Glossary of Terms

The following terms relate to the installation and use of Vitrified Clay Pipe.  Many of these terms are used in reference to all pipe installations while some are specific to VCP installations.  These terms can be found in
ASTM C 896 - Standard Terminology Relating to Clay Products.


approving authority: the individual official, board, department, or agency established and authorized by a state, county,  city, or other political subdivision, created by law to administer and enforce  specified requirements.

all the material used to fill the trench from bedding to finished surface.

backfill, final: material used to fill the trench from initial backfill to finished surface.
backfill, initial: material used to fill the trench from top of bedding to a designated height over the pipe.
backfill, unconsolidated: non-compacted material in place in the trench.
barrel: the cylindrical portion of a vitrified clay pipe exclusive of branches, spurs, joints, and handling rings or lugs.
bearing strength:

the non-destructive limit of pipe load, as determined by 3-edge bearing test method, used to determine  field supporting strength.

bedding: the materials, their placement, consolidation, and configuration, as designed to support, and to develop field  supporting strength of vitrified clay pipe.
bell: the flared-end portion of a vitrified clay pipe or fitting, designed to function in the joining of other such pipe.
beveled pipe: a pipe with an end angled to mate with a complimentary pipe end or adjust to another surface.
blister: a convex, raised area on the pipe surface indicating an internal separation.
body: See pipe body.
chip: a small piece of broken-off material, or the location where a small piece of the unit material has been broken off.
clay: an earthy or stony mineral aggregate consisting essentially of hydrous silicates of alumina, plastic when sufficiently  pulverized and wetted, rigid when dry, and vitreous when fired to a sufficiently  high temperature.
closure: See compression joint.

mechanical or hydraulic consolidation of backfill to achieve stability.

compression coupling: See compression joint.
compression disk: a disk of compressible material placed between the ends of adjacent pipe for the purpose of distributing  the jacking force.
compression joint: a joint designed so that a sealing action is obtained by compressing elastomeric components.
conduit: a pipe for conveying fluid.
consolidation: the gradual reduction in volume of backfill matter to achieve stability.
constant weight: the condition of a substance in which all volatile components have been vaporized, and repeated exposure  to a specified temperature, for any period of time, causes no change in weight.
controlled low strength material (CLSM): flowable low compressive strength cementitious material used in the pipe zone  as a bedding material. Also referred to as controlled density fill, flowable  fill, slurry, or lean concrete.
crack: an irregular separation with well-defined sharp edges visible on the surface of a pipe.
deadload: the load imposed on pipe, that is determined by depth and width of the trench at top of pipe, as well as  unit weight and character of backfill material.
drains: a piping system used to collect and carry off surface and ground water.

special materials, their placement and configuration which are designed to fully surround the pipe, and develop  a field supporting strength which exceeds that developed by other commonly  used installation and bedding techniques.

exfiltration: the quality of water leaving the test section during a specified time period.
face: to cover with a new surface.
filter block:

a cellular vitrified clay block unit, of proprietary configuration, designed to underbed the media in  trickling filters.

fire clay: a sedimentary clay of low-flux content.
fitting: products such as wyes, tees, elbows, adapters, etc. used in the installation of vitrified clay pipelines.
flooding: a means of compacting trench backfill by the introduction of water by gravity.
flue lining: a manufactured tubular non-load bearing fired clay unit, normally used for conveying hot gases in chimneys. 

that portion of a vitrified clay pipe from which a fragment has been broken. It is distinguished by well-defined  fracture faces and sharp edges where the fracture faces meet the surface of  the pipe.

glaze: a hard glassy fused coating.

that portion of the pipe barrel extending from bottom to springline.

haunching: the act of placing bedding material around the haunch of the pipe.
inch-pound units: the units of length, area, volume, weight, and temperature in common use in the United States at the  present time. These include, but are not limited to: ( 1) length-feet, inches, and fractional inches, ( 2) area-square feet and square inches, (3)  volume-cubic feet, cubic inches, gallons, and ounces, ( 4) weight-pounds and ounces, and (5)  temperature-degrees Fahrenheit.
industrial waste: the water-conveyed residues resulting from manufacturing or processing operations.

the quality of ground water entering the test section during a specified time period.

initial backfill:

location for placement of selected material, native or import, extending from the top of the bedding  material to an elevation 1 ft above top of pipe.

jacking: a method of installing pipe by the trenchless method using equipment and pipe designed for this purpose.
jacking force: the force applied to the pipe along the longitudinal axis of the pipeline by the pipe jacking equipment.
jacking frame:

A structural component that houses the hydraulic cylinders used to propel the tunnel equipment and pipeline.  The jacking frame serves to distribute the axial thrust load to the pipeline and the reaction to the shaft wall or thrust wall.

jacking or launch shaft or pit:Excavation from which trenchless technology equipment is launched for the installation or renewal of a pipeline.
jetting: a means of compacting trench backfill by the introduction of water under pressure through a nozzle.
joint: an individual length of pipe, or the means of closure to form a pipeline.
lamination: a stratification of the material in the plane of the wall of a unit.

liquid drainage normally associated with contaminated soils and solid waste landfills.

live load:

the portion of the load transmitted to pipe from wheel or tread impacts.


specific group of clay products having characteristics of sufficient similarity that individual specimens selected  from that group may be considered representative of the whole group.


trenchless installation of pipe by jacking the pipe behind a remotely controlled, steerable, laser guided, microtunnel boring machine that provides continuous support to the excavated face under various geotechnical conditions including the presence of groundwater.

mitered fittings: fittings manufactured by using beveled pipe segments.
mitered pipe: See beveled pipe.
nominal diameter:

references the internal diameter in name only to the nearest unit dimension.

pilot tube microtunneling (PTMT):

Also known as the guided boring method (GBM), a multistage method of accurately installing a product pipe by use of a guided pilot tube and followed by upsizing to install the product pipe.  In PTMT, the guidance system consists of a LED target housed in the steering head, digital theodolite with camera, and a monitor screen.


a small solid bump or protrusion on the pipe surface.

pipe: See vitrified clay pipe.
pipe body: the clay material or mixture of clay materials from which vitrified clay pipe is made.
pipe bursting:

process by which existing pipelines are broken by mechanical fracturing from either inside or outside with the remains being pushed into the surrounding soil while simultaneously inserting a new pipeline of equal or larger diameter.


pipes joined to provide a conduit through which fluids flow.


soil consolidation by agitating by means of poles, a mixture of soil and sufficient water to leave a puddle  on the surface.

reach: the section of a sewer between structures.
reception or exit shaft or pit:Excavation into which trenchless technology equipment is driven and recovered following the installation of the product pipe.

each piece or group of pieces selected from a lot and used to determine whether the product complies with the specification  criteria.


process of selecting samples from a lot for use in testing.

sealing element:

a separate or bonded material between the sleeve and the pipe that forms a seal.

segmental testing:

a method of isolating and testing portions of an installed pipeline to determine the location of  an air loss in excess of the standard.

segmented testing: a method of testing vitrified clay pipe using segmented bearings as detailed in Test Method C 301.
selected material:

finely divided material free of debris, organic material, and large stones.

sewage: waste matter carried off by sewers.

generally, an underground conduit usually carrying waste matter in a liquid medium.

sewer line: See sewer.
sewer pipe:

vitrified clay pipe as described in Specification C 700.



system for collection, treatment, and disposal of sewage.


a thinly stratified, consolidated, sedimentary clay with well-marked cleavage parallel to the bedding.

shovel slicing:

mechanical action of causing bedding material to uniformly contact the pipe haunches.


a piece of vitrified clay pipe made so that one end has a plane of approximately 45° or 60° to its longitudinal  axis. The end may be made with a contoured surface to fit another pipe.


a coupling which contains or compresses the sealing element and meets the requirements of the standard. The sleeve  may be affixed to one end of the pipe at the factory.


a method of inserting new pipe into an existing pipeline.

socket: the portion of a jointing system that is designed to accept a plain-end pipe or a spigot-end pipe.

see  shovel slicing. 

specifying agency:

the individual engineer, firm, or political subdivision charged with and having the responsibility  for the design of a facility, product, equipment, or material requirements. 


sample, or portion thereof, which is to be tested and the test results to be reported.


that portion of a vitrified clay pipe that fits into the bell or socket of the preceding pipe.

spring line:

the line of maximum horizontal dimension of the transverse cross section.

steering head:In pilot tube microtunneling, a rotatable slant faced unit located directly in front of the lead pilot tube that can be adjusted to steer the bore.
suitable materials:

Suitable material is well-graded 3/4 to  1/4 in. (19 to 6mm) crushed stone, having a minimum of one fracture face, or other angular, non-consolidating bedding materials not subject to migration.

superimposed load:

load imposed by travel over, or by material brought and placed over the trench area, after pipe installation. 

surface clay:

an unconsolidated, unstratified clay, occurring on the surface.

test section:

the portion of pipeline under test.

test specimen:

specimen, or portion thereof, which is to be tested and the test results reported, or which is to be prepared  for further testing, and the test results reported.


An instrument for measuring both horizontal and vertical angles.

thrust ring:

A fabricated ring that is mounted to 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.

trench foundation:

the area below the pipe and bedding which supports the pipe bedding structure.

trenchless technology:

Also no-dig, techniques for underground pipeline and utility construction and replacement, rehabilitation, renovation (collectively called renewal), repair, inspection, leak detection, and so on, with minimum or no excavation from the ground surface.

trickling filter: a facility for the waste waters which utilizes a flow of liquid over fixed-media.
unaided eye:

visual inspection, without the use of special equipment or enhancement excepting the use of corrective  lenses.

vitrified clay pipe:

a pipe made from various clays or combinations thereof which are shaped, dried, and fired to a point  where the glass-forming components fuse to form a bond between the crystalline  grains.


exterior vertical sides of vitrified clay filter block.


interior supports separating channels of vitrified clay filter block.