The International Society for Trenchless Technology

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There are 211 entries in this glossary.
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Term Definition
Adapter Ring

A fabricated ring, usually made from steel, that serves to mate the microtunneling machine to the first pipe section. The purpose of the adapter ring is to create a waterproof seal between the machine and the spigot of the first joint.

Advance Rate

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.


Planned and actual location in the vertical and horizontal direction of the product from the entry pit to the exit pit.

Allowable Bend Radius

The degree of deflection that the drill pipe and product can safely tolerate without risk of damage to the pipe or product.

Angular Deflection

The angle between two consecutive pipes

Annular Filler

Material for grouting the annular space between the host pipeline and the lining system.

Annular Space

The void created by the difference in diameters between the shield and jacking pipe.

Articulated Head

A shield of two sections where the front section can be deflected to steer the shield or cutting head.

Auger Boring

A technique for forming a bore from a start or drive shaft to a reception shaft by means of a rotating cutterhead. Spoil is removed back to the drive shaft by helically wound auger flights rotating in a steel casing. This equipment may have limited steering capability.

Auger MTBM

Microtunnel boring machine (MTBM) that uses auger flights passing through the product pipeline to remove the excavated soil.

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