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Hard rock machines

Single shield TBM

A single shield machine uses pre-fitted segments to exert the blast force on the working face. Digging time represents approximately 80% of operating time, the remaining 20% corresponding to segment fitting.

Technical data sheet PAJARES.pdf

Hard-rock machines : single shield machine : Pajares
  1. Cutter head
  2. Shield
  3. Belt conveyor
  4. Excavated material removal trolley

Double shield TBM

Double shield machines allow for raster tunnel excavation as the segments are fitted in concurrent operation time during blasting (digging). In this case, digging time approaches 100% of operating time. The rear shield is fitted with grippers.

Machine progress is a 3-step process:

  1. Gripping of the rear shield onto the excavated surfaces,
  2. Digging by the cutter head (front shield advance), and laying of the lining,
  3. Rear shield advance (hence gripper advance) to the next digging position and back-up traction.

Technical data sheet CADIX.pdf

Hard-rock machines : telescopic shield TBM : Cadix

  1. Cutter head
  2. Shields
    2a - Front shield
    2b - Double shield
    2c - Rear shield and gripper
  3. Belt conveyor
  4. Excavated material removal trolley


Gripper TBM

Grippers are shoes that press radially against the walls of the excavated tunnel.

Contrary to shelded hard rock TBM, this tunnel-boring machine therefore does not rest against the lining. The force exerted by the grippers must be very high to prevent the thrust applied to the head from causing shield recoil.

Hard-rock machines : gripper TBM

1. Cutter head
2. Front shield
3. Main beam
4. Gripper trolley
5. thrust cylinders
6. Belt conveyor
7. Ring beam erector structure

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