Hydraulic and earth engineering – Foundation – Columnar structure
Reexamination Certificate
1999-07-12
2001-07-24
Bagnell, David (Department: 3673)
Hydraulic and earth engineering
Foundation
Columnar structure
C405S232000, C405S231000, C405S254000
Reexamination Certificate
active
06264403
ABSTRACT:
RELATED APPLICATIONS
This is a continuing application of pending PCT Application No. PCT/GB98/00082 which claims priority from GB9700607.6 filed Jan. 14, 1997 and GB9722039.6 filed Oct. 17, 1997.
The present invention relates to a pile and a method of driving a pile.
A pile is an elongate rod, often of reinforced concrete with a steel sleeve or similar material or of solid steel, which is used in construction to provide a foundation or support for buildings or as an anchor for many different applications. Various designs of pile are known.
A first type of known pile is simply a smooth elongate rod which may have a sharpened tip. This type of pile is driven into the ground by simple hammering on the non-sharp end to drive the pile into the ground.
Another type of pile is a so called screw pile, an example of which is shown in SU-A-1035133. The pile disclosed in this patent application is hollow and has a spiral blade on its external surface. A screw-threaded drive shaft is threaded into a nut which is fixed inside the pile. The exposed end of the drive shaft is struck with a hammer which, through the action of the screw thread on the drive shaft and the nut fixed inside the pile, causes the pile to rotate and thus drive itself into the ground by virtue of the spiral blade. However, this construction is relatively complex and expensive to manufacture and maintain.
U.S. Pat. No. 4,650,372 discloses a screw pile having two parallel helical flanges at its lowermost end only, each of which completes half a turn around the core of the pile. The helical flanges are ribbon-like and the lowermost edges of the helical flanges are bevelled. Conventional pile-driving equipment is used to drive the pile into the ground.
EP-A-0246589 discloses several piles having different constructions. In one construction, a single wedge-shape helical thread is provided along substantially the whole length of the pile. In another construction, two parallel helical threads are provided along the length of the pile, each thread having a convex external surface provided by an arcuate cross-sectional shape of the thread.
EP-A-0574057 discloses a screw pile having a single helical thread along its length.
EP-A-0311363 discloses a screw pile having a single helical thread along a part of its length.
Each of the prior art piles is unsatisfactory, for various reasons. For example, such piles are difficult to drive into a substrate, do not provide adequate load-bearing, do not adequately resist heave (i.e. upward movement of the substrate) and/or are large. Because conventional piles typically rely on friction between the surface of the pile and the substrate to resist heave, the conventional piles are long (typically 6 to 8 or 9 meters long) and wide (typically having an outside diameter of 150 to 300 mm) and are therefore heavy and difficult to handle and manipulate. Furthermore, because heave typically arises in the top meter or so of the substrate and therefore tends to act on the topmost portion of the pile only, conventional piles are often provided with a sleeve around the top 1 to 3 meters of the pile to prevent movement of the upper layer of the substrate tending to lift the pile. The addition of such a sleeve increases the installation time and costs. Furthermore, the downwards load-bearing ability of conventional piles is at least in part provided by the friction between the surface of the pile and the substrate, a requirement which again leads to conventional piles being relatively long and wide. Where a screw thread is provided only on a lowermost portion of a pile as in some prior piles, the screw thread has been found to loosen the soil or other substrate as the pile is screwed into the ground, reducing the ability of the plain portion of the pile above the screw thread to have good contact with that loosened soil, thereby in turn reducing the upwards and downwards load-bearing capabilities of the pile.
Accordingly, there is a need for an improved pile and method of driving a pile.
According to a first aspect of the present invention, there is provided a pile, the pile having a plurality of external helical fins along substantially the whole length of the pile, at least one of the fins having a wedge-shape cross-section.
It will be understood that the helical fins should extend along the whole of the load-bearing portion of the pile, i.e. that portion which is buried in a substrate in use; the fins need not extend to the uppermost portion (say the top few centimeters) of the pile, for example, which may be left blank to allow fixings for the pile to be fitted.
The fins are preferably substantially parallel.
In a most preferred embodiment, the pile has three external helical fins along substantially the whole length of the pile. The provision of three fins ensures that the pile screws into the substrate evenly without misalignment and ensures symmetrical load-bearing capability around the pile. Three fins also serve to prevent the pile bending as it is forced into a substrate.
The fins are preferably substantially identical.
The pitch of each fin may be in the range 100 mm to 500 mm.
The height of each fin may be in the range 10 mm to 50 mm.
The outside diameter of the pile may be in the range 25 mm to 150 mm.
Each fin may be hollow. The or each fin may be filled with a filling material.
Preferably, however, each fin is solid.
The pile may be hollow. The pile maybe filled with a filling material.
Preferably, however, the pile is solid.
According to a second aspect of the present invention, there is provided a method of driving a pile as described above into a substrate, the method comprising the step of applying a force to said pile substantially parallel to said longitudinal axis, said force having substantially no rotational component about the longitudinal axis, the helical fins on said pile causing said pile to rotate in the substrate and thereby penetrate the substrate as said force is applied.
The force may be applied repeatedly as a series of impulses to the pile. Thus, a repeated hammer-type action can be used to drive the pile.
A pilot hole may be formed in the substrate prior to driving the pile into the substrate.
An end of the pile may be allowed to protrude from the substrate after driving of the pile is complete, and the method may include the further step of fixing the protruding end against rotation relative to the substrate. The end may be fixed in concrete, for example.
The pile may be provided as plural sections. A first section may be driven into the substrate, a second section connected thereto, and a force then applied to the second section to drive said connected sections into the substrate. This may be repeated for third and further sections.
The present invention allows a pile to be screwed into a substrate such as the ground by simple application of a hammer-type force to the pile in a direction substantially parallel to the longitudinal axis of the pile. It is not necessary to provide a complex screw-driving mechanism for driving the pile, either in the pile itself or in the machine which provides the driving force. Manual application of a torque to screw the pile into the substrate is not required. The pile may be short and narrow compared to conventional piles and therefore is much easier to handle. The load-bearing capabilities and resistance to heave of the pile are greatly improved compared to conventional piles.
REFERENCES:
patent: 226664 (1880-04-01), Kirkup
patent: 683275 (1901-09-01), Hartung
patent: 2332990 (1943-10-01), Collins
patent: 4650372 (1987-03-01), Gorrell
patent: 4911581 (1990-03-01), Mauch
patent: 0246589 (1987-11-01), None
patent: 86047 (1957-08-01), None
patent: 1645368 (1991-04-01), None
patent: 9830757 (1998-07-01), None
Hall David J.
Hall Robert S.
Bagnell David
Conley & Rose & Tayon P.C.
Lagman Frederick L.
Target Fixings Limited
LandOfFree
Pile and method of driving a pile does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Pile and method of driving a pile, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Pile and method of driving a pile will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2487510