Glossary of Terms and Definitions

Term Definition

American Association of State Highway and Transportation Officials.


Removal of material due to a frictional contact.

Abrasion And Scratch Resistance

Ability of a material to resist the infliction of damage in the form of scratches, grooves and other minor imperfections.


Acrylonitrile-Butadiene-Styrene; a form of thermoplastic.


Asbestos Cement; a composite material used in pipe construction.


By the owner of the work as being fully complete in accordance with the contract documents.

Adapter Ring

In microtunneling, a fabricated ring, usually made from steel, that is mounted on the first pipe of the pipe string. This ring is intended to transfer the jacking force from the MTBM’s bearing area to the jacking pipe and to create a waterproof seal between the machine and the spigot of the first joint.


Written or graphic instruments issued prior to the execution of the agreement, which modify or interpret the contract documents, drawings and specifications, by addition, deletions, clarifications or corrections.


A substance added in a small amount, usually to a fluid, for a special purpose such as to reduce friction, corrosion, etc.


Ingredients added during mixing; often in construction to aid workability of concrete, mortar or grout.


The motion of the machine in a direction toward the face wall of the entrance pit.

Advance Rate

Forward progress over a given period of time; includes penetration rate, make-up time, downtime, and idle time; typically measured in feet or meters per shift.

Aerial Sewer

An unburied sewer (generally sanitary type), supported on pedestals or bents to provide a suitable grade line.


Presence of unreacted or free oxygen (02).


A property of water which favors the corrosion of its conveying structure,

Aggressive Index (AI)

Corrosion index established by the American Water Works Association (AWWA) Standard C-400; established as a criterion for determining the corrosive tendency of the water relative to asbestos-cement pipe; calculated from the pH, calcium hardness (H), and total alkalinity (A) by the formula AI = pH + log (A * H).


The written agreement between the owner and the contractor covering the work to be performed; the contract documents are attached to and made a part of the agreements. Also designated as the contract.


The capacity of a water to neutralize acids; a measure of the buffer capacity of a water. The major portion of alkalinity in natural waters is caused by (1) hydroxide, (2) carbonates, and (3) bicarbonates.


An oxide of aluminum present in clay.


Asset Management Plan; a structured approach for utilities to achieve long term defined service standards – or – an external bearing used to isolate the final drive from the thrusting force of the machine.