On 25 October, the Jay Dee – Michels – Traylor JV cracked the Big Walnut Augmentation Rickenbacker Interceptor (BWARI) scheme in Columbus, US, when it broke through its Lovat mixed face EPB machine after 23 months of boring.
The achievement marks the completion of Part 1of the tunnelling on the Project Clean Rivers initiative being undertaken by the Columbus Department of Public Works. Lovat said the JV praised the TBM saying, “its innovative systems performed with a high degree of reliability throughout the project”.
The 4.9m diameter mixed face EPB machine was equipped with a variable speed electric drive, a peripheral drive single stage screw conveyor and a two component grout system. It had to bore through geology characterised as soil deposits ranging from glacial till and glacio-fluvial outwash materials as well as uniform fine sands and man made fill. Numerous boulders were also encountered ranging in size from 0.3m to 1m in diameter.
The entire alignment was below the water table, with a head of 19m above the tunnel invert. Maximum EPB pressure used was 3.3bar.
The project team said that along the 6.3km long tunnel, the best daily performance was 26 rings or 39.6m advance, with a best week of 83 rings or 126.5m advance. The team also boasted the work was carried out “on time and on budget”.
