GB2055413A

GB2055413A - Tunnel segments

Info

Publication number: GB2055413A
Application number: GB8017728A
Authority: GB
Original assignee: FAIRCLOUGH CONSTRUCTION GROUP Ltd
Current assignee: FAIRCLOUGH CONSTRUCTION GROUP Ltd
Priority date: 1979-06-12
Filing date: 1980-05-30
Publication date: 1981-03-04
Also published as: GB2055413B

Abstract

An annulus for a tunnel lining is formed of concrete segments connected and urged together by mechanical members in recesses accessible from inside the annulus. The mechanical members may comprise bolts, flexible couplers or the recesses may contain upstanding stem members entering a recess of an adjacent segment and engaging a slotted plate urging the segments together.

Description

SPECIFICATION Tunnel segments This invention relates to a method of connecting together concrete segments to form a lining for a tunnel.

Such tunnel linings are generally formed of concrete segments which are joined together in the tunnel to form annuli, the successive annuli being placed side-by-side to form a continuous tunnel lining. Linings of this kind are described in British Patents 1,446,202 and 1,527,555.

The present invention is intended to provide a method of connecting concrete tunnel segments which is easily carried out entirely from within the tunnel and is capable of providing strong, positive mechanical joints between adjacent segments. Such a method should be simple and flexible in use and enable annuli to be assembled from a small number of segments, preferably identical, thus reducing the number of joints and the complexity of assembly from within a tunnel.

According to one aspect of the invention, adjacent segments of a tunnel lining are connected and urged together by mechanical members engaged in recesses in the segments accessible from the interior of a tunnel formed of the segments.

In one arrangement according to the invention the mechanical members include a screw-threaded bolt inserted through the recess and screwed into either a nut or into a sleeve mounted in an adjacent segment to clamp the segments together. Preferably, the head of the nut abuts a metal plate through which it passes, the plate being flush with the edge of the segment. This arrangement provides a strong positive connection between the segments which resists any bending movement which would deform the assembled annulus. Preferably the plate is welded to reinforcing bars which are cast into the segment to prevent displacement of the plate.

In another arrangement, when the segments contain reinforcing bars extending from one edge of a segment to the opposite edge the bars have screwthreaded ends in recesses at the edges of the segments and the bar ends of adjacent segments are connected by mechanical couples which are preferably flexible. This embodiment is especially useful when the tunnel has to resist internal pressure or water hammer as the bars and couplers provide a complete reinforcing ring in the concrete.

In yet another arrangement both adjacent segments have corresponding recesses from which extend flanged stems, preferably of mushroom shape, with the flanges positioned in a deeper part of the recess in the opposite segment, and a slotted plate is driven into the space formed by the two recesses to engage the flanges and thus urge the segment edges together. This arrangement gives a strong, moment-resistant joint and assembly is easy because a degree of play can be provided by making the flanges smaller than the recess portions of increased depth which they enter.

With all the above arrangements it is generally necessarv to complete the annulus by providing a key segment, which may be of a type known in the art. In another arrangement which can avoid the need for a key the edges of the adjacent segments have complementary steps forming an abutting surface at an angle to the radius of the annulus and a threaded bolt is passed through a hole in the step of one segment to engage a threaded sleeve in a hole in the step of the adjacent segment, the head of the bolt abutting against a plate within the segment. As the bolt is at an angle with the radius of the annulus a positive urging of the segments together is again obtained and the segment edges may be designed so that the annulus can be assembled entirely from identical segments without any key, the last segment being inserted from within the annulus.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure lisa view of the side of a segment forming part of a tunnel annulus, Figure 2 is a section along A-A of Figure 1 showing the manner of connection to an adjacent segment, Figure 3 is a section similar to Figure 2 showing an alternative connection using segments according to Figure 1, Figure 4 is a perspective view of a segment according to Figure 1, Figure 5 is a perspective view of a tunnel annulus comprising segments according to Figure 3, Figure 6 is a section of two adjacent segments connected according to another embodiment of the invention, Figure 7 is a section along B-B of Figure 6, Figure 8 is a section of a segment for which the connection of Figure 6 may be used, Figure 9 is a section of a segment side to be connected to an adjacent segment using another embodiment of the invention, Figure 10 is a section of a segment side to be connected to that of Figure 9, Figure 11 shows a connecting fork for use with the segments of Figures 9 and 10, Figure 12 is a view of the connecting fork perpendicularto Figure 11, Figure 13 is a section of segment sides to be connected using another embodiment of the invention, and Figure 14 is a plan of two segments connected using the embodiment of Figure 13, perpendicular thereto, Figure 15 is a perspective view of a tunnel annulus comprising segments connected as shown in Figures 13 and 14, Figure 16 shows the dimensions of a segment according to the embodiment of Figure 13.

Referring to Figures 1 and 2, a segment 1 of a concrete tunnel lining forming part of an annulus of the lining is provided, on an edge intended to abut an edge of the adjacent segment, with an edge recess 2 accessible from the inside of the annulus.

The recess is provided with a steel plate 3 which is cast into the concrete and is flush with the side of the segment. The plate is provided with reinforcing bars 4 welded thereto and embedded in the concrete. A hole 5 in the plate allows passage of a screwed bolt 6 from the recess.

A segment of an adjoining annulus 7 is provided with a threaded socket 8 in its side abutting the segment 1 to receive the bolt: the socket may be of steel and cast into the segment 7. The socket and plate are positioned so that with both segments in their desired positions the bolt 6 can hold them together.

The inside edges such as 9 of the segments are relieved so that a continuous groove is formed when the segments are assembled together. This groove may be filled with caulking material after assembly to renderthe joint between the segments watertight.

Also after assembly the recess 2 may be filled with cement or other filling material to provide a smooth, continuous inner surface of the tunnel.

It is preferred that the segments 1 and 7 each have a recess 2 on one side and a socket 8 on the other side so that the tunnel may be built up of a number of identical segments connected together with an upper key' segment. A preferred type of segment is shown in Figure 4.

The embodiment shown in Figure 3 is similar to that of Figure 2 but in this case both segments 1 and 7 are provided with similar recesses 2 and plates 3.

When the segments are assembled together the bolt 6 passes through both plates and is provided with a nut 10. After tightening the nut the recesses may be filled as in the embodiment of Figure 2.

The manner in which a tunnel annulus may be assembled using the embodiment of Figure 3 is shown in Figure 5. In this case both the abutting sides of the segments of one annulus and the sides of the segments which abut an adjacent annulus are provided with corresponding recesses 2 and plates 3 so that an individual annulus is held together in the same manner as adjacent annuli are connected.

Asegment using the embodiment of Figures 1 and 2 is shown in Figure 4. Opposite sides of the segment each have a socket 8 and a recess 2 with plate 3, allowing the segment to be used either way round. In this case the segments are connected to form an annulus using the embodiment of Figure 3 and the annuli are connected using the embodiment of Figure 2.

It will be appreciated that in all the embodiments of Figures 1-5 the bolts andfor nuts used provide a positive clamping action whereby the adjacent segments of an annulus are urged together. Such positive mechanical joints give the annulus considerable strength and resistance to deformation. Connection of the segments together is easily carried out, even in a confined space within a tunnel, as the recesses within which the bolts and nuts are manouvred are at the edges of the segments and alignment of the apertures in the respective segment edges is easy.

A coupling according to another embodiment of the invention is shown in Figures 6 and 7. This coupling is especially suitable for use with segments containing a steel reinforcing bar, as shown in Figure 8. The segment 11 is cast containing a bar 12 with screw-threaded ends 13 contained in recesses 14 accessible from the inside of the tunnel. When adjacent segments 11 are assembled together the opposed threaded ends 13 of the bars are connected by means of a flexible coupler. Once the annulus has been assembled the coupler and sleeves 17 are tightened on the ends 13 to clamp the adjacent segments together. As in the preceding embodiments caulking material may be applied to render the joint watertight and the recesses may be filled with concrete or other filling material.

The coupler may be of a type which is known in the art. Couplers of the type described in British Patent Specification 1517800 may be used. However it is preferred that the screw members which engage the bar ends are connected by wire rope instead of a rigid barto provide a flexible coupling assembly.

This embodiment is especially useful when the tunnel is to contain liquid which is subject to excessive pressure or water hammer: the bar in each annuli forms a continuous ring which resists internal pressure whereas the concrete of the segments is resistant to external pressure. If required the segments can contain more than one bar, thus forming more than one reinforcing ring. If desired the segments can contain such reinforcing bars running in the longitudinal direction of the tunnel, the successive annuli being connected to each other in the same manner.

Yet another type of joint which may be used for joining adjacent segments of an annulus as well as connecting adjacent annuli is shown in Figures 9,10, 11 and 12. In this case abutting sides of adjacent segments are each provided with a recess 18 extending from the interior surface of the segment and having a portion of greater depth 19. Each segment is also provided with a mushroom member 20 for example of steel having a stem cast into the concrete of the segment. The recesses and mushrooms are arranged such that the head of the mushroom of one segment fits into the recess portion 19 of an abutting segment, the stems ofthe mushrooms overlapping and being in line along a radius of the tunnel.

When the adjacent segments are assembled together in this manner a fork 21, shown in Figures 11 and 12, may be hammered into the recess 18 from the inside of the tunnel. The fork will engage the under-sides of both mushroom heads, thus clamping the segments together.

In order to fix the fork in place the bottom of recess 18 of at least one segment is provided with plate 22 cast into the concrete providing an upstanding edge 23. The angle of plate 22 is such as to tension the fork 21 thus drawing the segments together. The fork may be provided with a corresponding notch 24 on its surface which becomes engaged on to edge 23 when the fork is inserted, preventing removal of the fork. The notch 24 may be provided on both faces of the fork so that the fork may be used either way round.

The mushroom members 20, plates 23 and fork 21 should be of a material having a high tensile strength such as steel. In this embodiment, once the fork is hammered in there is no large recess left on the inside of the tunnel so that no filling will be required to produce a reasonably smooth tunnel surface.

Each segment side may be provided with two recesses and mushrooms, one being the inverse of the other as is the case with the plates and sockets of the segment of Figure 4, so that a segment may be used either way round.

In the arrangement of Figures 13 and 14 adjacent segments 25 and 26 are formed with respective steps 27 and 28 which interlock when the segments are assembled together. Step 27 is provided with a recess 29 and the segment has a plate 30 cast into the concrete covering the inside face of recess 29.

The plate has a hole 31 to receive bolt 32. Segment 26 is provided with a corresponding hole 33 containing an internally threaded sleeve 34 cast therein. The plate 30 has reinforcement bars 35 added to the top edge to secure the plate 30 within segment 25.

When the segments are assembled together, step 27 being inside the tunnel, they are held together by bolt 32 passing through hole 31 and being screwed into sleeve 34. Hole 33 may continue through the segment to prevent the threaded sleeve 34 becoming blocked.

Step 27 and segment 26 are provided with edge recesses 36 and 37 to form a gap which may be filled with caulking material.

Each segment may be provided with a step 27 on one side and a step 28 on the other so that a tunnel may be completely assembled from identical segments.

In this embodiment it is preferred to use bolts having a relatively "fast thread", such as about 1 turn per centimeter length of the bolt. The use of such a thread makes insertion and tightening of the bolts easier and the clamping action of the bolts urging the segments together is still sufficient to provide a strong, deformation-resistant joint.

The embodiment of Figures 13-15 has the advantage that the recesses on the inside of the annulus are small and very little filling is required subse quentlyto provide a smooth inner surface of the tunnel.

This embodiment also has the advantage that when the steps 27 and 28 have the appropriate dimensions, the complete annulus can be built up from the inside using identical segments and no key is required to complete the annulus. This feature is important in simplifying construction of an annulus.

Suitable dimensions for this purpose are shown in Figure 16 of the drawings.

Claims

1. A method of joining together adjacent concrete segments to form an annulus for a tunnel lining, in which abutting edges of the adjacent segments are connected and urged together by mechanical members inserted in recesses in the segments accessible from the interior of the annulus.

2. A method according to claim 1, in which said mechanical member comprises a screw-threaded bolt clamping the adjacent segments together.

3. A method according to claim 2, in which the bolt passes through and engages a hole in a metal plate mounted in and substantially flush wth an edge of one of the segments, the plate defining a wall of the recess.

4. A method according to claim 3, in which the bolt is screwed into an internally threaded sleeve positioned in a hole in the edge of the adjacent segment.

5. A method accordng to claim 3, in which the bolt passes through a metal plate mounted in and substantially flush with an edge of the adjacent segment, the plate defining a wall of a recess in the adjacent segment, and the bolt is screwed into a nut to clamp the plates of the respective segments together.

6. A method according to claim 3,4 or 5 in which the plate is attached to reinforcing bars cast into the segment.

7. A method according to claim 1, in which the segments contain reinforcing bars extending from an edge of the segment to the opposite edge, the bars having screw-threaded ends positioned in recesses at the edges, and the bar ends of adjacent segments are connected to each other by screwthreaded couplers.

8. A method according to claim 7, in which the couplers comprise screw-threaded members engaging the ends of the bars connected by wire rope.

9. A method according to claim 1, in which the abutting edges are provided with respective opposite recesses, each recess including a portion of increased depth and being provided with an upstanding stem member projecting from the recess into the portion of increased depth of the opposite recess, the upstanding stem members of both recesses being provided with flanged ends, and a slotted plate is inserted from inside the annulus into the space formed by the two recesses with both stem members in the slot so that the flanges of both stem members are clamped against the plate to urge the segments together.

10. A method according to claim 9, in which at least one of the recesses is provided with a portion of reduced depth defining an upstanding edge engaging the slotted member when the latter is inserted.

11. A method according to claim 10, in which the slotted member has a notch on at least one side thereof to engage the upstanding edge.

12. A method according to claim 11, in which the slotted member has a notch on both sides thereof.

13. A method according to any preceding claim, in which opposite edges of a segment are identical so that the segment is reversible.

14. A method according to claim 1, in which the edges of the adjacent segments have complementary steps forming an abutting surface at an angle to the radius of the annulus and a threaded bolt is passed through a hole in the step of one segment to engage a threaded sleeve in a hole in the step of the adjacent segment, the bolt being inserted through a recess in the step of said one segment and the head of the bolt abutting against a plate mounted within said one segment.

15. A method according to claim 14, in which the steps are of such dimensions that a complete annulus can be assembled from identical segments, the final segment of the annulus being mounted in place from within the annulus.

16. A method of joining together concrete seg ments to form a tunnel annulus, substantially as hereinbefore described with reference to the accom panying drawings.