GB2186010A

GB2186010A - Improvements in or relating to methods of erecting tunnel linings

Info

Publication number: GB2186010A
Application number: GB08602712A
Authority: GB
Inventors: Rupert John Sidney Mcbean
Original assignee: Charcon Tunnels Ltd
Current assignee: Charcon Tunnels Ltd
Priority date: 1986-02-04
Filing date: 1986-02-04
Publication date: 1987-08-05
Also published as: EP0234762A1; GB8602712D0; JPS62186000A; KR870008097A

Description

GB 2 186 010 A 1

SPECIFICATION

4 10 o Improvements in or relating to methods of erecting tunnel linings This invention relates to methods of erecting tunnel linings.

The principal of expanding tunnel segments in good cohesive soil iswell known, well tried tunnelling technique and hasthe advantagethat little or no void is left around thetunnel lining which would require filling with grout. For non-cohesive soils itis necessaryto use a tunnelling shield to supportthe tunnel as it is excavated and in which each tunnel 15 lining ring is erected beforethe shield is advancedto leavethe ring in the ground. This results in a cavity around the ring previously occupied bythe shield which hasto befilled subsequently with groutto supportthe ground around the ring.

The invention provides a method of erecting a tunnel lining using a tunnelling shield comprising the steps of erecting a ring of segments within the shield, each segment having a recess around an outer peripheral edge thereof to provide, in the erec- ted ring, a recess around the outer periphery of the ring of segments atthe leading end of the ring in the direction of advance along thetunnel, advancing the shield with respectto the erected ring until thetrailing end of the shield locates in said recess in the lead- 30 ing end of the ring, expanding the ring againstthe tunnel wall by separating adjacent segments atat least one location around the ring whilst supporting thetunnel wall atthat location against collapse, and inserting a supplemental segment between said 35 adjacent segments to complete the ring.

Since the ring is expanded against the ground the need for grouting around the ring is minimised and in most circumstances eliminated.

Preferably a ground supporting cover is located overthejoint between adjacent segments wherethe segment ends areto be separated to expand the ring to support the tunnel wall in the gap until the supplemental segment has been located in place.

In one specific method a ground supporting cover 45 is provided for each ring to be erected and is leftin situ across the gap between the separated ends in the ring afterthe supplemental segment has been inserted.

In an alternative method the ground supporting covercomprises a part of the shield which projects from thetrailing end thereof and coversthe location in the ring where adjacent segments are separated.

In any of the claims wherein the segments of the ring are loosely connected together asthey are erec- ted in the shield and the connections between the rings are f inally tightened after expansion of the ring and insertion of said supplemental segment.

The segments in the ring may be loosely connected to the segments of the previously erected ring as the segments are erected in the shield and the connections between the segments of the newly erected ring and the segments of the previously erected ring are tightened after expansion of the ring and insertion of said supplemental segment.

65 In accordancewith one method according tothe invention the segments are connected together by bolts.

In afurther method the segments may be connected together by radially expandable fasteners driven 70 between overlapping hoops projecting from the adjacent pairs of edges of the segments and then expanded againstthe hoopsto drawthe segment ends together.

In yet a further method the adjacent pairs of seg- 75 ment edges in each ring may be shaped to interfit one with anotherto and provide joints which are self supporting in the radial direction of the joint with regard to the axis of the ring of segments.

In any of the above methods one adjacent pair of 80 ends of the segments in the ring may be formed to converge towards the trailing end of the ring in the direction of drive of the tunnel and the supplemental segment may comprise a tapered wedge keywhich is driven between the tapered pair of ends to expand 85 the ring after the shield has been advanced to engage the trailing end of the shield in the peripheral recess of the ring.

More specifically the tapered wedge key maybe partially inserted between the pair of converging 90 segment ends in the ring as the ring is erected and maybe driven fully home between the converging ends to expand the ring and the shield has been advanced to engage the trailing end of the shield in the peripheral recess at the leading end of the ring.

In an alternative method in accordance with the invention the adjacent segments which to be separated may have parallel ends and the supplemental segment which is inserted in the resulting gap may have parallel sides to engage said ends.

In the latter method the pair of segments maybe separated by a jacking device applied to the segments.

In any of the above methods the tunnelling shield may have a trailing part which reduces in thickness 105 towards the trailing end of the shield to facilitate erection of the partially erected ring in the shield and advance of the shield to engagethe trailing end of the shield in the peripheral recess of the leading end of the ring.

The following is a description of some specific embodiments of the invention, reference being made to the accompanying drawings in which:

Figure 1 is an end view of a tunnel lining ring formed from arcuate segments in the course of erec- 115 tion using the method according to the invention; Fiyure2 is a sectional viewthrough the ring on the lineA-Aon Figure 1; Figure 3 is a view of a development of the lining; Figure 4and 5 are detailed views of the form of 120 connection between adjacent segments in the ring; Figure 6 is a sectional view through an upper part of the ring showing a key segment inserted in the ring; Figure 7is a plan view of the keysegment; Figure 8 is a plan view of an alternative form of key segment; and Figures9to 13 illustrate the sequence of operation in erecting a ring of segmernts.

Referring firstlyto Figures 1 and 2 of the drawings, 130 there is shown a ring of arcuate pre-cast concrete 2 GB 2186010 A tunnel lining segments 10. Each of the segments except forthe uppermost pair of segments 10a is of similarform and the joints between adjacent segments in the ring are of the form described in our 5 U.K. Patent Nos: 2004931 and 2131514 and are illustrated in Figures 4 and 5 to which reference will now be made.

The adjacent axially extending end faces of the segments are spaced apartwith a biturnous packing 10 11 and each end face of a segment is formed with two spaced semi- cylindrical recesses 12 extending part-way across the face from the inner side thereof to align with a corresponding recess on the opposite segment. One recess in each face has a spaced pair 15 of mild steel hoops 13 embedded into the concrete and projecting into the recess to receive a single mild steel hoop 14 projecting into the recess from the other segmerit. Expandable fasteners 15 are driven through the overlapping hoops to firmly lockthe 20 ends of the segments together.

Adjacent segments in adjacent rings are secured together by means of the connection arrange described and illustrated in our U.K. Patent No. 2139268. The arrangement is illustrated diagrammatically in 25 Figure 3 to which brief reference will now be made. At the centre of each segment there isan axially extending bore 17 in which an elongate bolt is mounted having a T-shaped head at one end and a threaded opposite end which opens into a counter bore in the 30 edge of the segment. A washer and a nut are located on the end of the bolt in the counter-bore. The leading circumferential edge of each segment in the direction of drive of the tunnel lining has two spaced sockets 18 disposed one on eitherside of the central 35 hole in the segment each of which may receive a Tshaped end of a boltwhich is locked in the socketby rotating the head through 90 after inserting the head in the socket. As can be seen from Figure 3 of the drawings, each ring of segments is erected adjacent the previously erected ring segmentswith thejoints in the ring staggered in relation to thejoints in the previously erected ring and with the bolts aligned with the sockets disposed to one side of the bolts of the previously erected ring. The bolts are pushed to 45 insertthe heads of the bolts into the sockets of the previously erected ring and then rotated to lockthe bolts in the sockets. The nuts on the bolts atthe exposed circumferential edge of the newly erected segment can be partially turned up but are notfullytightened at this stage.

Reverting again to Figures land 2 of the drawings, the outer surfaces of the segments areformed around the leading edge of the ring with a shallow recess 20to co-operate with an edge of a tunnelling shield to be used in erecting the segment. The depth of the recess is approximately the same as that of the trailing edge of the shield.

The upper pairof segments 10a of the ring do not have the hoop/dowel connection provided between the remaining adjacent edges of the segments. Insteadthe segments have plates 23 (see Figure 6) cast into the ends of the segments with pockets 24 formed behind the plates. A key segment 25 is disposed between the adjacent edges of the upper seg- 65 ments 1 Oa in engagement with the end plates. The key segment is a parallel sided concrete casting having two spaced apart internally screw threaded tubes 26 casttherein as can be seen in Figure 7. The key segment is secured in place between the end of the 70 segments 1 Oa by means of bolts 28 extending through the end plates of the upper segments and screwed into opposing ends of the screw threaded tubes 26.

Itwill be appreciated that when a ring of segments 75 is initially erected, the upper edges of the upper segments 1 Oa will be in abutment with one another. The segments are separated by means of hydraulicjacks which engage in the pockets in the segments behind the end plates.

In orderto support the ground of the tunnel wall where the segments are separated to receive the key a thin plastic sheet 29 is placed across the gap between adjacent segments. The outer edges of the segments 1 Oa attheir upper ends have recesses 30to 85 receive the sheet and the depth of the key is such that when inserted in place, the outerface of the key is flush with the bottom faces of the recesses. The width of the recesses and the dimension of the sheet are such that even when the segments have been 90 separated to receive the key, the sheet extends well overthe gap between the segment ends on to the recessesto provide adequate supportforthe tunnel wall above the gap.

The tunnel lining described above is erected using 95 a standard form of tunnelling shield 40 modified by the provision of an extended tail skin which, preferably is of higher grade steel than conventionally used and reduced in thickness from the usual 28mm to approximatelyto 8 to 1 Omm. A higher grade steel 100 is required forthe extended tail skin to provide adequate strength in compensation forthe reduced thickness.

The arrangement illustrated has an extended tail of uniformly reduced thickness compared with the 105 main part of the shield. The tail of the shield may however be tapered to the reduced thickness at its trailing edge as an alternative construction.

The sequence of operations in erecting a ring is segments is illustrated in Figures 9to 13 to which 110 referencewill now be made. A ring of segments is erected in the shield 40,the adjacent segments in the ring being connected together otherthan atthetop of the ring and are connected to the previouslyerected ring as described above. Athis stagethe ring is 115 whollywithin thetail skin 41 of the shield. The plastic sheet 29 isthen inserted overthejoint atthe upper end of the ring between the adjacenttop segments 1 Oa as shown in Figure 10 and itwill be noted thatat this stagethe outer surface of the segments 1 Oa at 120 thetop of the ring lie slightly belowthe innersurface of thetail skin. The shield 40 isthen advanced using conventional hydraulic rams 42 built into the shield until thetrailing edge of the tail skin of theshield reaches and drops into the recess 20 encircling the 125 outer side of the leading edge of the newly erected ring. The abutting edges of the segments 1 Oa atthe top of the ring are then jacked apart using hydraulic jacks disposed in the pockets 24 atthe upper ends of the segments 1 Oa as shown in Figure 12 to expand 130 the lining ring against the exposed ground and the 1 GB 2 186 010 A 3 key segment 25 is inserted between the separated ends of the segments. The plastic sheet 29 fully covers the gap created between the adjacent ends of the segments to prevent the tunnel lining collapsing 5 into the gap. The key segment is then bolted in place and the jacks are removed. The expandable fasteners 15 between the adjacent segments are then driven fully home to lockthe segment ends together and the nuts on the through bolts connecting the segments to the previously erected ring are then tightened to lockthe segments firmly together and to the previous ring. The hydraulic rams of the tunnel shield are then retracted to clearthe space in front of the last erected ring ready to receive the next ring of seg- 15 ments as shown in Figure 13. The operation is continued forthe length of the tunnel. The joints in the rings of the segments are staggered alternately clockwise and then anti-clockwise along the tunnel as shown in the development of the tunnel lining il- 20 lustrated in Figure 3 so thatthe joints between adja cent segments do not directly align.

Itwill be appreciated that since the ring of segments is expanded into engagement with the ground there is no residual void around the ring requiring to 25 be filled with grout.

Many modifications may of course be made to the above described embodiment without departing from the scope of the invention. For example the upper segments 1 Oa in each ring may be formed with 30 edges which converge atthe top of the ring to receive a tapered wedge key 25a as shown in Figure 8 which can be driven between the edges to expand the lining in place of the jacking system. The key is then bolted in place to the ends of the segments 1 Oa.

The expandable fastening devices for coupling adjacent segments in each ring could be replaced by conventional bolting and, likewise, the segments in adjacent rings could be simply bolted together or connected by dowells as described in our U.K. Patent 40 Specification No. 2,004,931.

In a further development, the axially extending edges of adjacent segments in the ring may be formed to provide an interlocking jointsuch as a halflapjointora knuckle-joint which is sufficientto pre- vent relative radial movementof the segmentwith respect to the tunnel axis and avoidsthe needforany direct mechanical connection between the adjacent segments.

In the case of a tunnel driven through wet of loose 50 ground, thetrailing edge of thetail shield may be provided with an annular seal to engagethetunnel lining ring as it is erected in the shield and prevent ingress of moisture or spoils into the newly erected lining.

In a modification of thetunnelling shield, a short cover plate isformed integrallywith and extends rearwardlyfrom thetrailing end of the shield to engage overthejoint between the segments 10awhere the segments areto be separated to receivethe key 60 segment. The shield cover plate will of course advance with the shield after erection of one ring of segments has been completed readyto supportthe ground overthejointto be separated in the next ring.

Claims

1. A method of erecting a tunnel lining using a tunnelling shield comprising the steps of erecting a 70 ring of segments within the shield, each segment having a recess around an outer peripheral edge thereof to provide, in the erected ring, a recess around the outer periphery of the ring of segments at the leading end of the ring in the direction of advance 75 along thetunnel, advancing the shield with respect to the erected ring until the trailing end of the shield locates in said recess in the leading end of the ring, expanding the ring against the tunnel by separating adjacent segments at at least one location around 80 the ring whilst supporting the tunnel wall at that location against collapse, and inserting a supplemental segment between said adjacent segments to complete the ring.

2. A method as claimed in claim 1 wherein a 85 ground supporting cover is located over the joint between adjacent segments where the segment ends are to be separated to expand the ring to support the tunnel wall in the gap until the supplemental segment has been located in place.

3. A method as claimed in claim 2 wherein a ground supporting cover is provided for each ring to be erected and is left in situ across the gap between the separated ends in the ring after the supplemental segment has been inserted.

4. A method as claimed in claim 2 wherein the ground supporting cover comprises apart of the shield which projects from the trailing end thereof and covers the location in the ring where adjacent segments are separated.

5. A method as claimed in any of the preceding claims wherein the segments of the ring are loosely connected together as they are erected in the shield and the connections between the rings are finally tightened after expansion of the ring and insertion of 105 said supplemental segment.

6. A method as claimed in any of the preceding claims wherein the segments in the ring are loosely connected to the segments of the previously erected ring as the segments are erected in the shield and the 110 connections between the segments of the newly erected ring and the segments of the previously erected ring are tightened after expansion of the ring and insertion of said supplemental segment.

7. A method as claimed in any of the preceding 115 claims wherein the segments are connected together by bolts.

8. Amethodasclaimed inanyof claims 1 to6 wherein the segments are connected together by radially expandable fasteners driven between over120 lapping hoops projecting from the adjacent pairs of edges of the segments and then expanded against the hoopsto drawthe segment endstogether.

9. A method as claimed in anyof claims 1 to4 wherein the adjacent pairs of segment edges in each 125 ring are shaped to interf it with another to provide joints which are self supporting in the radial direction of the jointwith regard to the axis of the ring of segments.

10. A method as claimed in any of the preceding 130 claims wherein one adjacent pair of ends of the seg- 4 GB 2186010 A 4 ments in the ring are formed to converge towards the trailing end of the ring in the direction of drive of the tunnel and the supplemental segment comprises a tapered wedge key which is driven between the tap- 5 ered pair of ends to expand the ring after the shield has been advanced to engage the trailing end of the shield in the peripheral recess of the ring.

11. A method as claimed in claim 10 wherein the tapered wedge key is partially inserted between the 10 pair of converging segment ends in the ring asthe ring is erected and is driven fully home between the converging endsto expand the ring and the shield has been advanced to engage the trailing end of the shield in the peripheral recess atthe leading end of the ring.

12. Amethod as claimed in anyof claims 1 to 10 wherein the adjacent segments which are to be separated have parallel ends and the supplemental segmentwhich is inserted in the resulting gap has par- 20 allel sides which engage said parallel ends.

13, A method as claimed in claim 12 wherein the pair of segments are separated by a jacking device applied to the segments.

14. A method as claimed in any of the preceding claims wherein the tunnelling shield has a trailing part which reduces in thickness towards the trailing end of the shield to facilitate erection of the partially erected ring in the shield and advance of the shield to engage the trailing end of the shield in the peripheral 30 recess of the leading end of the ring.

15. A method of erecting a tunnel lining substantially as described with reference to and as illustrated in the accompanying drawings.

16. Atunnel lining erected in accordance with the methods of any of claims 1 to 15.

Printed for Her Majesty's Stationery Office by Croydon Printing Company (L1 K) Ltd,6187, D8991685. Published by The Patent Office, 25 Southampton Buildings, London, WC2A lAY, from which copies maybe obtained.

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