Hydraulic and earth engineering – Foundation – Columnar structure
Utility Patent
1999-02-23
2001-01-02
Lillis, Eileen D. (Department: 3673)
Hydraulic and earth engineering
Foundation
Columnar structure
C405S236000, C405S232000, C405S253000
Utility Patent
active
06168350
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to a method and apparatus for forming enlarged pile heads in driven cast-in-situ piling as well as continuous flight auger (CFA) piling techniques.
2. Prior Art
Piles are used in the construction industry to provide foundation support for building and the like. Two common piling techniques are driven cast-in-situ and CFA piling. In driven cast-in-situ piling, a piling tool is driven into the ground to the required depth. The piling tool is then withdrawn, and concrete or grout is concomitantly pumped to the tip of the piling tool so as to fill the underground void left by the tool during withdrawal. In CFA piling, a continuous flight auger is rotated and allowed to penetrate the ground to the required depth. The auger is then withdrawn, with or without rotation, and concrete or grout is pumped to the tip of the auger so as to form a pile in the same manner as described above. CFA piling techniques are discussed in more detail in GB 2 303 868, the disclosure of which is incorporated into the present application by reference.
It is advantageous in some applications for the top, or head, of the resultant pile to have a larger diameter than the main shaft. The ground beam of a building which is to be supported by piles of this sort can be made more efficient than that of a building supported by conventional piles, since the load can be spread over a wider area. This is currently achieved by casting a pile with a straight shaft and subsequently excavating a volume of soil around the head of the pile so as to enable additional concrete to be poured about the head of the pile. In order to obtain the greatest structural integrity, this must be done before the concrete forming the main shaft of the pile has set, which is a difficult and time-consuming task.
OBJECT AND SUMMARY OF THE INVENTION
According to a first aspect of the present invention, there is provided a method of installing a cast-in-situ pile, comprising the steps of:
i) fitting a collar device having a central aperture to a lower end of a piling tool;
ii) penetrating the ground with the piling tool and the collar device for a first period until the collar device has displaced or removed a predetermined surface volume of soil;
iii) disconnecting the collar device from the piling tool and penetrating the ground with the piling tool for a second period until a predetermined depth is reached, the piling tool passing freely through the central aperture of the collar device;
iv) withdrawing the piling tool while concomitantly supplying concrete or grout to the lower end of the piling tool so as to form an underground column of concrete or grout;
v) withdrawing the collar device as the end of the piling tool is withdrawn from the ground, thereby leaving an enlarged diameter void at the surface of the ground while concomitantly supplying concrete or grout to the lower end of the piling tool so as to fill the void with concrete or grout and form an enlarged diameter pile head.
According to a second aspect of the present invention, there is provided a device for forming an enlarged head in a cast-in-situ pile, the device comprising a collar adapted to be releasably fitted to a lower end of a piling tool.
The method and device may be used both with driven cast-in-situ piling techniques and CFA piling techniques. When used with driven cast-in-situ techniques, the collar is advantageously tapered, with the narrower end penetrating the ground first as the piling tool is driven into the ground. This eases the required displacement of the surface volume of soil. For CFA piling applications, the collar is initially rotated with the auger, and is provided with one or more cutting tools on its lower surface which are adapted to cut into the soil. The collar may be tapered, as before, or may have a substantially flat lower surface. The tapered embodiment removes a smaller volume of soil than the flat-surfaced embodiment, and is therefore more economical with concrete, but may be more likely to rise upwards during subsequent excavation of the bore hole in which the eventual pile will be formed.
When used with driven cast-in-situ piling techniques, the collar is initially placed on the ground above the location to be piled, and a drive shoe is located on the ground within the central aperture of the collar. A dolly is placed onto the drive shoe and the collar, and the lower end of a piling tube placed on the dolly. A hammer is then applied to the upper end of the piling tube so as to drive the collar and drive shoe into the ground until the collar has displaced the required surface volume of soil. At this stage, the piling tube is raised and the dolly removed. The piling tube is then lowered again so as to pass freely through the central aperture of the collar and onto the drive shoe, and then hammered to the required depth while the collar stays at the surface of the ground. Once the required depth has been reached, the piling tube is filled with a predetermined volume of concrete or grout and then withdrawn. As the piling tube is withdrawn, the concrete or grout flows out of the lower end of the piling tube so as concomitantly to fill the void left by its withdrawal. As the lower end of the piling tube nears ground level during extraction and concreting, the collar is lifted so as to allow the space from which the surface volume of soil has been displaced to become filled with concrete or grout, thereby forming a pile with an enlarged or “mushroom” head. Advantageously, the volume of concrete or grout initially supplied to the piling tube is calculated so as to be just sufficient to form the shaft and the enlarged head of the cast-in-situ pile. The collar is advantageously provided on its upper surface with a pair of hooks or loops so as to allow the collar to be lifted by a fork-lift truck or the like, or alternatively to which a lifting winch may be attached. A suitable pile reinforcement may then be inserted into the concrete or grout before this has set.
In CFA piling applications, the central aperture of the collar is adapted to fit about the flights of an auger, and the collar is releasably attachable thereto so as to allow the collar to be rotated with the auger. The attachment means may comprise sliders on the collar which are engageable with slots provided on the flight of the auger at its lower end. Alternatively, bolts or clamps or any other suitable and releasable attachment means may be employed. In use, the auger is lowered to the ground through the central aperture of the collar and positioned for excavation. Advantageously, the auger may be rotated for a brief initial period so as to start the excavation. The collar is then connected to the auger by sliding the sliders into the slots on the flight of the auger or by engaging other suitable attachment means, and rotation of the auger and the collar is recommenced until the auger has penetrated a predetermined distance into the ground and the collar has excavated the required surface volume of soil. Once this has been achieved, rotation may be temporarily halted and the collar released from the flight of the auger. Excavation then proceeds to the required depth while the collar remains at the surface of the ground. The auger is then withdrawn, with or without rotation, and concrete or grout is concomitantly supplied to the tip of the auger so as to fill the void thereby created. When the lower end of the auger is brought up to ground level, the slides or other attachment means on the collar are re-engaged with the auger, and the collar is thereby lifted from the ground. The void left by the collar is concomitantly filled with concrete or grout so as to form an enlarged pile head. In order to avoid contamination of the pile head, it is advantageous to clear the excavated soil from the region surround the entry point of the auger into the ground. This may be achieved by any convenient means.
It may also be advantageous to provide a plate or the like for holding the collar in place while
Browdy and Neimark
Kvaerner Cementation Foundations Ltd.
Lagman Frederick L.
Lillis Eileen D.
LandOfFree
Method and apparatus for forming enlarged pile heads does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for forming enlarged pile heads, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for forming enlarged pile heads will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2529116