Earth Pressure Balance

Earth Pressure Balance

Earth Pressure Balance (EPB) tunneling is a trenchless method often used on soft, wet, or unstable ground under the water table. EPB machines are considered closed‐mode machines and rely on excavated soil to provide continuous support at the tunnel face.

The earth pressure at the cutter head of an EPB machine is balanced by controlling the tunnel’s advance rate with the discharge rate of the excavated soil. As the EPB is advanced by either pipe jacking or cylinders located at the rear of the machine, the excavated material is mixed inside the plenum chamber. Earth pressure sensors on the bulkhead and screw conveyor and the steering cylinder pressure transducers provide feedback to the operator for EPB control adjustments. Ground conditioning agents like foam and other polymers can be injected into the plenum to increase the soils’ plasticity and impermeability.

EPB systems are widely known for large‐diameter projects. Technology advancements have made it possible to manufacture EPBs for smaller diameter pipe jacking installations from 72‐inches and larger with pressure capabilities up to one‐bar.

For more information on Akkerman EPB system and our capabilities, please see the equipment section or contact your Akkerman sales representative today.

Case Studies

Blacks Run Interceptor Division 1B Replacement

The Blacks Run Interceptor – Division 1B –Replacement project scope included 3,700-lf. of 48-in. sanitary sewer installed by open-cut and trenchless methods.

A 200-lf. section that crossed under Stone Spring Road requiring a tunnel boring machine to maintain traffic on a busy arterial roadway.

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Tunneling