Compressed Air Method

General term which, in trenchless technology, refers to the use of compressed air within a tunnel or shaft in order to balance ground water and prevent ingress into an open excavation.

Compression Gasket

A device which can be made of several materials in a variety of cross sections and which serves to secure a tight seal between two pipe sections (e.g., “O” rings).

Compression Ring

A ring fitted between the end-bearing area of the leading pipe bell and the trailing pipe spigot to help distribute jacking forces more uniformly. A compression ring is attached to the trailing end of each pipe and is compressed between the pipe sections during jacking. The compression ring compensates for steering corrections, pipe misalignment, and pipe dimensional tolerances. Also referred to as a packer.

Conductivity

A measure of the ability of a solution to carry an electrical current. conductivity varies both with the number and type of ions the solution carries.

Conduit

A broad term that can include pipe, casing, tunnels, ducts or channels. The term is so broad that it should not be used as a technical term in boring or tunneling.