| Term | Definition |
|---|---|
| Bore |
A term borrowed from mined tunneling to describe a cell.
|
| Boreability |
A value expressing the boring properties of rock in terms of the penetration rate with certain numbers/types of cutters and amount of pressure applied. Equivalent to "tunnelability", the ease or difficulty with which a rock type can be penetrated by a tunnel boring machine.
|
| Bored construction |
Construction by tunnelling with only limited access points from the surface
|
| Bottom heading |
The excavation of the bottom half of a tunnel after the top half has been excavated for the full tunnel length.
|
| Box (shape) |
An indication that the overall cross-section of the tunnel is approximateley rectangular
|
| Brattice (brattishing) |
A partition formed of planks or cloth in a shaft or gallery for controlling ventilation.
|
| Break |
Fragmentation of solid rock as a result or the explosion of an explosive mixture in drill holes at the heading.
|
| Breast boards / Breasting |
Boards placed and braced temporarily across the face of a tunnel drive to support incompetent materials.
|
| Bridge action time |
The time that elapses between the exposure of an area at the roof of a tunnel and the beginning of noticeable, unprovoked inward movement of the ground above this area; sometimes described as "stand-up time".
|
| Building permit / permission |
Permit required for new buildings, extensions and certain more important alterations to buildings.
|
| Bulkhead (1) |
An airtight partition of steel or concrete used to retain air pressure within a tunnel. The man locks and muck locks are constructed through the bulkhead.
|
| Bulkhead (2) |
An upright watertight partition used to generate compartments. Temporary bulkheads are provided at the ends of tunnels elements to keep water out (make them watertight) during the floating and installation stages
|
| Bulkhead forms |
Forms placed in the top and sides of the pour between the forms and the tunnel surface. These forms are placed in a vertical line to form a vertical construction joint.
|
| Bulkhead pour |
Concrete placed in a short section of tunnel between two bulkhead forms or between another bulkhead pour and a bulkhead form.
|
| Bull gang |
Crew of laborers usually used on the day shift to lay rail track, install pipes, clean up the tunnel, and perform any other necessary work that is located in the tunnel but not at the face.
|
| Buoyancy |
(1) The resultant upward force on a body partially or fully immersed in a liquid, caused by the pressure of the liquid acting on the body. The magnitude of the force is equal to the weight of liquid displaced. (2) Positive buoyancy or Negative Buoyancy: Jargon expressions for the amount by which buoyancy exceeds the weight of a body when totally immersed in a liquid. Positive buoyancy indicates that the body tends to float (buoyancy > weight); negative, that it tends to sink (buoyancy
|
| Burn cut |
Drilling pattern of large "relief holes" drilled horizontally in the center of the face to provide space for the expansion of rock broken by a blasting agent.
|
| Burn-cut drill |
Large drill used for the large-diameter holes in the center of a burn cut.
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| Busway |
Special lane or roadway for exclusive use by buses
|
| Cable drive system |
A material transport system of the general type employing individual units or trains of load-carrying vehicles pulled by a continuous loop cable and travelling on a conventional dual rail track.
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