Page 7 - TunnelTalk Annual Review 2017

Mega TBMs begin Tokyo ring road drives
TSracking the world’s mega TBMs
ignificant achievements and forced the 16.2km section of the ring road decisions were recorded during 2017 underground into a deep-level twin-tube and into early 2018 for the industry’s highway with three lanes in each tube.
elite sector of mega TBM applicatons. Breakthroughswerecelebrated,neworders were placed and machines of more than 14m diameter were launched or progressed on their journeys to leave in their wake underground infrastructure of truly awesome scale and monumental endeavour.
TBM Bertha arrived!
To the great relief and credit to all involved, TBM Bertha, at 17.48m diameter, broke through in April 2017.
After a marathon journey that began in July 2013, the giant EPBM, manufactured by Hitachi Zosen of Japan and operated by the Dragados/Tutor Perini Seattle Tunnel Partnership JV (STP), broke through the headwall of the north portal reception structure to complete its 2,848.5m (9,265ft) drive for the double-deck highway tunnel in Seattle, USA.
In December 2013, just six months and less than 1,000m into its drive, the mega TBM was found to have suffered major damage to its main bearing. Through the next two years, a recovery shaft was built and the TBM main components were lifted to the surface for repair and to fit a new bearing. Following relaunch in late December 2015, it was a slow, careful and steady operation that progressed the machine under the operating elevated highway viaduct and beneath the streets of Seattle to its final successful breakthrough.
The tunnel, for project owner WSDOT (Washington State Department of Transportation), will replace the earthquake damaged elevated Alaskan Way Viaduct that currently runs across the foreshore of the city.
Mega TBMs in Tokyo
Continuing in the footsteps of previous mega TBMs, in Japan four machines of more than 16m in diameter are excavating a major section of an outer ring road around the capital city of Tokyo. Fierce opposition to the original plan for an elevated highway
When completed, the project will be the largest shield-driven road tunnel in Japan, larger in diameter than the eight 14.14m TBMs used to bore the tunnel drives of the Tokyo Bay Aqua Line highway in the early 1990s (Table 1).
The budget estimate for the new expressway is ¥1.6 trillion or about US$15.6 billion. In planning for construction of the project, the authorities considered the risks of meeting the requirements of large diameter, long distance, time efficient construction, and fixed on procuring four TBMs and a contractual strategy for making it possible to continue tunnel boring from either of the four tunnel portals, should any one excavation heading run into construction difficulty.
In the strategy, the two TBMs from the south working shafts will start first and progress for about 9km each. The second two machines will launch subsequently from the north end and advance for about 7km towards in-tunnel breakthroughs for each pair.
The four TBMs for the project are procured, one from Kawasaki and three from JIM, the collaboration between Japanese TBM manufacturers Mitsubishi, IHI, and the country’s steel manufacturer JFE Engineering. One JIM machine and the Kawasaki TBM were the first manufactured and were launched in February 2017 from the south working shaft. Once the second two JIM TBMs launch from the north shaft, excavation of the main tunnels, with four TBMs in operation simultaneously, is expected to take 30 months and be complete in 2019.
Operation and success of the Tomei - Kan-Estu west will influence construction plans for other missing sections of the orbital expressway.
Success in Sicily
After two years of tunnelling below an urban area and overcoming geological challenges,
TunnelTalk reporting bored excavation for the Caltanissetta
highway tunnel using a 15.8m diameter EPB TBM manufactured by NFM was completed in June 2017.
The new twin tube tunnel, awarded by the national highways authority to a JV led by Italian contractor CMC is about 4km long and runs under the city of Caltanissetta.
The parallel tunnels run between 35m and 85m apart and through complex conditions comprising clay and marl deposits, with faults towards the ends of the alignment, squeezing ground including under the city, and a 200m long stretch of highly fractured limestone with the risk of karst features and high groundwater inflows. While the overburden was typically up to 120m, cover over the limestone stretch was about 90m with a groundwater head of 60m to 70m.
After launch on its first drive in June 2014, the mega NFM EPBM completed the first 3,878m long tunnel drive in October 2015. In April 2016, the EPBM was relaunched on the parallel tunnel and completed the 3,993m drive in mid-June 2017.
Dewatering efforts in the limestone involved sinking wells between the tunnels, to draw down the water table to a head of approximately 40m. Half way through the second drive, the machine met an unexpected calcareous limestone formation, through which dewatering from the surface was not possible. The solution was to use the completed parallel tunnel to bore a series of 40m-50m long, sub-horizontal drainage pipes into the problem zone ahead of the TBM to lower the groundwater level sufficiently to allow the shield to continue under 5-6 bar pressure.
As the TBM advanced, it erected a 14.65m o.d. segmental lining formed of 2m long rings comprising eight 600mm thick segments plus a key, each with an average weight of 16 tonne. Performance of the 13.45m i.d. segmental lining is designed to withstand the full hydraulic load of the
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