technology: tunnel boring machines

Mike Martin was familiar with tunnel boring machines from his
experience in commercial real estate in Texas. After he escaped from
jail in the wake of the CEO Trials in 2048 and came up with the
lunatic idea to fly to the moon, he bought a crappy used TBM on the
black market, fixed it up himself with a few friends in an Idaho
warehouse in 2049 and 2050, then flew it to the moon and started
tunneling what would later by the city of Aristillus.

What is a TBM?

A tunnel boring machine (TBM) also known as a “mole”, is a machine
used to excavate tunnels with a circular cross section through a
variety of soil and rock strata. They can bore through anything from
hard rock to sand. Tunnel diameters can range from a metre (done with
micro-TBMs) to 19.25 m to date. Tunnels of less than a metre or so in
diameter are typically done using trenchless construction methods or
horizontal directional drilling rather than TBMs.

Tunnel boring machines are used as an alternative to drilling and blasting (D&B) methods in rock and conventional “hand mining” in soil. TBMs have the advantages of limiting the disturbance to the surrounding ground and producing a smooth tunnel wall. This significantly reduces the cost of lining the tunnel, and makes them suitable to use in heavily urbanized areas. The major disadvantage is the upfront cost. TBMs are expensive to construct, and can be difficult to transport. However, as modern tunnels become longer, the cost of tunnel boring machines versus drill and blast is actually less—this is because tunneling with TBMs is much more efficient and results in a shorter project.

The largest diameter TBM, at 19.25 m, built by Herrenknecht AG for a recent project in Orlovski Tunnel, St.Petersburg. The machine was built to bore through soft ground including sand and clay. The largest diameter hard rock TBM, at 14.4 m, was manufactured by The Robbins Company for Canada’s Niagara Tunnel Project. The machine was used to bore a hydroelectric tunnel beneath Niagara Falls, the machine has been named “Big Becky” in reference to the Sir Adam Beck hydroelectric dams to which it is tunnelling to provide an additional hydroelectric tunnel.

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Here are my notes:


  • hard rock (used on moon)
  • soft ground (not relevant)
  • “main beam”


  • 2012 max: 20m


  • cutter head
  • shield
  • thrust system
  • support mechanism

options / weird technology:

  • 2-part shields
  • 3-part shields
  • articulated cutterheads allow machine to bore a hole bigger than it is


  • Herrenknecht AG
  • The Robbins Company


  • upfront cost 2012: $15-20 mill (for size??)
  • TJIC answer: 2060: $20 mill for a 20 meter dia built via CNC
  • operating cost assumption: 2 x 10hr shift/day, 5 days/ week

turning radius

  • A-class: 4m cutter= 105m radius
  • B-class: 10m cutter = 250 m radius [ TJIC guess ]
  • C-class: 20m cutter = 600 m radius [ TJIC guess ]
  • D-class: 40m cutter [ does not exist yet! ]

cutting speed

  • 37 m /day
  • 235 m / week = 50 m /day
  • word records:
  • 4m dia
    • best day: 172 m
    • best week: 703 m
    • best month: 2,066 m
  • 10m dia
    • best day: 105 m
    • best week: 435 m
    • best month: 1,600 m
  • TJIC answer: 50m/day = 1,500 m /month = 1.5 km / month

amount of tunnels on moon (see spreadsheet)

case studies


Spanning 20 years and using over 30 TBMs, Chicago’s massive Tunnel
and Reservoir Plan (TARP) has been possibly the largest clean water
project of the twentieth century.

The Mainstream Tunnel System was composed of 65.2 km (40.5 mi) of
tunnel, the Des Plaines System with 41.2 km (25.6 mi), the O’Hare
System with 10.6 km (6.6 mi), and the Calumet System of 59.1 km
(36.7 mi).

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