GB2453443A

GB2453443A - A pile cage with test pipes and method of assembly

Info

Publication number: GB2453443A
Application number: GB0818152A
Authority: GB
Inventors: Stephen Render
Original assignee: Romtech Ltd
Current assignee: Romtech Ltd
Priority date: 2007-10-05
Filing date: 2008-10-06
Publication date: 2009-04-08
Anticipated expiration: 2028-10-06
Also published as: GB0818152D0; GB0719433D0; GB2453443B

Abstract

This invention relates to a pile cage having one or more test pipes 22, 24, 36 and 40, and to a method of assembly. The test pipe has a flared end (26, FIG 1) for receiving an end (44, FIG 1) of another test pipe, the test pipe also having a part of a latch mechanism 54, 56, by which the test pipes can be secured together. The flared end enables a push-fit connection of the respective test pipes. In the method of assembling a first pile cage and a second pile cage the first pile cage is lowered into a pile hole and located with its upper end projecting from the pile hole. The second pile cage is positioned above the first pile cage with the second test pipe aligned with the first test pipe. The second pile cage is lowered relative to the first pile cage so that the end of the second test pipe enters the flared end of the first test pipe. The latch mechanism is actuated to secure the first and second test pipes together.

Description

PILE CAGE AND METHOD OF ASSEMBLY

FIELD OF THE INVENTION

This invention relates to a pile cage and to a method of assembly, and in particular to a pile cage having one or more test pipes.

In the following description, directional and orientational terms such as "top", "upper" etc. refer to the normal orientation of use, with the longitudinal axis of the pile cages substantially vertical. 1 0

BACKGROUND TO THE INVENTION

Reinforced concrete piles are known for use in the foundations of roadway is bridges and the like. The piles are sunk deep into the ground and can for example provide a link between the bridge supports and the underlying rocks.

The pile comprises a metallic pile cage embedded in concrete, the pile cage acting both as a reinforcement for the concrete and also as a means to tie the bridge support or the like to the pile. The pile cage comprises a number of cage bars which in use are arranged to lie substantially along the longitudinal axis of the pile. These bars are interconnected by one or more frames which maintain the separation and alignment of the cage bars, and in many designs of pile cage the frame comprises a helical wire which surrounds and interconnects the cage bars.

Often the cage is assembled off-site at a dedicated manufacturing plant, and is delivered to the site for insertion into the hole created for the pile.

If the depth of the pile is greater than the length of the available pile cages, then the piling contractor will have to splice together two or more pile cages, i.e. connect the top end of a lower pile cage to the bottom end of an upper pile cage.

The pile cage is lowered into a hole which has been drilled into the ground by a drill or augur. The pile cage can be pressed down into wet concrete, the concrete being pumped into the hole as the augur is removed therefrom. Alternatively, a casing is inserted into the hole and the pile cage is inserted into the casing, the concrete then being poured around the pile cage and the casing subsequently being removed (so that it can be reused). A casing will typically be used when the pile cages are required to be spliced.

When two pile cages are to be spliced together, the helical wire of one or both of the pile cages will typically be terminated away from the end of the cage bars, so that the cage bars project beyond the helical wire and allow an overlap to be created between the cage bars of the respective pile cages. The overlapping io ends of the cage bars of the respective pile cages are secured together by known means, and the pile cages are thereafter lowered together into the pile hole. The process can be repeated to splice a third pile cage if required, and so on.

It is sometimes desired for the piling contractor to test the concrete pile. One test is which is often undertaken is to check for the presence of voids in the concrete by way of sonic testing, another is to determine the inclination of the pile in those piles which are required to remain substantially vertical.

If the pile is to be subjected to a test for voids, the pile cage is typically assembled o to include at least two test pipes which are secured to the frame(s) and/or to a respective cage bar, the test pipes lying within the frame(s). After the concrete has set a transponder is lowered down one of the test pipes and a receiver is lowered down another of the test pipes, the transponder generating sonic signals which pass through the concrete and are detected by the receiver. Variations in the received signal as the transponder and receiver are lowered together down their respective test pipes are indicative of changes within the material of the concrete, and major variations are indicative of voids within the concrete. If the variation exceeds a predetermined threshold that indicates that the void is larger than permitted, usually requiring the contractor to sink a new pile.

Often four test pipes will be used in sonic testing, separated around the pile cage.

The contractor will use either two transponders in opposed test pipes and two receivers in the other test pipes, or one transponder and three receivers.

In order to determine the inclination of the pile it is necessary to pass an inclinometer down the pile. In such applications a single test pipe is provided, the test pipe having internal guides by which the inclinometer may be guided down the test pipe, the guides ensuring that the orientation of the inclinometer relative to the test pipe remains substantially constant as it moves down the test pipe. Since the test pipe is arranged substantially parallel to the longitudinal axis of the pile cage, variations in the signal issued by the inclinometer are indicative of changes in inclination of the pile. The inclinometer is lowered on a line containing a signal wire, and signals indicative of the inclination of the pile can be sent to the surface either continuously, or at chosen depths.

The transponders and receivers which are used in sonic testing typically require a test pipe having an internal diameter of around 60mm. The inclinometers which are used in inclination testing typically require a test pipe having an internal diameter of around 100mm or around 152mm. It is occasionally necessary for a pile to be subjected to both forms of testing, in which case the test pipe provided for the inclinometer is usually also used as one of the test pipes for a transponder or receiver.

If the depth of the pile does not exceed the length of the available pile cages, then the pile cage manufacturer will secure the required test pipes to the pile cage during manufacture of the pile cage. However, with deeper piles which require the pile cages to be spliced, the piling contractor will have to join lengths of test pipe together on site in addition to splicing the required number of pile cages. The present invention is directed to piles which require splicing of the pile cages, and require at least one test pipe.

It is not unusual for a pile which is to undergo sonic and/or inclinometer testing to be deep enough to require three pile cages to be spliced together, and consequently three lengths of test pipe to be joined, on site.

When the test has been completed, the testing tools are removed and the test pipe is filled with grout or other cementitious material.

DESCRIPTION OF THE PRIOR ART

The method of joining test pipes which has been employed by the UK piling industry since the 1960s involves the use of steel test pipes which have a male thread cut into each end. The test pipe(s) of each of the pile cages which are to be spliced together are mounted upon the respective pile cages, usually at dedicated manufacturing facilities.

The lower pile cage is fitted with a "trapping band" adjacent its upper end, i.e. a substantially circular band which is securely connected to the cage bars. This pile cage is lowered into the casing of the pile hole and a trapping bar or the like is laid across the top of the casing and underneath the trapping band so as to prevent the pile cage from falling into the casing and to hold the lower pile cage with a desired length projecting above the casing. The test pipe(s) of the lower pile cage therefore also project above the casing.

A sleeve having a female thread is secured to the test pipe(s) of either the lower (first) pile cage, or (more typically) the test pipes of the upper (second) pile cage.

The test pipe(s) of the upper pile cage are arranged to project a significant distance beyond the cage bars of that pile cage, so that as the upper pile cage is lowered by a crane over the casing the test pipe(s) of the upper pile cage meet the test pipe(s) of the lower pile cage before the respective cage bars overlap.

The test pipe(s) of the upper pile cage are then rotated (suitably by a "Stillson" or other suitable wrench) so that the sleeve is screwed onto the test pipe of the lower pile cage.

It will be understood that the test pipe(s) of the upper (second) pile cage are mounted so as to be rotatable relative to the pile cage, and are suitably mounted by stirrups or U-bolts to a cage bar or frame(s) of the pile cage, the mounting being sufficient to prevent the test pipe(s) becoming separated from the pile cage, but permitting rotation thereof when required. (On the contrary, the test pipe(s) of the lower pile cage are fixed against rotation, and are often tack-welded or otherwise permanently fixed to the cage bar or frame(s) of the lower pile cage.) In addition, the test pipe(s) of the upper pile cage are permitted some longitudinal s movement relative to the pile cage, so that after joining of the test pipe(s) the upper pile cage can be lowered relative to the lower pile cage (and relative to the test pipe(s)) until the cage bars overlap and can be spliced together by the chosen splicing method.

When the pile cages have been secured together the upper pile cage can be lifted (together with the lower pile cage) by a small distance allowing the trapping bar to be removed and the spliced pile cages are then lowered together into the casing.

The same procedure can be applied to add a third (and successive) pile cages, as is desired or required for a particular pile.

Notwithstanding the length of time for which the above-described method has been in practice, it has a number of disadvantages. The first disadvantage is that the screw threads often become damaged on site, especially during the splicing procedure. Thus, a pile cage can weigh several tonnes and during the splicing procedure a part of the suspended upper pipe cage can strike the test pipe of the lower pile cage. It is extremely difficult for the crane operator to lower the upper pile cage close enough to the lower pile cage for the sleeve to be screwed onto the test pipe, without impacting and damaging the screw threads, and it is relatively commonplace for the threads of the test pipe(s) to be damaged sufficiently that the sleeve cannot be threaded thereonto.

When this happens, the thread must be repaired or re-cut, requiring specialised tooling and a skilled operator. This is a time-consuming procedure, the time taken being increased by the Health and Safety requirement that the upper pile cage is removed whilst the operator repairs the test pipe(s) of the lower pile cage, rather than remain suspended above where the operator is working.

Alternatively, if the thread is badly damaged the contractor may decide it is more cost-effective to bypass the threads and instead weld the ends of the test pipes together, which itself requires specialised machinery and a skilled operator, and is also very time consuming. Furthermore, it is necessary that the upper pile cage S remains suspended above the lower pile cage during the (lengthy) welding operation, which is clearly not without risk.

In addition, in the case of the larger diameter inclinometer test pipes, it is not unknown for the friction between the test pipe and the stirrups of the upper pile cage to preclude relative rotation of the test pipe. In such cases, the operator will instead rotate the whole of the upper pile cage. Because the test pipe is located at the periphery of the pile cage the pile cage is required to rotate eccentrically upon the crane hook, and this can damage the thread even if the threaded connection between the test pipe and the sleeve has been started.

It is not unknown, for example, for the contractor to schedule the insertion of a pile cage to take four hours, and for the actual job to last eight hours, simply due to the threads of the test pipe(s) becoming damaged during assembly of the pile cage. Such an increase in time represents a considerable penalty in costs for the piling contractor.

A second disadvantage is that the test pipes typically used are of relatively thick section, for example 5mm wall thickness. Test pipes with such thick walls are very heavy, but are used because of the requirement to cut the thread. The weight of the test pipe(s) increases the weight of the pile cage, and therefore increases the likelihood of the threads becoming damaged if a suspended pile cage strikes a threaded test pipe.

A third disadvantage arises from the use of standard pipe material, typically gas pipe material, for the test pipe. The pipe is made in standard lengths, and a pile cage will typically also be made in (similar) standard lengths. It is often the case, however, that the pile will be of a depth which does not match an exact number of standard pile cages, and in such circumstances one of the pile cages will be cut to match the required depth of the pile. The test pipe will also have to be cut to length, and since the ends are threaded it will be necessary to rethread the new end of the pipe on site.

SUMMARY OF THE INVENTION

The present invention seeks to provide an a new design of pile cage, and in particular a new design of test pipe, and an alternative method of joining test pipes together, so as to reduce or avoid the above-stated disadvantages of the known joining method.

According to the invention there is provided a pile cage having a test pipe, the test pipe having a flared end for receiving an end of another test pipe, and a latch mechanism by which the test pipes can be secured together, the flared end enabling a push-fit connection between the test pipes.

Because the test pipes are joined by a push-fit connection it is not necessary to rotate one test pipe relative to the other test pipe, and there are no threads to damage. The absence of threads means that the wall thickness of the test pipe can be reduced, so reducing the weight of the test pipe and therefore reducing the weight of the pile cage.

The absence of threads also makes it more economic to assemble pile cages of any desired length, i.e. even if the test pipe is purchased in standard lengths it can simply be cut to the required length by removing part of the unflared end of the test pipe. The cut end of the test pipe can be inserted into the flared end of the adjacent test pipe without additional process steps.

The form of the flared end, and the relative sizes of the flared end and the end of the other test pipe, can in certain cases provide the required joining connection without requiring the latch mechanism. Nevertheless, the latch mechanism is desired to ensure that the test pipes will not become separated once they have been joined together.

The use of a push-fit connection between the test pipes is particularly advantageous for an inclinometer test pipe having internal guides, as it is easier to align the guides in the two test pipes when it is not necessary to rotate one of the test pipes relative to the other during the joining operation.

The latch mechanism is preferably a toggle clamp, or a nut and bolt connection.

There is also provided a first pile cage having a first test pipe and a second pile cage having a second test pipe, the first test pipe having a flared end, the end of the second test pipe being receivable within the flared end, the test pipes having respective parts of a latch mechanism whereby the test pipes can be secured together.

Typically, the first pile cage with the flared end will be the lower pile cage. If a particular pile requires three pile cages then the second pile cage will also have a flared end to receive the end of the test pipe of the third pile cage, so that during each of the splicing operations the lower pile cage has the flared end.

Providing the flared end at the top of the test pipe, particularly for the second pile cage, has the advantage that the flared end prevents the test pipe falling out of the pile cage when this is suspended vertically above the pile hole. Thus, it is intended that the test pipe of the second pile cage is mounted to be moveable longitudinally relative to the pile cage, and will desirably be mounted in stirrups or the like for this purpose. It is arranged that the stirrup is larger than the cross-section of the unflared test pipe but smaller than the cross-section of the flared end of the test pipe.

There is also provided a method of assembling a first pile cage and a second pile cage, comprising the steps of: {i} assembling a first pile cage with a first test pipe, the first test pipe having a flared end, and further having a part of a latch mechanism; {ii} assembling a second pile cage with a second test pipe, the second test pipe having another part of the latch mechanism; s {iii} lowering the first pile cage into a pile hole, and locating the first pile cage with its upper end projecting from the pile hole; {iv} positioning the second pile cage above the first pile cage with the second test pipe aligned with the first test pipe; {v} lowering the second pile cage relative to the first pile cage so that the end of the second test pipe enters the flared end of the first test pipe; and {vi} actuating the latch mechanism to secure the first and second test pipes together.

Preferably, the end of the first test pipe is sealed before or after step vi, suitably by adhesive tape, so as to prevent the ingress of concrete or other materials into the flared end.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention will now be described in more detail, by way of example, with reference to the accompanying drawings, in which: Fig.1 shows a schematic cross-sectional representation of three pile cages according to the present invention prior to splicing of the pile cages; Fig.2 shows a cross-sectional view of a pile cage having four test pipes; and Fig.3 shows an enlarged view of the joined ends of two test pipes according to the present invention. 1 0

DETAILED DESCRIPTION

Fig.1 shows three pile cages 12, 14 and 16 which are to be assembled together for installation in a pile hole (not shown). The pile cages may be spliced together in any known method, the most common being that described above in which the first pile cage 12 is lowered into a pile hole and suspended therein with its upper end 20 projecting from the pile hole.

The pile cages 12, 14 and 16 are preferably assembled at a dedicated manufacturing location and delivered to the site of use, although they could be assembled on site if desired. Typically, the pile cages are assembled with their longitudinal axes substantially horizontal as drawn.

According to the present invention, the pile cage 12 includes four test pipes, of is which only two (22 and 24) are shown in Fig.1. Each of the test pipes has a flared upper end 26, and a cap 30 sealing the lower end. The remainder of the pile cage is shown in dashed outline only in Fig.1, but will be understood from Fig.2 to include a number of cage bars 32 supported by one or more frames 34. In known fashion, the test pipes 22, 24 are located adjacent to the frame(s) 34 between adjacent cage bars 32.

The test pipes 22, 24 are mounted to the frame(s) 34 securely enough to prevent substantial longitudinal or rotational movement relative to the remainder of the pile cage 12.

The pile cage 14 also comprises a (similar) number of cage bars such as 32 and one or more frames such as 34, which are again shown in dashed outline in Fig.1.

This pile cage also has four test pipes, of which again only two (36 and 40) are shown in this view. The upper ends 42 of the test pipes 36 and 40 are flared, and the remainder of the length of the test pipes 36 and 40, including their lower ends 44, are unflared, and otherwise unaltered. The test pipes 36, 40 can therefore be made of standard pipe lengths with only the upper ends 42 requiring any modification (as is also the case with the test pipes 22 and 24).

In order to facilitate joining of the test pipe 36 to the test pipe 22, and the joining of the test pipe 40 to the test pipe 24, it is desired that the test pipes 36, 40 project beyond the cage bars of the pile cage 14 by a significant distance, so as to ensure that the test pipes can be joined before the cage bars of the pile cage 14 overlap the cage bars of the pile cage 12. The test pipes 36, 40 are therefore somewhat longer than the cage bars of the pile cage 14.

The test pipes 36, 40 are mounted to the frame(s) of the pile cage 14 by way of respective stirrups 46. The stirrups 46 are sufficiently loose to permit longitudinal movement of the test pipes 36, 40 relative to the remainder of the pile cage 14.

During construction of the pile the first pile cage 12 is lifted into a substantially vertical orientation with the flared ends 26 uppermost, and lowered into the pile is hole. The pile cage 12 is suspended with the top of the cage bars 32 and the tops of the test pipes 22, 24 projecting from the pile hole.

To join the test pipes 36 and 40 to the respective test pipes 22 and 24, the second pile cage 14 is raised above the first pile cage, with the test pipe 36 aligned with the test pipe 22 and the test pipe 40 aligned with the test pipe 24 (it is arranged that the first, second and third pile cages are manufactured alongside one another so that it can be ensured that all of the test pipes can be aligned). The second pile cage 14 is then lowered relative to the first pile cage 12 and the lower ends 44 of the test pipes 36 and 40 are guided into the flared ends 26 of the test pipes 22 and 24 respectively.

It will be understood that in a typical pile cage the test pipes 36 and 40 are approximately 8m long, of steel, with a diameter of around 60mm and a wall thickness of approximately 2mm. Each of the test pipes is therefore of significant weight, and if it is arranged that the lower ends 44 are a tight fit into the flared ends 26, a secure fitment can be obtained. Nevertheless, it is believed that most piling contractors will require additional security in the joint between the test pipes, and so a latching mechanism is provided, as shown in Fig.3.

In this embodiment, the latching mechanism comprises a first flange 50 mounted upon the flared end 26 of a first test pipe 22, 24, and a second flange 52 mounted upon the lower end 44 of a second test pipe 36, 40. A bolt 54 is mounted s between the flanges 50, 52 and a nut 56 can be tightened to secure the flanges 50, 52, and thereby the respective test pipes, together.

It will be apparent that the latching mechanism shown in Fig.3 is only one embodiment of the many types of latching mechanism which could be used, and alternative embodiments could use toggle clamps, over-centre latches, or the like.

In addition, one or both of the flanges 50,52 of Fig.3 could be open-ended, to facilitate ease of mounting of the bolt 54.

When the lower end of the respective test pipes 36 and 40 have been located is within the flared ends 26 of the test pipes 22, 24, the flared ends can be sealed by adhesive tape 60 as shown in Fig.3. The adhesive tape 60 can be added before or after the latching mechanism is actuated. The provision of the seal provided by the tape 60 is to ensure that concrete or other material cannot enter into the test pipe through the joint. In some embodiments the requirement for a seal will not be required as the connection between the test pipes is sufficiently tight to prevent the ingress of unwanted material, or alternatively the flared ends 26 could incorporate a sealing means for this purpose.

When the test pipes 22, 24 and 36, 40 have been joined, the pile cage 14 can be lowered so that the respective cage bars overlap and can be spliced in the desired manner. During this lowering movement the test pipes 22, 36 and 24, 40 remain substantially stationary, with the test pipes 36, 40 sliding relative to their stirrups 46.

Following the splicing operation, the assembly comprising the first and second pile cages 12, 14 can be lowered together into the pile hole, and suspended with the upper end of the pile cage 14 projecting from the pile hole. The operator can then join the lower ends 62 of the test pipes 64, 66 of the third pile cage 16 to the flared upper ends 42 of the test pipes 36, 40 respectively, in the same way as described above. It will be understood that the test pipes 64, 66 do not need initially to project beyond the cage bars of the third pile cage 16 by too large a distance as the test pipes 36, 40 will have been pushed out of the top of the second pile cage 14 sufficiently to ensure that the test pipes will engage before the cage bars of the pile cages 14 and 16 overlap.

The test pipes 64 and 66 are also mounted by stirrups 70 which allow the required longitudinal movement to permit the cage bars to overlap and be spliced after the test pipes have been joined.

Following the splicing of the third pile cage the assembled set of pile cages is lowered into the pile hole and the concrete is poured. When the concrete has set the protective cap 72 is removed from each of the test pipes, and the testing instrument inserted to undertake the test. After completion of the test the testing instrument is removed and the test pipe can be filled with grout or other cementitious material.

In an alternative embodiment it would be possible to form a lip or rim around the open end of the flared part of the test pipe, the rim being formed during the flaring operation. The provision of a rim can avoid the requirement for a flange 50, and a toggle or over-centre latch mechanism can be provided on the lower end of the upper test pipe which can engage the rim of the flared end of the lower test pipe.

Because the rim would surround the open end there would be no requirement to align the two test pipes and the latch mechanism could be actuated regardless of the relative rotational orientation of the upper and lower test pipes.

Claims

1. A pile cage having a test pipe, the test pipe having a flared end for receiving an end of another test pipe, the test pipe also having a part of a latch mechanism by which the test pipes can be secured together, the flared end enabling a push-fit connection of the respective test pipes.

2. The pile cage according to Claim 1 in which the test pipes have internal guides. 1 0

3. The pile cage according to Claim 1 or Claim 2 in which the latch mechanism is a toggle clamp.

4. The pile cage according to Claim 1 or Claim 2 in which the latch mechanism is a nut and bolt connection.

5. A pile cage assembly constructed from a first pile cage according to any one of Claims 1-5 and a second pile cage, the test pipe of the first pile cage being a first test pipe, the second pile cage having a second test pipe, an end of the second test pipe being receivable within the flared end of the first test pipe, the first and second test pipes having respective parts of a latch mechanism whereby the first and second test pipes can be secured together.

6. The pile cage assembly according to Claim 5 in which the first pile cage is arranged below the second pile cage.

7. The pile cage assembly according to Claim 5 in which the second test pipe is mounted to be moveable longitudinally relative to the second pile cage.

8. The pile cage assembly according to Claim 7 in which the second test pipe is mounted in at least one stirrup connected to the second pile cage.

9. The pile cage assembly according to Claim 8 in which the second test pipe has a flared end for receiving an end of a third test pipe, and in which the cross-sectional dimension of the stirrup is smaller than the cross-sectional dimension of the flared end of the second test pipe.

10. A method of assembling a first pile cage and a second pile cage, comprising the steps of: {i} constructing a first pile cage with a first test pipe, the first test pipe having a flared end, the first test pipe also having a part of a latch mechanism; {ii} constructing a second pile cage with a second test pipe, the second test pipe having another part of the latch mechanism; {iii} lowering the first pile cage into a pile hole, and locating the first pile cage with its upper end projecting from the pile hole; is {iv} positioning the second pile cage above the first pile cage with the second test pipe aligned with the first test pipe; {v} lowering the second pile cage relative to the first pile cage so that the end of the second test pipe enters the flared end of the first test pipe; and {vi} actuating the latch mechanism to secure the first and second test pipes together.

11. The method according to Claim 10 in which the joint between the first test pipe and the second test pipe is sealed before or after step vi.

12. A pile cage constructed and arranged substantially as described in relation to Figs. 1-3 of the accompanying drawings.