• TBM Bertha breaks through in Seattle

  • Mighty Hitachi TBM tested before delivery to Seattle

  • Waterview highway tunnel progress and breakthrough
DISCUSSION FORUM Tracking the world's mega-TBMs May 2017
TunnelTalk reporting
Recent news that a mega-diameter, single-tube, double-deck tunnel is the preferred option to build the 4.2 mile middle section of the 6.3 mile missing link of the I-710 freeway in Los Angeles, provides the opportunity to update the TunnelTalk Table of the world’s mega TBMs of 14m diameter and above. A machine for the Los Angeles project is yet to be procured but it will join an illustrious list of mega TBMs from the very first built and engaged to excavate the Trans-Tokyo Bay Aqualine highway project in Japan in the early 1990s.
Adding to the list in 2017, is also the four machines ordered and being launched for excavation of another mega-TBM tunnelling project in Japan for the twin-tube Outer Ring Road highway tunnel project in Tokyo, and the Zhuguang toad tunnel in Shanghai China for which the TBM used previously on the Waterview highway project in Auckland, New Zealand, is rebuilt and ready for its second project.
Fig 1. Three new mega-TBM highway tunnels in Shanghai bring the city’s total to 10 since the first in 2004

Fig 1. Three new mega-TBM highway tunnels in Shanghai bring the city’s total to 10 since the first in 2004

China continues its application of mega-TBMs for road tunnels, particularly in Shanghai, where two additional mega-TBM road tunnels in 2016 (Fig 1), bringing the city’s total to 10 since the first in 2004. China is also excavating another mega-diameter TBM highway tunnel in the city of Zhuhai near Macau on the southern coast of Guangdong which is also the landfall of the country’s Pearl River Delta bridge and immersed tube tunnel highway fixed link from Landau Island, Hong Kong.
These projects are add to a list of more that 30 projects of mega-diameter TBM road tunnels in the world (Table 1) since the first in early 1990s.
To keep the record up to date, please do let us know via our Contact Us service of any new mega TBM projects in the planning and added to the discussion about the possible limitations or potential for TBMs of increasingly large dimension.
Start date/
Country Project
* = TunnelTalk reference article - See References below
TBM manufacturer Diameter
In planning
USA Los Angeles I-170 Highway Tunnel* Yet to be procured 16m plus
2017 Japan Tokyo Outer Ring Road Kan-etsu to Tomei* 4 machines
1 Kawaski, 3 JIM
2017 China Shanghai Zhuguang Road Tunnel 1 Herrenknecht Mixshield
Ex Auckland Waterview TBM
2016 China Shanghai Yanjiang A30 Motorway 2 Herrenknecht Mixshields
Ex Shanghai Changjiang under river project
2016 China Shanghai Bei Heng Motorway 1 Herrenknecht Mixshield 15.53m
2016 China Zhuhai Hengqin Tunnel 1 Herrenknecht Mixshield
Ex Shanghai Hongmei Road Tunnel TBM
2016 Italy Santa Lucia Highway Tunnel,
A1 near Firenze
1 Herrenknecht EPBM 15.87m
2015 Hong Kong Tuen Mun - Chek Lap Kok
subsea highway link
1 Herrenknecht Mixshield 17.6m
2015 Hong Kong Liantang Highway Project NFM machine 14.1m
2015 China Wuhan Metro road/metro river crossing* 2 Herrenknecht Mixshields 15.76m
2013 China Shouxhiou Lake Highway Tunnel 1 Herrenknecht Mixshield
Ex-Nanjing Machine
2013 Italy Caltanissetta highway tunnel, Sicily* 1 NFM Technologies 15.08m
2011 China Shanghai West Changjiang Yangtze River Road Tunnel 1 Herrenknecht Mixshield
Ex-Shanghai Changjiang highway Project
2013 New Zealand Waterview highway connection, Auckland* 1 Herrenknecht EPBM 14.41m
2011 USA Alaskan Way highway replacement tunnel* 1 Hitachi Zosen EPBM 17.48m
2011 China Weisan Road Tunnel, Nanjing* 2 IHI/Mitsubishi/CCCC slurry TBMs 14.93m
2012 China Shanghai Hongmei Road 1 Herrenknecht Mixshield 14.93m
2011 Italy A1 Sparvo highway tunnel* 1 Herrenknecht EPBM 15.55m
2010 Spain Seville SE-40 Highway Tunnels* 2 NFM Technologies EPBMs 14.00m
2010 China Hangzhou Qianjiang Under River Tunnel 1 Herrenknecht Mixshield Ex-Shanghai Changjiang highway tunnel Project 15.43m
Design started
Russia Orlovsky Tunnel, Saint Petersburg* 1 Herrenknecht Mixshield
Project on hold
2009 China Yingbinsan Road Tunnel, Shanghai 1 Mitsubishi EPBM Ex-Bund Tunnel machine 14.27m
2008 China Nanjing Yangtze River Tunnel* 2 Herrenknecht Mixshields 14.93m
2007 China Bund Tunnel, Shanghai 1 Mitsubishi EPBM 14.27m
2006 China Jungong Road Subaqueous Tunnel, Shanghai 1 NFM slurry shield Ex-Groenehart machine 14.87m
2006 China Shanghai Changjiang under river highway tunnel 2 Herrenknecht Mixshields 15.43m
2006 Canada Niagara Water Diversion Tunnel* 1 Robbins hard rock gripper TBM
Rebuilt Manapouri tailrace tunnel machine
2005 Spain Madrid Calle 30 Highway Tunnels 2 machines
1 Herrenknecht, 1 Mitsubishi
2004 Russia Moscow Silberwald Highway Tunnel 1 Herrenknecht Mixshield
Ex-Elbe project machine
2004 China Shangzhong Road Subacqueous Tunnel, Shanghai 1 NFM Technologies
Ex-Groenehart machine
2004 Japan Tokyo Metro 1 IHI EPBM 14.18m
2001 Russia Moscow Lefortovo Highway Tunnel* 1 Herrenknecht Mixshield
Ex-Elbe project machine
2000 The Netherlands Groenehart double-track rail tunnel 1 NFM Technologies 14.87m
1997 Germany Hamburg 4th Elbe River Highway Tunnel* 1 Herrenknecht Mixshield 14.2m
1994 Japan Trans Tokyo Bay Highway Tunnel* 8 machines
3 Kawasaki, 3 Mitsubishi, 1 Hitachi, 1 IHI
* TunnelTalk reference below.
The largest TBM ever used on a project in Europe is the 15.87m EPBM being used to excavate the Santa Lucia Tunnel on the A1 highway north-west of Florence in Italy. It is the fourth super-sized TBM to be engaged for highway projects in Italy with others in Europe completed in Spain, Germany and The Netherlands.
In North America, the 17.48m diameter EPBM on the Alaskan Way viaduct replacement highway tunnel project in Seattle recently completed its troubled drive, breaking through finally at the north portal structure on 4 April 2017 and the largest rock tunnel ever engaged was used in Canada for the Niagara water diversion tunnel in Ontario.
Fig 1. Multi-modal Tappan Zee alternative

Fig 1. Multi-modal Tappan Zee alternative

Interestingly, the table highlights that a number of the projects have been opportunities for reuse of mega machines from previous projects and some for the second and third times.
The table is also indicating that the number of mega-TBM tunnelling projects is increasing rapidly with the first four between 1994 and 2001 matched by a recent four in 2016 alone.
Our classification of a mega-TBM is also set as a machine with a cutterhead diameter of 14m or more, which excludes the many TBMs manufactured and operated on highly challenging projects of 13.9m and less. These include the 13.5m diameter Mixshield TBM that completed the 3.34km highway tunnel drive under the Bosphorus Strait in Istanbul, Turkey in August 2015 among many others.
With the success of mega-TBM tunnel drives of 15-17m diameter and more, it was inevitable that sooner or later a TBM order would be for a multi-mode transportation tunnel. This has happened - for what is believed to be the first time - in China, for the combined three-lane highway and metro crossing of the Yangtze River in the city of Wuhan.
In the early 2000s, a similar road and rail crossing of the Hudson River in New York was suggested for urgent replacement of the ageing, deteriorating and seriously overloaded Tappan Zee highway bridge across the Hudson River (Fig 1). The New York authority instead progressed a replacement bridge, missing an opportunity to clear a blot on the fabulous river vista, improve the environment, and increase property tax revenues for properties on the river banks.
Workers dwarfed by a 17.48m diameter Hitachi EPBM

Workers dwarfed by a 17.48m diameter Hitachi EPBM

Any discussion of mega-TBM applications must also refer to the troubles experienced by the mega machine used to complete the Alaskan Way viaduct replacement highway tunnel in Seattle. The two years lost in the programme to excavate a recovery shaft and raise the TBM drive unit and cutterhead to replace the main bearing and complete of repairs is no reason for assigning blame or fault. The situation was a result of having the courage to advance engineering possibilities and expand existing technological boundaries. There are few tunnel projects around the world that have never been completed. Faced with mechanical or geological adversity, the projects do get finished and the relaunched Seattle TBM made steady progress towards its project breakthrough in April. The assurance of this, to the industry and its new generations of risk-takers, is that lessons are learned from those who took risks in the past, and that when the project is eventually open to service, the memory of cost and time overruns is quickly forgotten as the element of underground infrastructure becomes indispensible and taken for granted.
That does not excuse the necessary process of investigation and examination of potential negligence or incompetence, but it does warn against moves to stifle innovation and technological advance by overstating the associated risks. The problems, technical failings, and situations that appear to be non-recoverable will be overcome and the tunnel will be completed.
For all proposed projects that push at existing technological boundaries the industry, as a whole, must stay united in its support and overall determination to take the possibilities to the next level.
Have your say!
Join the discussion via the TunnelTalk Feedback facility.
Single bore solution for LA freeway missing link - TunnelTalk, May 2017
Mega TBMs begin Tokyo ring road drives - TunnelTalk, May 2017
China's mega Hong Kong-Zhuhai-Macao sea link moves forward - TunnelTalk, June 2011
Bosphorus Eurasia highway TBM breaks through - TunnelTalk, August 2015
Mega-EPBM for Italian highway tunnel - TunnelTalk, September 2016
Sparvo mega-TBM system available for new project - TunnelTalk, September 2014
Hong Kong awards major undersea highway - TunnelTalk, September 2013
Mega-TBMs for China double-deck link - TunnelTalk, May 2014
Video: Addressing Bertha's bearing seal issues in Seattle - TunnelCast, February 2014
'Yes' to bored tunnel alternative in Seattle - TunnelTalk, August 2011
Mega-TBM order is NFM's biggest ever - TunnelTalk, January 2013
Technical parameters of Seattle's mega EPBM - TunnelTalk, Dec 2012
Mega-EPBM naming ceremony at Hitachi Zosen - TunnelCast, December 2012
New Zealand joins the mega-TBM tunnelling set - TunnelTalk, August 2011
Russia confirms order for largest TBM ever - TunnelTalk, Aug 2011
A second mega-TBM river crossing for Nanjing - TunnelTalk, Aug 2011
Robbins TBM rolls into hard rock history - TunnelTalk, May 2011
Nanjing Highway Tunnels - TunnelTalk, Sept 2009
Seville SE-40 Highway Tunnels - TunnelTalk, April 2010
Giant TBM accepted and heading for Italy - TunnelTalk, Dec 2010
Seattle Alaskan Way bored highway tunnel - TunnelTalk, Oct 2009
Speedy mega TBM for Moscow Lefortovo highway - TunnelTalk, Oct 2002
4th Elbe tube inspires cutting edge technology - TunnelTalk, Jan 2000


UK contributor, name withheld by request

It is hard to say when the era of the mega-machine started. There was a time when 10m in diameter was considered the largest likely, or indeed possible. But whatever was once considered the technological limit for the size of TBMs, there are now many dozens of machines exceeding the 10m diameter size. This, of course, increases the benchmark for current mega-machine criteria. The need for ever-larger diameters is driven by the demand for ever-larger diameter tunnels able to incorporate extra and wider traffic lanes for heavy freight trucks as well as cars. Larger diameter bores are also needed to accommodate the latest in multi-modal transportation tunnels which will house both road and rail services as well as pedestrian and cycle-ways and perhaps also utility corridors.

Discussions in the past have considered the manufacture of the main bearing a limiting factor but these can now be designed and delivered in sections. Precision machining and welding has these vital components of the new mega-machines completed and built into them on site. A limit to the size and load of a single component to job sites was also considered a controlling barrier but first time on-site assembly, as promoted by Robbins in particular, overcomes some of these limitations.

Another consideration, as explained by Yasunori Kondo San at Kawasaki in Japan, is application of the thrust needed to advance such mega machines. For soft ground TBMs this force is applied directly to the precast concrete segments of the tunnel lining. These, as well as the number and size of the thrust rams around the perimeter of the machines, must be designed to take and deliver the powerful forces needed to move a mega-machine forward. There is a controlling factor on the number and power of the thrust rams needed to apply the force, as well as the surface area and ability of the precast concrete lining segments to accept the load.

Other considerations will be explored and added to the Discussion Forum as they are contributed.


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