Products > Equipment: Construction, Civil engineering, Mining... > Tunnel boring machine > The Robbins Company

Earth pressure balance tunnel boring machine (EPB TBM)
ø 5 - 50 ft (1.6 - 15 m) The Robbins Company

Earth Pressure Balance Machines (EPBMs) are shield machines specially designed for operation in soft ground conditions containing water under pressure. Loose sedimentary deposits with large boulders and a high water table will challenge ordinary TBMs, but not Robbins EPBMs. Robbins EPBMs have an articulated shield that is sealed against the pressure of water inflows up to 10 Bar. Robbins EPBMs control the stability of the tunnel face and subsidence of the ground surface by monitoring and adjusting the pressure inside the cutterhead chamber to achieve a balance with the pressure in front of the cutterhead, hence the name "Earth Pressure Balance."

The working area inside the EPBM is completely sealed against the fluid pressure of the ground outside the machine.

A screw conveyor removes the fluidized muck behind the cutterhead and in front of the "pressure bulkhead". The screw conveyor's speed and discharge rate is controlled by the operator and is used to control the pressure at the working face and match the muck discharge rate to the advance rate of the EPBM.

The articulated joint between the forward shield and tail shield is equipped with a high pressure seal that allows angular movement between the shields and prevents water from seeping into the interior of the EPBM.

The EPBM erects the segmented tunnel lining as it advances. Specially designed high pressure seals in the tail shield effectively seal the machine to the outside of the tunnel lining and create a barrier against ground pressure.