US1778925A

US1778925A - Cast-in-place pile

Info

Publication number: US1778925A
Application number: US228985A
Authority: US
Inventors: Joseph H Thornley
Original assignee: Individual
Current assignee: Individual
Priority date: 1927-10-27
Filing date: 1927-10-27
Publication date: 1930-10-21
Anticipated expiration: 1947-10-21

Description

driving [TED STATES I Pri JOSEPH E. THOBNLEY, OF CHICAGO III'I'INOIS cAsr-m-Pnacn rrLE Application filed camber are, 1927. Serial no. 228,985.

My invention relates to that type of castin-place pile characterized by a point or base section which is driven into the ground and from which the upper column portion of the 5 pile extends.

One of the principal objects ofthe invention is to provide an improved method of formingpiles of the above description. According to this method, the point section is such operation being performed above ground level. The joining of the point section to the shell is through a joint, which, as will be presently described, resists any separating stresses tending to part the point section and shell, and which also retains the base end of the shell substantially water-tight. The combined point section and shell is now swung.

up between the derrick leads, and the driving operationis started. The driving blows of the pile driving hammer are transmitted directly to the point section through. an intermediate driving member which is interposed between the hammer and the point section, whereby the light shell is not called upon to withstand any of these driving forces. Preferably the intermediate driving member consists of a heavy casing which surrounds the light shell and which has its lower end bearing on the point section. After the point section and shell have been driven to the desired depth, the column or shaft por tion of the pile is completed by dumping concrete into the upper end of the shell, any

reinforcing means being-also placed in the shell, as desired. The outer driving casing can be pulled up outof the ground, either before or after the dumping of this concrete.

It will be seen from the foregoing that the present methodsimplifies and reduces the number of operations usually necessary in the making of these piles. It also eliminates the failures frequently resulting in the making of these piles, and produces a stronger pile having maximum certainty of load bearing value. For example, there is no possi- -bility of the'point section separating from the column portion of the pile under inertia forces, such as frequently happens; when first rigidly joined to a light tubular shell,

ving blows without fracture.

a pre-cast pile through driving blows 'im arted directly to'the-poin't section. The lig t shell has negligible inertia andhence it can follow the point section without any harmful inertia forces being created, whereas in the method above referred to, the great weight of the superposed column portion of solid concrete establishes inertia forces which frequently result in tensile fracture of the pile. It will also be evident that the great weight of a pre-cast ile requires the pile driving derrick for its andling, whereas the light shell and lpoint section of the present invention can e placed in position and swung up into the derrick leads by hand. i

The present practice of rigidly joining the shell to the point section above ground also has numerous advantages. Where it is attempted to drive the point section firm, and to thereafter lower a shell or casing into the hole for engagement with the point section, it will be evident that various difliculties are likely to arise. For example, water or soil is likely to enter between the point section and shell. It is also practically impossible to sesoil. Moreover, the subsequent lowering of the shell or casing involves another operation of the pile driving derrick, which slows up operations.

Another object of the invention is to reduce the cost of producing such piles, by utilizing a novel construction of point section which is composed substantially entirely of concrete. Heretofore, these point sections have beenconstructed of metal, or of concrete protected by a heavy outer casing of metal, such constructions having heretofore been necessary to enable the point section to withstand the driv- The relatively high cost of these metallic point sections, particularly for piles of large diameter, increases" the cost of this type of piling to anobjection able. degree. The present invention contenn: plates avoiding this objectionable cost by the use of a point section composed of reinforced.

concrete, unprotected byany outer metallic being made possible by an improved manner of driving the point section, whereby the driving forces are transmitted thereto as inwardly acting compression stresses, instead of shearing or tension stresses, which have a tendency to shatter the concrete.

Another object of the invention is to provide a pile of the above type wherein the point section and the uppershell rising therefrom are fixedly joined together by an improved form of joint which renders the base end of the shell substantially water-tight, and which prevents any possibility of the shell and point section separatingunder the upheaving action of earth stresses which may be set up by the driving of other piles in close proximity thereto.

Other objects and advantages of the invention will appear in the following descri tion wherein I have described a preferred em odiment of the pile and the preferred method of forming the same.

through In the drawing accompanying such description: I

Figure 1 is a longitudinal sectional view the point section and through the upper shell, after their assembly above ground and preparatory to being driven into the ground.

Figure 2 is a fragmentary sectional view illustrating a slightly modified construction.

Figure 3 is a fragmentary sectional view on a smaller scale, illustrating the operation of (cllriving the point sectioninto the ground; an

Figiire 4 is a similar view, illustrating the completed pile after the removal of the outer driving casing.

The two main elements of the pile consist of a concrete point section 6, and an upper tubular shell 7, in the latter of which is' formed'the shaft or column portion of the pile as will hereinafter appear. The point structed of concrete,

section section 6 is constructed in the form of a head having a relatively long conical taper, so as to facilitate the driving of the same into the ground. Such point sections are to be conand ordinarily would be pro-cast in the desired quantities before being brought to the site of the pile forming operation. It will be observed that this point has no outer protective casing of metal and hence can be constructed at a relatively low cost. The concrete is strengthened by a reinforcing member form of a conical, spiral coil of rod or bar stock, with the apex of such spiral coil extending down into proximity to theapex of the concrete section, Additional reinforce radiate outwardly and upwardly from the apex of the spiral reinforcing coil 8 along tho. inner sides of the convolutions. The rods or bars 9 are preferably welded or Wired to the upper and lower 8 constructed in the successive convolutions of the coilso as to maintain the convolutions at a definite spacing and to join all of the reinforcing members into a single unit.

Imbedded in the upper end of the point or head is a short section of a tubular shell or casing 11, the upper end of which constitutes an attaching portion adapted to effect ready attachment to the main upper shell 7. In the preferred embodiment the shell 7 is constructed of corrugated stock of relatively light gage so as to reduce the cost thereof to a minimum, and in such embodiment the lower attaching portion 11 is also constructed of this .corrugated stock. In securing the shell 7 to the point section, the shell may be passed over the upper end ofthe attaching portion 11, or into the end of such attaching portion, and the shell and attaching portion then clamped or otherwise secured together. However, I consider it preferable to place the ends of the shell and of the attaching portion substantially coextensive in endwise abutment and to join these ends together by an outer sleeve member 12. Such sleeve member is also 001'- rugated to match with the corrugations of the shell and of the attaching portion, and contractible clamping bands 13 encircle the portions of the sleeve and serve to contract t e same into rigid locking engagement with the shell and attaching portion. A joint of this type can easily be made "Such driving casing-"fits down 'ovr the shell 7 for engaging with the point section 6, having a driving surface 16 at its lower end which is adapted tobear' against 'a companion driving surface 17 on the point section. One or 'both of such driving surfaces is sloped to transmit the driving forces to the point section as inwardly acting compression stresses.

Preferably both of said surfaces are annular and each has a downwardly and outwardly inclined taper substantially as shown. By

"virtue of the slopin formation of these surfaces, the driving orces transmitted down through the casing 15 are transmitted to the point section in the direction of inwardly acting compression stresses. The dotted a rows X in Figure 1 represent approximately the directions of these inwardly acting compression stresses, it being evident that the particular angle of thesestresses will be dependent upon the conical angle of the

surfaces

16 and 17. Stresses acting in this direction in the point section will have practically no tendency to fracture the same. Heretofore,

- create outwardly acting, disrupting stresses which will shatter the oint section. The present construction resu ts in a considerable portion of these driving forces being translated inwardly as compression stresses, which the concrete is particularl capable of bearing without in ury. If desired, a ring .16 ma be welded or riveted within the lower en of the casing, such ring having a sloping inner surface for increasing the effective area of the driving force 16.

Figure 2 illustrates a modified construction wherein the lower end of the driving casing is provided with a heavy reinforcing ring 18, on the inner side of which is formed the conical surface 16. The compression pressures set up in the driving of the point section react outwardly in the driving surface 16, and such ring amply reinforces this driving surface against spreading. Moreover by the provision of such ring, the driving surface 16 may be given a more extended area for enagement with the cooperating conical surface 17 on the point section.

The operation of forming the complete pile is as follows: The pre-cast oint section is first secured to the shel 7 above ground, by connecting the two through the joining sleeve 12. The unit is then erected between the leads of the pile driver derrick and the drive casing 15 is slipped down over the shell 7. The driving blows of the ile driver hammer are transmitted to a hea 19 on the upper end of the casing, which head may be connected to the base of the hammer unit 21 or may be arranged to receive the driving blows in any other preferred manner. It will be noted that the penetration of the point section 6 Will open. a. hole of slightly larger diameter than the diameter of the drive casing, so that there will be a minimum earth friction against the sides of the casing. After the pile has been driven to the desired depth for obtaining the required load bearing value, the driving operation is interrupted and the interior of the shell 7 is completely filled with concrete as indicated at 22 in Fig. 4. The operation of placing the concrete filling in the shell may be performed while the drive casingv is in the ground surrounding the shell, or it may be performed after the drive casing has been removed. Where the earth pressure is such that the shell 7 might be collapsed, the operation of filling the same with concrete is, of

course,-perforn1ed before the removal of the drive casing 15, so that the latter will serve as a protecting member against these earth pressures until the concrete has been poured.

f desired, any suitable reinforcin rods or be exten ed down other reinforcement ma ling in the shell 7 through the concrete The concrete fills the up er end of the at taching portion 11 and e ectively binds the point section and the up er column section together. The corrugate formation of the attachin portion 11 is advantageous in this respect in that the under sides of the inwardly extending corrugations form projecting or overhanging surfaces which become embedded in the concrete and thereby establish an interlocking) tension-resisting bond of great strength etween the point section and the column portion'of the pile. The hammer unit 21 may be provided with any suitable construction of releasable hooks 23 for engaging under the head of the drive casing,. whereb the casing can be withdrawn by the li ting of the hammer unit in the derrick leads. In the event of the casing resistin removal with an abnormal pressure the ling 22 of concrete can be utilized as a core against which reacting pressure can be exerted for the hoisting of the drive casing, in a manner well known.

The joint established between the point section and the shell 7 by the contracted sleeve 12 efl'ectively excludes water from the lower end of the shell. This is advantageous in Wet soils, as 'it prevents the possibility of an accumulation of water in the lower end of the shell, which would interfere with the dumpin and the setting of the concrete therein. oreover, such oint rigidly unites the shell and point section against separating stresses. It frequently happens that when piles are driven close to gether, the driving of a subsequent pile will create considerable earth pressure, tending to separate the shell 7 from the point section 6 of an adjacent, previously driven pile. The rigidly clamped engagement of the sleeve 12 over the shell and over the attaching portion 11 effectively prevents this separation. The relatively large diameter of the point section affords a broad base for the pile, having a large bearing value.

What I claim as m invention and desire to secure by Letters atent is:

1. A solid, precast point section for piles of the class described composed of concrete comprising an-outwardly and downwardly slo ed driving surface on its upper portion, a tubular metallic attaching member having its lower end imbedded in said point section and having its upper end rojecting therefrom for attachment to t eupper metallic shell of the pile in a tension resistin'g, water-jtightjoint.

' 2. A ile of the class described comprising a so id, pro-cast concrete point section, having a downwardly and outwardly sloped driving surface adapted to be en aged by a driving member, a metallic attac 'n memher having its lower end imbedded 1n said oint section and havin its upper end ro- 1ecting therefrom, a tu ular metallic s ell and means for rigidly connecting said shell to said attaching member, the latter being adapted, to be joined together in a tension resisting joint above ound level, preparatory to drivin the ie.

3. A pile o the c ass described,'com rising a pro-cast concrete oint section, a s ort len h of corrugated tu ing having its lower end imbedded in said point section and having its upper end projecting therefrom, a corrugated metallic shell adapted to constitute t e outer casing for the column portion of the pile, a sleeve for' engaging over the upper end of said tubing and over the lower en of said shell, and means for clamping said sleeve over said tubin and shell.

JOSEPH H. HORNLEY.