TUNNELLING EQUIPMENT - Tunnel Enlarging Machine (or Reaming TBM)

Reaming is an alternative to full face tunnelling and offers a whole series of advantages.

A tunnel boring machine is first used to bore a pilot tunnel along the centre line of the planned tunnel. The reaming machine then grips the pilot tunnel in front of the cutter head and drives the tunnel’s target cross-section, support is installed immediately behind the cutter head and no longer has to bear the machine’s weight and the forces transmitted by it.

Tunnel reaming makes possible

  • Detailed geological surveying through the pilot tunnel
  • Implementation of preventive safety provisions from the pilot tunnel
  • Reliable drainage through the pilot tunnel
  • Simple ventilation arrangements through the pilot tunnel
  • Early access to critical tunnel sections and ventilation shafts
  • Fast, trouble-free completion of support work immediately behind the cutter head, thanks to generous unobstructed space
  • Easy variation of bore diameter during tunnelling

West Bypass Project in Zurich

This project consists of two 4.4km long parallel tunnels through Uetiberg and Ettenberg where the geology is soft-rock mixed formations. A WIRTH TBM 500/1440 H-HST reaming tunnel boring machine was deployed here to bore the tunnel, particularly for a 2800m long rocky section. Boring of the first tunnel started in early May 2002 and breakthrough was made in February 2003. Cutting of the second tunnel commenced at the end of April 2003 and breakthrough was completed in November of the same year. Reaming of the first tunnel was initiated on 11 April 2003.