401:"Units have failed by creating a hinge in the concrete section. The hinge has rotated downwards, which is consistent with the crown of the arch moving downwards under excessive load and/or the sides of the arch moving outwards under too little lateral restraint. This problem would have been made worse if there was a significant difference in the level of the fill on the two sides. At the section that is still standing the central hinge has bent down indicating an imbalance between the vertical and horizontal loads and a failure by outward spreading of the arch." He added that heavy rainfall, which had hit Gerrards Cross several days before the collapse, may have made the problem worse. "It is possible that rainfall increased the vertical load on the tunnel. At the same time, if the fill at the sides is not completely free draining, it could have led to a reduction in the passive pressure available from the fill on the sides." Another construction specialist said: "You could trigger failure if you go straight from full depth fill over one section straight to no fill; that is, a section that's fully flexed next to one that's unflexed."
352:, the last stop before Gerrards Cross, before the driver was warned by radio. He reversed the train to Denham Golf Club, where all passengers were let off. Additionally, a London-bound train was standing at the eastbound platform at Gerrards Cross waiting to depart. The driver of this train had just set the train in motion when he saw the collapse, stopped his train using the emergency brake, and informed the railway signallers by radio; they in turn stopped other trains. There were no casualties as a result of the incident. One witness told a news channel that he was parking his car when he heard "what sounded like a clap of thunder - I thought it was an earthquake. I saw the tunnel falling on to the rail track." Reg Whittome, chairman of the Marylebone Travellers' Association and the Chiltern Railway Passenger Board, said after the incident that, had a train been going through the tunnel when it collapsed, there would have been an "almighty tragedy". He added: "Had it been during the rush hour, hundreds could have been killed."
376:"The tunnel has collapsed. We've now got to assess today why that happened," said Robin Gisby, head of operations for Network Rail. "Experts are in there right now and they will work through the tunnel and decide what was the cause of the delay. Then we're going to make it safe, then we're going to work out how we're going to clear up the considerable problem we've got. There's a couple of thousand tonnes of material in there that we've got to move. We've got to get the concrete structure, that has collapsed, out. We've probably got to do all of that by road. Although we brought the material in by rail, we don't think we can get it out by rail, but we won't assess that until later on today and through the night. I think that's going to be at least a week's work, possibly longer, before we can restore rail services on this route. Passengers are being advised to travel via alternative routes and buses have also been ordered. We are currently putting arrangements in place to minimise disruption."
37:
436:
424:, said: "If this particular disaster encourages Tesco to not go ahead with the scheme, everyone in Gerrards Cross will be absolutely delighted." Peter Hardy, the leader of South Bucks district council, added after the landslide that there would be "further years of disruption ... It would be better to abandon the project. I'm not against Tesco as such, but as a council, we want the inquiry into the collapse of the tunnel to be open and transparent. We want to know why such a hugely complex engineering process has been deemed necessary to build a relatively small new Tesco store. And we want something positive back from Tesco."
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At the time of the accident, James Ford added that no further work would be carried out on the tunnel unless it had been certified as safe. "As to whether or not Tesco plans to continue building above the tunnel, we just don't know," he said. "What we do know is that there will be no further work, or
364:
were operated. The 29 precast concrete segments that had collapsed were removed, together with another 16 segments that were damaged. Extensive design checks were carried out to ensure that the sections of tunnel lining that had not collapsed were safe. 15,000 tonnes of material were removed from the
459:
as lead designer. In light of the collapse, a far more cautious approach was taken to the design. Precast concrete arch sections were used, but these simply act as formwork for a 600mm (2 foot) thick in-situ concrete continuous arch, a much more robust structure. To further reduce the loading on the
392:
operation. The tunnel segments allowed for substantial vertical settlement during construction, and it was vital that the material was built up evenly on both sides and over the crown of the arch. Shortly after the incident, however, Gisby said that "something" about the backfilling "is not right."
474:
reported that there was still opposition to the "controversial" store. The newspaper reported that "some have complained about dust coming from the site, as well as traffic delays while roadworks were carried out." A local resident, who protested against the project since it was announced, said:
467:
The store opened in late
November 2010, 5 years later than originally planned, and 14 years after the project started. The store manager, Lizzie Field, said: "We are really pleased to support our local community at a time when so many people are looking for jobs, and there is so much competition
397:
commenting in the wake of the incident expressed surprise at the difference in fill levels on either side of the arch, and doubts were expressed that the backfilling had been in accordance with the method statement. "The collapse was probably due to too much load on the crown of the arch and not
427:
There were protests by local residents against the store. One protester said they were "fighting to get Tesco to tell us exactly why the tunnel collapsed, and to stop them from succeeding in winning further planning permission to continue work on the store." Some were less opposed to the store.
380:
anything that could have an effect on it, unless
Network Rail and the HSE are satisfied that it's safe to do so. Network Rail will consult us if this situation arises. Tesco may, however, choose to continue work on parts of the supermarket project that are not directly connected to the tunnel."
265:
contract to
Jackson Civil Engineering, who announced the store would be designed by White Young Green, and specialist supplier Reinforced Earth Company. Work started on site in early 2003. At the time Jackson Civil Engineering were part of the Peterhouse Group, which was subsequently bought by
337:
257:
John
Prescott overturned the council's ruling on the basis of the recommendations of an independent planning inspector. Due to a lack of space in the area, Tesco had proposed building over the railway line, which would free up a large area of land suitable for the development.
252:
Tesco, the third largest retailer in the world measured by revenues and the second largest measured by profits first proposed a store on the site in 1996. The local council also objected to the development and a public inquiry endorsed this decision. In July 1998, however,
404:
The Health and Safety
Executive launched an investigation into the collapse in 2005. Owing to the complex nature of the probe, it remained open until 2015. A final report has been prepared, but has not yet been made public pending resolution of legal issues.
615:
286:, "and something like a thousand worldwide." At the time of collapse, construction work on the tunnel segments had finished, and the backfilling operation was taking place. The foundations had been built and the steel frame of the supermarket erected.
282:. These segments were connected to each other at the middle of the arch, and material then built back up over the arch, known as backfilling. The method of construction was not unique. "There are eight tunnels like this in Britain," said James Ford of
270:
in 2004, after the
Jackson Civil Engineering division had been sold in a management buyout. Babcock were still subject to the parent company guarantee that Peterhouse Group had entered into when the contract to build the tunnel was let.
365:
area which had suffered the collapse, and 12,000 tonnes of backfill was removed from the undamaged sections. Despite the railway line reopening, approval was not given to carry on with the work as originally proposed.
236:
on 30 June 2005. No-one was injured in the accident, although a train heading towards the tunnel when it collapsed had to perform an emergency stop. Early reports suspected the cause was the backfilling operation; the
567:
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344:
At 7.34pm on 30 June 2005, 30 metres (33 yards) of the 320 metre (350 yard) tunnel collapsed. At the time, there were no trains passing through the tunnel, although one train, heading west towards
1240:
244:
Despite the incident, the construction continued in 2007 with different contractors building the tunnel. The store opened in
November 2010, fourteen years after the project was commissioned.
225:
supermarket to be built over the railway line. Plans were initially met with anger by local residents, and the council refused planning permission but this decision was overturned by
475:"It's been very very frustrating. I won't be using the store and a lot of people in Gerrards Cross feel the same way. I think the traffic situation is going to be horrendous."
393:
The chief executive of
Jackson Civil Engineering, however, said that the process used was "in line with what the design allowed. There was a strict loading regime in place."
1154:
340:
During the collapse, the crown of the tunnel caved in on itself, bringing the tonnes of soil piled on top down onto the railway tracks, which are visible in the foreground.
254:
325:
over the railway line, pictured three months before the collapse. While the council blocked the store, the decision was overturned and construction began.
519:
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between applicants. The quality of applicants was fantastic and my new team and I are already enjoying working together." When the store opened, the
90:
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have been installed either side of the tunnel, and a lighter fill material—including foamed concrete—used over the top of the arch.
1098:
360:
Service was disrupted for two months after the collapse, until 22 August 2005, so material could be removed from site. The line was closed and
241:
are yet as of
December 2020 to release their findings owing to legal issues. A freedom of information request on 10 December 2020 was denied.
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428:"People here like to have a go at Tesco," an estate agent said. "I suppose most of us would have preferred a
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589:
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590:"Gerrards Cross Tunnel Collapse Report - a Freedom of Information request to Health and Safety Executive"
859:
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In 2006, Tesco appointed a new team to carry out the design and construction of the tunnel and store.
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appointed a new team to continue the design and construction of the tunnel and store.
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Construction of the tunnel, which was meant to enable the construction of a new
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advised that further checks were required to confirm the safety of the design.
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The incident brought protests from local residents and the council. The local
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950:
389:
1215:
1099:"Backfilling thought to be culprit in Gerrards Cross rail tunnel collapse"
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enough fill on the sides," the head of a specialist consulting firm said.
1038:"Calling the shots: How supermarkets get their way in planning decisions"
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The initial investigations into the cause of collapse focused on the
708:"Tesco finally restarts work at Gerrards Cross tunnel collapse site"
440:
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The store being erected shortly after construction restarted.
348:, had to make an emergency stop. The train had passed through
828:, Babcock International Group PLC, p. 31, archived from
741:
Controversial
Gerrards Cross Tesco store opened today
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1241:Railway accidents and incidents in Buckinghamshire
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946:"Railway tunnel collapse will cost Tesco millions"
1186:"Tesco to finally open after 14 year controversy"
1004:
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432:food hall, but we'll all shop in Tesco anyway."
221:. The purpose of the tunnel was to enable a new
1068:"No early opening for Tesco at Gerrards Cross"
568:"Freedom of Information request Ref 201702198"
8:
918:"Railway tunnel collapses at Gerrards Cross"
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278:sections, each of which made up half of a
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767:"Babcock grows with £105m Peterhouse buy"
520:List of structural failures and collapses
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621:. Deloitte. p. 14. Archived from
570:. whatdotheyknow.com. 15 February 2017
232:During construction of the tunnel, it
1131:. whatdotheyknow.com. 18 October 2010
7:
664:Glancey, Jonathan (25 August 2005).
1010:"Tunnel collapse causes rail chaos"
858:Wynne, Alexandra (19 March 2009),
738:Cain, Rebecca (29 November 2010),
706:Hansford, Mark (14 January 2009),
205:is a 310-metre-long (340 yd)
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616:"Global Powers of Retailing 2010"
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1129:"Freedom of Information request"
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311:
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1155:"Tesco finally opens its doors"
1153:Abell, Jack (3 December 2010).
822:Annual Report and Accounts 2009
765:Reece, Damian (23 March 2004),
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1:
916:Brunetti, Nic (1 July 2005).
540:"Railway tunnel lengths, G-P"
362:rail replacement bus services
233:
944:Smith, Lewis (2 July 2005).
975:The Chiltern Railways Story
268:Babcock International Group
239:Health and Safety Executive
1287:
1256:History of Buckinghamshire
1246:Railway tunnels in England
1236:Tunnels in Buckinghamshire
798:, Jackson, archived from
493:South East England portal
261:The work was let under a
34:
350:Denham Golf Club station
151:310 metres (340 yd)
879:(subscription required)
727:(subscription required)
544:www.railwaycodes.org.uk
451:were assigned as main
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395:Geotechnical engineers
341:
106:51.588343°N 0.553007°W
1223:at Wikimedia Commons
1221:Gerrards Cross Tunnel
438:
339:
255:Deputy Prime Minister
203:Gerrards Cross Tunnel
30:Gerrards Cross Tunnel
18:Gerrards Cross tunnel
1251:Engineering failures
1045:Friends of the Earth
973:Jones, Hugh (2010).
111:51.588343; -0.553007
835:on 12 December 2010
802:on 4 September 2012
430:Marks & Spencer
234:partially collapsed
102: /
31:
1104:New Civil Engineer
1073:New Civil Engineer
981:. pp. 12–13.
864:New Civil Engineer
795:Management Buy Out
712:New Civil Engineer
596:. 10 December 2020
515:Structural failure
507:Engineering portal
445:
356:Service disruption
342:
219:Chiltern Main Line
62:Chiltern Main Line
47:and tunnel in 2009
1219:Media related to
1161:on 17 August 2011
988:978-0-7524-5454-2
979:The History Press
895:RailwayPeople.com
371:Chiltern Railways
284:Chiltern Railways
280:three-pinned arch
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16:(Redirected from
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1191:Bucks Free Press
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1157:. Archived from
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897:. 26 August 2005
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1195:. Retrieved
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1047:. p. 23
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800:the original
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676:. Retrieved
671:The Guardian
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623:the original
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547:. Retrieved
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1165:13 December
666:"In a hole"
462:piled walls
390:backfilling
323:supermarket
171:Track gauge
109: /
84:Coordinates
1230:Categories
1197:8 November
1022:14 October
958:14 October
929:14 October
901:14 October
839:12 January
806:12 January
779:12 January
751:12 January
526:References
453:contractor
248:Background
127:Work begun
94:51°35′18″N
1051:3 January
951:The Times
632:18 August
409:Aftermath
217:, on the
143:Technical
122:Operation
97:0°33′11″W
78:, England
1135:25 April
1015:BBC News
954:. London
775:, London
674:. London
600:21 April
574:25 April
549:30 March
479:See also
460:tunnel,
332:Collapse
190: in
68:Location
53:Overview
1114:17 June
1083:17 June
873:17 June
721:17 June
678:17 June
449:Costain
185:⁄
45:station
985:
161:tracks
148:Length
135:Opened
1041:(PDF)
833:(PDF)
826:(PDF)
626:(PDF)
619:(PDF)
441:Tesco
223:Tesco
1199:2010
1167:2010
1137:2018
1116:2009
1108:EMAP
1085:2009
1077:EMAP
1053:2011
1024:2010
983:ISBN
960:2010
931:2010
903:2010
875:2009
868:EMAP
841:2011
808:2011
781:2011
753:2011
723:2009
716:EMAP
680:2009
634:2010
602:2021
576:2018
551:2020
455:and
369:and
138:2010
130:2003
58:Line
209:in
159:of
157:No.
1232::
1188:.
1175:^
1145:^
1106:,
1102:,
1075:,
1071:,
1043:.
1012:.
997:^
948:.
920:.
893:.
866:,
862:,
848:^
769:,
744:,
714:,
710:,
688:^
668:.
642:^
592:.
559:^
542:.
420:,
418:MP
229:.
213:,
74:,
1201:.
1169:.
1139:.
1055:.
1026:.
991:.
962:.
933:.
905:.
682:.
636:.
604:.
578:.
553:.
196:)
192:(
187:2
183:1
180:+
178:8
165:2
20:)
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