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.

A rock tunnel boring machine which generally utilizes roller disc cutters as excavation tools and which moves forward by reacting (i.e., exerting shove forces) against the tunnel walls through a hydraulic gripper reaction system.

Part of a ground support system consisting of a tendon inserted in a drilled hole, secured at the remote end, usually by means of a grouted plug, and tightened or tensioned against the ground retaining member in the system. Se also rock bolt.

The rock located immediately above a tunnel which transfers the overburden load onto rock located on both sides of the tunnel. The zone of arching is usually equal in height to 1.5 times the tunnel diameter. Overburden rock / ground above the ground-arch remains unaffected by the tunnel operations.

The application of processes which strengthen the soil, especially by filling pores and increasing shear strength.

Water contained in the ground below the upper level (the water table) of subsurface water.

A pumpable slurry of neat cement or a mixture of neat cement and fine sand, commonly forced into holes drilled from a tunnel to strenghthen incompetent soil/rock or to prevent groundwater from flowing into the excavation. See also chemical grout.

A foundation formed by filling the space between the underside of an element of an immersed tunnel and the pre-excavated trench bottom with grout. Until this operation is complete, elements require temporary support

Injection of grout through drilled holes, under pressure, to fill seams, fractures, or joints and thus seal off water inflows or consolidate fractures rock.

Original name for shotcrete (sprayed concrete) sometimes still (inappropriately) used for fine-aggregate dry-mix shotcrete.

A form of mortar consisting of fine sand, cement, and water which is sprayed on freshly excavated rock by air pressure to prevent deterioration of the rock, and in some instances to provide structural support.