Crown bars that are slid forward over sets as mucking advances, in order to protect the workmen and support the back.

A closed-face shield designed for tunnelling in very soft, wet, or running ground by use of circulating, pressurized clay slurry against the face to counterbalance earth pressures, prevent ingress of water, and also to carry away the cuttings.

A muck train composed of a locomotive and articulated muck cars. During the mucking cycle, the locomotive furnishes power to operate a scraper which runs along the top of the train; as the lead car is loaded by the mucking machine, the scraper drags the material back from the lead car and loads the others.

A technique of using carefully controled shot hole drilling and specially prepared charges in peripheral blast holes to reduce overbreak. Se also pre-splitting.

See : Access Shaft

Costs for an activity or project that are borne by a community

See social costs

Effects arising from social structures or institutional structures and their interaction

A discrete section of shaft lining of lower strebgth designed to be excavated at the start of a tunnel drive from that shaft or the breakthrough of a drive into the shaft

Heavy ground or rock about underground openings that does not stand well and requires heavy timbering

Any tunnel shield which moves forward by reacting (i.e., exerting shove forces) against the tunnel lining and generally utilizing drag type excavation tools that can be mounted on a backhoe, rotating wheel or oscillating arm.

Same as earth tunnel. The ground may be hard or soft in consistency, the word "soft" differentiating it only from "hard" rock.

Any naturally occuring loose or soft deposit resulting from weathering or breakdown of rock formations or from decay of organic matter

Solid products useless that have to be eliminated.

A rail used by mine surveyors for hanging a plumb bob as a mark for a survey station, generally with a hole or notch in it for a plumb bob string.

The breaking off of thin surface sheets or plates in rock under excessive tension.

Part of a structure between two supports

Essentially the same as forepoling, but may also include steel bars drilled ahead of a rock tunnel face.

Related to all kind of oils and liquids of engines that can pollute the soil.

See muck.