Feedback - TunnelTalk
  • Alert Sign Up
Feedback

The following are the Letters to the Editor and Feedback entries that we have received as a result of our editorial content and weekly Alert Editor's Desk Comments. To Have your say on industry news and developments, complete the form and submit to our Editor’s Desk for processing and publication.
Signup to our free weekly Alert and be updated on the world's tunnelling news and views.

Design and performance of cast-in gasket discussion continues

Feb 2017

Article reference: New technology to avoid segment cracking - TunnelTalk February 2017
In response from Steve Casey, B.Sc MIMMM C.Eng, Sales & Technical Director, VIP to the Feedback contribution below from Peter Tiedemann of Dätwyler:
VIP recognises Dätwyler as a longstanding manufacturer of high quality tunnel segment gaskets. Both our organisations have made significant contributions in the development of high performance tunnel segment gasket design and manufacture. In response to Peter’s comments, we would like to clarify the following.
VIP cast-in tunnel segment gaskets, created using the technology outlined in the original TunnelTECH Modern seals for segment lining integrity article on TunnelTalk in May 2016, do not have ‘soft corners’. The advantage of the VIP approach is that the corner performance in terms of compressibility is consistent with the rest of the gasket, with proven sealing performance as demonstrated in recent contracts secured by VIP.
Using solid corners, by definition, exhibit a different compression behavior, compared to the rest of the gasket, and may lead to performance issues. The ability to create a gasket corner angle equal to that of the segment, as opposed to ‘forcing’ a solid right angle corner to work on acute or obtuse segment corners, is self-evidently a better option. The inventive steps in the VIP gasket fabrication process, relates to how the extruded lengths of gasket are joined to form the gasket corners. This unique process is the result of the development work VIP has undertaken, which requires bespoke manufacturing equipment exclusive to VIP.
Steve Casey, B.Sc MIMMM C.Eng,
Sales & Technical Director, VIP Polymers

The debate concerning the design and performance of cast-in sealing gaskets for tunnel lining segments continues with feedback on a VIP Polymer News Release article published on TunnelTalk from Peter Tiedemann of competitive gasket supplier Dätwyler.
Tiedemann contends that producing “soft corner is easy, but [the design] has no water tightness performance. The importance is to find the balance of a strong corner with high water tightness performance and in consideration with concrete strength and other parameters.”
He adds that: “The cutting [technique] mentioned is done already for years” and that “if doing it now, then they are years behind”.
The track record for the design, manufacture, production and application of cast-in segmental lining gaskets is relatively limited but growing steadily. The topics were discussed in the Modern seals for segment lining integrity TunnelTECH article on TunnelTalk in May 2016.
Share your comments and experiences of researching or working with the technique via our Feedback facility.
References
Modern seals for segment lining integrity - TunnelTalk May 2016

Considering the real costs of driving TBMs into predictably difficult situations

Article reference: TBM rescue for Tapovan hydro challenge - TunnelTalk December 2016
Feedback from: Dr Nick Barton
Dear TunnelTalk,
Maybe those contemplating long TBM drives into predictably difficult conditions should consider the time delays likely to be incurred for dealing with fault zones, and the deceleration of TBM progress as the drive advances. These two realities are, and have been, largely ignored by the industry these last 15 years.
My lecture for the ISRM (International Society for Rock Mechanics), entitled TBM Performance: From Best to Not So Good and Why, addresses these issues squarely and may be of interest to your readers.
With regards,
Dr Nick Barton

ISRM lecture by Dr Nick Barton - ISRM, September 2015
(Note: Lecture begins at 04.50 after the introduction)
Freeing stricken TBMs in tough Asian conditions - TunnelTalk, March 2012
Subsea tunnels for oilfield development - TunnelTalk, November 2013

Rail-bound support on the Doha Metro

Aug 2016

Article reference: Doha Metro set for final project breakthrough - TunnelTalk August 2016
Feedback from: Philip G Graham Retired, Tasmania, Australia
Dear TunnelTalk,
I would like to point out that not all the Doha projects used the pneumatic-tyred multi-service vehicles sourced from the various subsidiaries of the TBM manufacturer nor did they all use continuous conveyor mucking systems.
Rail-bound mucking on Red Line South

Rail-bound mucking on Red Line South

I endeavor to follow the products of the rail-based construction suppliers and in the case for the Red Line South (RLS) Package 2, the contractor, the Qatari Diar/Vinci (QDVC JV)/GS Engineering/Al-Darwish grouping used rail bound systems including locomotives supplied by SCHÖMA of Germany and rolling stock supplied by Mining Equipment Ltd of the USA. Mucking out over this section was achieved using rail-mounted lift-off muck cars. I note that the tunneling on this section was the first to start boring.
This illustration shows the Schöma CHL350-BB diesel-hydrostatic locomotive paired with a powered platform car, also hydrostatically-driven from the locomotive, and contributing to the tractive force utilizing the weight of the lift-off muck car it carries. The balance of the rolling stock rake consists of the slightly larger hauled muck bins.
The Package 1 Red Line North (RLN) contractor, the Salini-Impregilo/SK Engineering/Galfar Al Misnad grouping also used rail-based equipment for their section of the project. At some stage it might be interesting to look at the types of equipment used in the back-up systems supporting the major TBM manufactures\types.
The recent trends towards using the pneumatic-tyred multi-service vehicles have limitations dictated by tunnel diameter of a minimum of 6~7m in the metro tunnels. Below this it is still usually the preserve of rail-bound rolling stock for excavation support. Above this, it is optional with some contractors still electing to continue with rail-based equipment.
Philip G Graham
Tasmania - retired

Adding to the decompression discussion

Dec 2015

Article reference: Experience with German decompression tables - TunnelTalk Dec 2015
Feedback from: Dr Donald Lamont C.Eng, FICE, Director, Hyperbaric and Tunnel Safety Ltd, UK
Dear TunnelTalk,
I very much welcome the article by Assenmacher and Förster on the use of German decompression tables. Whilst the decompression outcome on individual contracts can sometimes be found in the literature, there is little published information on national experience. It is particularly interesting having the authors’ views on the practical issues surrounding compressed air working in accordance with German practice and to realise how similar their experience has been in many ways to my UK experience.
As the authors note, oxygen decompression has become mandatory in many European countries over the past two decades. Although the UK Blackpool Tables with oxygen is the approved decompression regime in the UK, most of what little compressed air work has been undertaken in the last 15 years in the UK, has been done using variants of the German tables. Contractors prefer the shorter more aggressive decompression to the longer slower decompression of the Blackpool Tables. The UK HSE (Health and Safety Executive) Research Report RR126 found that, of the European oxygen decompression tables modelled, no one table was best or worst overall.
With one or two exceptions, the decompression outcomes reported from the use of German oxygen tables appear generally good, for which the authors should be congratulated.
The results for the Lübeck Tunnel, at a decompression illness incidence of around 2%, in the pressure range 1.8 to 3.1 bar, is consistent with UK figures for the Blackpool Tables without oxygen.
In reviewing the factors that appear to affect decompression outcomes, the authors mention the problems of lack of working space. In the days of hand tunnelling in compressed air, with many weeks of man exposures, the manlocks were often fairly large and relatively spacious, particularly if they were combined man-material locks. The men could walk around during decompression. Although seating was often provided, it was usually fairly spartan or rudimentary. Now, with TBM locks, there is a lack of space in the manlocks leading to poor posture and inability to move or even to stretch the legs. In drafting EN 12110 we were certainly acutely aware of the need to balance the space requirements of those being decompressed, with the space constraints in modern TBMs.
The problem of posture, which the authors identify, is also familiar. This was not restricted to TBM airlocks. Comments in the lock attendant’s register to report that an operative “fell asleep with arm against chamber wall” were not uncommon against entries recording Type 1 decompression illness in a miner’s arm.
I also recognise the issue of forced posture, especially kneeling, leading to decompression illness events. The problem, in my experience, seemed to occur particularly with fitters and electricians when major failures of pumps and motors occurred, leading to urgent extended maintenance work. I routinely met with the contract medical adviser at the end of a contract to go through the compressed air working data and try to find reasons for decompression illness events.
On the issue of acclimatisation, I have changed my opinion over the years. The pattern of compressed air working has changed with the increased use of TBMs. We have moved from daily exposures for months on end, to intermittent exposures which can be on a weekly or even monthly basis.
Acclimatisation was described by Paton and Walder in their 1954 paper(1). They observed the same group of miners over a period of days, from the start of a contract, and noticed that the daily incidence of decompression illness reduced over time. They considered that observation to be evidence of acclimatisation. In my analysis of UK decompression illness records, I observed a similar effect in groups of miners who had all experienced multiple decompress illness events on UK contracts between 1984 and 2001. However, if acclimatisation exists, then the effect should be demonstrable in both groups and individuals. I postulated that the effect of acclimatisation on individuals should mean that, for persons with multiple decompression illness hits on the same contract, it would be possible to demonstrate longer intervals between successive decompression illness events. I looked at the individual miners on the assumption that acclimatisation would make them less susceptible to decompression illness, and hence increase the time between subsequent decompression illness events, and could find no evidence to support my hypothesis that individuals could become acclimatised.
Of particular interest is the conclusion by the authors that a major reason for a change in the incidence of decompression illness in 2006 was the more flexible application of the tables. The ad-hoc introduction on site of “factors”, has been a feature of decompression procedures in tunnelling for many decades but often went unreported. The ‘one table higher and/or one pressure increment longer’ approach has been used, effectively, as a way of making up for deficiencies in the tables, leading to more acceptable decompression illness incidents. Being aware of such adjustments is very important when analysing or comparing the effectiveness of different tables.
Although the authors, in their symptoms and findings, mention incorrect behaviour by the workers, I wonder whether we should accept that their behaviour is not ‘incorrect’ but ‘normal’ and make adjustments accordingly in the tables.
In looking at the authors’ conclusions, I recognise and agree with most of them, however I wonder if ‘adaptations’ and ‘time surcharges’ is the way forward, or whether more conservative tables are required which take better account of deficiencies in the behaviour of the humans involved. After all, we now have the mathematical modelling capability to predict the likely outcome from any given decompression profile, and, with the use of post-decompression monitoring, we are able to link outcome with prediction and hence reduce the risk of decompression illness in the workforce.
With regards,
Dr Donald Lamont C.Eng, FICE
Director, Hyperbaric and Tunnel Safety Ltd, UK
References
1. Paton W.D.M. and Walder D.N. (1954) Compressed Air Illness An Investigation during the Construction of the Tyne Tunnel 1948-50, Special Report Series No 281, London, Medical Research Council

Donald Lamont is a member of the CEN/TC151/Working Group 4 committee responsible for drafting European standard EN 12110 on Airlocks – safety. He is a member of the Compressed Air Working Group of the British Tunnelling Society (BTS) and is Animateur of the ITA Working Group 5 on Health and Safety in Works. As a member of both, Lamont led the publication of the joint BTS/ITA Compressed Air Working Group Guidelines for good working practice in high pressure compressed air

Correcting the record of the first EPBM operation in the USA

Sep 2015

Article references: From the Archive: Anacostia challenges America's first EPBM - TunnelTalk March 1987
Feedback from: Pete Petrofsky
One has to be careful in making a claim of first of anything.
In the case of first use of an EPBM in the USA, the actual first use of an EPBM was by Obayashi on the San Francisco North Shore Outfalls Consolidation Contract N-2 in 1979. This was a 3.7m o.d. Mitsubishi machine working through wet silts and sands under North Point Street in the Fisherman's Wharf area. The bidding documents allowed use of either a TBM or compressed air, with temporary support to be designed by the contractor and I helped Obayashi with their bid by producing estimates for the alternatives that clearly showed the savings in using an EPBM.
Their bid easily won the contract and left their American competitors thinking they had "bought the job" to gain a foothold in the USA. In fact, they made a profit on the job and opened a few eyes to this new technology for tunnels in wet soils.
The lining design was a relatively light bent steel plate type designed by the late Jim Wilton, my partner at Jacobs Associates. My memory is that progress averaged about 60ft/day.
Feedback from: Victor Romero
Dear TunnelTalk: Your Archive article on the WMATA Green Line crossing of the Anacostia River in 1987 was very interesting and highlighted what a great achievement that project was for all involved.
Such acknowledgment is also deserved by the North Outfall Consolidation Sewer N-2 Tunnel in San Francisco, which was completed in 1980 by Obayashi with a TBM supplied by Mitsubishi. This project can be recognized as the first use of EPB technology in the United States. An excellent paper on the N-2 project was authored by Clough, Sweeney and Finno in 1983 in the Journal of Geotechnical Engineering.
Feedback from: Russell Clough
I believe the first EPB in the US was the Mitsubishi machine on Obayashi's N-2 project in San Francisco in 1979-1981. This was some six years before the Anacostia crossing project in Washington DC.
Obayashi was low bidder on two projects in San Francisco (N-1 and N-2) and they asked me to be Project Manager on both jobs. Tunnels & Tunneling did an article about that particular management choice that featured Mr Obayashi on the cover and quoted him as asking Joe Casey the President of Dillingham if it was okay to hire me.
N-1 was a Mitsui roadheader excavation operation with ribs and boards for immediate support while the N-2 contract was based on an EPB operation using steel liners. If you go back into the T&T archive you will find several articles about the jobs.
Both tunnels were about 12ft diameter excavated and I recall Richard Lovat asked me if he could visit the job and I took him in on night shift in order not to disturb the OG people who did not realize that this was common practice in the States (I believe that was the first EPB Richard had seen).
Several years after the jobs were completed and all the controversy was settled, the OG people honored me with a special awards dinner and I believe we all have great respect for the first EPB job in North America. The Japanese equipment engineers and contract managers etc were excellent and the American workers performed well.

Personal thoughts on the application of mega-TBMs

Apr 2015

Article references: Discussion Forum: Reflections on the Alaskan Way mega-drive - TunnelTalk Apr 2015
Yes for decades TBMs and a few digger shields have had similar problems as those being experienced currently on the SR99 TBM project in Seattle. That is why it is so SAD to see what highway engineers are doing for tunnels in Seattle and Los Angeles, thinking: “I can run a dozer. TBMs are not much different.”
In 1985, I was assisting the first underground railway in Guangzhou, China for the heavy rail subway. French engineers wanted to give them a 25ft diameter enclosed face shield. I told them as long as it is free and to ask for 10 spares for anything made of rubber, plastic, and flexible piping.
Bertha probably had an equipment and operator error. It is called torque for a 60/30ft lever arm. Probably no pressure gauges in the TBM to measure torque or the 1% change in face alignment or the operator wasn’t watching and no on-board CAO system was in place, operating, or being read. With torque, seals, gaskets, and bearing crash. This isn’t rocket science. TBMs have been operating since 1982 or before.
I prefer open face mining like the 2014 completion of Caldecott fourth bore highway tunnel and the Devil’s Slide highway tunnel in the San Francisco Bay Area in California. No TBM problems.
Bertha's problems are applicable for comments in California where the Los Angeles SR-710 DEIR [draft environmental impact report] is proposing four (4) 60ft diameter TBMs to meet at 2 miles in. No inventory of abandoned water wells has been conducted. Many homes in the 1900-1930 period may have had their own water wells for irrigation. Sometimes they used steel pipes for casing the wells and most drillers of the period would use standard oil field technology – up to about 300ft deep – and including 8in steel pipes. If abandoned they would normally dump cement and sand down the hole. If Big Hilda TBM ran into such a pipe without proper pressure monitoring – poor Hilda stuck again – we told you so!
Dr Tom Williams
USA

Exploring the development of embedded liners on tunnel lining segments

Nov 2014

Article references: First use of embedded line in tunnel segments - TunnelCast video, Oct 2009
Dear TunnelTalk,
I was interested in the video article on your latest TunnelTalk Alert entitled First use of embedded liner in segment.
It describes the first use of a plastic liner fixed to the precast concrete segments during their fabrication which was developed for the Sacramento Upper Northwest sewer project in Northern California and managed during installation by Project Manager on site, Pat Doig, for Construction Management team Hatch Mott MacDonald for the owner, Sacramento Regional County Sanitation District.
Although it is the first use of an embedded plastic liner on precast concrete segments, as a matter of historical interest, it is not the first use of an embedded liner on concrete segments.
An earlier use was for the second Dartford road tunnel under the Thames in the UK that was built by Balfour Beatty in the 1970s and with Mott MacDonald as the project engineer and designer.
In that case it was a steel liner attached to the precast concrete segments by steel fishtails. Steel strips were then welded over the joints to make the lining watertight. Unfortunately the water pressure got behind the liner and in some places pushed it off the concrete segments, with the result that the tunnel started to leak in some places. As far as I know it was never used again.
Best regards,
Alastair Biggart,
UK Tunnelling Consultant
From the Editor: For those who have access to a print magazine archive, construction of the second Darford road tunnel was the topic of an article by Piers G Harding in the Jan/Feb 1997 issue of Tunnel&Tunnelling, the official magazine of the BTS-British Tunnelling Society

Response to macro-synthetic fibre critique

Nov 2014

Article references: Critique of synthetic-fiber FRS paper - TunnelTalk, September 2014
From Dr Stefan Bernard, TSE Laboratory, Australia
Dear TunnelTalk,
Thank you for providing me the opportunity to respond to the recent criticism published in TunnelTalk by Mr Pierre Rossi[1] as Critique of synthetic-fiber FRS paper. The criticism concerned a paper I published at the WTC 2014 conference at Iguassu Falls in Brazil in May 2014[2]. The original article is titled The Use of Macro-synthetic FRS for Safe Underground Hard Rock Support but unfortunately was not included with the criticism thereby making assessment by others somewhat difficult. I would like to respond to the criticisms levelled against that paper through the following series of points.
The article by Mr Rossi comes as no surprise given that he has published previous papers promoting steel fibres[3] and is a consultant to Bekaert. His criticisms essentially mirror the stock standard arguments that steel fibre manufacturers have promoted for many years. However, there appears to be a discontinuity between the theory Mr Rossi likes to base his criticisms upon and reality, given that several million m3of macro-synthetic fibre reinforced shotcrete (MSFRS) is now successfully performing its role as ground support in underground hard rock excavations around the world, with a further 1.5 million m3 being added annually. In addition, recent civil tunnels in Norway have seen macro-synthetic fibres used in more than 80% of the shotcrete used for ground support, with the remainder comprising steel fibres or rebar. The great success that macro-synthetic FRS has enjoyed internationally suggests the basis of the steel fibre industry's arguments against macro-synthetic FRS needs revision.
As noted in my paper at the WTC 2014, the main drivers for the adoption of macro-synthetic fibres as reinforcement in shotcrete for hard rock support have been its demonstrated performance in the field, together with economic and corrosion-based advantages over steel fibre reinforcement. Its effectiveness in the field has defied the many naysayers who fret about alleged creep problems. The simple fact is that engineers employed in the hundreds of mines and civil tunnels internationally that now use MSFRS do not care what material the reinforcement is made of provided it performs the roles required of it. But unlike engineers in the field, advocates for steel fibres prefer to rely on theory as a basis for claims against macro-synthetics rather than actual performance in the field. Numerous papers have also been published on the problems steel FRS has exhibited in relation to corrosion at cracks or embrittlement in concrete of 40MPa 28 day strength and upwards[4-9], yet these studies are conveniently ignored.
In relation to technical criticisms, one can firstly ignore the comments about 'retaining walls' and 'ductility in the interior of cracks' since neither of these topics was mentioned in the WTC 2014 paper. However, Mr Rossi made the following explicit claim in relation to macro-synthetic FRS:

"With this type of fiber reinforced concrete, the only way to ensure the stress hardening behaviour of the material, and therefore to permit redistribution of forces, is to have a hyperstatic mechanical system. This is the case when the underground support interacts with rocky ground with hard rocks."

This passage implies that 'stress-hardening behaviour' is a requirement for shotcrete to perform successfully as ground support in hard rock applications. I challenge anyone to point out an example of the successful use of a 'stress hardening' FRS anywhere in the world! One of the most successful and widely used approaches to the design of ground support with FRS is the Q-system[10, 11], which has been shown to work very effectively with strain-softening FRS exhibiting an energy absorption of only 1,000 Joules at 25mm deflection in the EN14488.5 square panel test[12] (or 400 Joules at 40mm deflection in the ASTM C1550 round panel test[13]). There is no requirement for stress hardening behaviour in this or any other widely used design method for hard rock FRS linings. This is one of the reasons why dosages of macro-synthetic fibres are seldom required to exceed 7kg/m3, and steel fibre dosages seldom exceed 40kg/m3, to achieve satisfactory support of hard rock. In shotcrete there is a diminishing return in post-crack performance as fibre dosage increases since fibre rebound increases rapidly as dosages exceed the levels indicated above. Dosages of 50-60kg/m3 of steel fibres are also exceedingly difficult to spray, which anyone familiar with fibre reinforced shotcrete would know.
On embrittlement (or post-crack performance loss with age), Mr Rossi says:

"I assert that the steel fibers usually used in shotcrete, having a length of around 30mm, can be used in a matrix for which compressive strength can reach 90MPa with only a small percentage of them breaking."

This unsubstantiated claim flies in the face of numerous experimental studies conducted on both shotcrete and cast FRC with steel fibres, incorporating thousands of test specimens, including recent research published at the WTC 2014 in Brazil[9], an international symposium on shotcrete held in Norway in June 2014[8], and a tunnelling conference held in Sydney in September 2014[7]. One has to ask the question: how many times does the same investigation have to be performed, resulting in the same damaging outcome, before the reality is accepted that steel FRC loses performance with age? The continued denial by the steel fibre industry of the insidious problem of performance loss with age reminds me of the tobacco industry's response to lung cancer in the 1970s.
In relation to corrosion, I agree with Mr Rossi's claim that the small diameter of steel fibres means that disruption of the concrete matrix is minimal when corrosion occurs. However, the small diameter also means that only a shallow degree of surface corrosion is required before substantial loss of fibre cross-section occurs, leading to rapid loss of structural capacity at cracks, as demonstrated by Kaufmann in his recent research performed in Switzerland[9], and Nordstrom in earlier work performed in Sweden[14]. It merely needs to be pointed out that ground water leaks through shotcrete tunnel linings in road tunnels or metro tunnels are widely observed and evident to most members of the travelling public. Cracks can therefore allow water to pass through a lining directly to exposed fibres at a crack. The claim that cracks in shotcrete linings heal themselves and are therefore nothing to worry about is commercially-driven wishful thinking. Pressure gradients give rise to transport of oxygen and aggressive agents directly to steel fibres at cracks rather than via slow diffusion-based transport mechanisms. This is why corrosion occurs much faster in real tunnels than in lab tests.
In relation to creep, users of steel fibres remain constrained by crack widths to 0.30mm or less because of concerns about corrosion of steel and mistakenly assume the same constraints apply to MSFRS. These concerns are misplaced because there is no steel in a MSFRS lining, and thus there is no need for crack width limits related to corrosion. Use of macro-synthetic FRS is a 'liberation' from the constraints implied by the use of old corrosion-sensitive technology like steel reinforcement. The underground mining industry discovered this many years ago and has consigned steel fibres and mesh to the dustbin of 'technologies we no longer need's[15]! The more conservative civil tunnelling industry is taking longer to come to the same conclusion but is clearly moving in the same direction as evidenced by the increasing number of civil tunnels using MSFRS in preference to steel reinforcement[16, 17].
In summary, the criticisms levelled by Mr Rossi represent the viewpoint of steel fibre advocates that are primarily based on theoretical arguments against macro-synthetic fibres that do not match the reality seen in hard rock ground support internationally. The reason for this reliance on theoretical arguments is that these same advocates cannot point to any actual tunnels lined with MSFRS that have suffered distress in the form of excessive convergence or any other form of unsatisfactory in-service performance of the type they have frequently claimed will happen. To the contrary, macro synthetic FRS has performed very well, justifying its near universal adoption in underground mining in countries such as Australia, and rapidly advancing adoption elsewhere[15]. Steel fibres were an advance over alternatives when they first emerged commercially in the 1970s, but macro-synthetics represent a further advance in fibre technology by providing complete protection against corrosion and other serviceability-related concerns.
Regards,
Dr Stefan Bernard
Author references
1. Critique of synthetic-fiber FRS paperTunnelTalk, September 2014
2. Bernard, E.S. The Use of Macro-synthetic FRS for Safe Underground Hard Rock Support, World Tunnelling Congress 2014, (Edited by Negro, Cecilio and Bilfinger), Iguassu Falls Brazil, p40.
3. Rossi, P. Steel Fibres or Synthetic Fibres?, – Tunnels & Tunnelling, July 2009
4. Banthia, N. & Trottier, J-F, 1994. Concrete Reinforced with Deformed Steel Fibers, Part 1: Bond-Slip Mechanisms, ACI Materials Journal, Vol. 91, No. 5, Sept-Oct, pp 435-446.
5. Bernard, E.S. & Hanke, S.A., 2002. Age-Dependent Behaviour in Fibre Reinforced Shotcrete, Fourth International Symposium on Sprayed Concrete, Davos, Switzerland, 22-26 September, pp11-25.
6. Bernard, E.S. 2008. Embrittlement of Fiber Reinforced Shotcrete, Shotcrete, Vol. 10, No. 3, pp16-21, American Shotcrete Association
7. Bernard, E.S., 2014. Age-dependent Changes in Post-cracking Performance of Fibre-Reinforced Concrete for Tunnel Segments, 15th Australian Tunnelling Conference 2014, Sydney, 17-19 September, pp229-235.
8. Bjontegaard, O., Myren, S.A., Klemtsrud, K., and Kompen, R., 2014. Fibre Reinforced Sprayed Concrete (FRSC): Energy Absorption Capacity from 2 Days Age to One Year, Seventh International Symposium on Sprayed Concrete, Sandefjord, Norway, 16-19 June, pp 88-97.
9. Kaufmann, J.P., 2014. Durability performance of fiber reinforced shotcrete in aggressive environment, World Tunnelling Congress 2014, (Edited by Negro, Cecilio and Bilfinger), Iguassu Falls Brazil, p279.
10. Barton, N. & Grimstad, E. 2004. The Q-system following thirty years of development and application in tunnelling projects, Rock Engineering - Theory and Practice, Proceedings of the ISRM Regional Symposium EUROCK 2004, Salzburg, Austria, pp. 15-18
11. Barton, N., 2012. Defining NMT as part of the NATM SCL debateTunnelTalk, September 2012
12. BBS-EN 14488, 2006, Testing Sprayed Concrete, British Standards Institute, London
13. ASTM International, C1550, Standard Test Method for Flexural Toughness of Fiber Reinforced Concrete (Using Centrally Loaded Round Panel), ASTM International, West Conshohocken, 2012
14. Nordström, E., 2001. Durability of steel fibre reinforced shotcrete with regard to corrosion, Shotcrete: Engineering Developments, (Edited by Bernard), pp213-217, Swets & Zeitlinger, Lisse
15. Bernard,E.S., Clements, M.J.K, Duffield, S.B., and Morgan, D.R., 2014. Development of Macro-synthetic Fibre Reinforced Shotcrete in Australia, Seventh International Symposium on Sprayed Concrete for Underground Use, June 16-19, Sandefjord, Norway.
16. Decker, J.B., Madsen, P.H., Gall, V, and O’Brien, T.M., 2012. Use of Synthetic, Fiber-Reinforced, Initial Shotcrete Lining at Devil’s Slide Tunnel Project in California, Transportation Research Record: Journal of the Transportation Research Board, No. 2313, pp. 147-154.
17. Gonzalez, M., Kitson, M., Mares, D., Muir, M., Nye, E., and Schroeter, T., 2014. The North Stratfield Rail Underpass – Driven Tunnel Design and Construction, 15th Australian Tunnelling Conference, Sydney, pp369-374.

The cons for having all the TBM delivery eggs in one basket

Mar 2014

Article references:
Soft ground challenge for Doha EPBMs - TunnelTalk, February 2014
Herrenknecht sweeps Doha Metro Phase 1 - TunnelTalk, January 2014
Weekly Alert Editor's Desk Comment - TunnelTalk, 27 February 2014
Dear TunnelTalk,
I read with interest the article by Peter Kenyon reporting on the Acceptance of the first TBM for the Doha Metro. This follows the January 2014 article which headlines Herrenknecht sweeps Doha Metro Phase 1.
The 'green giant' certainly has done well on this project and the article certainly sings its praises. I was interested to see Gunther quoted as saying after the first machine, three more were nearly finished in the Schwanau factory. Does this mean the remaining 11 machines are being delivered from the Herrenknecht Chinese factories?
Following these two articles, on the 27 February, the TunnelTalk Editor's Desk Comment reads:
"Owners and contractors.... are increasingly breaking with conventional wisdom.... of spreading.... risk between machine suppliers ....[and] make working with a single manufacturer an increasingly attractive option".
Speaking as an independent, I cannot agree with the Comment. I have the highest regard for Herrenknecht, both as a company and for the high quality machines it produces, but it cannot be good for the industry, for the owners or for the contractors, when there is a monopoly of supply of such an important piece of equipment.
The numbers of TBM suppliers has been slowly dwindling over the last 10 to 15 years, and now it is true that Herrenknecht is the leading supplier. Its market share must be extremely high, and we, as an industry, should be encouraging other suppliers to compete more vigorously, rather than suggesting or implying that a single supplier has benefits.
I question the three reasons given in the TunnelTalk Comment.
"Economies of scale"
The suggestion that a single supplier, with no competition, will offer more economical machines is flawed. Whilst there are some aspects of the manufacturing process that a large quantity may produce higher efficiencies, it is a fact that every machine is slightly different, and every TBM is treated as a one-off.
"Non-repetition in the design process"
This does not always follow as every contractor and every project has its own needs and requirements. A perfect example is in Hong Kong where two TBMs supplied by Herrenknecht for the same project and to work through basically the same ground, but for different contractors, are manufactured to two completely different designs.
"Carefully phased rollout programmes"
I am not sure of the logic here, but every factory has a limit to the number of TBMs that can be produced at a single time. For a factory that becomes so busy, there is the reality of delivery schedules slipping and quality suffering.
Any industry that relies on a single supplier of important components will ultimately suffer. Without getting too political, it has to be true that competition is healthy for innovation, for quality and for price. Once it is seen that one supplier is so dominant and that contractors are always going to use the one dominant supplier, the potential competitors stop quoting for supply to that contractor. The feeling is "why waste our time quoting when we know we won't get an order?"
The longer this dominant position goes on, the harder it is to break the situation.
Both owners and contractors continually ask for track record of the manufacturers and as long as buyers stick with the same supplier, no-one else gets the chance to demonstrate its capability and build a track record. I know that there are some in the industry, amongst both contractors and owners, who are equally worried about this, but who do not have the courage to go out on a limb.
As a single supplier becomes busier, and is not pressed by competitors, the quality of the supply is bound to deteriorate, both because of lack of alternative pressure and because the workplaces and factories become so busy that there is not time to keep up a high quality. Without wanting to make specific allegations, this is certainly true in my experience over the last two years with the TBMs that I have seen.
In this respect, praise must be given to MMC-Gamuda on the KVMRT Metro in Kuala Lumpur, Malaysia. The JV purchased six machines of a very special design, and for which there was no possible competition, from Herrenknecht, but they refrained from putting all their eggs into one basket, and purchased two of the remaining four standard EPB machines from a Chinese supplier CREC-TBM (now known as CREG). And, it must be emphasised, the JV has not regretted its decision. The price competition achieved the desired result and the technical performances of the Chinese machines is not disappointing. It must be hoped that other buyers on other projects have the courage to follow this excellent example, and that CREG continue to be seen on other projects outside of China.
There is more that can be said in this respect and in response to the TunnelTalk articles. For example, the emphasis on the German connection with Qatar seems out of place when the Red Line North contract is awarded to an Italian contractor, the Red Line South to a consortium that includes a French contractor, and the Green Line has a main Austrian contractor, but this letter is offered as a start of a discussion about competition, or lack of it, within the industry.
Best Regards,
Richard Lewis, YL Associates Limited, Hong Kong

Soft ground challenge for Doha EPBMs - TunnelTalk, February 2014
Herrenknecht sweeps Doha Metro Phase 1 - TunnelTalk, January 2014
Weekly Alert Editor's Desk Comment - TunnelTalk, 27 February 2014

Jury out on green infrastructure

Feb 2014

Article references: DC Water scales back CSO tunnel plans - TunnelTalk, January 2014
Dear TunnelTalk,
I have followed DC sewer issues since 1968, although I am not a professional engineer. I was a stakeholder representing the Sierra Club during the formulation of the Long Term Control Plan back in 1999-2000 and am representing them in this current discussion.
The DC Water proposal is just the beginning of a long process to request a modification to the Consent Decree governing the deadlines in the Long Term Control Plan - a request that must be approved by the EPA and the Department of Justice. While the proposal does a good job of outlining the costs of treating impervious surfaces in the District, there remains the question about how effective these measures will be and how quickly they can be implemented. DC Water concedes that green infrastructure on this scale has never been attempted and that there may be institutional barriers to solve, including long-term ownership and operation and maintenance issues.
I am still digesting the 700+ pages of the report (Long Term Control Plan Modification for Green Infrastructure) but so far it is less than clear whether green infrastructure can substitute for the additional tunnel along the Georgetown waterfront (along the Potomac). On the Piney Branch (Rock Creek) tunnel, the overflows in that sewershed have much less volume and less duration and other structural changes may be cheaper and more effective and less impactful than a tunnel. But it is still early days on this and I am sure there will be robust discussion.
DC Water will accept comments until March 14.
Regards,
Marchant Wentwort,
Wentworth Green Strategies, Washington, DC

Jan 2014

Article references: Subsea tunnels for oilfield development - TunnelTalk, November 2013
Dear TunnelTalk,
I read with interest the article by EivindGrov and NTNU/Sintef colleagues about the continued interest in multiple TBM tunnels for personnel access and pipeline transport/production to-and-from off-shore petroleum locations, in their article Subsea tunnels for oilfield development.
This of course shows some interesting developments in relation to the Troll-i-Fjell project that some of us worked on in Norway in the mid-1980s for the company Petromine. The stability of circular openings in some assumed weaker sedimentary rocks was the focus for NGI studies at that time.
Fig 1. Synthesized present world-record data for different sizes of TBMs using a log-log-log plot of penetration rate (PR) on the left axis only, advance rate (AR) in the remainder of plotted area, and time (T) as total hours

Fig 1. Synthesized present world-record data for different sizes of TBMs using a log-log-log plot of penetration rate (PR) on the left axis only, advance rate (AR) in the remainder of plotted area, and time (T) as total hours

The purpose for this letter is to show and discuss where TBM world records plot on the QTBM deceleration plotting routine, based on 1,000km of TBM case records using mostly open-gripper TBMs (Fig 1). In the same diagram, the predicted Grøv et al "283m/wk average" advance is plotted as a star, assuming this is the 'constant' rate of progress converted to m/hr. In relation to world record monthly rates, shown as two small circles on Fig 1, it would indeed appear to be "by far world record speed" and shows the need of continuing the deceleration out to performances seldom achieved (Fig 2).
The world record performance at present is recorded as 16km in one year, providing a mean advance of 2m/hr. This is better than a mean of 283m/wk, so there is hope for this predicted performance (see the smiling face at 2m/hr mean for one year on Fig 1).
The results in Fig 1 are based on data provided by The Robbins Company for all sizes of machines and including data for projects using TBMs supplied by other manufacturers. Day, week and month records (given in meters) have been converted to uniform m/hr rates by dividing assumed by the 24hr, 168hr and 720hr. Data from eight countries are represented chiefly from the USA and China. The record mean monthly data plots at advance rate (AR) = 1.7m/hr for the 3m to 6m TBM diameter class and at AR = 1.1m/hr for TBMs in the 6m to 10m diameter class. This is shown as the two small circles on Fig 1. The larger crossed-circle to the right is 54 weeks for 5.8km of the Svea Tunnel, achieved as the current drill-and-blast excavation record set by Norwegian contractor LNS. The tunnel was driven in coal-measure rocks and required significant shotcreting and bolting due to varied Q.
Fig 2.  Trends from open-gripper case records representing 145 cases and approximately 1,000km of TBM tunneling(1)

Fig 2. Trends from open-gripper case records representing 145 cases and approximately 1,000km of TBM tunneling(1)

The five typical lines of performance in Fig 2. are the same as shown in Fig 1. There is some evidence, such as 56km of TBM tunnelling for the Guadarrama high speed railway tunnels in Spain, that very efficient double-shield operations could, at best, halve the general decelerations of data in Fig 2. The TBM world records plotted in Fig 1, however, using the same deceleration trend-lines, actually follow this general deceleration-with-time pattern, as do large EPB machines, but at much lower rates when operated in closed mode(1).
The star in Fig 1 marks the presumed requirement for development of the sub-sea tunnels for oil-field production caverns as suggested by Grøv et al in their TunnelTalk article, if 283m/wk is indeed the intended mean. An estimated time of 13,095 hours or 77.7 weeks for one tunnel of 22km is of course, significantly less than the "generous" 210 weeks mentioned in the article for completion of a project that comprises drill-and-blast tunnelling of the access ramps and crystalline rock kilometers, the three 22km TBM tunnels, and excavation caverns etc.
Grøv and his colleagues mention the results from the Fullprof software, applying the NTNU prognosis model estimate of 283m/wk, based on various feasible assumptions concerning cutter life and joint/bedding spacing. Rock mass strength is not mentioned but presumably is included, as in the QTBM prognosis method. As a weekly result this 283m/wk converts, by division with 7 days x 24hr, to a mean 1.68m/hour, which would indeed be a world record for a TBM in the 6m to 10m diameter range, if considered as a monthly average, or if continued for 22km which would imply 77.7 weeks, or 1.55 years, for completion, assuming 50 weeks of 7 day x 24hr production. Reaching the star in Fig 1 is indeed a significant goal.
The authors Grøv et al, 2013, mention that "scheduling would require a TBM in each of the parallel tunnels to operate simultaneously and at high advance rates, working around the clock and for several years through challenging ground conditions". However, it is necessary to reconcile the presumed 77.7 weeks theoretical result with the "several years", as access to get the TBM in place is going to use a significant part of the predicted overall 210 weeks. It is indeed wise to assume that 283m/wk would not apply when there were challenging conditions.
Regards,
Dr Nick Barton
Author references
1. Barton, N. 2013. TBM prognoses for open-gripper and double-shield machines: challenges and solutions for weakness zones and water. FJELLSPRENGNINGS-TEKNIKK-BERGMEKANIKK-GEOTEKNIKK, Oslo, 21.1-21.17, Nov 2013.
2. Barton, N. 2000. TBM Tunnelling in Jointed and Faulted Rock. 173p. Balkema, Rotterdam.

Subsea tunnels for oilfield development - TunnelTalk, November 2013
Record drill+blast work in Norway - TunnelTalk, January 2009

Overly optimistic forecasts for PPP toll project proposals

July 2013

Article references: Australia suffers toll concession failures - TunnelTalk, July 2013
Dear TunnelTalk,
From Brisbane, Australia: Easy, lower the tolls. More cars will then use toll tunnels, revenue will flow, and people will be happy to use the infrastructure. It may take a little longer to recoup the cost but you will have happy customers.
From Greater Boston area, Australia: A good read. Sound assessments and risk profiling needs to be applied to these PPP projects. The goose does not always lay the golden egg.
From Brisbane, Australia: Interesting reading. I have worked on the Airport Link in Brisbane both the design and construct contract and now on the operations and management side. It is truly a fantastic piece of infrastructure lead by some highly experienced Directors. ARUP/PBA really need to be held accountable and honestly, prosecuted for getting the projections so so so WRONG.
From Brisbane, Australia: I understand this tactic, and by no means condone the methodology used by those to build these models, but we need to remember, false projections are easy to target, but if these organisations were not able to substantiate or, more likely, ‘sell’ these claims and projections initially, the financiers would not have supported the project and would not have had the opportunity to build these wonderful pieces of infrastructure.
See the original postings on our LinkedIn account.
Further comments will be added as they are received.
To add your comment, send us a message via our Feedback facility

Hands on experience to assist legal hearings

Dec 2012

Article references: Expert witnesses and forensic consultants - TunnelTalk, Dec 2012
Dear TunnelTalk,
I believe hands on experience alongside academic expertise are invaluable when seeking help with arbitrations to assist the legal team to put forward a fully rounded case.
Regards,
Ray Naughton, TBM Operator at Crossrail

'Imminent' and 'eminent' dangers

Dec 2012

Article references: Tunnel ceiling collapse kills in Japan - TunnelTalk, Dec 2012
Dear TunnelTalk,
Apparently, in addition to failing bolts, some of them were missing. This is a perfect example of failure resulting from failing to consider 'imminent' and 'eminent' dangers.
Regards,
Peter J. Tarkoy, Geotechnical and Underground Construction Consultant
From the Editor: An article to expand on this topic is to be published on TunnelTalk.

Being short-changed by 'local practice'

Oct 2012

Article references:
Rekindled NATM debate - SCL debate opens - TunnelTalk, Aug 2012
Defining NMT as part of the NATM SCL debate - TunnelTalk, Sept 2012
Dear TunnelTalk,
It seems that the opinion of the unnamed UK correspondent (see below) that: 'local practice should decide' on the method of tunnelling selected and applied to any project is 'sticking' as if recommended.
Is this the best we have? I do not think so. If this were so then some good aspects of NATM or NMT or hybrids of both as appropriate to conditions, would be lost and time and cost would suffer in relation to the 'local practice'.
Regards,
Nick Barton, International Consultant, Rock Engineering, Norway

Adding to NATM, SCL, NMT definitions

Sep 2012

Article references:
Rekindled NATM debate - SCL debate opens - TunnelTalk, Aug 2012
Defining NMT as part of the NATM SCL debate - TunnelTalk, Sept 2012
Dear TunnelTalk,
This may be a very naive view but I find the debate about the difference between SCL and NATM very confusing.
I have always thought that the term SCL (Sprayed Concrete Lining) simply refers to the use of sprayed concrete to form a tunnel lining. There are of course numerous philosophies and design methods surrounding this technique but to me the term SCL is simply a term for a specific construction method.
As for NATM, the way I have viewed that is the use of convergence confinement principles applied to a deep tunnel with the use of Sprayed Concrete Lining to enable the installation of a tunnel lining at the appropriate level of convergence. With a definition like this it becomes obvious why NATM is not applied to typical tunnelling in the UK (or at least urban tunnelling in the UK).
Firstly one of the primary aims for urban tunnelling is to avoid excessive ground movements and this approach is fundamentally different to NATM where ground movement, up to a certain point, is actively encouraged to develop arching in the ground around the excavation.
The depth of a typical NATM tunnel is also important because with large depths significant arching can be developed. For shallower tunnels the lack of overburden can inhibit the amount of arching of vertical loads that can occur.
There are also issues related to ground behaviour; the magnitude of loads applied to the lining; and the required structural thickness of the lining that also prohibit a typical urban UK SCL tunnel being designed to pure NATM principals.
Regarding the difference in philosophy between the Norwegian Method and NATM, I see these as just differences in philosophies. Local practise often dictates what is considered to be a good, safe, efficient, tunnel and what is considered poor construction practice. In different parts of the world, with different geologies, different histories, different construction constraints and different operational constraints, it is inevitable that different local construction practice applies. This seems to be particularly the case in rock engineering where you can find large differences in support in different regions. All too often one method is not necessarily better than any other. It is just different.
Maybe in one region a thick shotcrete arch is a preferred solution, despite the fact that it is stiff and can attract extra loads. Elsewhere, for a similar tunnel, heavy bolting and a thin shotcrete shell might be the preferred solution for just as valid reasons. It is the skill in selecting from a suit of different design philosophies and tools to suit local geology, local construction practice and local constraints that separate an adequate design from a good design. No one philosophy is necessarily the right one for all tunnels.
UK contributor, name withheld by request

NMT added to the NATM-SCL-SEM debate

Sep 2012

Article reference: Rekindled NATM debate - SCL debate opens - TunnelTalk, Aug 2012
Dear TunnelTalk,
Congratulations on a masterful summing-up and reminder of earlier NATM contributions to UK tunnelling. It is nice to know that good quality shotcrete as 'single-shell' has now found its way into English tunnelling (Hindhead, Crossrail etc).
Although the authors of three articles in T&T recently, who stimulated the TunnelTalk moderating comments, made reference to 'the Norwegians' and we could throw NMT into the pool of names, as this is a reflection of what has been going on in Norway/Sweden/Finland for many decades, first B+S(mr), then, after about the 1978-1983 transition, B+S(fr).
NMT principles (single-shell) are not just applied in the granitic gneisses of the Fennoscandian bedrock, as many assume. There were, in fact, 50 rock types in just 212 cases in the 1974 Q-system development. Application of S(fr) in over consolidated London Clay via the Q-system logic was suggested in 1994. See pdf download: Updating the NATM
Regards,
Nick Barton, International Consultant, Rock Engineering, Norway

NATM-SCL-SEM definitions and debate

Sep 2012

Article reference: Rekindled NATM debate - SCL debate opens - TunnelTalk, Aug 2012
Dear TunnelTalk,
I read with interest your supplement to David Hindle's article on NATM-SCL-SEM.
While I sympathise with the general thrust of some of Dave's comments, especially the desire to avoid over-conservatism, many of his detailed points are misguided.
For example, a lining sprayed in four passes - well, what happens in a traditional shotcrete supported lining? An initial sealing layer, a first layer of mesh, the main shotcrete pass, a second layer of mesh, a final shotcrete pass and then the secondary or final shotcrete or in-situ concrete lining inside. Is not that four passes? Except of course, because bars and lattice girders are used, a client like LUL would not accept the primary shotcrete passes as part of the permanent works. That itself is a point Dave has completely missed in his critique. The drive to use fibres in a (largely) unreinforced lining is partly to assuage the concerns of clients who doubt the durability of a bar reinforced primary lining.
There are numerous points in Dave's comments on the Crossrail design which are inaccurate and, had he known or spent the time to find out the constraints, he would understand why it is how it looks. I daresay that it could be improved and I believe some in the Crossrail SCL design team have sent a detailed response to the original article published in T&T, elaborating on the misguided nature of the comments.
Perhaps I misunderstood the thrust of the TunnelTalk article but at one point it seemed to imply that, after Channel Tunnel, UK designers had pinned a badge to themselves as SCL experts without bothering to try to understand the method. A few people in Mott MacDonald, for example, might take issue with that suggestion, given their own contribution to the Channel Tunnel's SCL design alongside ILF of Austria, their subsequent work on Roundhill (there are other contemporary SCL road tunnels too, including Pen-y-Clip) and the SCL trials at Heathrow, as well as Red Cross Way, the SCL trial tunnel for the Jubilee Line Extension of the London Underground near London Bridge, and the major investment in SCL R&D thereafter, including a series of PhDs and joint research projects, such as Brite Euram. It is worth noting that UK engineers have played a role in innovation of SCL tunnelling in recent years and in fact, in some cases, lead a path that the Austrians and others have followed.
Dave did ask for a definition and some explanation on the role of monitoring (in soft ground applications). If it helps, here is my definition:

"An SCL tunnel is a tunnel with a Sprayed Concrete Lining. The Sprayed Concrete Lining interacts with the ground and, through the choice of excavation sequence, this interaction can be optimized to minimize the loads on the ground support. Monitoring is required for 'performance verification', to ensure that the tunnel is performing within the limits required by the design (given natural variations, for example, in advance rates and ground conditions), to determine when certain contingency measures are needed (such as temporary inverts)."
Regards,
Alun Thomas, BA PhD CEng MICE,
Author, Sprayed Concrete Lined Tunnels
Tunnels Head of Department, Ramboll, Denmark

Sprayed Concrete Lined Tunnels - TunnelTalk, Books & Reports

Personal friends and character appreciations

Sep 2012

Article reference: Rekindled NATM debate - SCL debate opens - TunnelTalk, Aug 2012
Dear TunnelTalk,
I think that you have done Dave an injustice.
"For those who know Dave Hindle personally", you missed out a cantankerous Lancastrian who does not wear fools gladly.
Regards,
Phil Richardson, Natural Cement Distribution Ltd, UK
Personal friend and colleague

High speed, early strength shotcretes

June 2012

We at Natural Cement Distribution in the UK have been producing fast setting, fast curing, high early strength, waterproof shotcretes since 1996 that will out-preform the product described in the article War on terror heralds shotcrete breakthrough. We have shotcretes that are not a mixture of many additives, will not poison future generations, and are better for the environment than the product describe. May I suggest that you look at Shotcrete 513 in the Shotcrete section of our website to know more.
Regards,
Phil Richardson, Natural Cement Distribution Ltd, UK

War on terror heralds shotcrete breakthrough - TunnelTalk, June 2012

Fatal ring-build accident at Lake Mead

June 2012

Detail is not provided but from the read it seems the thrust ring was retracted to be ready for the next set. If so, the TBM was not moving forward so the tapered segment would not have been pulled.
Might the taper have been the source of the movement? The exterior pressures were reported to be quite high. The resulting squeeze might have been sufficient (depending on joint friction) to cause the movement. Sort of like squeezing a watermelon seed in your fingers.
Carl Linden, P.E., Senior Construction Manager, URS Corporation (Los Angeles office)

Fatal ring-build accident at Lake Mead - TunnelTalk, June 2012

Sochi winning on the Olympics alpine route

February 2012

Further to the story:
Two of the TBMs used on the project are in fact refurbished Robbins TBMs. The 10m double-shield machine that excavated the 4,564m rail tunnel for the Tunnel System 3 started its working life as a new Robbins machine as did the 6.2m TBM used for the3,197m System 3 service tunnel. Once refurbished and delivered to the project by Lovat-SELI, Robbins was contracted to supply service and technical support in the mobilization, operation and maintenance of the equipment. This included the supply of critical spare parts for continual TBM operation.

Sochi winning on the Olympics alpine route - TunnelTalk, Feb 2012

Tunnel death leads to $55,000 fine

October 2011

In reading this item the level of fine seems relatively low considering the loss of life, which is tragic under any circumstances. One wonders if the contractor knew fine levels were low and therefore permitted a superficial culture on safety and operation to exist.
Charles W. Egerton

Tunnel death leads to $55,000 fine - TunnelTalk, Oct 2011

Allowable volume loss calculations

September 2010

In reference to maximum allowable volume losses as discussed in the Crossrail settlement control measures article.
When I worked in the UK I always wondered how to get along with the historical progression of allowable volume losses. According to the British Standard some companies told me that they do some calculations about volume losses in every phase of design, let's say C then D, E, and by F, and for most design-build criteria as well, they go from 3.5% to 2.5% then 2% and arrive later at 1.5% or 1% in Stage F. Good practice would be to use the same allowable volume loss criteria during all stages of design and invoice the client accordingly. Instead of using the actual allowable volume loss from the beginning, the actual rate they will use for the final design turns up in stage F. In this way the design hangs on a rate that for some tunnel shapes will not be accepted in design stage C because the maximum allowable volume loss is too high! If they would use the actual 1% rate from the start it would be fine.
Further this calculation is very conservative for the actual volume of the tunnel shape x percentage of the actual progress, or let us say the indicator time. How long will the excavation and support go on? Also, the method of excavation, whether by TBM or NATM (SCL), is not indicated in this calculation. So it is just a total guess and will never reach true accuracy.
Tunnelling in London has been going on since Brunel's Thames Tunnel in 1825 and it is only now, in the last few years, that there is a real start to calculate this issue. By now we should be able to know what is feasible or what is not doable. With regard to applying the reduced assumption of 1% face loss on Crossrail, has someone just woken up and started thinking about this? Let us hope for better news from the island.
Robert

Crossrail geotechnical series - 3 - Settlement control measures - TunnelTalk, Aug 2010

Dublin Port Tunnel's successful DRB panel

August 2010

We have learned the composition of the DRB that facilitated settlement of outstanding claims between the owner and the design-build contractor of the Dublin Port Tunnel in Ireland. The three-member panel comprised:
Peter Chapman, Chair (UK), Brian Eggleston (UK), and Dr Terry Mellors (UK).
Contributing to the debate about the selection of a successful DRB, we can confirm that all three members of the panel are engineers, with one also a qualified barrister.
Chapman is an engineer, as well as a qualified UK Solicitor, and a past President of the DRB Foundation (2004-2006). He is a well-respected member on dispute resolution, mediation and arbitration panels.
Eggleston is an engineer and involved in dispute resolution through mediation and arbitration. He is regarded as the expert on the application of NEC3 Contracts and has written several books on the subject.
Mellors has a degree in civil engineering, an MSc in Engineering Geology and a PhD in Engineering Geology, all from Imperial College London, and has extensive experience as a design consulting engineer. He is a past Chairman of the British Tunnelling Society (BTS) (1999-2001) and was Joint-Chairman of the Working Group that produced The Joint Code of Practice for Risk Management of Tunnel Works in the UK, prepared jointly by the BTS and the Association of British Insurers as well as a primary author of the international version.
Further discussion on the topic reveals that most commentators agree that DRBs need an engineering pragmatism to succeed, and a agree concern that DRBs in both Europe and in the United States are tending towards appointing more lawyers. Another point of concern expressed was that members on DRBs in the USA are becoming partisan, adopting a position of protecting the Party that has appointed them, which is contrary to the understanding that appointees are meant to be independent and strictly non-partisan.
The debate continues.

DRB scores success in Dublin - TunnelTalk, Aug 2010
Advocating for more DRBs in Canada - TunnelTalk, Aug 2010
Dublin Port Tunnel settles claims disputes - TunnelTalk, Aug 2010
DRBs in North America - knowing and playing by the rules - TunnelTalk, Aug 2008
Enhancing the success of DRBs - TunnelTalk, Oct 2008

Safety first!

August 2010

We are grateful to Jim Hinze, Senior Safety Engineer with Cal-OSHA, who pointed out that a photo we published last week on the Caldecott fourth bore start of excavation included evidence of safety violations.
Visitors watching the launch of the roadheader at the start of the Caldecott highway tunnel fourth bore excavation in Northern California are photographed not wearing a hard hat. As Hinze said: "Down in a deep portal cut with all kinds of possible overhead hazards is no place to be without a hard hat!"
Remember guys, accidents are not selective. A hard hat is as essential as steel-toed boots, ear defenders, goggles and an acute awareness of your surroundings when visiting any job site.
We have removed the photo from the Digging begins at Caldecott article and post it here as a reminder that safety is always first.
Thanks to Jim Hinze for making the point once again.

Learning from mistakes

July 2010

Interesting report on collapses!
One could add a long list of other collapses (NATM, TBM or not), like Glendoe and Gigel Gibe II etc.
I also agree with you: one should learn from successes not mistakes. Confucius says: "Experience is like a lantern in your back. It lights only the already traveled path!"
If you look at the top sports trainers, they never tell of the mistakes you've made. Only of what you've done well and to improve on it!
Carlo Bretz
Switzerland

Discussion Forum - Symptoms of the collapse syndrome - TunnelTalk, July 2010
Rock falls shut down Glendoe power plant - TunnelTalk, Aug 2009
Glendoe rockfalls more serious than initial fears - TunnelTalk, Oct 2009
Recovery contract for failed headrace at Glendoe - TunnelTalk, Feb 2010
Collapse of headrace tunnel after grand opening - TunnelTalk, Feb 2010
Repair of limited collapse in Ethiopia - TunnelTalk, Mar 2010

Fundamental contributors to industry problems

July 2010

Big problems for the industry, in my personal opinion, are price dumping, budget cutting, assssnd time saving - and that in a field of highest safety requirements. Tunnelling industry has sometime not too much respect for its own achievements, and should not let advocates make the business. Most importantly on the negative side is talking badly about competition and badly about the industry itself.
A reader in Germany

Discussion Forum - Symptoms of the collapse syndrome - TunnelTalk, July 2010

Adding to the symptoms of the collapse syndrome

July 2010

You touch on the fact that supervision at night tends to be lessened and that the construction team is often the B team. It has been observed on many occasions that junior newly qualified engineers on the night shift are placed with an experienced team headed by a foreman or supervisor who is usually older and in theory should have more experience. Whilst many young engineers see things being done that they consider as being wrong, they cannot comment for the reason that they will be referred to as being 'wet behind the ears' and by being told that "this is the way it has to be done". Another syndrome that takes place on the night shift is that the absence of watching eyes results in the cutting of corners.
Any senior engineer on the night shift will be working alone and will have been left with a list of functions related to sorting out the back-up infrastructure and completing unfinished paper work.
There are two things that should be dispensed with:
a) Advance rate bonuses, which have the effect of making it almost inevitable that requirements in other areas will be forgotten. An example is quiet simply blocked annular grouting pipes resulting in not being able to keep grouting at the same speed as TBM advance, but carrying on with excavation regardless.
b) 12 hour shift patterns, which lead to workers, in an already stressed environment, being over tired and taking their minds off the ball. Cutting down shift times is an area that meets with considerable hostility. It is time for projects to be managed by the engineers (managers) who must face the flack of any incident, rather than finding someone lower down the chain of command to take the blame.
You also mention the failure in Cairo, in which you mention that bolts were "forgotten". Were they forgotten or did someone come to the conclusion that bolts are to be removed later, so why put them in the first place! People forget the rotational forces applied by the TBM. Cutterhead torque has to go somewhere. As Newton's Third Law that states: "For every action there is an equal and opposite reaction." I have observed personally segment joints opening up as a result of cutterhead torque. In some instances this has sheared both dowels and bolts and opening up the longitudinal segment joints.
Charles W. Egerton
North Ayrshire, UK

Discussion Forum - Symptoms of the collapse syndrome - TunnelTalk, July 2010

Learn young and from small mistakes is the key

July 2010

I think you might want to modify slightly your comments on learning from failures to include the following:
All of us should be lucky enough to start in our 20s learning from our own small failures. More is learned from bad jobs than good jobs. Perhaps as important is to pay attention to details of mistakes that "almost" or "could have" resulted in very serious consequences.
I believe that most of the serious cave ins you write about would not have occurred had a couple of the people in charge (including designers, owners, engineers, contractors, etc) had more 'failure' experiences in their 20s. Unfortunately that kind of good experience is less common now and perhaps the reason why we are seeing more of these unnecessary problems.
Thank you for writing about this topic in your editorials. It needs more knowledgeable discussion.
A reader in the USA

Discussion Forum - Symptoms of the collapse syndrome - TunnelTalk, July 2010

Filling in the list of giant TBMs

June 2010

Thanks to the readers who let us know of the missing entry on our list of mega +14m diameter TBM projects. The 14.2m diameter Herrenknecht Mixshield used to excavate the 4th Elbe River Road Tunnel in Hamburg in 2000 is added to the list along with the two highway tunnels in Moscow that the machine went on to excavate. Also added is the 14.4m diameter Robbins open main-beam gripper machine working on the hydro scheme water diversion tunnel at Niagara in Canada.
Good to know you are paying attention.

Taking mega TBMs to greater diameters - TunnelTalk, June 2010

Natural cement contributes to waterproofing of the Hindhead project

March 2010

In reference to the spray-on waterproofing of the Hindhead tunnel, I would wish to advise of some of further information.Among several methods tried to prevent and divert areas of water ingress ahead of application of the spray-on membrane, one the most effect ways was application of a natural cement based shotcrete call Shotcrete 513. Many tonnes of this material were used to stop the water ingress and allow the application of the Masterseal. the day joints were not always water proof and that by over spraying afterwards with our Shotcrete 513 it stopped the ingress of water allowing the application of the Masterseal which cannot be applied to areas of tunnels where there is an ingress of water.
Regards,
Phil Richardson, Natural Cement Distribution Ltd, UK
TunnelTalk: While the text doesn't state the case specifically, it does address the "permeability specification of 1 x 10-12m/s for the primary shotcrete provides a waterproofing barrier of quality itself". The natural cement based product would have contributed to achieving that quality.
Phil Richardson: The problem was that the day joints were not always waterproof and that by over spraying afterwards with our Shotcrete 513 it stopped the ingress of water allowing the application of the Masterseal.

UK applies spray-on waterproofing TunnelTalk, March 2010

Various support products but spray-on is the waterproofing system throughout

March 2010

The natural cement product was used but as one of a number of measures that were adopted for the purpose of dealing with areas of water ingress. The project adopted a methodology of having a suite of solutions available to the construction team allowing them to respond immediately to the conditions that presented themselves. We used it to cover damp blooms or to cover strips of water channeling Delta membrane. There are a number of products used to assist in the application and performance of the Masterseal. There are no areas of the mined section of the tunnel where other products are operating instead of the Masterseal.
Roger Bridge,Tunnel Manager, Balfour Beatty,Hindhead Project

UK applies spray-on waterproofing TunnelTalk, March 2010

Providing useful information

March 2010

Dear TunnelTalk,
In reference to the Hindhead spray-on waterproofing article, you published all the right info - very useful. All too often key productivity and other data that lets the reader estimate costs are omitted from articles. Observations of crew size, equipment, and time to perform, including work schedule, go a long way to letting readers conclude for themselves how cost effective is the process.
With thanks,
John M. Stolz, PE, Principal,
Jacobs Associates,
San Francisco, California
TunnelTalk: Thank you. Reporting information for advancing the art and science of successful tunnel and underground space excavation is the mission.

UK applies spray-on waterproofing TunnelTalk, March 2010

NATM more cost effective than TBMs for Santiago Metro

March 2010

Last week, when reporting on the consequences of the massive 8.8 earthquake on underground structures in Santiago, Chile, we included by mistake reference to TBM driven tunnels for the Metro system. The error was pointed out to us by a reader and has since been corrected. All underground sections of the Metro de Santiago are either cut-and-cover structures in earlier times, or NATM excavations for stations and running tunnels since the mid-1990s.
Reprint of articles from our archive explores the introduction and development of the NATM concept as a highly cost effective method of metro construction in Santiago and and refers to the results of a study that confirmed the advantages of NATM over the TBM alternative for construction of metro running tunnels in the Chilean capital.

Santiago goes underground with NATM TunnelTalk, April 2003
Optimised NATM designs for Santiago Metro TunnelTalk, April 2003
Santiago Metro withstands massive earthquake TunnelTalk, March 2010

Inclined TBM drives and a rival TBM decline record holder

February 2010

11m diameter drive on a 30° decline

Last week we published news of a new 8.03m diameter Aker Wirth TBM claiming to drive the world's largest inclined TBM tunnel. On order by a Swiss contractor, the TBM will drive a 4km long, 24% inclined access tunnel for a hydropower plant expansion project in Switzerland.
We have since had news from Lovat claiming a larger, steep gradient TBM drive although this time on a decline rather than an incline. An 11m diameter mixed ground machine was used to excavate a 150m long x 30° declined escalator access shaft for the Moscow Metro system in Russia. The first of many planned escalator access drives for the Metro was completed in January 2009 and the machine now awaits start of the second drive, once funding allows.

LOVAT EPBM ready to head to Moscow

From our Archive we publish an article about another Lovat TBM incline of 30° completed in 1997 as part of an emergency to finish the top 400m of the steep penstock for the Cleuson-Dixence hydro project in Switzerland and not a long way from where the new Aker Wirth TBM will work on its steep incline for the Linth-Limmern power plant expansion project in the Canton of Glarus, south of Zurich.
While there is a difference direction, an incline and a decline are both working off grade and a decline can be considered the more challenging and potentially dangerous. There have been many steel inclined TBM tunnel drives but we know of only the Lovat Moscow Metro system large diameter TBM decline drive. If you know of other incline or decline TBM drives, do let us know and we will keep the record.

Top down TBM escalator drives - TunnelTalk, February 2009
Steep TBM drive for Swiss hydro scheme - TunnelTalk, February 2010
Steep incline drive saves critical deadline - TunnelTalk, April 1997

EPB and slurry machine mix up

October, 2009

A reader has informed us of an error in the our report about the Cairo Metro tunnel sinkhole article. In it we mentioned other TBM metro tunnel collapses and wrongly stated that it was a Mixshield working on the Porto metro project in Portugal. It was in fact an EPB machine that was working on the project and on which a tunnel sinkhole caused a building to collapse and claimed the live of one victim.

Cairo Metro TBM tunnel collapse TunnelTalk, September 2009

Ring beam erector still there at Jinping

October 5, 2009

TunnelTalk stated recently and incorrectly in the London conference report, that the ring beam erector on the 12.4m diameter Robbins TBM working on the Jinping project in China had been removed. Lok Home, President of The Robbins Company, has corrected the information saying that in fact Robbins had wanted to remove the ring erector as part of the rock-support installation equipment modifications but that the client insisted that it be rebuilt and retained. That was done and the ring erector is still on the machine, with the introduction of the man-carrier booms making it easier to access the large diameter span and install the ring beams. Home remains of the opinion however, that ring beams have no place as rock support elements in tunnels of 8m in diameter or more and that NATM support elements of rockbolts, mesh and shotcrete are more effective and easier to apply on such large diameter rock-TBM tunnels.

Conference report: London's eye on the underground scene TunnelTalk, October 2009
Onsite build for giant Jinping-II TBM TunnelTalk, October 2008

Safety regulations grow from disaster

September 17, 2009

Kudos to Tunnel Talk and the author of the Hawk's Nest Tunnel Tragedy Article. Modern miners often forget how many lives were lost during the dark times of lax and/or criminal neglect regarding environmental and workplace safety in underground excavations.

Sincerely,
Gordon Revey, P.Eng.

Hawk's Nest Tunnel tragedy TunnelTalk, September 2009

Contract termination - the expensive no-return option

April 2009

On a recent e-alert, the “From the Editor's Desk” message asked: "How do relations between Owner and Contractor become so intractable when contracts get into trouble and end up in termination?" It went on to ask: "Where was the dispute resolution process? Where was the co-operation to work through a difficult situation? Is termination the only solution when relations breakdown? Is the cost of rebid always fully appreciated by the boards of public owners ahead of termination?"

With respect to some of the questions about this topic, one of the ways these things fall apart is when the parties take the back-and-forth rhetoric personally. Once you begin to think in terms of “making a point”, and lose the focus on “how do I finish the job”, all hell can break loose. I’ve seen it happen, especially with big egos on either (or both) sides of the table.

William W. Edgerton, P.E.
Principle and President,
Jacobs Associates
San Francisco, California

TunnelTalk: Would it not serve the public and the project better to include a clause in the contract that senior management on both sides be turned out and new negotiators brought in before failure of discussions heads towards contract termination? There will be contract terminations in the future but the damage, the delay, and the cost make it no easy or simple solution. Recent rebid of the terminated Seymour-Capilano project in Vancouver is double the original contract price and the same was true for rebid of the DRO-2 outfall tunnel project in Detroit, which has been recently terminated for the second time due to financial constraints. The appointment and operating procedures of DRBs (Dispute Review or Resolution Boards) and methods of enhancing their potential for success has also been the topic of Discussion Forum.

Seymour-Capilano restart comes at a high price TunnelTalk, April 2009
Detroit outfall contract terminated TunnelTalk, April 2009
DRBs - knowing and playing by the rules TunnelTalk, August 2008
Enhancing the success of DRBs TunnelTalk, October 2008

Detroit water tunnel projects crippled

April 2009

Anonymous

Shouldn't the alert headline this week read; "Detroit is incompetent in more areas than just the motor industry"? They seem to be able to destroy any decent contract from any position. I cannot imagine the ground conditions are so overwhelmingly bad that it is impossible to mine. Amazing!

Detroit outfall contract terminated TunnelTalk, April 2009
Funding crisis cripples Detroit tunnel projects TunnelTalk, April 2009

Brightwater under pressure

February 2009

Lionel Suquet, Project Manager for the Vinci/Parsons RCI/Frontier-Kemper JV

“There have been more than 250 hyperbaric man-entry interventions at up to 4.8 bar pressure during the 12,500ft (3,800m) of tunnel completed to date by the two Herrenknecht slurry Mixshields being used on our Central Tunnel contract for the project. This allows only 45 minutes of work in the air by our compressed air maintenance crews with three hours in decompression. There are up to six three-member maintenance crews available in a 24-hour period and it is taking up to three times 45 minutes to change just one cutter.”

Name withheld

Investigation reveals that factory testing of the integral airlocks delayed delivery of West Tunnel contract’s TBM to site. Contract documents set rigorous pressure loss vs time specifications that had to be met before acceptance and ex-works delivery of the machine.

Name withheld

The remote camera sent in to check cutters on the LOVAT EPBM working on the West Tunnel contract, confirmed them as “like new” after 700 rings (1.5km) of tunnel excavated. This is a positive situation in the abrasive glacial conditions of the alignment.

Brightwater under pressure TunnelTalk, February 2009

In response to the article, 'AMR India Project'

January, 2009

It seems the Alimineti Madhava Reddy (AMR) Project with it 43km long irrigation tunnel to deliver water from the Srisailem Reservoir to a vast drought-prone area of farmland and villages in the central state of Andhra Pradesh in India has a long history. Feedback and anecdotes from readers in the UK tell of an attempt in the 1970/80s to design and build the tunnel.

Let us know if you recall earlier attempts to develop this benchmark project.

Maurice Gooderham, Retired, Formerly Director of Thyssen (GB) in the UK, Surrey, UK

“I read with interest the Srisailem article. In 1986 Thyssen GB was interested in the project with designers Howard Humpreys. The original documents noted that the tunnel route traverses "an area inhabited by wild and ferocious beasts”. I assume the risk of a survey team being eaten by tigers was avoided by the current availability and use of GPS.

Maurice Gooderham, Retired
Formerly Director of Thyssen (GB) in the UK
Surrey, UK

David Hindle, Tunnelling Engineer, Director, OTB Consultants, London, UK

“Believe it or not, this is the project that first got me working with Maurice Gooderham back in 1978. I was a grubby junior tunnelling engineer working for Howard Humpreys, fresh out of the mines of Africa and the burning deserts of Oman.

We got an enquiry from the Government of Andrah Pradesh to bid for the project in partnership with a suitable international tunnelling contractor. I ring Maurice and he suggested we should meet that very afternoon to discuss the options.

Howard Humpreys (now Jacobs Engineering) was based in Leatherhead, Surrey in England and the Thyssen’ offices were in Llanelli in Wales. It is a fair old way between the two and after starting at 11am and travelling on several connecting trains I arrived hot and bothered some time after 6pm, thinking I would be too late and they would have all gone home. Not a bit of it. I was ushered into Maurice’s grand office and money changed hands between Maurice and a colleague who had laid a bet on whether I would get there that day. "Never mind lad," said Maurice. "It’s not urgent we can talk about it tomorrow.” It marked the beginning of a beautiful friendship.

The Srisailem job died a death at that time and has been resurrected several times over the years - a bit like other major projects, including Crossrail in London, except that it is being built at last.

David Hindle, Tunnelling Engineer
Director, OTB Consultants
London, UK

In response to the article, 'Rebid Reprieve for Seymour-Capilano'

January, 2009

John Penner, Manager, Contracts, Bilfinger Berger Canada Ltd.

Dear TunnelTalk,

In the article Al Johnson, Regional Director for Construction, WorkSafeBC, discusses shutting down work operations on the Seymour Capilano project and comments that he could not recall if workers exercised their right to refuse to work.

Bilfinger Berger notes that his statements are misleading and inaccurate.

First, on January 22, 2008, WorkSafe BC issued orders to Metro Vancouver and Bilfinger Berger Canada and verbally directed and required the delivery of an investigation report and a safe design before any work was to proceed. To date, neither of the orders has been rescinded. In addition, WorkSafe BC has not approved any plans to resume tunneling or varied its directives to allow any tunneling.

Second, the three unions representing workers on the project all agreed with Bilfinger Berger's decision to stop tunneling after workers were injured. In a May 30, 2008 letter to Metro Vancouver's Greater Vancouver Water District, the three union leaders stated: "After our members were injured and exposed to unsafe conditions at the site, Bilfinger Berger made the correct decision to temporarily suspend the work pending a review and analysis of the rock behavior."

The safety of Bilfinger Berger workers is the company's No. 1 priority. The fact is representative worker unions and their workers are fully onside with Bilfinger Berger's position: They agree that working conditions were not safe; they agree that suspending work was the correct decision; and they have asked Metro Vancouver to review its decision to terminate Bilfinger Berger's contract.

Yours sincerely,

John Penner
Manager, Contracts
Bilfinger Berger Canada Ltd.

California fixes high-speed rail route

July, 2008

Name withheld

I am working on a study for upgrading a rail system for the east coast of the United States. This is new investment to increase rail capacity to accommodate separate intercity, commuter and freight services. These are co-mingled in most places at the moment and separation is essential ahead of projected doubling of freight rail in the region by 2030. Rail must relieve highways.
Alameda Corridor LA

Alameda Corridor LA

TunnelTalk: Separating freight from passenger traffic is the conundrum the world over. Japan and Europe bit the bullet early with construction of d edicated high-speed lines for passengers but the needs of the freight traffic have really come into their own and especially with the dramatic rise in fuel prices for truck t ransportation. The Swiss baseline rail tunnels were promoted as the green alternative to trucks that were killing off the trees through the mountains with acid rain - remember that? - but they will be ahead of the game now on the more urgent need to address fuel prices. Discussions on all these topics - and particularly about the cost of building passenger train tunnels as opposed to freight train tunnels - was very interesting at the project in Austria. It seems to be the beginning of a sea change in high-speed rail thinking in Europe. Another issue that the US is yet to address seriously is the issue of grade separations to be rid of the many disruptive and dangerous level crossings on their networks.
Alameda Corridor map

Alameda Corridor map

Much of the $950 million set aside by the California HSR Authority for service upgrades on existing feeder lines is to construct the over and under passes to eliminate level crossings. The $2.4 billion Alameda rail corridor linking the ports of Los Angeles and Long Beach to East Los Angeles rail yards was designed in large part t o eliminate traffic congestion at road grade crossings. http://www.acta.org Some 30 roads were elevated above the tracks while more than 200 other grade crossings were elimin ated depressing the two express rail tracks in a 10m deep cut for a distance of more than 15km.
Name withheld

Grade separations to avoid level crossing are the required course for speeds in excess of 160kph but the bigger issue is more tracks entirely for capacity for both freight and passengers and still not have the footprint of big highways.

Australia’s highway tunnel pain continues

February, 2007

City Link Tunnel
David Baxter, CPEng. FICE; MIE(Aust) Melbourne, Victoria Australia

Recent events on Melbourne’s City Link highway tunnel in Australia underscore FIDIC’s view that the Silver Form Conditions of Contract (EPC/Turnkey Projects) are not suitable for underground work (reference: Introduction to First Edition).

In essence Australia’s design-build contracts adopt a Silver Form approach by having detailed performance specifications, putting all the risk on the contractor including ground conditions and so-called reference material and workmanship specifications as provided by the client’s consultant, which the contractor is free to adopt or write it’s own.

In January 2007, Transurban, the owner/operator of the City Link Burnley Tunnel issued a statement saying it plans to sue the contractor, Transfield-Obayshi JV, because the tunnel was unlikely to last its’ forecast 100-year lifespan because its’ cast concrete walls were too thin. City Link has been plagued with problems on the tunnel since design and construction began. Many of the issues have been reported in the media. A settlement of the claims between all parties back in 2001 was mediated behind closed doors, losing a prime opportunity to improve industry practices.

Recent reports in the Australian media refer to walls not being built to specification. This implies a breakdown of the contractor's quality assurance system leading to a construction defect - not a design error. The self-certification process, intended to certify construction integrity without the need for independent checking, was relied upon by the client to indicate that construction quality was adequate.

A newspaper article in late January alleges claims by the independent assessor that he was pressured to approve the tunnel for opening. If this was so, and no denial has been published so far, the Melbourne public should be somewhat alarmed that the check to avoid faulty design and/or construction has been subverted.

There have been claims in the industry that the City Link’s Burnley Tunnel situation is a worse indictment of the industry’s ills than the circumstances that led to the Heathrow Express station cavern collapse in London in 1994 (Heathrow failures highlight NATM misunderstandings). It certainly has similarities due to inadequate construction standards. Reliance on design-build procurement and self-certification procedures on these projects certainly vindicate FIDIC’s reservations about the use of the Silver Form of contract for underground works.

Responsibility: Why We Don't "Just Do It"

February, 2007

William Edgerton, Jacobs Associates, San Francisco, USA

As I read the article about the Lane Cove tunnel collapse, it occurs to me that we need to have a better understanding of our responsibility for safety of both workers and the general public. I wondered how we as engineers, and indeed as an industry, are able to bear the burden of responsibility that we should feel for the performance of the projects we design. And it occurred to me that perhaps we bear it by not keeping it in the forefront of our minds as much as we should. A failure should always remind us to review our practices, because a failure offers more opportunities to learn than a success ever will. Success sometimes happens "in spite" of our efforts; failures always happen because of things we did wrong. In this respect, our projects are a bit like Tolstoy’s view of families as expressed in Anna Karenina: “Happy families are all alike; every unhappy family is unhappy in its own way.” We each fail to assume our responsibilities in unique ways.

Each party in an underground project has a set of responsibilities when it comes to safety. Owners set the stage for a safe project and serve as the behavioral model for all of the other team members. Not only do they approve the concept, but they significantly influence the safe design, construction, and operation of the facility by: (1) establishing realistic schedules and budgets for investigations, design, procurement, construction, and operational testing, (2) requiring detailed occupational health and safety plans to be implemented during construction, and most importantly, (3) insisting upon inter-team communication protocols that enable all project participants to be made aware of previously-collected information that can influence their judgment and affect their own responsibilities. Designers must recognize all potential risks, and present to the clients recommendations for ways to manage them. It is incumbent upon the designer to identify and convince the client of the importance to fund appropriate site investigations, geotechnical and otherwise. Not only must we establish design and material parameters for the final facility that enable it to perform to the intended criteria, but we must perform the detailed analysis, including necessary modeling, to indicate the ground and structure behavior during construction, and to ensure that the work can be constructed without damage or injury to third parties. And most importantly, we must evaluate the actual ground conditions during construction to verify that they agree with the assumptions made during the design process, and notify our client in the event that they do not. On design-build projects, in serving our contractor clients, we are obligated to assist in developing economical means and methods of excavation support, but in so doing we must never compromise our obligations to public safety that result from our engineering licenses. Contractors have an obligation to their workers to provide a safe work place. To do this they must plan the work in advance, establish appropriate work methods to accomplish it, employ workers who are competent for the work anticipated and have a safety focus, provide suitable training, and supervise the day-to-day activities such that workplace safety is paramount in everyone’s mind. Many construction contracts make the contractor responsible for the design of initial excavation support in portals, shafts, and tunnels. As a result the contractor must employ and direct suitably licensed professionals to perform the necessary analysis in order to ensure safety of the resulting underground openings.

Though I've outlined these responsibilities separately, owners, designers, and contractors don't fulfill their responsibilities in isolation. The responsibilities of one party overlap with those of another, and the actions of one party cause reactions and impacts. Yet, the actions that need to be taken are themselves relatively clear. So why don't we take them?

Sometimes, the parties are ignorant of their responsibilities. An owner may be building a project of a type they haven't built before, or a designer or contractor may be working with material that hasn't been used on similar projects. Other times, we may know of a responsibility or opportunity to be more thorough, and simply ignore it. Or, we may be so focused on a particular goal that we lose sight of some of the other aspects of the project that require our attention and planning. We have to guard against each of these tendencies, in ourselves and in the people with whom we collaborate. In a true partnership, the parties help bring each other into balance to achieve success. Only when we recognize the ways in which we fail to assume our responsibilities can we begin to correct our habits and build projects that are successful because of us, not in spite of us.

CERN's success, an underground triumph

September, 2008

Trans-border SSC
Clair Murdock, Heavy Construction Consultant, Ottawa, Canada

Even more distressing than collapse of the SSC in mid-tunnelling were the raw politics that sited it in Texas; not across the Canada-USA border near Malone, NY. Better rock, cheap electricity from Canada, and Canadian (and other international) funding possibilities ignored. The trans-border site would have been seen as international, not as Domestic, and some of the funding since committed to CERN would have supported the project. A compounded tragedy, with the best and brightest scientists going to CERN, not Montreal.