Term applied to a tunnel not designed to leave the fabrication facility until the external concrete structure is essentially complete. Steel plate, if used, is usually limited to acting as a waterproofing membrane. (See also Steel Tunnel)

A method used in soft ground tunnels that calls for concrete to be placed every day. During two shifts the tunnel is mined; on the third shift the newly mined section is concreted. The method enables a light primary lining to be used, and in some cases eliminates it entirely.

Being limited in movement, view, travel, etc. May induce variable psychological responses in persons using underground spaces

Earth materials, generally of sedimentary origin, which have been firmly densified or converted into rock by compaction, deposition of cement in pore spaces, and/or by physical and chemical changes in the constituents.

In soil mechanics, the adjustment of a saturated soil in response to increased load involving the squeezing of water from the pores and decrease in void ratio.

In classical geology, any or all of the processes whereby loose, soft, or liquid earth materials become firm and coherent.

The cost to create a facility. Depending on the specific context, this term may include land purchase, design fees and all costs necessary to put a facility into operation; or it may be limited only to the costs of physical construction work

Introduction into water of any undesirable substance not normally present.

A mixer into which the concrete or shotcrete ingredients (cement, aggregates, fiber, water, etc.) are measured volumetrically and fed continuously (usually into an auger-type mixer).

Process in which a concrete pour in a tunnel is poured as a continuous operation. The only shutdowns are for unforseen delays and weekends.

Change in a construction contract that either increase or decrease the scope of work, amount of materials, or length of performance time originally envisaged.

Traditional, labor-intensive excavation such as hand mining in soft ground and drill-and-blast mining in rock. Distinguished from the more highly mechanized methods of mining.

Changes in the distance between fixed points on a (cross-section of a ) tunnel lining as a result of loading on the lining

In rock core drilling, the amount of the drilled rock withdrawn as core (i.e., recovered); generally expressed as a percentage of the cored interval or coring "run". Examples: a 5 ft coring run that yields 4 ft of rock core constitutes a recovery of 80 percent.

Compression strength test on a concrete sample cut from hardened concrete or shotcrete by means of a core drill.

Group of measures adopted in order to restore environmental damages caused in the construction.

Having a benefit-cost ratio greater than 1 when all costs and benefits can be monetarized. Otherwise, cost judged to be worthwhile against benefits. When several options are being compared, the option with the highest benefit-cost ratio

Totality of expenditures implied by the implementation of that project. If expenditures are spread over time, they must normally be discounted, which is indicated by using the term "discounted cost".

Cost-benefit analysis consist of identifying and quantifying the costs and benefits and, where possible, ascribing values to them. It is used particularly for non-marketable goods.

The material, including soil and/or rock, as measured along a perpendicular from the tunnel crown to the ground surface. See also overburden.