What Does Earth Pressure Balance (EPB) Mean?
Earth pressure balance is a tunneling method that makes use of excavated material to stabilize the tunnel face with constant pressure. It is the concept behind the earth pressure balance tunnel boring machine (EPBTBM), a commonly-used piece of equipment in large-diameter trenchless tunneling projects.
The method is used for soft soils, particularly beneath the water table.
Trenchlesspedia Explains Earth Pressure Balance (EPB)
The Japanese were the first to use the earth pressure balance method in a 1974 tunneling project. The resulting tunnel was 11-feet in diameter and more than a mile long.
Earth pressure balance uses the cuttings from the tunnel excavation to provide continuous support to the tunnel face. Special foam is added to the spoil to create the desired mixture.
The consistency of the spoil is monitored with sophisticated technology so that a perfect balance is maintained in order to avoid a soil collapse at the tunnel face.