| Term | Definition |
|---|---|
| Cover |
In reinforced concrete or shotcrete, the least distance between the surface of the reinforement and the outer surface of the concrete or shotcrete
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| Criteria |
Factors by reference to which a decision is taken. Multi-criteria analysis may also be carried out, possibly incorporating cost-benefit analysis as one of the criteria.
|
| Cross tunnel |
Tunnel to give access between tubes for the operators and the emergency services
|
| Crown |
The highest point of an arched tunnel cross section; the roof or back of a tunnel.
|
| Crown |
The configuration of the upper portion of a tunnel section above the springline.
|
| Crown bars |
Timbers or steel members cantilevered from previously installed sets nearest the heading to temporarily support a rock tunnel roof while the next set is being installed.
|
| Curbs |
Small pour made on the bottom and at each side of a tunnel and generally located outside the minimum concrete line; used as a reference point and support for invert and arch pour in the tunnel.
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| Cut |
A drilling pattern in the tunnel face which provides relief for an explosive charge.
|
| Cut and cover construction / method |
Underground construction involving open-cut excavation followed by eventual covering with a slab or arch structure to support a replaced ground surface. A temporary covering at ground level may be provided for the passage of traffic or environmental reasons.
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| Cut and cover tunnel |
A tunnel constructed by excavating a trench from the surface and then decking it over, usually with timber, so that traffic can be maintained while the structure is built within the trench.
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| Cutterhead / Cutting head / Cutting wheel |
The rotating front end of a mechanical excavator which actually cuts through rock or soft ground.
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| Dam Plate |
Term used in the United States for the temporary end bulkhead.
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| Damp |
Miner's term for gases other than air which might be encoutered in an underground excavation.
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| Dangerous occurrence |
An unplanned event which exposed persons to danger but which did not cause personal injury or acute ill health.
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| Day shift |
Shift that extends from 8:00 am to 4:00 pm. See swing shift.
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| dB, dBA |
Decibel -- a measure of sound level and used as a measure of noise pollution. dBA indicates a weighting of the measurements to increase the importance of low frequency sounds
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| Decanting basins |
Basins used for decanting of drilling bentonite mud.
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| Decibel |
A measure of sound level. Used as a measure of noise pollution
|
| Decision maker |
A person who makes decisions. The term usually refers to people making decisions on behalf of businesses or government.
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| Deep shaft |
A shaft of relatively (but not formally defined) great depth, usually associated with mines and underground waste storage and less often with civil engineering projects which are relatively shallow.
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