A Robbins TBM is breaking records as quickly as it breaking rock on the $168.7M Little Calumet Leg tunnel in south suburban Chicago (T&TNA, May 2003, p29).
Although early into its drive, the 5.6m diameter machine has broken records for a hard rock machine for: the best advance in a single eight hour shift – 45.75; best advance in a day – 116.7m; best advance in a week – 474.7m; and the most rock excavated in 24 hours – 2,837m3.
Affholder will excavate the 12.8km long tunnel in two drives from a central shaft. After the first 6.1km long drive, the head and gripper support will be lifted out of the reception chamber and reunited with the body and back-up, which will be taken back through the tunnel, for the second drive.
The tunnel forms the final part of Chicago’s Tunnel and Reservoir Plan phase one, which has involved the construction of 175km of tunnels.
