A mixture of cement, aggregate, and water projected pneumatically at high velocity from a nozzle onto a surface to produce a layer or layers of concrete. Shotcrete normally incorporates admixtures, especially accelerators, and may also include fibers. (also called Sprayed Concrete). (see dry-mix shotcrete, gunite, and wet-mix shotcrete)

The act of advancing a mole or shield with hydraulic jacks.

The process of advancing a subaqueous tunnel shield while its face is closed.

The pedestrian walkway at the side of a street (U.S. usage). Equivalent to pavement in U.K. usage

An extremely fine by-product of the manufacture of silicon metal as the gases escaping from the electric-arc furnace condense. It is used in concrete and shotcrete to improve their properties. In shotcrete its use reduces rebound increases thickness per pass, and improves properties of the hardened shotcrete.

A lung desease caused by breathing dust from rock drills over a long period of time. Rocks with high silica content are the most harmful.

Spelling in United States for Cill.

Crew of men located at one entrance to the tunnel who only excavate one heading at any one time for this entrance.

To excavate a shaft downwards from the surface, in distinction from raising.

Container used in hoisting muck from a shaft.

Rock cut through by finely parallel joints and/or cleavage planes so that it breaks into tabular plates upon exposure in an excavation.

The crumbling and disintegration of rock or hard soil upon exposure to air or water

The operation of enlarging a pilot shaft to full diameter by conventional methods.

Section of the discharge line from a concrete placer that is embedded in the fresh concrete during arch or full-circle pour.

The polished and sometimes striated surfaces on the walls of faults and shear zones, resulting from rubbing during earth movements. Sometimes referred to by construction people as "slicks".

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