A system for parking cars mechanically. Allows the cars to be parked in less volume per car which can be important in underground parking

A rail-based urban mass transport system -- usually with a substantial portion of the route length underground

See : Silica fume.

Construction underground with only limited points of access from the surface

A tunnel excavated without removing the overlying rock or soil and, except for shaft connections, open to the surface only at one or both ends during construction.

A skilled underground worker.

A drill hole in which all part of the explosive has failed to detonate.

The lessening of a problem by an action or change in design

Mixture of materials including cement, aggregates, additives, admixtures, and, possibly fibers used to make concrete or shotcrete (sprayed concrete).

A tunnel requiring excavation of both earth and rock materials in the same heading at the same time. Some owners may extend the definition of rock to include boulders larger that 3 ft in diameter because of similar difficulties of removal.

A short steel-pointed chisel wedge or bar for breaking and wedging out rock.

A tunnel-boring machine (TBM)

A tunnel lining that is cast in place and continuous.

Excavated soil or rock that must be removed from the tunnel or shaft in order to continue advancing. The removal operation is termed "mucking" or "mucking out".

The process of loading and transportation of the excavated ground from the face to the point of disposal.

Machine for loading excavated material into haulage units.

See Muck removal

Any type of equipment used to load muck at the tunnel face.

Continuous horizontal member installed along the side of a tunnel at the lowest excavation line to support sets or take the load of the supports from the wall plate.

Excavation of a tunnel by driving two small drifts along each side of the tunnel, which allow the side support to be placed. A top drift is then and widened out slowly to take the roof support.