| Term | Definition |
|---|---|
| Hand mining |
Tunnel excavation by means of hand-helded tools rather than by heavy, mechanized cutting or digging equipment.
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| Hard and intact rock |
Massive rock containing no significant joints. When fractures by blasting, it breaks across sound rock.
|
| Hard rock |
In construction, rock having a strongly bonded nature such as to require excavation by blasting or the use of specially hardened cutters; generally includes igneous and metamorphic rock and the more strongly bonded sedimentary rocks.
|
| Harmful gases |
Dangerous gases produced by engines.
|
| Haunch |
A thickening of a wall or slab to increase locally the bending strength and shear capacity of the section.
|
| Hazard |
A source of posible injury or damage to health
|
| Headframe |
Tower built over a shaft to support the ropes for raising and lowering men, equipment, and material in the shaft.
|
| Heading |
The area at the front of the tunnel construction beyond the completed ring. Or a small tunnel constructed ahead of the main tunnel
|
| Heading |
A small advance tunnel driven for the purpose of enlarging to creat the main tunnel; similar to drift, but generally driven above the springline as a top heading.
|
| Heading / Heading face |
The wall of unexcavated ground at the advance end of a tunnel. Similar in use to face
|
| Heading-and-bench construction |
A tunnelling method in which a top heading is excavated, followed (within one to a few blasts or shoves) by excavation of the lower bench. Distinguished from top heading construction.
|
| Heave |
Ground movement in a tunnel in the form of upward deflection of the invert
|
| Heavy ground |
Very incompetent rock, usually found in faults or in shear zones; highly weathered or decomposed material having a tendency to move into the open tunnel area.
|
| Heavy rail |
High capacity rail system with longer trains and heavy rolling stock
|
| Heritage value |
Value in connection with the history or culture of a people and/or place
|
| High air |
Compressed air used in tunnels to operate pneumatic tools. Generally supplied at 100 psi.
|
| High pressure grouting |
Consolidation grouting used to strengthen rock or cutt off water inflows.
|
| High rock |
A rock surface extending above the invert of a tunnel that would otherwise be driven entirely in soft-ground conditions.
|
| Hog rods |
A steel tumbuckle rod installed horizontally across a shield driven tunnel and fastened on each side to the liner plate, remains in position until the shield tail void is filled with pea gravel and grouted; prevents deflection of the liner plate.
|
| Hoist |
An apparatus for raising rock from a shaft and for lowering and raising men and material. It consists of a load-carrying vehicle attached to the end of a cable or rope usually employing a guideway to stabilize a vehicle.
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