The International Society for Trenchless Technology

The process by which substances in gaseous, liquid, or solid form are assimilated or taken up by other substances.

When a continuous series of lots or batches is considered, the quality level which for the purpose of sampling inspection is the limit of a satisfactory process average (see ISO 2859-1 and ISO 3951). NOTE the designation of an AQL does not imply that a manufacturer has the right knowingly to supply any non-conforming unit of product.

Entry onto land to perform an assessment inspection.

Temporary access shafts are commonly provided to allow entry of personnel and occasionally equipment to the interior of an immersed tunnel.

Has a pH of water less than 5.5; pH modifier used in the U.S. Fish and Wildlife Service wetland classification system; in common usage, acidic water has a pH less than 7.

The transfer of acidic or acidifying substances from the atmosphere to the surface of the Earth or to objects on its surface. Transfer can be either by wet-deposition processes (rain, snow, dew, fog, frost, hail) or by dry deposition (gases, aerosols, or fine to coarse particles).

The volume of water needed to cover an acre of land to a depth of one foot; equivalent to 43,560 cubic feet or 325,851 gallons.

Possibility for a tunnelling machine to adapted to other type of work.

A short length of tunnel driven from the surface to the main tunnel to enable more headings to be driven or to provide permanent access to the tunnel.

Part of a manhole or inspection chamber between the cover and frame and the shaft. This is used to adjust the level of the cover and frame to accord with the required surface level.

The adherence of gas molecules, ions, or molecules in solution to the surface of solids.

Distance excavated during a given time (shift or day).

Where the tunnel is excavated in sections, a heading within the final cross section, constructed ahead of other parts of the tunnel.

Speed of advance of a pipe jack or other trenchless installation through the ground, generally expressed as either millimetres per minute or metres per day.

The distance excavated during a given time (shift, day).