GB2280466A

GB2280466A - Sectional piles

Info

Publication number: GB2280466A
Application number: GB9415116A
Authority: GB
Inventors: Roger Alfred Bullivant
Original assignee: Roxbury Ltd
Current assignee: Roxbury Ltd
Priority date: 1993-07-30
Filing date: 1994-07-27
Publication date: 1995-02-01
Anticipated expiration: 2014-07-27
Also published as: GB9315813D0; GB2280466B; GB9415116D0

Abstract

A pile comprises a plurality of similar sections 10 arranged in end-to-end relationship, each section 10 being formed from concrete and having a central steel reinforcing bar 12 cast therein with the bar projecting beyond the, in use, lower end of the section to form a spigot receivable within a socket 18 formed on the bar at the other end of the section. The uppermost section of the pile has a socket 18 at its, in use, lower end which receives a dowel 25. <IMAGE>

Description

Improvements in or relating to Pile Joints The present invention concerns improvements in or relating to pile joints, especially but not exclusively joints between concrete pile sections, each section having a central reinforcing member and the joint incorporating means for interconnecting the reinforcing member of one section with the reinforcing member of another section.

Our Patent GB2172038 relates to concrete pile sections having central reinforcing steel rods therein each section having a socket connected to the steel reinforcement at one end and the reinforcement projecting beyond the other end to form a spigot which inter fists with the socket when two pile sections are placed in end-to-end relationship. The contact between the spigot and socket is a relatively loose or low interference fit and the connection between the pile sections and the reinforcing bars is enhanced by the use of epoxy resin located in the socket and across the pile section ends prior to the interconnection of the piles, the epoxy resin, after setting, enhancing the joint.

In certain instances a disadvantage is encountered when driving sectional piles of this nature. As the first pile section is driven into the ground it provides a close fit between its sides and the surrounding ground but as a progressively increasing number of pile sections is driven, the pile hole, at ground level, tends to enlarge whereby when the final section is driven it is not positively located by the surrounding ground and consequently may be capable of limited movement within the pile hole until the epoxy resin sets.

Additionally, if the pile is not used as a compression pile that is, it is used as a pile to which limited tension or full tension is applied, then the spigot and socket connection enhanced by setting epoxy resin is not totally suitable.

It is an object of the present invention to obviate or mitigate these disadvantages.

According to one aspect of the present invention there is provided a pile comprising a plurality of sections each formed from concrete with a central reinforcing bar therein the reinforcing bar having a projecting spigot at one end thereof and a socket fixed to the other end thereof, the socket terminating at the other end of the pile section and being internally threaded or otherwise serrated, all sections of a pile with the exception of the uppermost section having downwardly projecting spigots, the spigot of the uppermost section projecting upwardly with a threaded or serrated dowel engaged in the downwardly facing socket of the upper section, the dowel being driven with a tight interference fit into the upwardly facing socket of the next to upper section.

Preferably, unset epoxy resin is spread between the ends of the pile sections prior to driving. The resin may include an inert filler.

Preferably an expanded metal sheet is provided between the ends of the pile sections prior to driving.

Preferably the reinforcing bar of a pile section has a helical protrusion therefrom and the internal diameter of the threaded socket is equal to or slightly greater than the external diameter of the protrusion.

Preferably the socket is fixed to the bar by fitting a length of bar within one end of the socket and compressing the socket against the bar. It follows from the above that the external diameter of the threaded dowel is greater than the external diameter of the reinforcing bar.

According to a further aspect of the present invention there is provided a sectional pile comprising a plurality of concrete sections each including a central steel reinforcing bar provided at its lower, in use, end with a projecting spigot and having a coarse thread formed thereon and a socket at the other end contained within the concrete pile section fixed to the bar and having an internal thread capable of threadably receiving the spigot.

As described in the preceding paragraphs, the facing faces of the sections may be coated with epoxy resin which may be contained in an expanded metal disc.

Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings, in which: Fig. 1 shows two sections of a compression pile during a pile driving operation; Fig. 2 shows the joint between the pile sections of Fig. 1 prior to the interconnection of sections; Fig. 3 shows two sections of a limited tension pile during a pile driving operation; .

Fig. 4 shows the joint between the pile sections of Fig. 3 prior to interconnection of the sections; Fig. 5 shows two sections of a full tension pile during a pile driving operation; Fig. 6 shows the joint between sections of the pile sections of Fig. 6 prior to interconnecting the sections; and Fig. 7 shows diagrammatically a connection of a tube to a reinforcing bar of a pile section to provide a socket.

Figs. 1 and 2 show respectively the upper section of a sectional pile and the joint between the pile sections of a pile as disclosed in our Patent GB2172038.

Each pile section comprises a square cross-section concrete member 10 having a steel reinforcing bar 12 along its centre and a steel end ring 14 at each end.

By referring to Figs. 2 and Fig. 7 it can be seen that at each pile joint there is provided a spigot and socket connection, the spigot 16 being formed by a projection of the reinforcing bar 12 beyond the lower end of the pile section. At the other end, normally the end which is uppermost in use, the reinforcing bar 12 terminates short of the end of the pile and has fixed thereto a threaded steel tube 18 which is compressed onto the bar to form a socket, the upper open end of which is flush with the end of the pile section.In use when a spigot 16 is inserted within a socket 18 there is a limited clearance space 20 which is normally filled with a filled epoxy resin, this resin also coating the facing faces of the pile sections and being held in place during the pile driving operation, to give a hydraulic shock absorbing effect, by a collapsible expanded metal (EXPAMET, Registered Trade Mark) sheet or disc 22 (Fig. 2). The reinforcing bar 12 employed is a standard reinforcing bar which is often provided with a rough, long pitch, helical protrusion 24 thereon (Fig.

7).

Piles of this nature are suitable for use as compression piles, that is, where the load to be transmitted through the reinforcing bar 12 will not be subjected to particularly great tensile stresses, especially until after the resin has set.

It is recognised, however, that in certain applications limited tension piles and in other applications full tension piles are desirable and in view of the success of the concrete pile sections of our Patent GB2172038 the present invention envisages modifications enabling such pile sections to be utilised as limited tension or full tension piles without any considerable disruption or inconvenience.

Figs. 3 and 4 show the use of pile sections as described in our Patent GBZ172038 in a limited tension pile with the minimum modification.

A pile is driven using sections as described with reference to Figs. 1 and 2, that is with the spigot lowermost and the socket uppermost until the last pile section has to be driven. At this point the pile section is reversed such that its socket is lowermost and, if desired, its spigot 16 can be removed from the now upper end of the section.

A threaded dowel 25 is screwed into the threaded upper socket 18 thereby presenting a spigot for insertion in the upwardly facing socket 18 bf the next to uppermost pile section. The dowel has an external diameter greater than the internal diameter of the socket. The upper pile section can therefore be threadably connected to the lower pile section by inserting the spigot into the socket and rotating the upper pile section relative to the lower pile section.

In practice it has proved to be unnecessary to provide a fully threaded connection as if the pile section is driven downwards relative to the already driven pile sections the spigot formed by the dowel 24 projects into the threaded upwardly facing socket 18 and as a result of the relative diameters thereof provides a tight interference fit thereby providing a limited tension pile.

In a modification of the embodiment shown in Figs.

3 and 4 a limited tension pile can be provided utilising pile sections which are slightly modified when compared with the pile sections in our Patent GB2172038. The modified pile sections are provided during the manufacturing stage with a socket at each end thereof so that the connection between each pile section requires a threaded dowel 25.

This solution to the problem is less desirable as it results in a modification in pile section manufacturing techniques giving rise to increase in cost and involves the fitment of dowels on site.

Further modifications are required for the full tension pile, illustrated in Figs. 5 and 6. In this modification each pile section 10 is provided with a modified reinforcing bar 12 which has formed at least at its end portions but preferably along its entire length with a relatively coarse threaded protrusion 24. The socket 18, swaged to the bar, has a matching internal coarse thread 26 so that interconnection between pile sections is achieved by rotating the upper section, which is still to be driven, relative to the lower driven section in the manner shown by the arrow 28 in Fig. 6.

Various modifications can be made without departing from the scope of the invention, for example, the pile sections could be circular, eliptical or multi-sided as opposed to square. The pile sections in the Figs. 1 to 4 embodiments could be provided with more than one reinforcing bar and the concrete making up the piles could have reinforcing fibres cast therein, the fibres being of plastics material or steel. The sockets in the Fig. 3 and 4 embodiment could be serrated rather than threaded.

Material other than epxoy resin could be utilised between the section ends, for example, a bitumastic material could be employed. Preferably where an epoxy resin is being utilised, for economy reasons, it is filled with sand or some other suitable inert material.

Claims

1. A pile comprising a plurality of sections each formed from concrete with a central reinforcing bar therein the reinforcing bar having a projecting spigot at one end thereof and a socket fixed to the other end thereof, the socket terminating at the other end of the pile section and being internally threaded or otherwise serrated, all sections of a pile with the exception of the uppermost section having downwardly projecting spigots, the spigot of the uppermost section projecting upwardly with a threaded or serrated dowel engaged in the downwardly facing socket of the upper section, the dowel being driven with a tight interference fit into the upwardly facing socket of the next to upper section.

2. A pile as claimed in claim 1, in which unset epoxy resin is spread between the ends of the pile sections prior to driving.

3. A pile as claimed in claim 2, in which the resin includes an inert filler.

4. A pile as claimed in claim 2 or claim 3, in which an expanded metal sheet is provided between the ends of the pile sections prior to driving.

5. A pile as claimed in any one of the preceding claims, in which the reinforcing bar of a pile section has a helical protrusion therefrom and the internal diameter of the threaded socket is equal to or slightly greater than the external diameter of the protrusion.

6. A pile as claimed in any one of claims 1 to 5, in which the reinforcing bar of a pile section has a helical protrusion therefrom and the internal diameter of the threaded socket is equal to or slightly less than the external diameter of the protrusion.

7. A pile as claimed in any one of the preceding claims, in which the socket is fixed to the bar by fitting a length of bar within one end of the socket and compressing the socket against the bar.

8. A pile as claimed in any one of the preceding claims, in which the external diameter of the threaded dowel is greater than the external diameter of the reinforcing bar.

9. A pile as claimed in any one of claims 2 to 8, in which the unset epoxy resin is contained within an expanded metal disc.

10. A sectional pile comprising a plurality of concrete sections each including a central steel reinforcing bar provided at its lower, in use, end with a projecting spigot and having a coarse thread formed thereon and a socket at the other end contained within the concrete pile section fixed to the bar and having an internal thread capable of threadably receiving the spigot.

11. A sectional pile as claimed in claim 10, in which the facing faces of the sections are coated with epoxy resin.

12. A sectional pile as claimed in claim 11, in which the epoxy resin is contained in an expanded metal disc.

13. A pile substantially as herein before described with reference to Figs.3 and 4 or Figs. 5 and 6 of the accompanying drawings.

14. Any novel subject matter or combination including novel subject matter herein disclosed, whether or not within the scope of or relating to the same invention as any of the preceding claims.