% to 4%.

In a typical embodiment of the instant invention, the shell 10 has an inside diameter of 12 inches, and the wall thickness is within the range of 0.1 inch minimum to 0.3 inch maximum. The length of shell 10 which will be utilized preferably varies in 1 foot increments up to feet or more. The precast concrete plug 11 is typically of a length of 12 inches plus or minus 4 inch and is of a frusto-conical design, the larger base being of a diameter of 12% inches plus or minus inch, and the smaller base being of a diameter of 11 /2 inches plus or minus of an inch.

It should be noted that an important requirement when the plug 11 is externally tapered inwardly and upwardly is that the taper be such that when the plug is fully seated within the lower end of the shell 10, as will be more fully explained hereinafter, the circumferential elongation of the lower end 13 will be within the desired range. Likewise if the sides of the plug are internally tapered outwardly and upwardly, such as is shown in FIG. 8, the internal taper of the plug 11a must be such that when the lower end of the shell 10 is seated within the sides of the plug, as will be more fully explained hereinafter, the circumferential length thereof will be compressed within the aforementioned desired range. It has been found that such a change in the circumferential length of the lower end 13 of the shell 10 will more adequately transfer the loading upon the pile to the soil below and provide a reliable water tight fit without danger of splitting the pile.

Various drive cores and methods of driving the shell and closure plugs to form the pile of this invention have been disclosed and claimed in applicants aforementioned parent application, and such disclosure is incorporated herein for reference. However, it will of course, be understood that such drive cores and methods of driving are only exemplary of drive cores and methods of driving which may be utilized to drive a shell and closure plugs to form the pile of this invention.

Turning now to FIGS. 14, an exemplary method of driving a shell 10 and externally tapered closure plug 11 to form the pile of this invention will be explained.

In FIG. 1, the open end of a shell 10 is disposed over an externally tapered closure plug 11 of this invention which has been placed on the ground at the location where the pile is to be driven. A segment 15 of the drive core 14, having thereon a standard bottom 21 and a drive head 16, is then disposed within the thin walled shell 10, such that the drive head 16 receives the butt of the shell 10 and the standard bottom 21 rests in a non-load transmitting position against the working face 22 of the externally tapered closure plug 11.

The driving means (not shown) next applies driving pressure to the head 16 of the drive core 14, whereby the shell 10 is pressed down to drive the closure plug 11 into the ground. The resistance of the closure plug 11 to driving causes the lower end of the shell 10 to telescope with the tapered closure plug 11 and over the tapered sides.

Additionally, the closure plug 11, when embedded within the lower end of the shell 10, pushes the standard bottom 21 upwardly against a segment 15 of the drive core 14 from a non-load transmitting fit to a load transmitting lit. The driving means now furnishes driving pressure through the head 16 simultaneously and directly to the shell and through the drive core 14 to the closure plug 11 until the lower end of the shell 10 reaches a desired depth and/or hearing.

The method of driving a shell 10 and internally tapered closure plug 11a, as best seen in FIG. 5, to form the pile of this invention is substantially identical with that for a shell 10 and externally tapered closure plug 11, with the exception that the standard bottom 21 rests in a non-load transmitting position against the working face 110 of the internally tapered closure plug 11a outside the shell 10. However, when the shell 10 is subsequently driven so that the plug 11a is forced into the ground and the lower end of the shell 10 is forced into the plug against the internally tapered sides, the standard bottom 21 is then in a load transmitting position against the working face 110.

Additionally, it should be noted that where a very thin shell 10 is being driven, either the tapered sides of the closure plug 11 or 11a, or the inside of the lower end of the shell 10, may be lubricated to facilitate the telescoping of the shell 10 with the plug 11 or 11a.

A great many of the reported pile collapse problems of presently driven shell piles are, in fact, failures due to the pile tip encountering an eccentric tip load during driving. This may be caused, for example, by the tip striking boulders, underground obstructions, irregular rock or hard pan formations. With flat closure plug ends there is no tip reinforcement to effectively distribute the eccentric load over the entire shell cross section just above the flat end, and extremely high localized stresses are developed which cause the shell wall to buckle just above the fiat end of the closure plug. While the instant invention substantially eliminates these problems, since the tip of the shell 10 will be heavily reinforced by either the closure plug 11 or 11a, and, if the externally tapered closure plug 11 is used, the bulk of the driving energy will be transferred to the tip through the drive core 14 and closure plug 11 rather than through the shell wall 10, various protective means are often necessary to protect the tip of the shell and to seat the shell adequately in hard rock or other impenetrable formations without damage to the lower face of the closure plug 11 or 11a or tip of the shell 10. FIGS. 6-10 disclose various exemplary closure plug reinforcements which have proven to be most satisfactory.

As was previously stated, the closure plug 11 or 11a has a body with either externally ,or internally tapered sides so that the lower end of the shell 10 telescopes therewith and the change in circumferential length thereof is within the aforementioned desired range. Preferably, the closure plug 11 comprises a precast body of concrete with the sides tapered upwardly in substantially frusto-conical form, and the top or working face thereof comprises a substantially flat face. The closure plug 11a, as best seen in FIG. 5, preferably comprises a fiat metal bottom plate having sides which are internally tapered outwardly and upwardly in frusto-conical form and which flare outwardly at the top thereof.

FIG. 6 discloses a reinforcement for the closure plug 11, and hence the tip of the pile, which comprises at least two cross stiffener bars 50 cast in the closure plug 11, the bars protruding from the lower base of the frustoconical body.

FIG. 7 discloses a formed steel pan shield 51 which is placed beneath the closure plug 11 before the open end of the shell 10 is disposed over the closure plug 11. As shown in FIG. 8, the pan or shield 51 may have other reinforcement attached thereto, such as, for example, the fabricated steel cross 52.

A steel plate shield 53 is disclosed in FIG. 9. This reinforcement shield may be attached to the closure plug 11 by suitable means, such as, for example, a bolt 54 which is embedded in the closure plug 11. Additionally, a fabricated steel cross '55 may be provided to add further reinforcement.

A fabricated steel cross 56 attached to a plate 57 may be partially embedded within the lower end of the closure plug 11, as disclosed in FIG. 10.

The closure plug 11a may, of course, also incorporate the exemplary closure plug reinforcements disclosed in FIGS. 6-10.

A further embodiment of the instant invention is the provision of at least two holding tabs 59 extending from the periphery of the larger base of the substantially frustoconical body of the closure plug 11, as shown in FIG. 11. The purpose of the tabs is to preclude the entry of the closure plug 11 into the open lower end of the shell 10 beyond the full seating depth when the shell is partially driven without the drive bore.

The closure plug 11, preferably of precast concrete, and as heretofore described, may include a precast concrete pile section 60 of any length or downward configuration, as shown in FIG. 12. Additionally, reinforcement, such as the reinforcing bars 61, may be utilized as required.

It would, of course, be possible to utilize a previously driven pile 10a as a plug, in which case the butt would he upwardly tapered so that the circumferential length of the lower end of the next shell to be driven will be enlarged within the aforementioned range. For example, FIG. 13 shows a previously driven shell 10a having an inwardly and upwardly tapered butt 10a which acts as a plug for the next shell 10b to be driven. The drive core 16 (not shown) will then extend only within the shell 10!) and rest on the tapered butt 10a of the previously driven shell 1011. It will be obvious that the tapered butt 10a of the shell 10a may be provided with reinforcing, such as a steel plate, as desired.

A further embodiment of the closure plug 11 is shown in FIG. 14, wherein the lower end of the closure plug 11 includes a precast pedestal 62 which rapidly mo bilizes high tip bearing in weak soil strata. The pedestal closure plug 62 may, of course, be reinforced with the reinforcing bars 63, as required.

While closure plugs 11 and 11a are preferred, other closure plugs have also proven to be satisfactory. FIGS. 15-17 disclose other tapered closure plugs made from east or fabricated metal which have been found to be acceptable in that they maintain the change in the circumferential length of the lower end of the shell 10 within the forementioned desired range, while at the same time, if the closure plug is externally tapered, the standard bottom 21 of the drive core 14 is still provided with a surface upon which it may rest in a non-load transmitting position until such time as the driving cap 19a has furnished driving pressure through the drive head 16 and the shell 10 is pressed down to drive the plug 11 into the ground, the resistance of the closure plug to the driving causing the lower end of the shell 10 to telescope with the tapered closure plug, pushing the working head 21 of the drive core 14 from a non-load transmitting fit to a load transmitting fit if an externally tapered closure plug 11 is being utilized.

The closure plug 70 of FIG. 15 comprises a substantially flat circular section 71 having externally tapered sides 72 which depend outwardly and downwardly therefrom. Additionally, a cross stiffener rib 73 may be provided on the under side of the circular section 71 between the tapered sides 72 for additional reinforcement.

The closure plug 74 of FIG. 16 comprises a substantially flat circular section 75 having externally tapered sides 76 extending inwardly and upwardly therefrom. Fabricated cross stiifeners 77 depending from the flat circular section 75 may be utilized for additional reinforcement. Further, the closure plug 74 may be fabricated with shoulders 78, as shown in FIG. 17.

It will, of course be obvious that the sides 76 of the closure plug 74 may be provided with an external taper extending outwardly and upwardly from the flat circular section 75 and flaring outwardly at the top thereof. Accordingly, the lower end of the shell will be forced inside against the internally tapered sides of the plug.

It will be understood that modifications may be made without departing from the spirit of the invention, and therefore, no limitations other than those specifically set forth in the claims are intended or should be implied.

What is claimed is:

1. A thin-walled hollow pile which comprises a thin walled steel shell of a length to form a pile, and a closure plug, said closure plug having a frusto-conical body with the frustrum in contacting engagement with the lower end of said shell, whereby when said shell is driven the lower end thereof telescopes with the tapered sides of said plug and the change in circumferential length of the lower end of said shell at the point of maximum deformation is within the range of 0.2% to 4.0%.

2. The hollow pile according to claim 1 wherein the sides of said body are externally tapered extending upwardly and inwardly and the lower end of said steel shell is forced over the tapered sides of said plug so that the circumferential length thereof is elongated within said range.

3. The hollow pile according to claim 1, wherein the sides of said body are internally tapered extending outwardly and upwardly and the lower end of said steel shell is forced inside against said internally tapered sides of said plug so that the circumferential length thereof is compressed :within said range.

4. The hollow pile according to claim 1, wherein said shell is provided with at least one stepped diameter, and wherein the varying diameters of said shell are joined by a tapered, drive fit, stepped diameter transition ring, said transition ring connecting the shell ends of varying diameters by employing driving pressure to press the ends into said tapered transition ring.

5. The hollow pile according to claim 1, wherein said closure plug comprises a precast body of concrete with said sides tapered upwardly in substantially frusto-conical form, and the top of said closure plug comprises a substantially flat face.

6. The hollow pile according to claim 5, wherein said precast body of concrete includes at least two cross stiffener bars cast therein, said bars being cast into said concrete so as to protrude from the bottom of said frustoconical body.

7. The hollow pile according to claim 5, wherein said closure plug is reinforced at its lowermost end by a formed steel pan shield, said shield having depending edges which surround the lower end of said steel shell as said shell is forced down over the tapered sides of said plug.

8. The hollow pile according to claim 7, wherein said pan shield is provided with tip reinforcement on its underside in the form of a fabricatedsteel cross.

9. The hollow pile according to claim 5, wherein said closure plug is reinforced at its lowermost end by a steel plate tip shield, and means are provided to fix said shield to said plug.

10. The hollow pile according to claim 5, wherein a plate having a fabricated steel cross depending therefrom is embedded within said plug such that said fabricated steel cross extends from the bottom of said plug.

11. The hollow pile according to claim 5, wherein the lower base of said frusto-conical precast concrete body has at least two spaced apart holding tabs extending from the periphery thereof, whereby said closure plug is prevented from entering the lower end of said steel shell beyond the full seating depth when said shell is partially driven without the drive core.

12. The hollow pile according to claim 5, wherein said closure plug includes a downwardly convex working face for penetrating the soil.

13. The hollow pile according to claim 1, wherein said body of said closure plug comprises the substantially fiat circular section, said tapered sides depending outwardly and downwardly therefrom, and wherein a cross stiffener rib is provided on the underside of said circular section between said tapered sides.

14. The hollow pile according to claim 1, wherein said body of said closure plug comprises the substantially flat circular section, said tapered sides extending inwardly and upwardly therefrom.

References Cited UNITED STATES PATENTS 1,831,209 11/1931 Thornley et al 6l-53.7X 2,465,557 3/1949 Thornley 61-53.52. 2,933,899 4/1960 Cobi 6153 X 3,333,428 8/1967 Dougherty 6153 JA'COB SHAPIRO, Primary Examiner U.S. Cl. X'R. 61-53.6, 53.7

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