Page 485 - Trenchless Technology Piping Installation and Inspection

Glossary of Terms 435

Thermoset (TS): A polymer material, such as rubber, that does not melt
when reheated. TS polymers can be formed initially into almost any
desired shape, but they cannot be reformed at a later time.

Thermoset resin: A material, such as epoxies, that will undergo or has
undergone a chemical reaction by the action of heat, chemical catalyst,
ultraviolet light, etc., leading to an infusible state.
Thrust: Force applied to a pipeline or drill string to propel it through the
ground.
Thrust block: See backstop.
Thrust boring: A method of forming a pilot bore by driving a closed
pipe or head from a thrust pit into the soil which is displaced. Some
small-diameter models have steering capability achieved by a slanted
pilot-head face and electronic monitoring. Back reaming may be used to
enlarge the pilot bore. Also loosely applied to various trenchless
installations methods. See rod pushing.
Thrust jacking method: Method in which a pipe is jacked through the
ground without mechanical excavation of material from the front of the
pipeline.
Thrust pit: See drive pit.

Thrust ring: A fabricated ring that is mounted on the face of the jacking
frame. It is intended to transfer the jacking load from the jacking frame to
the thrust bearing area of the pipe section being jacked.

Top Inversion: The CIPP tube is inverted from an inversion ring located
at the top of the inversion platform.
Torque: The rotary force available at the drive chuck.
Track: A set of longitudinal rails mounted on cross members that support
and guide a horizontal auger boring machine.
Trench (trench excavation): A narrow excavation (in relation to its length)
made below the surface of the ground. In general, the depth is greater
than the width, but the width of a trench (measured at the bottom) is not
greater than 15 feet (4.6 m). If forms or other structures are installed or
constructed in an excavation, so as to reduce the dimension measured
from the forms or structure to the side of the excavation to 15 feet (4.6 m)
or less (measured at the bottom of the excavation), the excavation is also
considered to be a trench.
Trenching: See open-cut or conventional trenching.
Trenchless: A technology that is used for renewal of existing pipelines,
typically without any excavation.

Trenchless methods: See trenchless technology.