Bertha breaks into repair pit
3 March 2015Washington - Seattle Tunnel Partners (STP) advanced the TBM mining the Alaskan Way Viaduct replacement tunnel in late February into the access pit where it will disassemble the machine to perform repair work.
The 17.5m-diameter TBM, with a damaged seal system, mined through 20ft (6m) of unreinforced concrete to reach the interior of the pit.
Crews completed excavation on the 80ft-wide circular shaft, 120ft (37m) deep on January 30, and then built a concrete cradle on the bottom to support the TBM upon reception, before the TBM began mining on February 17.
