| Term | Definition |
|---|---|
| Environmental elements |
Parts or elements of the environment that could be modified by the construction activities.
|
| Environmental impact |
Damage on the environment caused by an activity.
|
| Environmental Impact Assessment (EIA) |
Assessment of the effect of an action or project on a local or regional environment. A formal requirement for certain classes of projects in many countries and with specific analysis requirements.
|
| Environmental Impact Evaluation Procedure (EIEP) |
Particular type of Environmental Impact Assessment carried out in the European Union.
|
| Erector / Erector arm |
Swing arm on boring machine or shield, used for picking up supports and setting them in position.
|
| Exhaust |
Gases from engines, pollutant emissions.
|
| Exhaust scrubber |
Equipment installed in all diesel vehicles working in underground works. It depurates gases from engines.
|
| Exploratory adit |
A tunnel driven before the tunnel design is finalized, to obtain information about the ground, its behaviour and ground water characteristics
|
| Exploratory shaft |
A shaft constructed for the purpose of studying ground conditions in the vicinity of a future underground opening.
|
| Extensometer |
A device for precisely measuring the convergence or divergence of reference points along a common axis.
|
| External effect / cost |
An effect or cost of a project or action that is real but is not of direct interest or concern to the decisionmaker involved. Also called "externality".
|
| Externality |
See external effect / cost
|
| Extra |
Additional payment made to a contractor as a result of work or use of materials beyond the scope of the original contract.
|
| Extrados |
The exterior surface of an arch. In a tunnel, it is the arch surface lying against the excavated rock or soil surface.
|
| Fabrication |
The stage of construction of a tunnel element before it can float.
|
| Face |
Vertical wall at the end of the excavation in a tunnel.
|
| Face |
The advance end or wall of a tunnel at which work is progressing.
|
| Factor of Safety (with regard the uplift) |
The ratio of the weight of a tunnel, or a portion thereof, to the buoyancy. Different required factors of safety may be specified depending upon whether backfill is included or removable items are excluded, and depending upon the stage of construction. Water density must be specified, since buoyances will vary with changes in water density.
|
| False portal |
A tunnel portal built in the open air, possibly by the cut and cover method. Free standing structure cast against the ground to ensure stability at the start of a tunnel drive.
|
| Fan |
Machine that allows to remove the polluted air of the tunnel.
|
