WO2012168729A2

WO2012168729A2 - Lining segment

Info

Publication number: WO2012168729A2
Application number: PCT/GB2012/051299
Authority: WO
Inventors: Iain Hogg; Stephen HOGG
Original assignee: Macrete Ireland Limited
Priority date: 2011-06-09
Filing date: 2012-06-08
Publication date: 2012-12-13
Also published as: GB201210113D0; GB201109633D0; GB2491714B; WO2012168729A3; GB2491714A

Abstract

The present invention relates to pre-cast lining segments particularly, but not exclusively, for use in segmental shaft construction. In accordance with the invention a pre-cast lining segment comprises a first surface, a second surface, and a number of side surfaces thereinbetween, a circumferential gasket groove around the side surfaces and intermediate the first and second surfaces and at least a first bolting hole extending from an entry hole in the first surface to an exit hole in a side surface, and at least a second bolting hole extending from an entry hole in the second surface to an exit hole in the side surface.

Description

Lining Segment

The present invention relates to a pre-cast lining segment, particularly but not exclusively for use in segmental shaft construction.

Segmental shaft construction offers a cost effective, efficient and safe method for creation of below-ground chambers, from as low as lm in diameter, to up to 25m in diameter or beyond. Typical uses are in the formation of storage tanks and pumping stations from around 4m deep to 40m deep, typically for foul water and/or sewage. Such shafts are generally created directly from ground level, for shaft depths of up to 30m. There are two main methods of this type of shaft construction. In the 'caisson' method, where the ground is soft or weak, such that the ground is generally incapable of supporting itself or otherwise standing up on its own, a shaft can be constructed by creating a cutting edge at ground level, and building rings of segmental linings on top of the cutting edge, such that the shaft is then pushed down from the surface as the underground material is excavated from inside the shaft. As the shaft is gradually pushed down, new segmental rings are added to the top of the shaft, usually every time the shaft sinks by a certain depth such as lm. In this way, each ring of the shaft is built at or near ground level, so that the abutting lining segments can be bolted together for securement from the "extrados" or back surfaces of the lining segments. Bolting from the extrados is generally preferred as it does not require users to be inside the shaft, removing the risk of a fall.

The second method of construction is generally termed the 'underpinning' method. Where the ground cannot be 'cut' and the shaft gradually pushed down, a ground level shaft ring or rings is first formed, followed by excavated the area below the shaft from inside the bottom of the shaft. New shaft rings are then added below the existing shaft rings in the excavated area. Thus, there is typically never more than one meter of ground opened, and the segmental rings are built sequentially below one another, with the annulus between their outside perimeter and the excavated ground is immediately grounded.

The underpinning method is common where cutting through the ground by a cutting edge is not possible. More typically, the sinking of a shaft is commenced by the caisson method, and when the cutting edge hits rock, the shaft is continued by the underpinning method.

In the underpinning method, as each new shaft ring is created by the location of the lining segments below the previously built ring, their bolting together once in position is only possible from the "intrados" or front surface of the segments. Shaft lining segments are generally bolted together by the use of large curved bolts which extend in an arcuate manner from an extrados or intrados entry hole at each end of each lining segment, to a corresponding extrados or intrados hole on the neighbouring lining segment. Shaft lining segments include a circumferential gasket between the extrados and intrados, to surround each individual lining segment and form a barrier between the segments to prevent liquid (water) getting either out of the shaft or into the shaft through the abutting segments. Conventionally, to maintain the liquid barrier, the bolting holes are never allowed to extend across or through the plane of the gaskets, otherwise liquid would simply bypass the gasket by going through the bolting holes. Thus, to make it easier for the manufacturer of the segments to locate the intermediate gasket location beyond the path of the bolting holes, where lining segments are to be bolted from the extrados, only extrados bolting holes are formed in the pre-cast process; and where the lining segments are to be bolted from the intrados, only intrados bolting holes are formed. Thus, the water barrier is maintained whether the lining segment has extrados bolting holes or intrados bolting holes. However, the manufacturer of lining segments is also limited by this consideration. Where a shaft constructor requires both intrados and extrados bolt connections, two different pre-cast constructions are required from the manufacturer.

An example of a lining segment having intrados bolting holes only is disclosed in JP 2002-030892A. JP 2002-030892A teaches the use of a second gasket when the bolting holes extend through the plane of a first gasket. Alternatively, JP 2002- 030892A also teaches the use of a wide belt-like gasket which significantly overlaps the bolt exit holes through which the bolts extend in use. The use of a second gasket or a wide belt-like gasket introduces significant additional cost to the expense of producing such a lining segment.

It is therefore an object of the present invention to provide a lining segment not so limited and which overcomes the disadvantages of the prior art.

Thus, according to one aspect of the present invention, there is provided a pre-cast lining segment comprising a first surface, a second surface, and a number of side surfaces thereinbetween, a circumferential gasket groove around the side surfaces and intermediate the first and second surfaces, and at least a first bolting hole extending from an entry hole in the first surface to an exit hole in a side surface, and at least a second bolting hole extending from an entry hole in the second surface to an exit hole in the side surface.

In this way, there is formed a 'universal' lining segment, able to be bolted to another lining segment from either the first surface, or the second surface, or both. In this way, only one casting is required to form such a lining segment for use both in the caisson method and the underpinning method. According to an embodiment of the present invention, there is provided a pre-cast lining segment comprising a first surface, a second surface, and a number of side surfaces thereinbetween, a circumferential gasket groove around the side surfaces and intermediate the first and second surfaces, and at least a first bolting hole extending from an entry hole in the first surface to an exit hole in a side surface, and at least a second bolting hole extending from an entry hole in the second surface to an exit hole in the side surface, wherein at least one bolting hole extends through the plane of the gasket groove, and the exit hole for said bolting hole includes a seal seating.

Where either or both of the at least first bolting hole or the at least second bolting hole extend(s) beyond the plane of the gasket groove, suitable seals can be located at either or both exit holes of the bolting holes on the relevant side surface. In this way, the liquid barrier effect of the lining segment is maintained by the use of the additional seal in the seal seating of the bolting hole extending through the gasket plane.

Pre-cast lining segments are known in the art, and are generally formed of a castable material such as concrete. Such lining segments can be of any size, shape and dimension, whilst having first and second surfaces, with a number of side surfaces thereinbetween. Typically lining segments are elongate, and can extend from under lm long to being <lm, <2m, <3m, etc long. Other typical dimensions of lining segments, including thickness are not limited by the present invention, and are those expected in the art for the nature of the construction, generally a shaft, being formed by the lining segments.

Ring-shafts can be relatively small in diameter, going up to much larger diameter shafts having inner diameters of 20-30m or more. Lining segments for such rings are formed to withstand the required forces. Square or rectangular lining segments are included in the present invention. Generally, shaft lining segments are arcuate having a degree of curvature to form a circular pattern or ring, once the lining segments are located and abutted together.

The first and second surfaces of the lining segment may be different, similar or complementary. Where the lining segment is arcuate, one surface can be designated as the back or top or outer surface, generally known as the extrados, whilst the other surface may be the front or inner or bottom surface, generally known as the intrados. The gasket groove of the lining segment is generally formed along each side of the lining segment between the first and second surfaces in order to locate a suitable gasket therein or thereto prior to the fitting of the segment. The term 'groove' may include any line or marking intended to be the location of the gasket. Gaskets are well known in the art. They can include various types of rubber, such as, but not limited to EPDM rubber, which is compressed between each lining segment once located and abutting. Hydrophilic rubber may also be used. Hydrophilic rubber is designed to expand when in contact with water, so as to form a barrier between each lining segment once located and abutting. In any case, gaskets achieve the purpose of preventing liquid, either from inside the shaft or outside the shaft, from passing through the walls of the shaft.

The form, design and nature of bolting holes in lining segments is also know in the art. Generally, near each end of a lining segment, one or two holes are created from an 'entry hole', usually with an initial cut or opening in the segment wall for the accommodation of the fastenings, generally being one or more nuts, within the overall shape of the lining segment. Once two lining segments are abutting in position, a curved bolt can be passed through to an aligned bolting hole in the end of the next lining segment, and the bolt fastened at each end so as to secure the two lining segments together. The seal for location in the seal seating around the or each relevant exit hole located in the side of the lining segment of the present invention may be any suitable size, shape and design, typically being formed of a rubber or water-resistant plastic. Whilst bolting holes are often circular in cross section, the seal is not limited thereto. Generally, the seal may be in the form of a ring, such as a toroidal ring, usually of circular cross-section, such as an 0-ring.

The ability to provide only one casting for such a lining segment reduces the manufacturing time, effort and cost to provide a lining segment that is suitable for use by the shaft constructer independently of the nature of the method of shaft construction, thereby reducing the overall shaft construction manufacture and cost.

The use of the present invention allows the segment manufacturer to form bolting holes which can extend across the plane of the gasket groove irrespective of the thickness of the lining segment, and the location of the plane of the gasket groove.

Ideally, lining segments in accordance with the present invention comprise two bolting holes from the extrados proximate each end, and two bolting holes from the intrados proximate each end,

According to a second aspect of the present invention, there is provided a method of manufacturing a pre-cast lining segment as herein defined, comprising the steps of:

(i) casting a lining segment having first and second surfaces, a number of side surfaces, and a circumferential groove around the side surfaces and intermediate the first and second surfaces; and

(ii) forming separately or integrally with step (i) at least one bolting hole extending from at an entry hole in the first surface to a side surface, and at least a second bolting hole extending from an entry hole in the second surface to an exit hole in the side surface; and optionally (iii) providing a seal in the seal seating around the exit hole of at least one of said bolting holes. Embodiments of the second aspect of the present invention may comprise one or more features of the first aspect of the present invention.

The present invention also extends to a shaft constructed from a plurality of lining segments as defined herein.

Embodiments of the present invention will now be described by way of example only, and with reference to the accompanying drawings in which:

Figure 1 is a schematic side view of a stage in a typical caisson method of shaft construction:

Figure 2 is a schematic side view of a stage in a typical underpinning method of shaft construction; Figure 3 is a cross-sectional planar view of the ends of two lining segments showing extrados bolting holes according to one embodiment of the present invention;

Figure 4 is a detailed view of the interface between the lining segments of Figure 3; Figure 5 is a cross-sectional view of two lining segments showing intrados bolting holes;

Figure 6 is a detailed view of the interface between the lining segments of Figure 5; Figure 7 is a plan view of a lining segment according to another embodiment of the present invention showing both extrados and intrados bolting holes; Figures 8a and 8b are perspective views showing opposing ends of a lining segment of Figure 7; and Figure 9 is a schematic plan view of an embodiment of an exemplary lining segment in accordance with the invention.

Referring to the drawings, Figure 1 shows a stage in a typical caisson method of shaft construction. Above a steel cutting edge 2 are a series of rings 4, each ring being formed of a set of pre-cast lining segments 6. As the cutting edge 2 is driven into the soft ground, a new ring 4 is added at the top of the shaft until the final shaft depth is reached.

Each new ring 4 is formed from a series of lining segments 6. As the lining segments 6 are located and abutted at ground level, they can be secured together safely through a series of extrados bolting holes, thereby preventing the need for any person to enter the shaft.

Figure 2 shows a stage in a typical underpinning method of shaft construction. Two initial rings 8 of pre-cast lining segments 10 are formed. Material below the lowermost ring 8 is cut out and excavated through the shaft, until the excavated area is big enough to locate another set of segmental linings 12 below the existing rings 8, and the process repeated until the shaft reaches its intended depth. As the new lining segments 12 are located and abutted from within the shaft, the lining segments 12 can only be bolted together by the use of intrados bolting holes.

As mentioned above, the sinking of a shaft is typically commenced by the caisson method, and when the cutting edge hits rock, the shaft is continued by the underpinning method. However, this requires the manufacture and supply of two different lining segments, one with extrados bolting holes and one with intrados bolting holes.

Figure 3 shows abutting end surfaces 18 of two pre-cast lining segments 20 according to an embodiment of the present invention. For clarity, only the bolting holes on the extrados are shown. Each lining segment 20 comprises a first surface 22 and a second surface 24. As each lining segment 20 is arcuate, the first surface 22 is an extrados, and the second surface 24 is an intrados. The two end surfaces 18 of the lining segments 20 provide one side surface of the lining segments 20 between the first and second surfaces 22, 24.

In Figure 4, which is a detailed view of the interface between the lining segments of Figure 3, a circumferential gasket groove 25 is created around the side surfaces and intermediate the first and second surfaces 22, 24 for the location of a gasket 26 therein. (A circumferential gasket groove, indicated by reference numeral 74, is shown more clearly shown in Figures 7, 8a and 8b). Gaskets 26 achieve the purpose of preventing liquid, either from inside the shaft or outside the shaft, from passing through the walls of the shaft. The gasket 26 can be formed from a suitable material such as rubber, for example, but not limited to, EPDM rubber, which is compressed between adjacent lining segments 20 once located and abutting. Other types of rubber, such as hydrophilic rubber may be used whereby the hydrophilic rubber expands when in contact with water, so as to create a seal between each of the lining segments 20 and form a complete liquid barrier between the inside and outside of the shaft once formed.

Near the end of each lining segment 20 in Figure 3, there is a bolting hole 28 extending from an entry hole 30 in the first surface 22, to an exit hole 32 in the side surface 18. Figure 3 shows the plane 34 of the gasket groove 25 created by its extension around the side surfaces of the lining segment 20. Conventionally, any bolting holes were not allowed to extend across or through this plane 34, as this would then provide a liquid pathway across the gasket barrier negating the barrier effect.

Figures 3 and 4 show the present invention providing the bolting holes 28 extending through the plane 34 of the gasket groove 25 (Figure 4), and hence also the plane of the gasket 26. This is possible with the addition of a seal 36 in a seal seating 38 (Figure 4) present at the exit hole 32 of one of the bolting holes 28. The seal 36, in the form of an O-ring, prevents the passage of a liquid, generally water, passing between the end surfaces 18 from inside the shaft, along the boltholes 28, and to outside (or vice versa). The general liquid barrier intended for the shaft is therefore maintained, whilst allowing for the extrados bolting holes 28 to extend through the plane 34 of the gaskets 26.

In this way, the manufacturer of the lining segments 20 no longer needs to particularly consider the location of the plane of the gasket groove to ensure that any extrados bolting holes do not extend through the plane of the gasket groove. This is particularly useful for thinner lining segments, and/or lining segments being able to have both extrados and intrados bolting holes as described hereinafter. Figure 5 shows two pre-cast lining segments 40 having an extrados 42 and an intrados 44, and abutting end side surfaces 46. For clarity, only the bolting holes on the extrados are shown. Figure 6 is a detailed view of the interface between the lining segments of Figure 5. A gasket 48 is located in a gasket groove 50 (Figure 6). An intrados bolting hole 52 is formed in each lining segment 40 from an entry hole 54 in the intrados 44 to an exit hole 56 (Figure 6) in each side surface 46, for the passage of a curved bolt 58, to be secured at each end by nuts 60 to hold to the lining segments 40 together securely.

Figure 7 shows a combination of the extrados and intrados bolting holes of Figures 3-6 in a single lining segment 66 according the present invention. Figure 7 shows the lining segment 66 having a first extrados surface 68 and second intrados surface 70, and a top and two side surfaces 72 thereinbetween. A circumferential gasket groove 74 is created around the side surfaces 72 and intermediate the first and second surfaces 68, 70. The lining segment 66 has two extrados bolting holes 76 at each end, located above one another such that only one is seen at each end in Figure 7. Similarly, the lining segment 66 has two intrados bolting holes 78 at each end located above one another such that only one is seen at each end in Figure 7. (Both intrados bolting holes 78 at each end are visible in Figures 8a and 8b).

The extrados bolting holes 76 extend through the plane 80 of the gasket groove 74 as discussed above in relation to Figures 3 and 4.

Figures 8a and 8b show the intrados entry holes 78 in a lining segment 66, and the intrados exit holes 82. Figures 8a and 8b also show the extrados bolting hole exit holes 84a and 84b. Only one of these exit holes 84b at each of the respective ends 72 of the segment requires a seal seating 86 for receiving a seal such as an O-ring, as each lining segment 66 will abut a similar lining segment 66. It will be appreciated that where the thickness of the thickness of the lining segment allows, bolting holes formed in the respective first and second surfaces and extending to exit holes on side surfaces need not extend through the plane 34, 80 of the gasket groove 25, 74 and hence need not extend through the plane of a gasket. In such an arrangement, as shown byway of example in Figure 9, there is no requirement for a seal, such as an O-ring, around the exit holes on the side surfaces, as the passage of liquid from the intrados to the extrados is barred by the gasket in use;

In Figure 9, an exemplary lining segment 90 in accordance with an embodiment of the present invention is shown having a first (extrados) surface 91 and a second (intrados) surface 92 and side surfaces 93. A circumferential gasket groove 94 is created around the side surfaces 93 and intermediate the first and second surfaces 91, 92 for the location of a gasket (not shown] therein. Bolting holes 96 extend from entry holes 97a in the extrados surface 91, to respective exit holes 97b in the side surfaces 93. Bolting holes 98 extend from entry holes 99a in the intrados surface 92, to respective exit holes 99b in the side surfaces 93. The lining segment 90 has two extrados bolting holes 96 at each end, located above one another such that only one is seen at each end in Figure 9. Similarly, the lining segment 90 has two intrados bolting holes 98 at each end, located above one another such that only one is seen at each end in Figure 9. None of the bolting holes 96, 98 extend through the plane 95 of the gasket groove 94 thus there is no requirement for seals such as o-rings around any of the exit holes 97b, 99b as the liquid barrier between the intrados to the extrados is maintained by the gasket located in use within gasket grove 94.

The present invention provides a single lining segment able to be formed with both intrados and extrados bolting holes, ready for use by a shaft constructor in either or both of the caisson or underpinning methods. Thus, two different lining segment manufacturing processes are no longer needed to provide the shaft constructor with different lining segments according to the shaft construction method being used. In particular, the present invention allows at least one of the bolting holes to extend through the plane of the gasket groove, and thus the gasket once fitted, to maintain the liquid barrier effect of the shaft despite passing through said plane.

Claims

1. A pre-cast lining segment comprising a first surface, a second surface, and a number of side surfaces thereinbetween, a circumferential gasket groove around the side surfaces and intermediate the first and second surfaces and at least a first bolting hole extending from an entry hole in the first surface to an exit hole in a side surface, and at least a second bolting hole extending from an entry hole in the second surface to an exit hole in the side surface.

2. A lining segment a claimed in Claim 1, wherein the first surface is an extrados and the second surface is an intrados.

3. A lining segment a claimed in Claim 1 or Claim 2, wherein the lining segment is arcuate.

4. A lining segment as claimed in any preceding claim, wherein at least one bolting hole extends through the plane of the gasket groove.

5 A lining segment as claimed in Claim 4, wherein the at least one bolting hole extends from the extrados to a side surface.

6. A lining segment as claimed in Claim 4 wherein the at least one bolting hole extends from the intrados to a side surface.

7. A lining segment as claimed in any one of claims 4 to 6, wherein the exit hole for said bolting hole includes a seal seating.

8. A lining segment as claimed in any one of the preceding claims comprising two bolting holes from the extrados at each end, and two bolting holes from the intrados at each end.

9. A lining segment as claimed in any one claims 7 or 8, including a seal in one or more of the seal seatings.

10. A lining segment as claimed in claim 9 wherein the or each seal is an 0-ring.

11. A lining segment as claimed in any one of the preceding claims including a gasket in the gasket groove.

12. A method of manufacturing a pre-cast lining segment as defined in any one of claims 1 to 11 comprising the steps of:

(ii) forming separately or integrally with step (i) at least one bolting hole extending from an entry hole in the first surface to a side surface, and at least a second bolting hole extending from an entry hole in the second surface to the side surface.

13. A method of manufacturing a pre-cast lining segment as claimed n claim 12, comprising the further step of:

(iii) providing a seal in the seal seating around the exit hole of at least one of said bolting holes.

14. A shaft constructed from a plurality of lining segments as defined in any one of claims 1-11.