What is an Earth Pressure Balance Machine?
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 work
