Dubai discusses industry concerns for the region
By Shani Wallis, Editor, TunnelTalk
Optimising the use of underground dimension and developing vital underground infrastructure within the environmental, social and economic circumstances of the rapidly expanding cities and states of the United Arab Emirates and the countries of the wider Arabian Gulf and Middle East region were among topics discussed when the Tunnelling Chapter of the United Arab Emirates’ Society of Engineers (SOE-UAE) hosted its fourth annual Arabian Tunnelling Conference (ATC) in Dubai this week.
Organised in conjunction with the annual meeting of the Gulf Engineering Union, hosted for 2017 by the SOE – UAE, regional delegates from Saudi Arabia, Oman, Bahrain, Kuwait and Qatar joined a contingent of international delegates for a total of between 400 and 500 attendees. The event was sponsored also by the International Tunnelling and Underground Space Association (ITA) and was attended by the Association’s President Tarcisio Celestino of Brazil and its Executive Director Olivier Vion. The meeting in Dubai this year was an important event in the run up to the hosting by the UAE of the World Tunnel Congress and ITA General Assembly in April next year (2018).
This year two-day ATC event presented a programme under the theme Advancing Underground Space and hosted an exhibition of leading international equipment and materials suppliers, and local contractors and clients.
Following the customary introduction of dignitaries, including special guest, the Ambassador of Sweden to the UAE, and recognition of supporters and organisers, proceeding got underway with a keynote address by ITA President Celestino about the design and construction of underground metro station.
Metro construction figured prominently in the programme with papers presented on the construction of the Doha and Riyadh Metros and comprehensive presentations by
- Alaeden Jlelaty, Senior Project Manager of Skanska covering construction of the Second Avenue Subway in New York City and by
- Anthony Harding of CH2M concerning the design criteria of the new Purple Line Extension of the Los Angeles Metro in California.
Several interesting papers about technical advances were presented. These included:
- Dr Wisam Farjow of the PBE Group who described several technological advancements in tunnels operating control systems;
- Mukesh Singh Tomar of Dar Al Handasah on a theoretical approach to evaluate peak HRR in road tunnel fires;
- Adam Thomas of CGG on the mapping of tunnel-related ground deformation using satellite InSAR monitoring ranging from pre-construction baselining to post-construction monitoring
- Diletta Traldi, of BASF concerning investigation of the interface behaviour between a sprayed double bonded waterproofing membrane in a composite shell structure; and
- Benoit De Rivaz of Bekaert Maccaferri Underground Solutions who discussed innovative FRC design for underground application using the new 5D generation of Dramix steel fiber.
Other important topics discussed included those by:
- Thomas Konstantis of insurers Marsh with an insight into the prominent causes of tunnel construction failures and discussion of mitigation factors and the contribution of risk engineering;
- Petr Salak of Dr Sauer & Partners who explained the process of optimising underground station openings using steel fibre reinforced sprayed concrete lining; and
- Leopold Winkler and Melanie Piskernik of TU Wien, Austria on the cooperative knowledge management systems for grouting works on tunnel sites.
Better use of underground space
Han Admiraal and Anotnia Coronaro, Chair and Vice Chair of the ITA committee on the use of underground space (ITACUS) gave a keynote presentation that inspired the delegates of engineers involved in the design and construction of tunnels to think about other types of underground space developments. “Planners and civil engineers need to work together to realise the potential of the urban underground space and use it to maximum effect,” said Coronaro. “If we don’t expand our thinking towards more creative use for underground space then the space under our cities is a waste space!” concluded Admiraal.
In reply to a question from the floor that asked: “How can we create public underground spaces without feeling we are in a small or confined space?”, Admiraal replied that it is the interface between the surface and the underground facility that is important. “We must explore methods of introducing more natural daylight into underground spaces and to ensuring that the space and the connecting passageways, entry and egress access structure and corridors are spacious and accommodating rather than feeling small and over crowded,” he said.
The presentation included a report on the Committee’s Think Deep initiative and the establishment of its Young Professionals Think Deep Programme (YPTDP) that sponsors workshops to investigate the potential contribution of underground solutions to urban problems. After a successful work in Scotland to examine the potential for redevelopment of the Clyde River waterfront in the city of Glasgow, there are developments to organize workshops in several other international cities including Dubai which is a city in search of new solutions to urban transportation and protection of the city’s population from its harsh summer climate.
TBMs versus drill+blast and open face excavation
A particularly engaging session was the panel discussion that had a panel of guest speakers and the audience discussed the merits and potential drawbacks and concerns of applying TBMs or open face excavation methods for projects where either would be suitable.
The debate opened with a call for standardization – of both TBMs and open face excavations – to help optimize investment in machinery and potentially reduce the costs of design and construction and the time to develop and realize projects.
The point was made that on a current road tunnel project in the UAE, three sets of in-situ concrete lining formwork will be obsolete and worthless at the end of the contract and the forms are project specific and highly unlikely to be applicable to any other road tunnel project.
In response, it was explained that all metro running tunnels for different cities in France from 1985 to 2005 were of the same diameter with the same TBMs being moved by contractors from city to city, and that in Norway open face road tunnels are of a standard size – T9.5, T10.5 and T12. It was said that metro tunnel diameters were now being revised in France towards a new standard.
An engineer working on Crossrail underground stations in London described how, for one particular large underground station, there were an initial 20 or so different cross sections. “We managed to reduce these to five standard cross sections but it was a difficult process as there were good arguments for why other cross sections were required.”
Comments of another case study described how open face excavations are often described as ‘conventional tunnelling’. “But there is nothing conventional about the designs put forward. In one case, the design called for a 2m thick heavily reinforced cast in-situ concrete lining. With further study it was revealed that such a lining was not needed and the lining was reduced to a 15cm thick unreinforced lining of shotcrete.”
In coming back to the topic of the debate, the experience of selecting the use of TBM excavation for a long headrace tunnel in India was a deliberate decision to establish the applicability of mechanized full-face excavation in the young geology of the Himalayas. “The selection of the TBM for the Kishanganga headrace tunnel was taken with the understanding that, if required, drill+blast could take over,” was the comment. “In the end both methods were used with the TBM progressing from the down stream end and drill+blast advancing from the upstream portal and until the two met for an in-tunnel junction. The TBM did have its periods of having to be assisted with the excavation of hand-mind bypass tunnels but it did complete many kilometers of the long headrace and proved the ability of TBMs to work in the Himalayas. Contractor and clients need to be brave to select to use TBMs and to persevere through difficulties.”
Another question in the debate asked if deciding to place metro and other transportation infrastructure underground is a waste of money? The conclusion after several contributions was that no matter the initial budget, or even the over run of costs and time that many tunneled options might have endured or the public backlash or outcry about costs and potential damage to surface structures etc, in the end, the underground infrastructure will become whole heartedly accepted and the woes and troubles of the construction time forgotten.
Similar debates and discussions will continue in the media and in the programmes of coming conferences and seminars – including again in Dubai next year, in April 2018, when the UAE will host the world of international professionals involved the development of underground infrastructure and facilities.
TunnelTalk has been a media partner of the four Arabian Tunnelling Conference since the series started in 2013 and will be the official media partner for the WTC2018 in Dubai next year. We look forward to meeting delegates, exhibitors, speakers, friends and colleagues again in April 2018.
Credits: TunnelTalk (click here to view the original article on tunneltalk.com)