Light, hand-held percussion drill.

A ducted propeller, usually mounted adjacent to or above the traffic, that helps to maintain air velocity within that cell.

The process of applying water or air under pressure to remove debris or laitance from structural surfaces.

Horizontal support for drifter drills bolted to a jumbo. These arms allow mechanical positioning of the drill at the tunnel face. Some jibs allow rotation of the drills so that side holes and lifters can be drilled closer to the final grade.

Horizontal support for drifter drills bolted to a jumbo. These arms allow mechanical positioning for the drill at the tunnel face. Some jibs allow rotation of the drill so that side holes lifters can be drilled closer to the final grade.

Manual or hydraulic rail bender.

In rock, a naturally occuring fracture or parting along which there has been no visible movement parallel to the fracture plane or surface.

(5) Immersion Joint: The watertight joint that is dewatered when an element is installed at the seabed. It may remain flexible or can be made rigid, as is usual with steel tunnels. A temporary immersion gasket or soft nosed gasket is usually used, and an omega seal may also be installed later.

(4) Expansion Joint: A special moveable watertight joint between segments of a tunnel element.

(3) Earthquake Joint: An immersion joint of special design to accommodate large differential movements in any direction due to a seismic event. It is also applied to a semi-rigid or flexible joint strengthened to carry seismic loads and across which stressed or unstressed prestressing components may be installed.

(2) Construction Joint: A horizontal or vertical connection between monolithic parts of a structure, used to facilitate construction. A waterstop is commonly placed in such a joint.

(1) Closure or Final Joint: Where the last element has to be inserted rather than appended to the end of the previous element, a marginal gap will exist at the secondary end. This short length of tunnel will need to be cast-in-place and is known as the closure or final joint.

Used in comparative travel time and travel cost calculations. Comparison is also bound with preferences among mode of travel, waiting versus travel time and variability of travel time.

See Drill jumbo.

Any travelling frame used to support other items, such as drills, men, pipe for conveying concrete and conveyors.

One steel rib or unit of timber framing installed between two overstressed sets or between two pre-existing sets.