Wood planking or other structural materials spanning the area between ribs.

Permission required to substantially change the land-level i.e. through excavation or land-filling within areas with development plans. Permission is obtained by the Building Committee

A term used for a discrete thickness of shotcrete (sprayed concrete), built up from a number of successive passes of the nozzle and allowed to set (see Pass).

(the making of) laws

The full period from the creation of a facility or object to its destruction, replacement and/or disposal. The planned life cycle may be very different from the actual life cycle

An analysis that compares project alternatives on the basis of a comparison over their respective full life-cycles taking account of differences in the timing of the investments. May focus only on issues that can be monetarized or may attempt to weigh monetarized issues against non-monetarized issues.

The cost of a project alternative resulting from a life-cycle analysis

Holes drilled in the bottom of the invert to fragment the rock in the invert. Because drills cannot be positioned to drill on the invert line, they have to be pitched slightly down in order to prevent tights.

Temporary lifting points from which an element is suspended during immersion, usually removed after an element is set on its foundation.

Low-medium capacity rail system that does not always require a dedicated right-of-way

Iron or steel plates which can be fastened together to support the arch, sides, and in some cases the invert of a tunnel.

A casing of brick, concrete, shotcrete, iron, steel, or wood placed in a tunnel or shaft to provide final everlasting bearing structure of underground space and/or to finish the interior.

Liquid polluted products.

A device for measuring axial loads by means of strain pages attached to an elastic structural member, for which a calibration curve between applied load and gage readings has been established.

Backfill, usually granular, placed carefully around the lower part of a tunnel to hold it in position.

Procedure of drilling long holes to contain powder for breaking the rock in underground excavation. As an illustration, a tunnel may be excavated by first driving a pilot drift near the center of the tunnel. Then approximately 10 ft lengths of this drift are enlarged to full tunnel dimensions at intervals of 100 to 200 ft. THese excavated areas are used as working chambers to drill holes in the remaining rock to the next enlarged section. Holes are then loaded and exploded, with relief for the explosion provided by the pilot drift.

Non-reversible modifications suffered by the ground, resulting of the decrease of one or several stresses near an underground cavity

Acoustic intensity.

Compressed air used to facilitate tunnelling in soft or very wet ground by counterbalancing external hydrostatic pressures.Supplied at 5 to 40 psi.

Grout pumped through the concrete lining under low pressure to fill any voids between the concrete lining and the tunnel surface or between steel tunnel liners and backfill concrete.