A dimensional line in a tunnel, outside of which excavation is not paid for;. May also be referred to as the "pay line"

Top of the arch of a tunnel

Filling voids immediately after placing lining

Any granular material which is used to fill the empty space between lagging and rock surface.

Material placed around the sides and over the top of the tunnel within excavated trench after the tunnel is installed in the trench.

Pry loose from the crown after a blast.

A below-grade portion of a partially or mostly above-ground building

The arrangement of rocks in layers, strata, or beds of varying thickness and character; usually applied to sedimentary rocks, in which case it is synonymous with "stratification".

The mid section(s) between the crown and the invert in the stepped excavation of a tunnel excavated in horizontally stepped stages

An issue that is considered of value. Often used interchangeably with advantage

The value of benefits divided by the cost of a project or alternative. By definition includes only those benefits that can be expressed in financial terms

A term used to describe an element consisting of two adjacent circular steel tunnels, usually each of two lanes, combined into a common structure.

Belonging to alive nature.

A star or chisel pointed tip forged or screwed (detachable) to the end of a drill steel.

Miner's term for gunpowder, a mixture of saltpeter, charcoal and sulfur formerly used for blasting.

Smoke composed by carbon particles in suspension, proceeding of diesel engines.

Blocks of wood or concrete installed between the lagging or steel sets or collar bracing and the rock surfaces of a tunnel to transfer stress to the support.

Rock having joints or cleavage spaced and oriented in a manner such that it readily breaks into loose blocks under excavation conditions.

The sudden escape of air from a tunnel driven under air pressure

Purchase cost minus accumulated depreciation (controlled by tax structure).