What Does Earth Pressure Balance Machine (EPBM) Mean?
Earth Pressure Balance Machines (EPBM) are microtunneling machines designed to prevent soil collapse or heave due to tunneling. EPBMs have a shield which holds the tunnel open, while a screw conveyer removes the cuttings from behind the cutting head. The rate of removal of the soil cuttings is used to control the pressure of the cutting head against the face of the tunnel.
Trenchlesspedia Explains Earth Pressure Balance Machine (EPBM)
Mictrotunneling through soft ground like clay, silt and sand can lead to problems in ground support during the tunneling process. EPBMs have been designed in order to balance the pressure inside the tunnel so that no collapse or heave events occur leading to delays, equipment damage or safety concerns. The open end of the tunnel is at atmospheric conditions, while the tunnel face experiences soil pressure related to the depth of the tunnel, soil texture and groundwater table.
By controlling the rate at which soil is removed, the thickness of the layer of spoil between the atmospheric conditions and the tunnel face conditions can be controlled to a level which prevents stability problems.