Page 467 - Trenchless Technology Piping Installation and Inspection

Glossary of Terms 417

Coefficient of thermal expansion and contraction: The fractional change in
length of a material for a unit change in temperature.
Collapse: Critical failure of a pipeline when its structural fabric
disintegrates.
Collaring: The initial entry location of casing or a cutting head into the
earth.
Collection system: A network of sewers that serves one or more catchment
areas.
Collector sewer: A sewer located in the public way collects the
wastewaters discharged through building sewers and conducts such
flows into larger interceptor sewers, pumping and treatment works
(referred to also as street sewer).
Combined sewer system: A single network of sewers designed to convey
stormwater as well as sanitary flows.

Competent person: One who is capable of identifying existing and
predictable hazards in the surroundings, or working conditions that
are unsanitary, hazardous, or dangerous to employees, and who has
authorization to take prompt corrective measures to eliminate them.
Compressed air method: In trenchless technology, refers to the use of
compressed air within a tunnel or shaft to balance ground water and
prevent ingress into an open excavation.
Compression gasket: A device that can be made of several materials in a
variety of cross sections and that 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 bell
and spigot to help distribute applied loads more uniformly. 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.
Compression rings are also referred to as spacers.
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.
Cone: The section between the top of a manhole wall and chimney or
the frame. The diameter of the manhole is reduced over the cone section
to receive the frame. The cone section may be concentric or eccentric.
Continuous sliplining: See sliplining.
Control console: An electronic unit inside a container located on the
ground surface, which controls the operation of the microtunneling
machine. The machine operator drives the tunnel from the control