Excavation that occurs outside of the "B" line of a tunnel owing to the irregular pattern of rock breakage; the definition also describes concrete required to fill this overexcavated space in lined tunnels.

This phase of construction covers preparation for immersion, the immersion, foundation preparation, backfilling, and completion of the interior works

A steeply inclined passageway between two underground workings.

Contamination of a liquid effluent which needs treatment before disposal

Criteria and specifications of chemical, physical and bacterial constituents of water supply, depending on its use for domestic, industrial or agricultural purposes; determination of organic and inorganic constituents, acidity, specific electrical conductance, temperature, colour, turbidity, odour, taste, coliform organisms.

Cables used to move elements. Warping is the act of moving elements using warps, usually out of a narrow channel or dock.

Polluted water that has to be eliminated through the drainage system.

Continuous horizontal members along the sides of the tunnel at or near the spring line, when a top heading or multiple headings is driven to support arch sets. Often two I beam are used for wall plates. After excavating the bottom heading, supports are installed to support the wall plate from the mud sill.

Any wedge-shaped piece of which an arch or vault is composed, or assumed to be composed for purposes of analysis. The center voussoir is keystone.

Pipeline used to ventilate the tunnel, eliminating polluted air.