EPB

In earth-pressure balance shields the material excavated by the cutting wheel sreves as support medium.

An earth pressure balance machine (EPBM) has a full face cutterhead.

Confinement is achieved by pressurizing the excavated material in the cutterhead chamber. Muck is extracted from the chamber continuously or discontinuously by a pressure-relief discharge system (generally a screw conveyor) from the confinement pressure to the ambient pressure in the tunnel.

EPBMs can also operate in open or with compressed air confinement if specially equipped.