GB2479199A

GB2479199A - In-situ foundation pile manufacture with simultaneous driving and filling

Info

Publication number: GB2479199A
Application number: GB1005572A
Authority: GB
Inventors: Paul Kiss
Original assignee: Abbey Pynford Holdings Ltd
Current assignee: Abbey Pynford Holdings Ltd
Priority date: 2010-04-01
Filing date: 2010-04-01
Publication date: 2011-10-05
Also published as: GB201005572D0

Abstract

A method of creating a foundation pile 1 is described, comprising the steps of: creating a pile bore by driving a shoe 13 into the ground 12 with a driving element 11, the shoe 13, which may be detachable, having a width greater than a width of the driving element, such that a void or gap is created between the wall of the bore and the wall of the driving element 11; wherein as the shoe 13 is driven, the void is simultaneously filled with a settable material 15; the settable material 15 is provided to the void through at least one port 20 in the driving element 11. The settable material may further be provided directly to the void through a gap between the driving element and an outer wall of the bore from a reservoir 14 surrounding the bore opening. The invention is intended to mitigate flash setting problems and reduce leeching.

Description

FOUNDATION PILE

The present invention relates to a method of creating a foundation pile for a building. In particular, the invention relates to the field of foundation piles made from a settable material.

A number of methods of creating a foundation pile are already known in the art. These known methods include the following. An open bored pile is known, where soil is removed by an auger or other drilling system and the resulting bore is filled with a settable material and steel reinforcements. A liner may be installed in the bore to stop the soil around the bore from collapsing before the settable material is placed. The liner is optionally removed from the bore. A continuous flight augured pile (CFA) is also known, where the auger is drilled into the ground and a settable material, such as concrete, is placed by pumping to the base of the auger via a central stem as the auger is withdrawn from the bore. A continuous displacement pile (CHD) is also known, where a bore is formed by an enlarged section at the end of a stem. This enlarged section and stem is drilled into the ground and displaces the soil as it progresses. Once it reaches the required depth, similarly to the CFA pile described above, concrete is pumped through the stem to the base of the enlarged section and the enlarged section is gradually withdrawn as the settable material is pumped to the base. This method is generally suited to softer soils.

A top driven pile is also known, where a steel tube or concrete section is driven into the ground with a top hammer, acting on the top of the section, similarly to a hammer driving a nail. A bottom driven pile is also known, where a steel tube or casing is driven into the ground by a drop weight acting on the bottom of the casing. Once the desired depth is reached, the weight is withdrawn and a settable material can be placed within the tube. A driven cast in place pile is also known, where a hollow liner is driven into the ground with a cap or plug at the bottom end, to prevent soil entering the liner. Once the desired depth is reached, the cap or plug is removed, concrete is placed and the liner is then pulled out of the ground. It is also known to use spinning tubes driven into the ground in combination with concrete jets, which serve to mix the soil and the concrete as the tube is installed. Screw piles are also known, which are most commonly metal sections screwed into the ground.

EP1046753 discloses a method for making piles by using a rotating screw to draw soil displacing members located on a shaft down through a body of soil by turning the screw at the lower end of the shaft.

NL1018792 describes a foundation pile made by sinking an empty hollow tube into the ground, the tube having its bottom end sealed with a shoe having a diameter greater than the external perimeter of tube. A grout tube is provided on the outer perimeter of the hollow tube for delivering grout to the outer perimeter.

A support with external dimensions which are smaller than the internal diameter of the tube is introduced into the tube, which is then pulled out of the ground.

According to the present invention there is provided a method of creating a foundation pile, comprising the steps of: creating a pile bore by driving a shoe into the ground with a driving element, the shoe having a width greater than a width of the driving element, such that a void is created between the wall of the bore and the wall of the driving eiement; wherein as the shoe is driven, the void is simultaneously filled with a settable material; the settable material is provided to the void through at least one port in the driving element.

The method of the present invention provides a number of benefits over the methods known in the art. As a shoe is driven into the ground the bore created by the shoe is liable to collapse unless it is filled with a material to help to support the walls. If the material added to the bore behind the shoe is a settable material, moisture from the settable material is liable to leech into the surrounding soil. This leeching can cause "flash-setting", where the settable material sets more rapidly than is usual. This can prevent the pile from being correctly formed during the driving process and can result in an inconsistent pile of reduced performance due to inconsistencies over its length. The provision of fresh settable material through at least one port in the driving element allows fresh settable material to be provided directly to the bore to replace some of the moisture that leeches into the surrounding soil. This can be achieved without the need for additional tubing to deliver the settable material into the bore if the settable material is delivered through at least one port in the driving element.

The settable material may be provided directly to the void through a gap between the driving element and an outer wall of the bore from a reservoir surrounding the bore opening. The above described flash setting can prevent any further settable material from travelling along the bore for an even distribution of the settable material during the driving of the shoe into the ground.

If the settable material is provided both directly to the void, through a gap between the driving element and an outer wall of the bore from a reservoir surrounding the bore opening, and also through at least one port in the driving element, fresh settable material is provided more directly to the lower parts of the bore without having to pass via any area of material in the upper part of the bore, which may be beginning to set or flash-set. Providing alternative routes for the fresh settable material to enter the void can also help to avoid flash setting by providing new material containing fresh moisture to areas where leeching is occurring. Providing a more direct route for the settable material to reach the void behind the shoe can aiso help to avoid the wails of the void directly behind the shoe from collapsing before the settable material has moved sufficiently to fill the newly created void. These benefits can result in a more consistent and reliably filled bore and is this in turn can result in a more consistent and generally better-formed foundation pile.

The method may further comprise the steps of: removing the driving element; and allowing the settable material to set to create a continuous foundation pile of settabte material. Removing the driving element and allowing the settable material to set to create the continuous foundation pile of settable material has advantages over prior art systems where the central shaft and soil displacing members are left in the bore while the concrete is allowed to set, The provision of a continuous foundation pile made of settable material in this way can result in a stronger foundation pile, since there are no interruptions to the settable material, which can provide weaknesses. Being able to remove and reuse the driving element also reduces the overall cost of the foundation pile formed by the method of the present invention.

The settable material that is provided directly to the void through the gap between the driving element and the outer wall of the bore may be provided from a reservoir surrounding the bore opening. Providing the settable material from a reservoir surrounding the bore opening is a direct and effective way of providing settable material to the bore without the requirement for complex or expensive pumping equipment. The continuous provision of a body of settable material above the bore also ensures that the level of settable material does not drop below the upper edge of the wall of the bore, which would potentially allow the wall of the bore to collapse.

The at least one port may be provided in a lower section of the driving element, substantially adjacent the shoe. Providing the at least one port in a lower section of the driving element ensures that fresh settable material is provided to the area in which the bore is being created. If the driving element and shoe are driven by impact, the rapid advancing of the shoe could potentially create a void directly behind the shoe and if this void were not filled sufficiently quickly by settable material, the wall of the bore could collapse into the void and the continuity of the foundation pile could be Jost, which wouid result in a weakened foundation pile.

A plurality of ports may be provided in the driving element to allow the settable material to flow through the driving element. The provision of a plurality of ports in the driving element can give the settable material a greater number of potential paths to follow to fill the bore created by the shoe and reduce the risk of collapse of the wall of the bore before any void is filled by settable material provided from the upper part of the bore or the ports.

The plurality of ports may be provided at a plurality of locations along the length of the driving element. The provision of a plurality of ports at a plurality of locations along the length of the driving element allows fresh settable material to be provided at a plurality of locations down the depth of the foundation pile. This can reduce the risk of the "flash setting" phenomenon by providing fresh settable material at a plurality of locations, If any of the plurality of ports provided along the length of the driving element is at the level of the reservoir, then this can provide a point for fresh settable material from the reservoir to enter the driving element in order to provide fresh settable material to any other port in the driving element. This may include providing fresh settable material directly from the reservoir through the driving element to a port provided adjacent the shoe, which helps in providing fresh settable material at the point at which the shoe is creating the bore.

The method may further comprise the step of: removing the driving element, whilst leaving the shoe in the bore.

Removing the driving element whilst leaving the shoe in the bore allows the driving element to be reused for a further foundation pile, whilst leaving the shoe in the bore avoids any risk of the act of withdrawing the shoe damaging the bore which has been created. Leaving the shoe in the bore can also provide a stable bottom to the bore while the settable material sets.

The settable material may form a longitudinally continuous pile. Allowing the settable material to form a longitudinally continuous pile can help to avoid any discontinuities in the settable material, which can result in stress concentrations and/or a weakening in the pile itself. A longitudinally continuous pile may be stronger and therefore more effective and reliable as a foundation pile than one which is divided by elements made of other materials.

A detailed description of a particular embodiment of the present invention will now be given, with reference to the following figures, in which: Figure 1 shows the early stages of driving a pile using the method of the present invention; Figure 2 shows a foundation pile driven by the method of the present invention, towards the end of the driving process; and Figure 3 shows a foundation pile created using the method of the present invention.

Figure 1 shows a foundation pile 1 being created by driving a driving element 11 into ground 12. On the end of driving element 11 there is provided a shoe 13 which can be of any shape, but has a form and rigidity suited to driving a bore 16 in ground 12. The shoe 13 is releasably attached to the end of driving element 13, such that at the end of the driving step, the driving element may be withdrawn from the bore, leaving the shoe 13 in place at the bottom of the bore.

Reservoir 14 is shown in position above the bore and filled with an amount of settable material 15. As driving element 11 drives shoe 13 into the ground, the level of settable material 15 in reservoir 14 will drop as the settable material enters the bore. Reservoir 14 may be refilled periodically during the driving process, or it may be continually fed with settable material from another source.

Alternatively, reservoir 14 may be suitably sized to hold enough settable material to create the entire foundation pile to avoid the need for refilling. Settable material 15 has two available routes from reservoir 14 to the void created by the shoe 13. The first route is in the direction indicated by arrow 17, from the reservoir directly to the void. The second route is in the direction of arrows 18 into the driving element through the hollow centre of the driving element and out in the direction of arrows 19 adjacent the shoe. The settable material may flow into or out of any of the ports 20, which are illustrated at a plurality of optional locations along the length of the driving element. The settable material may be provided to the hollow center of the driving element by any means and not necessarily uniquely from reservoir 14. An alternative arrangement may be to provide ports only at the lower end of the driving element and to provide settable material under pressure or under the force of gravity from a source not illustrated in the figures. During the driving process, in the illustrated example, the driving element is driven by a reciprocating hammer 21. Any suitable means of driving the driving element may be employed, such as hammering or vibration or other means.

Figure 2 shows a foundation pile 1 towards the end of the driving process. As previously, the settable material 15 can follow one of two alternative routes towards the void or bore 16 created by shoe 13. The settable material may flow in the direction of arrows 17 directly into the bore. Alternatively, it may flow in the direction of arrows 18, into the hollow driving element and out towards the bore in the direction of arrows 19. Any number of ports 20 may be provided in the driving element and the ports may be provided at any number of suitable locations to allow the flow of settable material in the desired direction. Once the driving process is complete, driving element 11 will be withdrawn and an amount of settable material displaced in the bore by the driving element may need to be left in the reservoir 14. On withdrawal of the driving element, the settable material can flow into the bore from the reservoir and the level of settable material in the bore may be prevented from falling below the surface of ground 12 in this way. This reduces the risk of the upper parts of the bore from collapsing upon withdrawal of the driving element.

Figure 3 illustrates foundation pile 1 after driving element 11 and reservoir 14 have been removed. Shoe 13 remains in place at the bottom of the bore.

Shoe 13 may be provided with an engagement portion 22 which allows some positive engagement between driving element 11 and shoe 13. This can help to ensure correct orientation of the shoe during the driving process. Engagement portion 22 may be configured to be passively engaged, without positive engagement with the shoe, or positively engaged, but releasable, such that the driving element can be easily removed from the shoe. As can be seen in the figure, foundation pile 1 is formed of a continuous body of settable material within the bore 16 created by shoe 13. Reinforcing elements commonly used in the art may be inserted into the foundation pile after the removal of driving element 11. These reinforcing elements may be suitably configured to provide reinforcement without unnecessarily creating interruptions to the longitudinal continuity of the foundation pile. A longitudinally continuous pile may contain some small degree of interruptions due to reinforcements inserted after the driving process. The method of the present invention allows the reinforcements inserted into the foundation pile to be designed independently of the driving process and thus the configuration of the reinforcements can be optimised for the most beneficial reinforcing effect in the resulting foundation pile without excessively reducing the longitudinal continuity of the pile.

Claims

CLAIMS1 A method of creating a foundation pile, comprising the steps of: creating a pile bore by driving a shoe into the ground with a driving element, the shoe having a width greater than a width of the driving element, such that a void is created between the wall of the bore and the wall of the driving element; wherein as the shoe is driven, the void is simultaneously filled with a settable material; and the settable material is provided to the void through at least one port in the driving element.
2. A method according to claim 1, wherein the settable material is provided directly to the void through a gap between the driving element and the wall of the bore.
3. A method according to claim 2, wherein the settable material that is provided directly to the void through the gap between the driving element and the outer wall of the bore is provided from a reservoir surrounding the bore opening.
4. A method according to any one of claims 1 to 3, further comprising the steps of: removing the driving element; and allowing the settable material to set to create a continuous foundation pile of settable material.
5. A method according to any preceding claim, wherein the at least one port is provided in a lower section of the driving element, substantially adjacent the shoe.7. A method according to claim 6, wherein the plurality of ports is provided at a plurality of locations along the length of the driving element.8. A method according to any preceding claim, further comprising the step of: removing the driving element, whilst leaving the shoe in the bore.9. A method according to any one of the preceding claims, wherein the settable material forms a longitudinally continuous pile.