The International Society for Trenchless Technology

A shield with a closed pressure chamber or cutting head which does not allow direct access to the face.

A ring fitted between the end-bearing area of the bell and spigot to help distribute applied loads more uniformally. The compression ring is attached to the trailing end of each pipe and is compressed between the pipe sections during jacking. The compression rings compensate for slight misalignment, pipe ends that are not perfectly square, gradual steering corrections, and other pipe irregularities.

Methods for identifying and locating features that may affect the integrity and performance of a utility including defects, obstructions, leaks, infiltration, inflow, etc.

Steel casing hammered or pushed into place where soil strata are high in gravel and cobble content or where formation strength is low and the bore would be unstable.

A cement or bentonite-cement based mixture injected to fill annular space between pipe and the surrounding formation, or other voids.

Method of lining with a pipe made continuous for the length of the section to be renovated prior to insertion, and which has not been shaped to give a cross sectional diameter smaller than its final diameter after installation.

An electronic unit inside a container located on the surface that controls the operation of the microtunneling machine. Electronic information including head position, steering angle, jacking force, progression rate, machine face torque, slurry and feed pressures, and laser position is transmitted to the console from the head of the machine. The consoles may be equipped with a computer that provides real-time analysis of the tunnel drive.

See Open Cut

Pipeline installation in which the primary purpose is to provide one or more passages beneath a surface obstruction.

See Pipe Eating.

Method of lining with a flexible tube impregnated with a thermosetting resin which produces a pipe after resin cure.

See Open Cut

A mechanical device for excavation within an open shield

Tool or system of tools on a common support which excavates at the face of a bore.

See Spoil