The International Society for Trenchless Technology

See Impact Moling

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.

See Launch Seal

See Launch 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.

See Reception/Exit Shaft/Pit

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.