PRESSURIZED FACE TUNNEL BORING MACHINES - EPBM, STBM
The EPBM is a sealed system that balances active earth pressure and hydrostatic
pressures in front of the EPBM, and it’s suitable for varying ground conditions
both above and especially below the water table. The EPB operator balances
external pressures by adjusting the machine advancement against the rate of
material extraction from the cutter chamber. Excavated material is continuously
conditioned to provide a homogenized waterproof soil mixture by the addition of
foam, bentonite, and polymers to the cutting chamber, cutter bit and screw conveyor.
This enables the cutter head operator to maintain the desired cutter head
torque and face pressure to balance the pressure of the existing soil at the cut
face. EPBM’s are compatible with pipejacking and tunneling support methods.
The STBM is a sealed system that provides continuous pressure to the face of the
excavation to balance active earth pressure and hydrostatic pressures in front of
the STBM. The STBM is suitable for varying ground conditions primarily below the
water table. Excavated material is removed via slurry discharge lines and placed
into a separation plant where the slurry is separated and recycled. The flow velocity
and the pressure is carefully regulated so that the slurry chamber pressure can
effectively counterbalance the groundwater pressure. STBM’s are compatible with
pipejacking and tunneling support methods.