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From the Field
The Latest Updates: Records in Toronto, the News from Nepal, and More
Much like the face of a TBM, tunneling’s wheels of progress are always turning. Join us as we check in on projects across the globe—including a breakthrough in Japan, record setting progress in Canada, and a new project ramping up in Nepal.
Setting Citywide Records in Toronto
Exciting progress is being made deep below Lake Ontario. The 7.95 m (26.1 ft) Single Shield Robbins TBM boring the 3.5 km (2.2 mi) long Ashbridges Bay Outfall tunnel is seeing record setting progress for the City of Toronto, ON, Canada. The machine, operated by contractor Southland Holdings, has recently completed 30 rings in a single day, at 1.5 m (5 ft) per ring, equating to 45 m (148 ft). With this accomplishment, the machine and crew surpassed a previous best day of 21 rings at a project with similar specifications. The Ashbridges Bay Outfall is anticipated to be the largest wastewater outfall in Canada and will improve the city’s shoreline, beaches, and Lake Ontario’s water quality.
The record-setting machine at Ashbridges Bay Outfall placed 30 rings in one day.
A Third Set of Records in Esme, Turkey
If two sets of records weren’t enough, the 13.77 m (45.18 ft) diameter Robbins Crossover (XRE) TBM boring Turkey’s Esme-Salihli Railway Tunnel has just set another precedent. In July and August 2021, the speedy machine outdid its previous records in the size class of 13 to 14 m (43 to 46 ft), boring 167.4 m (549.2 ft) in one week and 651.6 m (2,138 ft) in one month. The rates are the fastest ever recorded for any TBM over 13 m (43 ft) in diameter! They even surpass those set over a decade ago at the Niagara Tunnel Project by a Robbins 14.4 m (47.5 ft) diameter Main Beam TBM. Check out the records here.
The Crossover TBM at the Esme-Salihli Railway Tunnel is now the world’s fastest TBM over 13 m (43 ft) in diameter.
Breakthrough at Tamagawa
In June, JV contractors Obayashi & Kumagai celebrated their final breakthrough at the Tamagawa HPP #2, Lot 2 project in Yamagata Prefecture, Japan. During the bore, the crew faced unpredictable soft ground conditions and other challenges. To surmount these issues, an airborne electromagnetic survey was conducted for predicting soft ground conditions ahead of the tunnel surface and tunnel face stability was improved by using forepiling. The project, completed with the use of a Robbins 4.5 m (14.7 ft) Main Beam TBM, will supply 14,600 kw of renewable power to the region.
The Obayashi & Kumagai JV celebrate their final breakthrough at Tamagawa.
Double Shield to Bore Second Nepalese Tunnel
A record-setting 5.09 m (16.7 ft) Robbins Double Shield TBM is currently being rebuilt to tackle its second project for Nepal. The machine, which set multiple records and finished a year early at the Bheri Babai Diversion Multipurpose Project, has been chosen to bore the 13.3 km (8.2 mi) long Sunkoshi Marin Diversion Tunnel. Upon completion, the structure will divert part of the flow of the Sunkoshi River into the Bagmati river to irrigate farmland in the Tarai district. The project has been awarded to contractor China Overseas Engineering Co (COVEC), who will be bringing their expertise and experience from the Bheri Babai tunnel to this new endeavor.
The veteran Robbins Double Shield will now be rebuilt to bore a second tunnel for Nepal.