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.

Shotcrete (sprayed concrete) in which all of the ingredients, including water and fibers, are mixed then conveyed through the delivery lhose, either pneumatically or by positive displacement, then projected at high velocity to the surface being shot.

Special component embedded in concrete construction joints to reduce the permeability of the joints.

A measure of the capability of a tunnel to resist the penetration of water (leakage)

A skin provided external to the immersed tunnel to improve the watertightness of concrete. The membrane may be of steel or other more flexible materials.

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.