For the Crossrail project going under London, they used 8 machines in parallel and took 3 years to dig a total of 26 miles of 20 ft diameter tunnels. That's a

For the Crossrail project going under London, they used 8 machines in parallel and took 3 years to dig a total of 26 miles of 20 ft diameter tunnels. That's a little more than 1 mile/yr, an average number that includes overhead like moving the TBMs between the different boring sites. And the cutting surface area (which multiplies linear speed to give material removal rate) is (20/14)^2 = 2.04 times bigger for Crossrail than the Boring Co. machines.