Hydraulic and earth engineering – Foundation – Columnar structure
Patent
1991-09-11
1993-02-16
Corbin, David H.
Hydraulic and earth engineering
Foundation
Columnar structure
405240, 405243, E02D 538, E02D 718
Patent
active
051865823
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to piles and to their production.
Piles for use in supporting structures such as buildings are commonly pre-formed, in sections, and driven into the ground from the surface. Alternatively, they may be formed by driving a head into the earth to form a hole. A pipe extending down the hole supplies concrete or other pile material to the head. The head comprises a through passage which allows the pile material to fill the hole beneath the head as the head is withdrawn from the hole. A sacrificial cap closes the lower end of the through passage while the head is being driven to form the hole, and is left at the bottom of the hole when the head is withdrawn.
A major contribution to the supporting force provided by a pile arises from friction between the surface of the pile and the surrounding earth. This friction can be increased by increasing the size of the pile, but there is a resultant increase in the volume of pile material required. It is an object of the present invention to obviate or mitigate this problem.
According to the present invention there is provided a method of forming a pile comprising applying a downwardly directed force to a pile forming member to drive said member into the ground top a predetermined depth characterized in that said pile forming member has three or four fins projecting transversely thereof and is so driven into the grounds that the passage it forms in the ground has a cross-section corresponding to that of the member and fins and in that an upwardly directed vibratory force is applied to withdraw said member from the ground while simultaneously supplying a pile forming material through the member to fill said passage as the member is removed therefrom thereby creating a pile having a cross-section corresponding to that of the member and fins.
Preferably the pile member is driven into the ground by applying a downwardly directed vibratory force thereto.
Preferably a reinforcing member is positioned in the passage before the pile forming material sets.
Preferably the cross-section of the member is triangular.
Each fin is superimposed on said triangular cross-section member. Alternatively each fin is superimposed on an outline which is otherwise circular.
Further according to the present invention there is provided a pile formed in accordance with the method set out in the proceeding five paragraphs.
Embodiments of devices according to the present invention, and the piles produced by those devices will now be described in more detail, by way of example only, and with reference to the accompanying drawings in which:
FIG. 1 is perspective view of a pile-making head according to the invention;
FIG. 2 is a cross-section of a pile formed using the head of FIG. 1; and
FIG. 3 is an elevation of a further alternative head.
FIG. 1 shows a pile-making device 10 comprising a head 12 which, in use, is driven into the earth to form a hole. Means 14 in the form of a pipe are provided for supplying pile material (normally concrete) to the head 12. A through passage 16 within the head allows the pile material to fill the hole beneath the head 12 as the head is withdrawn from the hole. The device 10 may be driven into and out of a hole by any conventional technique, such as hammering, jacking or vibrating but a vibrating technique is preferred certainly for withdrawing the device from the hole.
The outermost outline of the head 12 is so shaped as to form a hole of non-circular cross-section.
In more detail, the head 12 comprises a block 18 in the form of a triangular prism whose central axis forms the axis of the head and the axis of the hole formed by the head. One end of the block 18 carries an extension 20 in the approximate form of a pyramid which causes the head to tapper from the outline of the block 18 to the mouth of the through passage 16, shown closed by a sacrificial cap 22.
The base of the pyramid is slightly larger than the cross-section of the prism, so that a small step 23 is formed where they meet. The outline of head is at its largest at this point
REFERENCES:
patent: 3420067 (1969-01-01), Bjerking
patent: 4126007 (1978-11-01), Mars
patent: 4165198 (1979-08-01), Farmer
Adams, III W. Thad
Corbin David H.
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