Heathrow failures highlight NATM (abuse?) misunderstandings
←
→
Page content transcription
If your browser does not render page correctly, please read the page content below
GroBbritannien
United Kingdom
Heathrow failures highlight NATM
(abuse?) misunderstandings
Shani Wallis
In February 1999 the heaviest Following a quite extraordinary four Beatty is set against an original cution's main expert witness
fines ever imposed following trial - which has actually left no party contract value of £ 60 million and report had been directed and
prosecution by the British Health & to the proceedings unscathed - against a company within a large in some cases written by the
Safety Executive were levied against Geoconsult has lodged an appeal corporation that accounts for about leading HSE inspector. The re-
Balfour Beatty and Geoconsult against both the conviction and the 10% to 15% ofthe group's £2 billion port could not be relied upon
following collapse of NATM station sentence. It claims that HSE annual turnover. The fact that Bal- as being independent and un-
tunnels on the Heathrow Express Rail "breached its paramount legal four Beatty admitted guilt, the biased. As a result prosecu-
Link Project at Heathrow Airport in obligation to prosecute fairly" and judge said, mitigated in its favour tion withdrew the report in its
London in October 1994. Balfour that rulings on procedural orders although it was made evident entirety and the court
Beatty, tunnelling contractor on the "resulted in prejudice" against the during the trial that Balfour Beatty allowed prosecution to
£440 million project, pleaded guilty company. Against the sentence it "must bear greater responsibility depend on the alternative
to violating two counts ofthe claims that the fine is excessive and for the collapse". expert witness of Sir Alan
country's Safety at Work Act 1974 overlooks guidelines that fines should Muir Wood and of Prof John
and was fined £1.2 million plus reflect the gravity of the offence but One of the major losers in this Hutchinson. These reports
£100,000 toward prosecution costs should not imperil the existence case is the prosecuting agency were introduced by
and were given 14 days to pay. ofthe company. The total £600,000 itself. The HSE was severely prosecution at a preliminary
fine for Geoconsult is levied against criticised by the trial judge for its hearing in November 1998, it
Geoconsult, as specialist designer an original contract value of £1 conduct of the case and was was said, to support the origi-
to Balfour Beatty for the NATM million and against a medium sized awarded only £200,000 of the nal and subsequently with-
works on the project, denied the consulting engineering company. The £880,000 claim for costs. In the drawn expert witness report
charges but was found guilty by a $1.3 million total fine for Bal- opening days of the trial and by submitted by Mr Guy Lance
jury of 12 after a 26-day criminal trial chance, the defence team found of WS Atkins. In response, de-
at the Old Bailey Criminal Crown that much of the prose- fence made application for
Court and was fined £500,000 with the case to be dismissed on
£100,000 towards costs and was the grounds of "abuse" and
given two-and-a-half years to pay. Balfour Beatty's lowest bid £60 million contract was to build 8.8km applied also for the expert
of shield-driven running tunnel and various NATM caverns including witness of Muir Wood and
The two charges laid against each the underground station complexes at CTA and Terminal 4 on the Hutchinson to be disallowed
company were for failing in their estimated £440 million Heathrow Express Rail Link Project. as substitute. Both applica-
duty to ensure the safety of their Geoconsult was specialist NATM design engineer to Balfour Beatty. tions were denied and the
employees during construction of NATM was specified for design of the stations following a successful trial proceeded. This matter is
the NATM station tunnels at the CTA trial of the method in London Clay at Heathrow in 1992. The trial was to be re-examined in Geocon-
(Central Terminal Area), and failing designed and supervised by the UK office of Austria's Dr Sauer sult's appeal. So although HSE
to ensure the safety of those not in company and was built by the Kier/Lilley/Kunz UK/German joint obtained a conviction, it was
their employ (the general public), by effectively fined £680,000 -
venture. This was the first use of NATM in London Clay and the
exposing them to danger. For not including the cost of the
method was subsequently adopted for the Waterloo and London
Geoconsult the charge included Lance report.
Bridge stations on the Jubilee Line Extension of London's
technical supervision of the works. Underground. At no time in the trial did HSE or prosecution suggest The trial
. that NATM as verified by the trial tunnel or designed by Geoconsult During the trial, evidence
Shani Wallis, Laser Line, for the Heathrow Express was defective in any way. Prosecution and revealed extremely poor
Surbiton/UK the HSE in its report "Safety of NATM with particular reference to workmanship; major flaws in
London Clay" stated that NATM is a safe and appropriate tunnelling construction management;
method in London Clay "providing enough care is taken" and that the and questionable
Heathrow NATM structures now open to the public since mid 1998, contractual arrangements.
are safe. Miners in the tunnelling
gangs told of difficulty in
66 Tunnel 3/99
constructing the invert joint
of the NATM side-wall drift
London Heathrow
Express Link
excavation sequence; of
problems with blockages and
delayed delivery of shotcrete; of
regular changes in the personnel
in the gangs and of little
continuity of routine. Con-
struction foremen and shift
engineers told of pressures from
management to improve
productivity and make up for
delays Site and supervising en-
gineers raised concerns about
over-excavation of rounds by the
miners; inexperience and lack of
skill in the crews; and higher than
expected surface settlement
leading to inspection and repair
of inverts where shotcrete was
50mm instead of 250 to 300mm 3 Plan of the excavation works completed at the time of the collapse of the Central Terminal Area
thick; where there was
insufficient overlap or no starter
bars at all in construction joints;
and where shotcrete was
sprayed over rebound. Senior
project management engineers 1 It was on the night of 21 Nov. 1994 that the Central Terminal Area station tunnels collapsed causing
questioned the apparent lack of extensive damage to the surface
an experienced supervision
team; the apparent disregard of
All of these flaws culminated Eventually the teams were or-
the many CARS (corrective action
in October 1994 with the ul- dered to vacate the tunnels at The prosecution
requests) raised by any engineer
timate collapse of the CTA NATM about 12am amid the sound of case
noticing poor workmanship;
tunnels. Cracks in the shotcrete cracking and the sight of shotcrete
apparent disregard of SDNs HSE as the prosecuting
started to propagate farther, particles raining down. At about
(system defect notices) raised by agency claimed that the col-
faster and grew wider during the 1am the abandoned tunnels
the project management team lapse "was the worst civil en-
early hours of the night shift started to collapse and continued
for the attention of senior gineering disaster in the united
(started at 7pm) and teams were over the two following days
contract managers; the Kingdom in the last quarter of
being moved from one area to creating a hole on the surface and
application of "self certification" a century" and that it was only
another to try and repair cracks causing extensive damage to
as part of the construction by chance that no-one was
and replace lumps of shotcrete surface structures. All stabilised on
contract; and early relaxation of seriously injured or killed. As
as they fell and wire mesh burst the third day and with much of the
the already disfunctioning well as endangering the lives
through the green shotcrete of underground cavity infilled with
auditing role by HEX of the of the workers, prosecution
earlier repairs. concrete.
contractor's self-certification suggested that the conse-
system. quences for the public could
Tunnel 3/99 67GroBbritannien
United Kingdom
have been disastrous, if the
collapse at one of the world's
busiest airports had occurred
during the day, and if the con-
course tunnel had "unzipped" to
beyond the Piccadilly Line
tunnels of the London under-
ground system which lie above
the Express Rail Link tunnels and
some 70m out in front of the
collapsed zone (Figs 2 and 3).
Prosecution claimed on the
basis of expert witness that
monitoring data indicated that
the collapse was evident up to
seven days before the event,
that Geoconsult was "the 3 Plan of the excavation works completed at the time of the collapse of the Central Terminal Area
watchdog that did not bark".
certification in that Balfour on-going repairs in the invert of double production by the end
Sir Alan Muir Wood for Beatty felt HEX should not be the CTA concourse had been of the week. He demands that
prosecution stated that in his involved". He felt, he said, that raised", (in evidence Sir Alan we open all six faces. Panic all
opinion, the collapse was caused Balfour Beatty were paying "lip Muir wood retorted that "Nero round". "Cracks in the tempo-
by the defective invert. He service" to self certification. in was fiddling while Rome was rary wall - expert foreign
claimed that recorded his read statement Bob Gee, burning".) in defence, it was sounding gentleman to inspect
monitoring data and other engineering design manager in made clear that Geoconsult was and instruct." "Oh dear, oh
contemporaneous evidence HEX, said other than increasing acting as part of Balfour dear, oh dear. Horizontal cracks
indicated that collapse was the initial prediction of 9.34mm Beatty's own engineering in concourse tunnel. The witch
imminent up to 14 days before. of settlement over the department under manager Ian hunt starts now." "Big
He criticised the NEC form of concourse tunnel at CTA, the Massey; and that Geoconsult movement in the concourse
contract as inappropriate for HEX team were satisfied with personnel were not invited to crown at chainage 31 to 40m.
tunnelling contracts; that self- Geoconsult's NATM design and project meetings; were not on Time to open up the invert for
certification as a method of the baseline criteria and the distribution list of letters or a look see.” "Work on inverts
quality control had failed; and assumptions used. There was meeting records; and were not [in section back to the shaft]
that (under cross examination) concern however of apparent party to various decisions still on-going. You might as well
"it is very unfortunate for lack of supervision and lack of including it was claimed the take the whole section out." in
Geoconsult to find itself where it experience in the construction programme of compensation his evidence Muir Wood
is" and that "morally it is very teams as work started and a "jacking" under Camborne suggested that removal of a
hard luck for them." He said that major concern that the process House in August 1994, nor the large section of the tunnel's
"the way in which the whole of self-certification and its audit decision to stop concourse infill clay over the defective
management of this contract by the HEX team was not tunnel invert repairs in August invert (rather than in 2m
was proceeding meant there working. He said that while rather than continuing back to sections as instructed and
was a great break between engi- compensation grouting had the access shaft; nor the carried out for the earlier re-
neering and construction which, been used in August 1994 to instruction to open the two pairs), together with starting
to my mind, is the fundamental counteract higher than parallel upline and downline the parallel platform tunnels,
ill effect which led to all these expected (18mm) settlement station platform tunnels in late initiated the collapse.
things happening". He said that under Camborne House above September to make up for
liability for the collapse "should the CTA concourse tunnel as it delays of 28 days and 80 days The case for the
extend to those who were passed underneath, the HEX on these headings. Further
defence
putting these sorts of contracts team was not alarmed by evidence read by prosecution
Of all the collapse reports
together". monitoring data they had seen from the Balfour Beatty section
produced so far, perhaps the
to date. "We did not spot the engineers log book prior to the
most thorough is that produced
Jonathan Allen, CTA area lead up to the collapse," he collapse gives an indication of
by defence expert witness Prof.
manager in BAA's (the private said, and that at the last the climate on the site. Entries
Reinhard Rokahr of Hanover
owners of Heathrow Airport) progress meeting between HEX read: "Alan (more muck) Myers
university. Sir Alan Muir Wood
HEX (Heathrow Express) man- and Balfour Beatty on the day [Balfour Beatty's construction
admitted that his report was
agement team said that he was of the collapse, "neither project director] demands we
prepared in a week
"concerned with the lack of settlement nor
understanding about self
68 Tunnel 3/99GroBbritannien
United Kingdom
and used "rough back of an
envelop” calculations; the Guy
Lance expert witness report was
withdrawn; an expert witness
report produced by Profs. Mair
and Potts of Cambridge
University for Balfour Beatty was
not made available, given
Balfour Beatty's guilty plea; and
the incident Report, called for by
the UK government and being
prepared as a statutory duty by
HSE with input from Guy Lance
of WS Atkins, Martin Thurgood
of HSE, and Sir Alan Muir Wood
among many others, is yet to be 4 BAA, known in the UK as a progressive client, chose the New Engineering Contract (NEC) for the project and
published. to adopt a system of "self certification" whereby contractors certify their own work and keep their own
quality assurance records. To manage the project, BAA established the HEX team comprising engineers from
Although Prof Rokahr criti- Mott MacDonald, BAA'S project engineer and designer of all the permanent works; Taylor Woodrow,
cised the lack of on-site NATM appointed before contracts award as construction manager; and members of its own engineering and
authority at Heathrow; lack of management staff, in addition, Mott MacDonald was appointed by BAA and under separate contract to
experience among the field monitor and control all surface settlement issues during construction of tunnels under the airport facilities. It
engineers, the tunnelling fore- undertook the same responsibilities for Balfour Beatty under a different contract and Keller was engaged as
the specialist contractor to undertake compensation grouting to control surface settlement under sensitive
men and the crews; poor quality
structures. Following the collapse, all parties to the project remained engaged and in a truly single minded
of the monitoring instru-
project oriented approach, some quite remarkable engineering and construction work, including NATM work
mentation data; lack of full time in the stations, was undertaken to restore the situation and complete the project just 6 months later than
geotechnical geologists within schedule - but at what cost depends where you start counting
an NATM supervision team that
already number too few; limited for the collapse given the
bore down on the concourse ening of the clay body caused by
instrumentation data available; circumstances of the work, the
tunnel which, with its defective starting the two parallel platform
serious omissions in the evidence, and the geotechnical
invert, could not act as a closed tunnel headings, and a soaking of
installed instrumentation data available. He said that the
ring. This imparted heavy loads the clay through the collapsed eye
regime; and of the "inadequate" speed of collapse could not be
onto the upline platform tunnel of an escalator box (excavated
computer software system predicted and that workers
where the new shotcrete could overhead and under a earlier
provided by Balfour Beatty for were not exposed to risk until
not carry the exceptionally high contract) could have initiated the
processing the instrumentation immediately before the collapse.
loads and failed. Thereafter the landslide. He claims that deforma-
data; he did state that there was
block subsided further and tion and settlement readings taken
sufficient recorded data to Hutchinson, professor of
caused the defective invert of the under Camborne House in August
indicate that: "In my view, the geology at imperial College as an
concourse tunnel to fold in on 1994, with an equally defective
causation of the collapse, in all expert witness for prosecution,
itself and the upper part of the invert, were higher and did not
probability and I think bordering stated that London Clay is a well
concourse to settle by ap- cause collapse than those
on certainty, is a large scale slide documented, largely
proximately 2m but without recorded, in the area that did
of the clay mass in the zone be- homogeneous, uniform and
leading to a complete collapse of collapse in October. All readings,
tween the downline platform extensive body of over
the crown. The defective invert, including the last taken before the
tunnel north heading and consolidated sedimentary clay
said Rokahr, and its ongoing collapse, he stated, were well
Camborne House (Figs 2 and with very few discontinuities and
repair could not on their own within the design's critical level
3)." The collapse, he claims, none identified in the area of the
have triggered the collapse. The criteria. Rokahr's expert evidence
started as horizontal shear CTA that could have caused a
report by Mair and Potts he said, is based on the theory that some
cracks in the walls of the ad- landslip such as the one
declared that even with part of unforeseeable and completely
vancing side wall drift of the described by Prof Rokahr. He did
the invert completely removed, unpredictable behaviour or
downline platform tunnel. After however criticise the site
the tunnel, as designed, should geotechnical mechanism in the
losing support in the area of the investigation carried out by Mott
still have stood up for up to 80 clay body is the only explanation
downline platform tunnel, a MacDonald as being
days. He suggested that a soft-
monolithic block of clay created "preliminary" and "surprising if a
by a number of bored piles near tunnelling expert
the working shaft and acting like
stiff dowels,
70 Tunnel 3/99GroBbritannien
United Kingdom
did not carry out a further sumed the role of construction The verdict was stopped near the end of the
investigation". quality control supervision. This After closing statements the Heathrow trial by the judge on.
was confirmed in a letter from jury was dismissed to consider the grounds that even though the
In a reverse of usual criminal Alan Myers, project director for its verdict. In his instructions, four accused were not on the site
prosecution proceedings, the Balfour Beatty, to the HEX the judge asked the jurors to when they clearly should have
burden of proof is on the defence management team a month consider: Did Geoconsult been, the event and its
to prove that all reasonably before the collapse that: "The endanger the lives of its workers consequences could not have
practicable was done by their staff primary function of the NATM and those of the general public been avoided. Equally, is
to avoid the collapse and avoid engineers is not quality control. and did they do every thing judgement by a lay jury of such
endangering the lives of workers Quality control is the "reasonably practicable" to complex technical matters
and the public. To this end responsibility of the construction avoid such risks? If yes to the appropriate? The industry itself
Geoconsult argued that its teams. This is in accordance with first part and yes to the second knows how difficult it can be to
responsibility on-site was greatly our self-certification scheme, we part - not guilty. If yes to the discuss technical engineering
reduced by Balfour Beatty in that repeat we have continuous NATM first and no to the second - principals even among skilled
its original proposal for three full engineering supervision and we guilty, it took the jury 10h - and professional engineers.
time employees (an experienced do not have project-wide quality a return to the court room to
site engineer and two full time problems as you suggest." Three hear further evidence about the So, Although the trial is over, the
NATM construction foremen) had engineers were provided by collapsed escalator box and the debate continues. First the result
been reduced to one site engineer Balfour Beatty to assist 3
13m of concrete pumped in to of Geoconsult's appeal is awaited
whose responsibility was to act as Geoconsult's engineer in the field fill the void created - before it and at some stage, the
site liaison with Geoconsult's de- but these had little or no on-site returned a unanimous verdict of international tunnelling industry
sign office in Austria, prepare the or NATM design experience and guilty against Geoconsult. will finally, after more than four
NATM working sheets as required, had to cover all NATM areas of years, have sight of the official HSE
interpret monitoring data, and work on the full project. in the aftermath of the trial, the report into the incident itself.
advise Balfour Beatty accordingly. UK technical trade press has
In his efforts Adrian Kattinger Wallis, S.: Heathrow rises from the
They further argued that the one carried numerous letters and mire and shines. Tunnel 6/1996, p. 6
on-site Geoconsult engineer, warned of poor workmanship and articles on various aspects of
Adrian Kattinger, tried to exert the the possible consequences to the case including criticism or
type of authority usually invested Balfour Beatty's engineering and support of the New Engineering Tunnel
in the NATM site Engineer on the management staff and to his
Continent and through a full team colleagues in head office in
Contract and of self-certification
while in the meantime the
Sonderdruck-
of equally skilled and experienced Austria. He raised several CARs, actual cause of the collapse service
field engineers, but against all the and had his instructions overruled remains a point of professional Sonderdrucke unserer
odds. - a point clearly illustrated in the dispute. Fachartikel sind jeder- zeit
trial evidence when the NATM
field engineer on night shift asks möglich-zu einem
Kurt Laubichler, Geoconsult's head On addition other serious issues
of NATM work at HEX, said in an of his fellow engineer "Was it erschwinglichen Preis: für
are being discussed. For
interview with HSE that Geoconsult agreed on the day shift that there Ihre Werbung, für
example is a criminal court
was "requested in writing by is no need to progress invert re- really the most appropriate Schulen, Weiterbildung
Balfour Beatty, after award of pairs in the concourse any further venue for investigating such und andere Veranstal-
contract I think, that we should back toward the shaft?" A "NO!" events? In an open letter to a tungen.
propose one man to work within in Kattinger's hand writing UK technical trade magazine
the framework of the services indicates the answer but Geoconsult stated that had the Wenn Sie interessiert sind
description". He said Geoconsult regardless, repairs of the con- collapse occurred in Austria, an und Einzelheiten wissen
had no choice other than to agree. course tunnel invert (following official investigation would have möchten - bitte rufen Sie
Balfour Beatty claimed that it had excessive settlement and been conducted but "it is
compensation grouting under die Redaktion an:
sufficient NATM experience from improbable that criminal
the Channel Tunnel and other pro- Camborne House during August +49 (0) 52 41 / 80-19 43.
proceedings would have
jects and that it could provide all 1994) was stopped at chainage resulted in a case where nobody
the necessary site foremen, shift 54m. it was during subsequent was injured or killed". The
engineers and field engineers. With repair of the invert from chainage criminal case against the four
only one Geoconsult engineer on- 54m back to the working shaft in construction site managers
site, defence claimed it was implicit October that the tunnels col- following the NATM tunnel
that Balfour Beatty had as- lapsed. collapse in Munich just weeks
before the Heathrow collapse,
and which killed four people,
72 Tunnel 3/99You can also read
