Cause of the Collapse of a Tunnel at Heathrow Airport - Case Study Example

Cause of the Collapse of a Tunnel at Heathrow Airport in Feburary1999 and What Should Have Been Done To Prevent It Introduction The Heathrow Junction was a short-lived railway station, which was constructed to serve London Heathrow Airport in the U.K. (Gallop 61). The Heathrow Express shuttle service was constructed from 1988 to 1998 to link to Heathrow Airport to Paddington Station (Connor 3). A new spur was constructed from the existing Great Western Railway pathway to the airport, travelling overly in tunnel. To save expenses, the tunnel was built using the NATM – New Austrian Tunneling Method. Sadly enough, the building was not accomplished, and, in 1994, some sections of the still-to-be-opened tunnels, close to the airport, collapsed (Connor 3). This paper will discuss the collapse of the NATM tunnel at Heathrow Airport and also present some of the measures that could have been undertaken to prevent the fall. Background The tragedy not only slowed the completion of the railway tunnel under the airport, but also led to the expulsion of Piccadilly Line Services (PLS) to Heathrow airport. With no rail transport, a ruling was reached to open a provisional surface-level station at the border of the airport even as construction went on (Saveur 55). The path to the new station tracked the course of a long-abandoned channel referred to as "Broads Dock" (Connor 24). The Heathrow Junction station was located in Stockley Park, somewhat to the north eastern side of Heathrow Airport (Sherwood 49). Heathrow Fast Train, or class 332 trains, ferried passengers from Paddington to Heathrow Junction and back in only 12 minutes, and a fleet of express shuttle buses ferried the commuters the remaining distance to Heathrow Airport (Saveur 55). On 23rd June, 1998, the Heathrow Express shuttle service instigated to Heathrow Terminals 1 to 3 railway station, as well as Heathrow Terminal 4 (Saveur 55). Trains no longer passed through the Heathrow Junction, and within 10 days the railway line leading to the junction had been destroyed (Sherwood 49). Consequences The heaviest fines ever were levied on Balfour Beatty and Geoconsult, in February, 1999, by the British Health and Safety Executive following the collapse of the NATM station tunnels (Wallis 1). Balfour Beatty, the contractor of the £440 million venture, pleaded guilty to infringing two counts of England’s 1974 Safety at Work Act, which led to a fine of £1.2 million plus another £100,000 toward prosecution expenses (Wallis 1). They were furthermore given only 14 days (2 weeks) to settle the fine. The two charges laid against the two firms were for not ensuring the safety of their workers during building of the New Austrian Tunneling Method station tunnels at the Central Terminal Area (CTA), and not ensuring the safety of the people not in their company, otherwise the general public, through exposing them to risky situations (Wallis 1). For Geoconsult, the charge comprised of also poor technical management of the construction. Reasons for the Collapse In order to understand why the tunnel collapsed, it is important to dwell on the court proceeding, which fully tackled why this happened in order to justify the huge fines imposed. Sir Alan Muir Wood, a member of the prosecution team, stated that the collapse of the tunnel was triggered by the substandard invert (Wallis 3). Sir Wood and his team claimed that the monitoring data evidence plus other contemporaneous evidence proved that the collapse was imminent two weeks prior (Sherwood 68). The team criticised the New Engineering Contract (NEC) as unsuitable for tunnelling pacts; that self-certification as a technique of quality management was botched; and that it is extremely unlucky for Geoconsult to find itself in such a position (Connor 56). The prosecution argued that the manner in which the entire management of this venture was proceeding implied that there was a huge break between construction and engineering which is the primary ill effect that caused all the havoc (Wallis 3). Jonathan Allen, the then CTA area manager in BAAs HEX (Heathrow Express) claimed that he was troubled with the lack of comprehension about self-certification given that Balfour Beatty felt Heathrow Express should not be drawn in (Sherwood 68). He felt that Balfour Beatty was only paying “lip service” to self-certification. Another engineering design manager in Heathrow Express, Bob Gee, said other than rising the former forecast of 9.34mm of settlement over the open space tunnel at CTA, the HEX engineers not satisfied with Geoconsults New Austrian Tunneling Method design, as well as the baseline criteria, together with assumptions used (Wallis 3). However, their main concern was the apparent lack of proper supervision and also experience in the building teams because work began and a key concern that the procedure of self-certification plus its review by HEX engineers was not functioning (Sherwood 68). The engineering design manager claimed that the HEX team was not worried by overseeing data that they had seen to date even as compensation grouting had been utilised in August 1994 to counter the unexpected (18mm) settlement beneath Camborne House and above the CTA open space tunnel because it passed below (Wallis 3). The team did not notice the lead up to the cave in and that, during the last meeting between Balfour Beatty and HEX on the day of the subside, neither on-going repairs nor settlement in the invert of the CTA open space had been brought up (Sherwood 68). In evidence, Sir Wood argued that Nero was cheating whereas Rome was burning. It was made clear during the defence that Geoconsult was only performing as part of Balfour Beattys private engineering subdivision under Ian Massey (manager) and that Geo workers were not called to meetings that related to project natters (Sherwood 69). Furthermore, they were not on the list of distributions of meeting records or letters and were not informed of vital decisions such as the decision to terminate repairs of open space tunnel invert, in August, instead of continuing back to the shaft; nor the decision to unlock the two parallel downline and upline station tunnels in late September to compensate for delays of the 28 days, as well as the nearly three months on these headings (Wallis 3). More evidence presented by prosecution from the log book of Balfour Beatty section engineers before the collapse provides an hint of the atmosphere on the site (Connor 57). Finally, in the evidence presented by Sir Wood proposed that removal of a huge section of the tunnels clay over the faulty invert (instead of in 2m sections as initiated and done for the previous repairs), plus opening the parallel platform tunnels, caused the collapse (Wallis 3). What Should Have Been Done To Prevent the Collapse? A lot of question started to be raised after the collapse of these tunnels. For instance, was it really the NATM method or sequential method excavation (SME) or sprayed concrete lining (SCL) design that caused the collapse? Are the essentials of the theory part of the design and building process? Is the nature of the passageway and are the rotations of the excavation sequences (bench, topheading, sidewall drifts and invert) suitable for the prevailing soil conditions? Inverts and flat inverts not closed to form rings of ample support are not going to do well in soft soil (Saveur 71). Therefore, the engineers should have applied the essential support at the required time to prevent the tunnel from collapsing. Collapse of this tunnel can be highly scrutinised under such criteria (Saveur 71). Another set of questions asked the time the collapse took place? The collapse in London, like almost all others, took place at night, on the night shift indicating two things; the lack of supervision and engineering staff on site to assume command if something irregular is arises and the seniors do not want to work at night and the “B” team is usually assigned to the night work (Gallop 98). Therefore, what could have been done to prevent this collapse what the assign a proper team both the day and night work and also ensure that there are supervisors on site to always check for any flaws. The third set of questions asked what was the real work experience of the NATM engineers and of the contractor firm and of the managers, engineers and tunnelling personnel in charge of the NATM project (Gallop 98). The excuse the defence team presented in court cannot be allowed. If the NATM engineers and managers have enough experience, then the collapse could have been prevented. However, the lack of experience significantly led to the collapse (Gallop 98). There can be no justification for inexperience of contractors or designers, the impacts are too critical, and the tunnelling personnel, whether qualified or not, should do the best job (Saveur 71). Conclusion In conclusion, this paper has discussed the collapse of the NATM tunnel at Heathrow Airport and also presented some of the measures that could have been undertaken to prevent the fall. Evidence shows that the collapse was mainly due to negligence among other factors. As a recommendation, tunnel proposals should overcome the hurdles presented in this paper and must depend more on political and public pressure instead of the objective evaluation their systems. A practical future strategy option could be to seek a greater social agreement on what elements of the quality of life and environment should be secured from the unfavourable impacts of new infrastructure, and identify less expensive solutions. Governments should be fully involved in setting such priorities. Works Cited Connor, John E. GWR Disused Stations in Greater London. Colchester: Connor & Butler, 2000. Print. Gallop, Alan. Time Flies: Heathrow at 60. Stroud: Sutton Publishing, 2005. Print. Saveur, Jack. Reclaiming the Underground Space: Proceedings of the ITA World Tunneling Congress, Amsterdam 2003. New York: CRC Press, 2003. Print. Sherwood, Philip. Around Heathrow through Time. The Hill, Stroud: Amberley Publishing, 2012. Print. Wallis, Shani. Heathrow Failures Highlight NATM (Abuse?) Misunderstandings. N.p, 2001. Web. < http://www.tunneltalk.com/images/laneCoveCollapse/Ref5-Heathrow-failures-highlight-NATM-misunderstandings-Shani-Wallis.pdf> Read More