Mechanised Tunneling

General principles


The general principle of the shield is based on a cylindrical steel assembly pushed forward on the axis of the tunnel while at the same time excavating the soil. The steel assembly secures the excavated void until the preliminary or final tunnel lining is built. The shield has to withstand the pressure of the surrounding ground and, if present, prevent the ingress of groundwater.

The stabilisation of the tunnel face can be done by various means :

 
  • natural face support

 
  • mechanical face support

 
  • compressed air face support

 
  • slurry face support

 
  • earth-pressure balance face suppport

 

Besides the specific way of supporting the tunnel face, the specific method of soil excavation is also an important characteristic of shield machines.