(1) A device that acts as a seal between two contacting surfaces.

Usually either hinged to a wall or floating, this structure is used to close off the fabrication facility from the adjacent water to allow dewatering of the facility.

Methods to acquire information about properties of bedrock, soil and groundwater

Increase of the temperature of the earth from the surface downwards, averaging about 1 degree Farenheit for each 60 feet

A steel (lattice) arch normally erected at regular centres as the tunnel advances. It is sequentially erected from component parts as the lining is progressively formed and encapsulated within the shotcrete. It is normally provided in the crown section to provide temporary protection to miners from the risk of collapse. The girders can be fully circumferential.

An analysis that attempts to treat issues on a global rather than local, regional or national basis.

Finely abraded or pulverized rock particles and claylike altered rock found between the walls or within the fractures of a fault or shear zone; the result of grinding movements that crushe the affected rock.

Mechanical device for taking up and holding excavated soil / rock to be lifted or moved.

The overall vertical alignment of an underground opening.

Locally, the same as "gradient", i.e., the rate of incline or decline in terms of degrees from the horizontal, percent of rise to the horizontal distance, or in feet of vertical projection per mile of horizontal projection.

The crossing of two transportation elements one above the other rather than at a surface intersection

The level of the ground surface

See Screeded Foundation.

The process of forcing pea gravel into the tail void created by a shield to prevent ground settlement. The process is always followed by cement grouting.

Shift that extends from midnight to 8:00 am. See Day shift, Swing shift.

An area that can be dewatered to form a casting basin

A ring or partial ring of green space planned around an urban area to control sprawl and/or to preserve natural areas close to the city

An area above water level converted to enable construction of tunnel elements, usually steel shell tunnels. The elements may be side or end launched into the water when capable of floating, or may be incrementally launched.

Areas created or preserved having a substantial natural character

A shielded rock or hard-earth tunnel boring machine equipped to move forward by reacting (i.e., exerting shove forces) against the tunnel walls through a hydraulic gripper reaction system.