earthpressurebalanced

Earth pressure balance (EPB) is a tunneling method that uses the excavated soil to support the face of the tunnel excavation. This technique is particularly useful in soft ground conditions, such as clay, silt, or fine sand, where the ground is unstable and prone to collapse.

An EPB tunneling machine, also known as an Earth Pressure Balance Machine or Slurry Shield Machine, operates by creating a sealed working chamber at the tunnel face. Excavation is performed within this chamber, and the spoil (excavated material) is mixed with bentonite or other additives to form a slurry or paste. This mixture then fills the chamber, exerting hydrostatic pressure on the tunnel face. The pressure of the slurry is carefully controlled to match the in-situ earth pressure, thereby preventing the ground from collapsing into the tunnel.

As the machine advances, the spoil is continuously extracted from the working chamber and transported to the surface for disposal or processing. The EPB machine simultaneously installs concrete lining segments behind the cutter head, which further supports the newly excavated tunnel. The key advantage of EPB tunneling is its ability to maintain face stability in a wide range of ground conditions, minimizing ground settlement and disturbance to the surrounding environment. This makes it a preferred method for urban tunneling projects where minimizing surface impact is critical.