Tunnel linings

Description

[0001] This invention relates to linings for tunnels which are built up of concrete segments, the segments being connected together edge-to-edge to form annuli and the end edges of the annuli being joined together to form a continuous lining for the tunnel. This invention is especially but not exclusively intended for use when assembling a tunnel lining having a smooth inner surface.

[0002] The invention is intended to provide a method of assembling a tunnel lining which is simple and easy to use when working in a confined space inside a tunnel, in which both the segments of an annulus and adjacent annuli are positively joined together so that the lining can resist internal hydrostatic pressure, and in which the assembled lining has a substantially smooth inner surface with no connecting elements extending radially inwardly of the lining.

[0003] An example of the prior art shown in GB-A-2,092,644 where arcuate concrete segments of a tunnel lining are joined together by means of a recess in a segment edge and a pair of abutment members projecting into the recess to define a constriction therein, the abutment member forming a pair of abutment surfaces facing inwardly of the constriction. A screw-threaded bolt is provided in an adjacent segment and when the segments are positioned edge-to-edge with the bolt inserted in the recess the segments can be moved relatively to each other so that the bolt head engages the abutment surfaces. The recess is accessible from inside the lining to allow the bolt head to be tightened.

[0004] NL-A-99,326 discloses a similar concept and in this case a U-channel type of insert is provided with inturned flanges in the concrete for joining the concrete segments.

[0005] According to one aspect of the present invention, there is provided a method of assembling a tunnel lining formed of concrete segments joined together at their side edges to form annuli and at their end edges to join the annuli together, the opposed side edges of adjoining segments of an annulus having interengaging joining means which are interengaged by sliding one segment relatively to the other in the longitudinal direction of the tunnel; said interengaging joining means comprising a recess in the side edge of one segment containing an insert comprising a channel member having two inturned flanges defining a slot in the side edge and the side edge of the adjoining segment being provided with a screw-threaded bolt screwable into the segment and projecting outwardly of the segment edge, and as one segment is slid in the longitudinal direction of the tunnel the bolt within said recess moves to a position between said flanges, the bolt having a head which abuts the inner surfaces of said flanges to clamp the segments together when the bolt is tightened by screwing into its segment, characterised in that said bolt has a portion located on its shank between the head and the screw-threaded portion, which portion is for receiving a spanner to screw the bolt into a screw-threaded socket in the adjoining segment, the bolt being dimensioned so that the bolt shank between said portion and said head passes through said slot defined by said flanges, whereas the head is wider than said slot.

[0006] It will be appreciated that the present invention allows the recess containing the insert to be comparatively shallow and to be provided partly in both of the adjoining segments.

[0007] According to a second aspect of the invention, there are provided tunnel lining concrete segments for joining together at their side edges to form an annulus, the intended opposed side edges of adjoining segments of the annulus having interengaging joining means which are interengaged by sliding one segment relatively to the other in the longitudinal direction of the tunnel; said interengaging joining means comprising a recess in the side edge of one segment containing an insert comprising a channel member having two inturned flanges defining a slot in the side edge and the side edge of the adjoining segment being provided with a screw-threaded bolt screwable into the segment and projecting outwardly of the segment edge, the bolt having a head which abuts the inner surfaces of said flanges to clamp the segments together when the bolt is tightened by screwing into its segment, characterised in that said bolt has a portion located on its shank between the head and the screw-threaded portion, which portion is for receiving a spanner to screw the bolt into a screw-threaded socket in the adjoining segment, the bolt being dimensioned so that the bolt shank between said portion and said head can pass through said slot defined by said flanges, whereas the head is wider than said slot.

[0008] The end edges of the segments of adjacent annuli can contain opposed sockets of substantially uniform cross-section, the sockets containing dowels having radially extending fins of resiliently deformable material of greater width than the sockets and extending into the opposed sockets so that after insertion of the dowels in the sockets of an annulus and sliding of a segment of an adjacent annulus in the longitudinal direction into abutment therewith the finned dowels retaining the segments of the adjacent annuli together.

[0009] The fins may be integral with the dowels and formed of a resilient plastics material. As they are inserted in the sockets the fins are deformed elastically so that they are inclined with their outer edges abutting the side of the socket to resist withdrawal of the dowel from the socket. As both ends of the dowel are engaged within opposed sockets of the adjacent segments, the finned dowels hold the segments (and thus the annuli formed of the segments) together.

[0010] The sockets are simple holes, generally but not necessarily of circular cross-section, formed in the segment edges. They may be formed when the segments are cast and do not generally require any lining element. The end edges of tunnel lining segments are commonly provided with such sockets for other reasons.

[0011] The interengaging joining means of the side edges of the segments may be of a type described in British Patent 2092644.

[0012] For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:

Figure 1 is an end view of an annulus for a tunnel lining,

Figure 2 is a cross-section of a tunnel lining made up of annuli according to Figure 1,

Figure 3 shows a recess formed in a side edge of a segment of an annulus of Figure 1,

Figure 4 is an edge view of the recess of Figure 3,

Figure 5 shows the side edge connecting means of the segments of the annulus of Figure 1,

Figure 6 shows an insert, and Figure 7 a bolt, used in the connecting means of Figure 5,

Figure 8 shows a dowel for connecting the end faces of segments of adjacent annuli, and

Figure 9 shows connection of segments of adjacent annuli using the dowel of Figure 8.

[0013] As shown in Figure 1, an annulus for a tunnel lining is made up of concrete arcuate segments 1, an invert segment 1A and a key segment 2 joined together side-by-side. Adjacent annuli are joined together side-by-side to form a continuous watertight concrete lining for a tunnel as shown in Figure 2.

[0014] The side edges of adjacent segments of an annulus are joined together by joints indicated generally as 3 and the annuli are joined together by joints 4. The side and end edges are orthogonal.

[0015] One of the side-to-side joints 3 is shown in Figures 3 to 7. The side edge of one of the adjoining segments is provided with a recess 5 which is elongate in the longitudinal direction of the tunnel lining. The recess is provided with a steel insert member 7 which comprises a generally U-shaped channel member 8 having a pair of inturned flanges 9 defining a slot capable of receiving the shank of a threaded bolt with a bolt head, of greater width than the slot, positioned within the channel member, so that on tightening of the bolt the bolt head may abut the rear surfaces 10 of the flanges. The base of the U-shaped channel member is welded to a stem 11 having an enlarged base 12. The channel member is cast into the recess, as shown in Figure 5, and is held firmly in place by the stem 11 and base 12. As shown in Figures 3 and 4, the channel member occupies the central part of the recess and the head of a bolt may be inserted in the recess at its ends which are not occupied by the channel member.

[0016] The side edge of the adjacent segment has a recess 13 opening into the tunnel lining interior and an internally screw-threaded steel socket 14 cast into the concrete. Socket 14 receives the end of a screw-threaded bolt 15 having a circular head 16 and a portion 17 which may be hexagonal to receive a spanner for screwing the bolt into the socket. The bolt is dimensioned so that the bolt shank between the hexagonal portion and the head may pass through the slot between flanges 9 whereas the head is wider than the slot.

[0017] When adjoining segments of an annulus are joined together the segments may be positioned edge-to-edge with the bolt head of one segment inserted in the end of a corresponding recess of the other segment. One segment may then be moved in the longitudinal direction of the tunnel lining so that bolt head 16 moves to within the insert 8, its shank being between flanges 9. The hexagonal part may then be rotated, using a spanner applied from the inside of the tunnel through recess 13, to screw the bolt into socket 14 and tighten head 16 against the rear flange surfaces, thus clamping the adjoining segments together. After assembly of the lining, the recesses may be filled with cement or other filling material to provide a smooth inner surface for the tunnel lining.

[0018] The joints 4 used for joining the end edges of the segments of adjacent annuli together are shown in Figure 9. The adjoining segment edges are provided with sockets 21 which may be simple holes of uniform circular cross-section formed in the segment edge on casting. The segments are held together by dowels, shown separately in Figure 8, comprising a cylindrical body 22 having tapering ends 23. Body 22 has radially projecting integral fins 24. The dowel is made of elastically deformable plastics material and the body has a diameter slightly less than the diameter of holes 21 but the fins have an external diameter greater than that of the hole. When the dowel is inserted in the hole the fins form an interference fit with the surrounding concrete and the fins are deformed on insertion to resist withdrawal of the dowel from the hole. Thus, when the segments are joined together as shown in Figure 9 the dowel holds them together.

[0019] When an annulus is assembled within a tunnel to be lined, the invert segment having recesses 5 on both its side edges is first located and the adjacent segments, having bolts on one side edge and recesses on the other, are then located with their bolt heads in the recesses of the invert segment and slid longitudinally into position so that their bolt heads are behind the flanges 9. The adjoining segments of the annulus are fitted in the same way and finally the key segment, opposite the invert segment is fitted to complete the annulus. The key segment has bolts on both of its side edges to engage the corresponding recesses in the adjacent segments.

[0020] Before assembling a segment in this way, the sockets 4 of the segments of the preceding annulus are fitted with finned dowels 22, extending into and outwardly of the sockets. The dowels are tapered at their ends to facilitate alignment with the sockets and the distance by which they are inserted, generally by tapping with a hammer, is not critical provided that the fins engage the wall of the socket. Invert segment 1A of the annulus is then located adjacent the invert segment of the preceding annulus, and applied to the dowels extending from the preceding annulus as shown in Figure 8. The adjacent segments are then located at a forward axial position with their bolts 15 extending into the sockets of the invert segment, and slid longitudinally towards the preceding segment so that the bolts move to between flanges 9 and their sockets engage the dowels extending from the preceding annulus.

[0021] The whole annulus is assembled in this way, and after tightening of bolts 15 the recesses 13 may be filled with cement.

Claims

1. A method of assembling a tunnel lining formed of concrete segments (1) joined together at their side edges to form annuli and at their end edges to join the annuli together, the opposed side edges of adjoining segments of an annulus having interengaging joining means (3, 8-17) which are interengaged by sliding one segment relatively to the other in the longitudinal direction of the tunnel; said interengaging joining means comprising a recess (5) in the side edge of one segment containing an insert comprising a channel member (8) having two inturned flanges (9) defining a slot in the side edge and the side edge of the adjoining segment being provided with a screw-threaded bolt (15) screwable into the segment and projecting outwardly of the segment edge, and as one segment is slid in the longitudinal direction of the tunnel the bolt within said recess moves to a position between said flanges, the bolt having a head (16) which abuts the inner surfaces (10) of said flanges (9) to clamp the segments together when the bolt is tightened by screwing into its segment, characterised in that said bolt has a portion (17) located on its shank between the head (16) and the screw-threaded portion (15), which portion (17) is for receiving a spanner to screw the bolt into a screw-threaded socket (14) in the adjoining segment, the bolt being dimensioned so that the bolt shank between said portion (17) and said head (16) passes through said slot defined by said flanges (9), whereas the head (16) is wider than said slot.

2. A method according to claim 1, wherein the end edges of the segments of adjacent annuli contain opposed sockets (21), the method further comprising inserting dowels in the sockets of a segment, and sliding a segment in the longitudinal direction of the tunnel so that its joining means interengage with those of an adjoining segment of the annulus and its end edge abuts a segment of the adjacent annulus with the dowels extending into the opposed sockets of the abutting segments.

3. A method according to claim 2, wherein the dowels have radially extending fins (24) of resiliently deformable material of greater width than the sockets (21) and the fins, which become deformed, are caused to engage the inner surfaces of both opposed sockets to hold the adjacent annuli together.

4. A method according to claim 2 or 3, wherein the ends of the dowels are tapered.

5. A method according to claim 2, 3 or 4, wherein the dowels are of plastics material.

6. A method according to any one of claims 2 to 5, wherein the sockets in which the dowels are inserted are unlined holes in the concrete of the segments.

7. A method according to any of claims 2 to 6, wherein the sockets (21) are of substantially uniform cross-section.

8. Tunnel lining concrete segments for joining together at their side edges to form an annulus, the intended opposed side edges of adjoining segments of the annulus having interengaging joining means (3, 8-17) which are interengaged by sliding one segment relatively to the other in the longitudinal direction of the tunnel; said interengaging joining means comprising a recess (5) in the side edge of one segment containing an insert comprising a channel member (8) having two inturned flanges (9) defining a slot in the side edge and the side edge of the adjoining segment being provided with a screw-threaded bolt (15) screwable into the segment and projecting outwardly of the segment edge, the bolt having a head (16) which abuts the inner surfaces (10) of said flanges (9) to clamp the segments together when the bolt is tightened by screwing into its segment, characterised in that said bolt has a portion (17) located on its shank between the head (16) and the screw-threaded portion (15), which portion (17) is for receiving a spanner to screw the bolt into a screw-threaded socket (14) in the adjoining segment, the bolt being dimensioned so that the bolt shank between said portion (17) and said head (16) can pass through said slot defined by said flanges (9), whereas the head (16) is wider than said slot.

9. Concrete segments according to claim 8, wherein edges which are intended to form the end edges of the segments of adjacent annuli contain opposed sockets (21) and there being dowels (22) for insertion in the sockets of a said segment.

10. Concrete segments according to claim 9, wherein the dowels have radially-extending fins (24) of resiliently deformable material of greater width that the sockets (21).

11. Concrete segments according to claim 9 or 10, wherein the ends of the dowels are tapered.

12. Concrete segments according to claim 9, 10 or 11, wherein the dowels are of plastics material.

13. Concrete segments according to claim 9, 10, 11 or 12, wherein the sockets in which the dowels are to be inserted are unlined holes in the concrete of the segments.

14. Concrete segments according to any one of claims 9 to 13, wherein the sockets (21) are of substantially uniform cross-section.

Ansprüche

1. Verfahren zur Montage eines Tunnelausbaus, der von Betonsegmenten (1) gebildet ist, welche, um Ringe zu bilden, an ihren Seitenrändern miteinander verbunden werden und an ihren Stirnrändern verbunden werden, um die Ringe miteinander zu verbinden, wobei die gegenüberliegenden Seitenränder der benachbarten Segmente eines Ringes ineinandergreifende Verbindungsmittel (3, 8 bis 17) aufweisen, die durch Schieben eines Segments relativ zum anderen Segment in Längsrichtung des Tunnels ineinandergreifen, wobei die ineinandergreifenden Verbindungsmittel an dem Seitenrand des einen Segments eine Ausnehmung (5) aufweisen, die einen ein Rinnenglied (8) bildenden Einsatz enthält, welches zwei einwärts gerichtete Flanken (9) aufweist, die einen Schlitz in dem Seitenrand begrenzen, und wobei am Seitenrand des benachbarten Segments ein Schraubbolzen (15) vorgesehen ist, der in das Segment einschraubbar ist und sich über den Segmentrand hinaus erstreckt, und der Schraubbolzen sich innerhalb der Ausnehmung in eine Stellung zwischen den Flanken bewegt, wenn das Segment in Längsrichtung des Tunnels verschoben wird, und der Schraubbolzen einen Kopf (16) aufweist, welcher, um die Segmente zusammenzuhalten, an den inneren Oberflächen (10) der Flanken (9) anschlägt, wenn der Schraubbolzen in seinem Segment festgeschraubt wird, dadurch gekennzeichnet, daß der Schraubbolzen ein Teil (17) aufweist, das an dessen Schaft zwischen dem Kopf (16) und dessen Gewindeabschnitt (15) vorgesehen ist, daß das Teil (17) zur Aufnahme eines Schlüssels zum Einschrauben des Schraubbolzens in eine Gewindebuchse (14) im benachbarten Segment dient, und der Schraubbolzen so bemessen ist, daß sein Schaft zwischen dem Teil (17) und dem Kopf (16) sich durch den von den Flanken (9) begrenzten Schlitz hindurch erstreckt, wobei der Kopf (16) weiter als der Schlitz ist.

2. Verfahren nach Anspruch 1, wobei die Stirnränder der Segmente benachbarter Ringe gegenüberliegende Buchsen (21) aufweisen und das Verfahren das Einsetzen von Dübeln in die Buchsen eines Segments und das Schieben eines Segments in Längsrichtung des Tunnels umfaßt, so daß dessen Verbindungsmittel mit denen des benachbarten Segments des Ringes ineinandergreifen und dessen Stirnrand an ein Segment des benachbarten Rings anschlägt, wobei sich die Dübel in die gegenüberliegenden Buchsen der aneinander anschlagenden Segmente erstrecken.

3. Verfahren nach Anspruch 2, wobei die Dübel sich radial erstreckende Rippen (24) aus einem federnd verformbaren Material aufweisen, die eine größere Weite als die Buchsen (21) haben, und die Rippen, die verformt werden, in die innere Oberfläche beider gegenüberliegender Buchsen greifen, um die benachbarten Ringe zusammenzuhalten.

4. Verfahren nach Anspruch 2 oder 3, wobei die Enden der Dübel verjüngt sind.

5. Verfahren nach Anspruch 2, 3 oder 4, wobei die Dübel aus Kunststoffmaterial bestehen.

6. Verfahren nach einem der vorhergehenden Ansprüche 2 bis 5, wobei die Buchsen, in die die Dübel eingesetzt werden, unausgekleidete Löcher im Beton der Segmente sind.

7. Verfahren nach einem der vorhergehenden Ansprüche 2 bis 6, wobei die Buchsen (21) im wesentlichen gleichförmigen Querschnitt aufweisen.

8. Betonsegmente zum Tunnelausbau, wobei die Segmente zur Bildung eines Ringes an ihren Seitenrändern zu verbinden sind und die beim Verbinden gegenüberliegenden Seitenränder der benachbarten Segmente des Ringes ineinandergreifende Verbindungsmittel (3, 8 bis 17) aufweisen, welche beim Verschieben in Längsrichtung des Tunnels des einen Segments relativ zum anderen Segment ineinandergreifen, und die ineinandergreifenden Verbindungsmittel im Seitenrand des einen Segments eine Ausnehmung (5) aufweisen, welche einen Einsatz enthält, der ein Rinnenglied (8) mit zwei einwärts gerichteten Flanken (9) aufweist, welche einen Schlitz in dem Seitenrand begrenzen, und der Seitenrand des benachbarten Segments mit einem Schraubbolzen (15) versehen ist, der in das Segment einschraubbar ist und sich über den Segmentrand hinaus erstreckt, wobei der Schraubbolzen einen Kopf (16) aufweist, welcher an die innere Oberfläche (10) der Flanken (9) anschlägt, um die Segmente zusammenzuhalten, wenn der Schraubbolzen in dem Segment festgeschraubt ist, dadurch gekennzeichnet, daß der Schraubbolzen an seinem Schaft zwischen dem Kopf (16) und dem Gewindeabschnitt (15) ein Teil (17) aufweist, daß das Teil (17) zur Aufnahme eines Schlüssels dient, um den Schraubbolzen in eine Gewindebuchse (14) im benachbarten Segment zu schrauben, und daß der Schraubbolzen so bemessen ist, daß der Schaft des Schraubbolzens zwischen dem Teil (17) und dem Kopf (16) durch den durch die Flanken begrenzten Schlitz durchgehen kann, wobei der Kopf (16) weiter als der Schlitz ist.

9. Betonsegmente nach Anspruch 8, wobei Ränder, die die Stirnränder benachbarter Ringe bilden, gegenüberliegende Buchsen (21) aufweisen und Dübel (22) zum Einsetzen in die Buchsen des Segments vorgesehen sind.

10. Betonsegmente nach Anspruch 9, wobei die Dübel sich radial erstreckende Rippen (24) aus federnd verformbarem Material einer größeren Weite als die Buchsen (21) aufweisen.

11. Betonsegmente nach Anspruch 9 oder 10, wobei sich die Enden der Dübel verjüngen.

12. Betonsegmente nach Anspruch 9, 10 oder 11, wobei die Dübel aus Kunststoffmaterial bestehen.

13. Betonsegmente nach Anspruch 9, 10, 11 oder 12, wobei die Buchsen, in die die Dübel einzusetzen sind, unausgekleidete Löcher im Beton der Segmente sind.

14. Betonsegmente nach einem der vorhergehenden Ansprüche 9 bis 13, wobei die Buchsen (21) im wesentlichen gleichförmigen Querschnitt aufweisen.

Revendications

1. Procédé pour assembler un revêtement de tunnel formé de segments en béton (1) reliés ensemble au niveau de leurs bords latéraux pour former des couronnes et, au niveau de leurs bords terminaux, pour relier les couronnes ensemble, les bords latéraux opposés de segments adjacents d'une couronne ayant des moyens de liaison coopérants (3, 8-17) que l'on fait coopérer en glissant un premier segment par rapport à l'autre dans le sens longitudinal du tunnel, ces moyens de liaison coopérants comprenant un évidement (5) dans le bord latéral du premier segment contenant un insert constitué par un élément de profilé en U (8) ayant deux rebords retournés vers l'intérieur (9) définissant une fente dans le bord latéral, le bord latéral du segment adjacent étant muni d'un boulon fileté (15) pouvant être vissé dans le segment et se projetant à l'extérieur du bord du segment, et, lorsque le premier segment est glissé dans la direction longitudinale du tunnel, le boulon à l'intérieur de l'évidement se déplaçant pour arriver dans une position entre ces rebords, le boulon ayant une tête (16) qui vient en butée sur les surfaces intérieures (10) de ces rebords (9) pour brider les segments ensemble lorsque le boulon est serré en le vissant dans son segment, caractérisé en ce que le boulon a une portion (17) située sur sa tige entre la tête (16) et la portion filetée (15), cette portion (17) étant prévue pour recevoir une clé pour visser le boulon dans une douille taraudée (14) dans le segment adjacent, le boulon étant dimensionné de telle sorte que la tige du boulon entre cette portion (17) et la tête (16) passe à travers la fente définie par les rebords (9), la tête (16) étant plus large que la fente.

2. Procédé selon la revendication 1, dans lequel les bords terminaux des segments de couronnes adjacentes contiennent des douilles opposées (21), le procédé consistant en outre à introduire des chevilles dans les douilles d'un segment et à glisser un segment dans le sens longitudinal du tunnel, de telle sorte que ses moyens de liaison coopèrent avec ceux d'un segment adjacent de la couronne et que son bord terminal vienne en butée sur un segment de la couronne adjacente avec les chevilles s'étendant dans les douilles en vis-à-vis des segments en butée.

3. Procédé selon la revendication 2, dans lequel les chevilles ont des nervures radiales (24) en un matériau élastiquement déformable, ces nervures étant plus larges que les douilles (21), et les nervures, qui ont été déformées, sont amenées à coopérer avec les surfaces intérieures de deux douilles en vis-à-vis pour maintenir les couronnes adjacentes ensemble.

4. Procédé selon la revendication 2 ou la revendication 3, dans lequel les extrémités des chevilles sont effilées.

5. Procédé selon l'une des revendications 2, 3 ou 4, dans lequel les chevilles sont en matière plastique.

6. Procédé selon l'une quelconque des revendications 2 à 5, dans lequel les douilles dans lesquelles les chevilles sont introduites sont des trous non revêtus dans le béton des segments.

7. Procédé selon l'une quelconque des revendications 2 à 6, dans lequel les douilles (21) ont une section transversale pratiquement uniforme.

8. Segments de revêtement de tunnel en béton destinés à être reliés ensemble au niveau de leurs bords latéraux pour former une couronne, les bords latéraux opposés de segments adjacents de la couronne ayant des moyens de liaison coopérants (3, 8-17) que l'on fait coopérer en glissant un premier segment par rapport à l'autre dans le sens longitudinal du tunnel, ces moyens de liaison coopérants comprenant un évidement (5) dans le bord latéral du premier segment contenant un insert constitué par un élément de profilé en U (8) ayant deux rebords retournés vers l'intérieur (9) définissant une fente dans le bord latéral et le bord latéral du segment adjacent étant muni d'un boulon fileté (15) pouvant être vissé dans le segment et se projetant vers l'extérieur du bord du segment, le boulon ayant une tête (16) qui vient en butée sur les surfaces intérieures (10) des rebords (9) pour brider les segments ensemble lorsque le boulon est serré en le vissant dans son segment, caractérisés en ce que le boulon a une portion (17) située sur sa tige entre la tête (16) et la portion filetée (15), cette portion (17) étant prévue pour recevoir une clé pour visser le boulon dans une douille taraudée (14) dans le segment adjacent, le boulon étant dimensionné de telle sorte que la tige du boulon entre la portion (17) et la tête (16) peut passer à travers cette fente définie par les rebords (9), la tête (16) étant plus large que la fente.

9. Segments en béton selon la revendication 8, dans lesquels les bords qui sont prévus pour former les bords terminaux des segments de couronnes adjacentes contiennent des douilles opposées (21), des chevilles (22) étant prévues pour être introduites dans les douilles d'un tel segment.

10. Segments en béton selon la revendication 9, dans lesquels les chevilles ont des nervures radiales (24) en un matériau élastiquement déformable, ces nervures étant plus larges que les douilles (21).

11. Segments en béton selon la revendication 9 ou 10, dans lesquels les extrémités des chevilles sont effilées.

12. Segments en béton selon l'une des revendications 9, 10 ou 11, dans lesquels les chevilles sont en matière plastique.

13. Segments en béton selon l'une des revendications 9, 10, 11 ou 12, dans lesquels les douilles dans lesquelles les chevilles doivent être introduites sont des trous non revêtus dans le béton des segments.

14. Segments en béton selon l'une quelconque des revendications 9 à 13, dans lesquels les douilles (21) ont une section transversale pratiquement uniforme.

Drawing