Largest concrete tunnel ring made for Seattle’s Alaskan Way Viaduct
Civil Engineer
The world’s largest concrete tunnel segment ring has been assembled by CBE Group. Nearly 56 feet in diameter, the ring is made from 10 segments that each weigh 17.6 tons. The tunnel ring will be used for Seattle’s Alaskan Way Viaduct Replacement project.
CBE Group has assembled the largest tunnel segment ring in the world at over 17m in diameter to be supplied to American precast company EnCon for the Alaskan Way project in Seattle, Washington.
The largest tunnel project in the world, the Alaskan Way Viaduct Replacement Tunnel, is a bored road tunnel large enough to accommodate the two vertical layers of traffic.
CBE’s 17,068m-diameter concrete ring is the result of ten of the 40 segment moulds that will be supplied by the firm for the lining of the ultimately 2.73km-long project.
In order to achieve the record-breaking diameter of more than 16 meters, CBE engineers developed a configuration of seven core and three key segments, each 610mm thick and with a width of 2133mm.
The project has also required Hitachi to create an extra-wide tunnel boring machine at a cost of $80m, and CBE’s subsidiary Acimex has had to manufacture new equipment just to load the TBM.
The net weight of the moulds is seven tons, and one single concrete segment weighs in at 16 tonnes.
CBE is now set to ship the moulds to an automated precast facility that will be set up near the construction site to fabricate the close to 13,000 segments required on the project.
