Self-propelled platform used in tunnel excavation.

The ratio of the floor area of a building project to the surface land area for the project. Often used to control the density of development in an urban area.

Flowing ground moves like a viscous liquid

A fine residue that results from the combustion of ground or powdered coal.

General term for a planar arrangement of textural or structural features in any type of rock, especially the planar structure that results from flattening of the constituent grains of a metamorphic rock. See also schistosity.

Blocks of wood or precast concrete placed under ribs or posts to provide bearing for horseshoe-shaped or non-circular tunnels.

Clause in the specifications that relieves the contractor of financial responsibility for certain events not under his control. Examples include acts of God, war, earthquakes, floods, and strikes

A ground improvement measure carried out by inserting bars, rods or tubes at the face so as to form a splayed arch ahead of the tunnel. It can involve areas of jet grouting or ground freezing. Previously, the term was used more narrowly. It related to polling boards driven on a splay ahead of the face of an excavation.

Traveling frame used to strip, collapse, and erect full-circle or arch forms.

Tunnel linings of performed metal or concrete

Timber or metal surfaces which retain wet concrete to form desired shape

Air at atmospheric pressure.

The height above the still-water surface of the highest part of a floating body.

A 3- to 8-ft long steel bar with a slot along its entire length, inserted in drilled holes of slightly smaller diameter around the periphery of a tunnel. The slot causes the stabilizer to be in compression and exert an outward anchoring force to tie rock-blocks or strata together and prevent their loosening or falling out.

Tunnel excavation to full cross-sectional size with each blast or shove. Distinguished from heading, bench, and multiple drift.

Process in which the complete concrete lining in a tunnel is poured in one operation. See Arch pour, Invert pour.

An excavation of the whole face in one operation.

Smoke produced in the construction site.

Walls or surfaces placed inside the structural walls of a tunnel or cavern. Furred out walls are usually for aesthetics purposes or to provide a space for water seepage and collection.