Glossary

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Earth Piercing

See Impact Moling

Earth Pressure Balance Machine (EPBM)

Type of microtunnelling machine in which mechanical pressure is applied to the material at the face and controlled to provide the correct counter-balance to earth pressure to prevent heave or subsidence. The term is usually employed where the pressure originates from the main jacking station in the drive shaft or to systems in which the primary counter-balance to the earth pressure is supplied by pressurised drilling fluid or slurry.

Entrance Seal

See Launch Seal

Entry Ring

See Launch Seal

Exit Seal

Same as launch seal except for the retrieval of the machine at the reception shaft. Used in high ground water to prevent the loss of ground.

Exit Shaft

See Reception/Exit Shaft/Pit

Eye (Pipe Jack Eye)

A sealing device placed in the shaft walls of the thrust and reception pits to allow the shield and pipes to enter and exit without soil, water and slurry flowing into the shaft.