A B C D E F G H I J L N P R S T U W

A

ABRATT

Brazilian Association for Trenchless Technology

ABS or Aristocraft Bristone Styrine

A rigid black plastic pipe used for drain, waste and vent lines.

Access Panel

An opening in the wall or ceiling near a fixture that allows for access to service the plumbing or electrical system.

Adapter Ring

A fabricated ring, usually made from steel, that serves to mate the microtunneling machine to the first pipe section. The purpose of the adapter ring is to create a waterproof seal between the machine and the spigot of the first joint.

Advance Rate

Speed of advance of a pipe jack or other trenchless installation through the ground, generally expressed as either millimetres per minute or metres per day.

Alignment

Planned and actual location in the vertical and horizontal direction of the product from the entry pit to the exit pit.

Allowable Bend Radius

The degree of deflection that the drill pipe and product can safely tolerate without risk of damage to the pipe or product.

Ambient curing

Liner cures without an extra heat source (hot water or steam).

Ambient cured systems were developed for the fast, economical repair and renovation of small diameter pipelines, particularly to domestic and business premises drains.

In particular, the inversion drum for smaller diameter liners has allowed the technology to have more control of installation and enable access to some difficult locations e.g. within buildings, or roof areas etc.

Angular Deflection

The angle between two consecutive pipes.

Annular Filler

Material for grouting the annular space between the host pipeline and the lining system.

Annular Space

The void created by the difference in diameters between the shield and jacking pipe.

APS testing guideline

An important on-site test is conducted by the IKT institute for subterranean infrastructure. The leak test is performed as follows: A sample section of about 30 x 20 cm is inspected by an independent expert. The IKT checks the leak tightness of three samples as shown in the images. The red drop consists of local utility water and should have a diameter of about 45 mm. The evaluation is based on the passage of testing liquid through all three sample sections. The two possible results are TIGHT and NOT TIGHT.

Articulated Head

A shield of two sections where the front section can be deflected to steer the shield or cutting head.

ASTT

Australasian Society for Trenchless Technology

Auger Boring

A technique for forming a bore from a start or drive shaft to a reception shaft by means of a rotating cutterhead. Spoil is removed back to the drive shaft by helically wound auger flights rotating in a steel casing. This equipment may have limited steering capability.

Auger MTBM

Microtunnel boring machine (MTBM) that uses auger flights passing through the product pipeline to remove the excavated soil.

B

Back Reamer

Cutting head attached to the leading end of a drill string to enlarge the pilot bore during a pull-back operation to enable the product pipe to be installed.

Backacter

A mechanical device for excavation within an open shield.

Backup

When a blockage causes sewage to accumulate to the point of original discharge, for instance, toilets, showers, and other fixtures, rather than flow into the collection system.

Backwater Valve

Sewer line valve that prevents sewage from flowing back into the house.

Base sanitary flow

The portion of wastewater including domestic, commercial, institutional, and industrial sewage that specifically excludes inflow and infiltration.

BATT

Bulgarian Association for Trenchless Technology

Beacon

See Sonde

Bent Sub

Offset section of drill stem close behind the drill head that allows steering corrections to be made by rotation of the drill string to orientate the cutting head.

Bentonite

A natural clay material having thixotropic properties which is used as a basic ingredient for drilling muds and lubricants.

Biochemical Oxygen Demand (BOD)

A gross measure of wastewater strength. The regional plant uses an accelerated treatment process in which living bacteria, thriving in an oxygen-rich environment, consume material in the wastewater. Industry wastewater that is high in BOD requires more oxygen and is therefore more expensive to process.

Biosolids

Digested solids removed from wastewater.

Blackwater

The waste from toilets, consisting of urine, feces, flush water, toilet paper, and other hygienic items.

Blockage

Flow restriction caused by root intrusion; debris (dirt, sediment, non-flushable wipes, etc.) accumulation; and/or fat, oil, and grease. Structural failures can also result in downstream blockages caused by dirt and debris entering the collapsed pipeline.

Bore

Void which is created to receive a pipe, conduit or cable.

Bottleneck

A restriction in hydraulic capacity due to blockages, undersized or clogged lines, inflow and infiltration, or malfunctioning equipment.

Branch

Any part of a drain system other than the main, riser or stack; also known as a lateral line.

Breakout Wrench

Manual or hydraulic tool used to connect or break tool joints at access points forward of the drill rig.

Building Sewer (In-House Sewer)

Small diameter sewer that connects a building or residence to the service sewer. The service sewer then connects the building sewer to the mainline. A cleanout is typically located at the connection between the building sewer and the service sewer.

Burp Hole

Excavation along the drill path to relieve excess pressure that has created hydrolock.

Burst lining

Burst lining describes a trenchless rehabilitation procedure by which the old pipe is destroyed and displaced by a hammering burster. In the same course, a new plastic or steel pipe of equal or greater diameter is drawn in.

Butt-end

Term used for square end jacking pipes.

C

Calibration Hose

Calibration Hoses are used in open-end installations to squeeze the liner to the wall of the pipe. Also used in the manufacture of glued open-end liner and to prevent excessive swelling of the liner in free space. Calibration Hoses are also available in flexible and heat resistant versions

Can

A principal module of a shield microtunneling or tunnel-boring machine (TBM). Trailing cans may be used to faciliate steering. It may also be referred to as a trailing tube.

Carrier material

Porous component of the liner, which carries the liquid resin system during insertion into the pipe being renovated and forms part of the installed lining system once the resin has been cured

Carrier Pipe

Pipe to be rehabilitated by any trenchless rehabilitation method.

Cased Bore

Bore in which a pipe, usually a steel sleeve, is inserted simultaneously with the boring operation. Usually associated with auger boring or pipe jacking.

Casing

A pipe to support the bore. Usually not the product pipe.

Catch Basin

A chamber usually built at the curbline of a street, which conveys surface water for discharge into a storm sewer.

Caulking

General trenchless technology term that refers to methods for closing joints within a pipeline or between lining segments.

Cement Mortar Liners

Spray-on coating used primarily for corrosion protection of small diameter metal pipelines. Cement mortar and concrete linings can also provide structural and leak protection benefits in larger man-entry pipes or tunnels.

Chemical Grouting

Method for the treatment of the ground around a shaft or pipeline, using non-cementitious compounds, to facilitate or make possible the installation of an underground structure.

Chemical Stabilisation

Renovation method which seals a length of pipeline between two access points by employing a chemical solution pumped into the pipe and surrounding ground. Such systems perform a variety of functions including sealing of cracks and cavities, the provision of a new wall surface with improved hydraulic characteristics or ground stabilisation.

CHKSTT

China Hong Kong Society for Trenchless Technology

CIPP

Cured-in-place pipe

Cured-in-place pipe product (CIPP product)

Cured-in-place pipe of a particular design, produced from a liner of specified materials, with a wall structure which is uniquely defined for each diameter/wall thickness combination, and which is impregnated with a specific resin system and installed by a specific process

CIPP unit

Specific cured-in-place pipe produced from a continuous liner, which has been impregnated in one process and installed as a single length

CISTT

Colombian Institute for Subterranean Infrastructure Technologies and Techniques

City Sewer

Sewage disposal system operated by the city or county.

Cleaning Systems

A system of centrifugal pumps, tanks with baffles, shakers screens, de-sanding and de-silting hydro cyclones for the removal of cuttings from the slurry for recycling and reuse.

Cleanout Plug

A plug in a trap or drain pipe that provides access to the drain line for the purpose of clearing an obstruction.

Close-fit

Situation of the outside of the installed liner relative to the inside of the existing pipeline, which may either be an interference fit or include a small annular gap resulting from shrinkage and tolerances only

Close-Fit Sliplining

Method of lining with a continuous pipe for which the cross section is reduced to facilitate installation, and reverted after installation to provide a close fit to the existing pipe.

Closed Circuit Television (CCTV)

Video cameras mounted on small tractor devices or sleds and driven or pulled through a pipeline commonly used to inspect repairs and to assess the condition of the pipe.

Closed Shield

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

Closet – Toilet

Also known as a water closet

Closet Auger

A flexible rod with a curved end used to access the toilet's built-in trap and remove clogs.

Closet Bend

A curved fitting mounted immediately below the toilet that connects the closet flange to the toilet drain.

Closet Flange

Anchoring ring that attaches to the closet bend and secures it to the floor. Closet bolts that secure the toilet in place are insert into slots in the closet flange.

Collection System

A system of collector and/or interceptor sewers that collects wastewater from a community.

Collector Sewer

The first element of a wastewater collection system used to collect and carry wastewater from one or more building sewer laterals to a main sewer.

Collectors

Small sewer pipes measuring twelve inches or less in diameter.

Combined Sewer Overflow

The portion of flow from a combined sewer sytem, which discharges into a water body from an outfall located upstream of a wastewater treatment plant, usually during wet weather conditions.

Combined system

Sewer system designed to carry both wastewater and surface water in the same pipeline.

Commercial Sewer Customer

Any business that produces wastewater, except a business that falls under the definition of an industrial sewer customer.

Composite

Combination of cured resin system, carrier material and/or reinforcement, excluding any internal or external membranes or any layer of excess neat resin.

Composite materials

A composite material is a composite that is made up of two or more components and that features other material characteristics than its individual components.

Compression Ring

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.

Condition Assessment

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

Conductor Casing

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.

Connection Liner

Piece made of felt or glassfiber to be mounted on a pipe branch. Ensures a durable and tight end result in pipe joints.

Contact Grout

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

Continuous Sliplining

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.

Control Console

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.

Conventional Trenching

See Open Cut

Corrosion resistance

The corrosion resistance describes the durability of a material against decay (Lat. corrodere = corrode, erode, gnaw away); it is measured for liners by their resistance against decomposition due to chemical or aggressive substances in the wastewater and the sewer atmosphere.

Crossing

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

Crush Lining

See Pipe Eating.

CSTT

China Society of Geology - Trenchless Technology Committee

CTSTT

Chinese Taipei Society for Trenchless Technology

Cured-In-Place Pipe (CIPP)

Cured-in-place pipe (CIPP) is a liner that provides a seamless, corrosion-resistant, jointless "pipe-within-a-pipe." CIPP is installed through existing manholes and does not require extensive digging.

Curing

Process of resin polymerization, which may be initiated or accelerated by the use of heat or exposure to light.

Cut and Cover

See Open Cut

Cutter Boom

A mechanical device for excavation within an open shield.

Cutting/Cutter Head

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

Cuttings

See Spoil

CzSTT

Czech Society for Trenchless Technology

D

Darmstadt abrasion resistance test

The Darmstadt abrasion resistance test is a test procedure in accordance with DIN EN 295-3 for examining the abrasion resistance of a liner or wastewater pipe and is part of the approval procedure for national technical approval of the DIBt. A half-shell is filled with pebbles, sand and water for the test and the application range is simulated by 200,000 tilting movements.

Design thickness

Required wall thickness of the composite, as determined by structural design.

Detergent

One of several drilling fluid additives that reduces clay balling and keeps tooling clean.

Deviation

The variation from line and level to that specified.

DIBt - Deutsches Institut für Bautechnik

Deutsches Institut für Bautechnik (DIBt) plays a pivotal role in the construction industry: with its approvals and assessments, it ensures the safety of construction works while fostering the development of innovative construction products and techniques. DIBt is a technical authority and a service provider for the construction sector.

Directional Drilling

See Horizontal Directional Drilling (HDD)

Discrete Sliplining

Method of lining with pipes shorter than the section to be renovated which are not jointed prior to insertion to form a continuous pipe, and which have not been shaped to give them a cross sectional diameter smaller than their final diameter after installation.

Diurnal flow

The daily fluctuation in sanitary sewer collection system flows that typically consists of a spike in flows in the morning and in the evening, when domestic water use is highest.

DKSTT

Danish Society for Trenchless Technology - NoDig Infra

Domestic wastewater

Wastewater discharged from kitchens, laundry rooms, lavatories, bathrooms, toilets and similar facilities.

Double Wye

A service connection where a single lateral branches to serve two homes. These services cause problems when one house sits higher than the other and a stoppage occurs in the lateral, causing sewage from the higher house to flow into the lower house.

Downhole Drilling Assemblies

Mud motors and mechanical downhole motors used primarily to excavate hard soils and rock.

Drain system

The network of pipelines and ancillary works that conveys wastewater and/or surface water to a cesspool, sewer system or other place of disposal.

The subject of this technical information system is sewers with enclosed, channels whereby the term sewer is also used below as a collective term for all piping types of a drain and sewer system to EN 752-1.

Drill Bits

Tools that excavate soil or rock and faciliate steering at the face of the bore. Common types of drill bits used in HDD include slant-face bits, slanted-face rock bits, rotary rock bits, and percussive bits.

Drill Rig

A trenchless machine that installs pipes and cables by drilling a pilot bore to establish the location of the underground utility before enlarging the hole if needed and pulling back the product.

Drill Rods

High strength hollow steel pipes joined to form a string used to transmit rotational torque and thrust, and to transport drilling fluid from the drill rig to the downhole tools.

Drill String/Stem

The total length of drill rods/pipe, bit, swivel joint etc. in a bore.

Drilling Fluid

Largely comprised of water, drilling fluids usually include bentonite and if warranted other additives such as soda ash, polymers, and detergents to address water and soils properties that could compromise the successful completion of the HDD installation.

Drive Shaft

See Jacking Shaft

Dry Bore

Method of creating a bore without the use of a drilling fluid. Usually associated with guided impact moling, but may also apply to some rotary methods.

Dry Weather Flow

Flow in a sanitary sewer during periods of dry weather in which the sanitary sewer is under minimum influence of inflow and infiltration

E

Earth Piercing

See Impact Moling

Earth Pressure Balance Machine (EPBM)

Type of microtunnelling machine in which mechanical pressure is applied to the material at the face and controlled to provide the correct counter-balance to earth pressure to prevent heave or subsidence. The term is usually employed where the pressure originates from the main jacking station in the drive shaft or to systems in which the primary counter-balance to the earth pressure is supplied by pressurised drilling fluid or slurry.

Easement

Also called utility easement, this is a portion of land, shared by a property owner and a public agency, that contains a public utility, such as a sewer pipe.

ECR glass

ECR glass (E-glass Corrosion Resistant) is an especially corrosion-resistant glass and, unlike the more commonly used E-glass, is not attacked by acidic or base environments. This makes it well suited for use in the aggressive environments of the wastewater sewers.

Effluent

Treated, or partially treated, wastewater.

Electrical Snaking

Also known as an auger, plumber's snake; a device for dislodging obstructions in curved pipes, having a head fed into the pipe at the end of a flexible metal band; also called wirepuller. a length of resilient steel wire, for threading through an electrical conduit so that wire can be pulled through after it.

Entrance Seal

See Launch Seal

Entry Ring

See Launch Seal

EPA

U.S. Environmental Protection Agency: the federal agency responsible for enforcing the Clean Water Act, Safe Drinking Water Act and other federal environmental regulations.

EPBM

Earth Pressure Balance Machine (EPBM): Type of microtunneling or tunneling machine with a closed face and pressurized much chamber that supports the face of the tunnel and counterbalances the earth and groundwater pressures. This is done by filling the chamber with soil excavated from the tunnel and pressurizing it by pushing the machine forward and removing the muck from the chamber in a controlled manner through a screw conveyor. Polymer foams are utilized to plasticize the muck if sands and gravels are encountered in the excavation of the tunnel. The term is usually not applied to those machines where the pressure originates from the main pipe jacking rig in the drive shaft/pit or to systems in which the primary counterbalance of earth pressure is supplied by pressurize drilling fluid.

ESD

Equivalent single family dwellings.

Escutcheon

A decorative metal flange or trim shield beneath a faucet handle that covers the faucet stem and the hole in the fixture or wall.

Exit Seal

Same as launch seal except for the retrieval of the machine at the reception shaft. Used in high ground water to prevent the loss of ground.

Exit Shaft

See Reception/Exit Shaft/Pit

External membrane

Membrane forming the outside surface of the pipe after installation

Extraneous water

Unwanted flow in a drain or sewer system.

Eye (Pipe Jack Eye)

A sealing device placed in the shaft walls of the thrust and reception pits to allow the shield and pipes to enter and exit without soil, water and slurry flowing into the shaft.

F

Face

The undisturbed soil immediately ahead of the shield.

Ferro-Cement

Material comprising cementitious and steel elements to form a structural lining, which is either placed in situ in a man-entry size pipeline or tunnel, or is preformed into segments for later installation.

Filter Cake

A thin layer of bentonite drilling fluid that seals the borehole preventing the flow of liquids from the borehole into the native soil.

First break

Elastic limit or first major discontinuity of the stress-strain curve associated with local failure of the resin matrix or reinforcing fibres.

FISTT

Finnish Society for Trenchless Technology

Fluid Assisted

Method of guided drilling using a combination of mechanical drilling and Boring/Drilling pressurised fluid jets to provide the soil cutting action.

Fluid Density

See Mud Weight

Fold & Form Lining

Method of pipeline rehabilitation in which a liner is folded to reduce its size before insertion and reversion to its original shape by the application of pressure and/or heat.

Frac-out

See Hydrofracture

Free Boring

Method of auger boring without a casing.

FSTT

French Society for Trenchless Technology

G

Gel Strength

The measure of electrical attractive forces of the drilling fluid that allows the drilling fluid to suspend drilled solids as they are transported by the slurry out of the bore hole.

Ground Penetrating Radar

Nondestructive method for detecting subsurface structures, voids, discontinuities, and changes in material. GPR uses radar pulses transmitted into the ground to image the subsurface by recording electromagnetic signals reflected back to the GPR system.

Grouting

The process of filling voids or modifying/improving ground conditions. Grouting materials may be cementitious, chemical or other mixtures. In microtunneling grouting may be used to fill voids around the pipe or shaft or to improve ground conditions.

GSTT

German Society for Trenchless Technology

Guide Rails

Steel or timber rails set firmly in the thrust pit to give directional control of the pipes to be jacked and for accurate location of the pipe joints.

Guided Auger Boring

Method of auger boring in which the guidance mechanism actuator is sited in the drive shaft. The term may also be applied to those auger boring systems with rudimentary articulation of the casing near the cutting head activated by the rods from the drive shaft.

H

Hot water curing

The hot water curing system was the earliest form of the hardening process for CIPP lining and if associated with the water inversion method to install, took advantage of that water circulating through the lining material and boiler unit. Installation by water inversion requires a water tower scaffold which in some cases can be significantly high as the head of water is required to push the liner to the furthest point of the lined pipeline design.

I

IATT

Italian Association of Trenchless Technology

IBSTT

Iberian Society for Trenchless Technology

Internal membrane

Membrane forming the inside surface of the pipe after installation

Inversion

Process of turning a flexible tube or hose inside out by the use of fluid (water or air) pressure

Inverted-in-place insertion

Method whereby the impregnated liner is introduced by inversion to achieve simultaneous insertion and inflation

ISTT

The International Society for Trenchless Technology

J

JSTT

Japan Society for Trenchless Technology

L

Lateral connection collar

Fitting for reconnecting a lined main pipe to an existing or renovated lateral pipe.

LIATT

Lithuanian Association of Trenchless Technology

Lining tube (Liner)

Flexible tube, consisting of carrier material, resin system and any membranes and/or reinforcement, as combined prior to insertion in the pipe to be lined.

N

NASTT

North American Society for Trenchless Technology

Nominal thickness

One of a range of discrete liner wall thicknesses dictated by the materials used for liner construction and chosen so as to result in a finished wall thickness of the composite not less than the design thickness.

NSTT

Netherlands Society for Trenchless Technology

P

PFTT

Polish Foundation for Trenchless Technology

Pipe bursting

Pipe bursting is a trenchless method of replacing buried pipelines (such as sewer, water, or natural gas pipes) without the need for a traditional construction trench. "Launching and receiving pits" replace the trench needed by conventional pipe-laying. Pipe bursting may also be used to expand pipeline carrying capacity by replacing smaller pipes with larger ones, or "upsizing." Extensive proving work by the gas and water industries has demonstrated the feasibility of upsizing gas mains, water mains and sewers.

Pipe coating

A pipeline coating is a cost effective and viable solution to maintain pipelines' integrity. This coating provides a constant protective lining that helps save pipelines from the damaging effects of corrosion. Pipeline coating is one of the most reliable corrosion prevention methods used by industries today.

Preliner

External membrane which is installed separately and before the resin-impregnated liner. Preliner is installed between old pipe and the liner in order to protect liner and resins for example from dampness and sharp edges. Preliner also avoids spreading of the dissolved resin and other substances from the liner to the area surrounding the pipe.

R

Reinforcement

Fibres incorporated in the liner, which enhance the dimensional stability of the liner and/or the structural properties of the cured composite

NOTE: The reinforcement can be incorporated in the carrier material, constitute the carrier material, or can be a separate layer

Resin system

Thermosetting resin including the curing agent(s) and any fillers or other additives, in specified proportions.

RoSTT

The Romanian Society for Trenchless Technology

RSTT

Association "The Russian Society Trenchless Technology"

S

SASTT

Southern African Society for Trenchless Technology

SgSTT

Singapore Society for Trenchless Technology

Sideliner

Lateral connection piece made of felt, membrane: polyurethane

Silicon Bladder

Installation tool for lateral connection piece

SIPP

Spray-in-Place Pipe (SIPP) lining systems use Cement Mortar, Epoxies, and Polyureas to efficiently rehabilitate aging pipelines with minimal excavations.

SSTT

Scandinavian Society for Trenchless Technology

Steam Curing

Steam was introduced to improve the installation of CIPP lining particularly when larger diameter pipe projects were being considered and huge volumes of water needed for a hot water cure solution were considered impractical. Nowadays, as the technology evolves, the steaming method is used also in small diameter pipes and in in-house lining.

T

Temporary membrane

Internal membrane, used to separate process fluid (typically water or air) from the resin system during liner insertion, which is withdrawn after resin cure

Trenchless rehabilitation

Trenchless rehabilitation includes such construction methods as sliplining, thermoformed pipe, pipe bursting, cured-in-place pipe (CIPP), grout-in-place pipe, mechanical spot repair, and other methods for the repair, rehabilitation, or replacement of existing buried pipes and structures without excavation, or at least with minimal excavation.

Trenchless technology

Trenchless technology is a type of subsurface construction work that requires few trenches or no continuous trenches. It is a rapidly growing sector of the construction and civil engineering industry.

Trenchless technology is the science of installing, repairing or renewing underground pipes, ducts and cables using techniques that minimise or eliminate the need for excavation.

TSITT

Turkish Society for Infrastructure and Trenchless Technology

U

UAMTT

Ukraine Association for Modern Trenchless Technology

UKSTT

United Kingdom Society for Trenchless Technology

UV Curing

UV curing is the process by which ultraviolet light is used to initiate a photochemical reaction that generates a crosslinked network of polymers. Ultra Violet Light (UV) is becoming a popular liner curing option - the speed of the installation makes this method cost-effective.

W

Winched-in-place insertion

Method whereby the flat impregnated liner is first pulled into the pipe to be lined and then inflated to bring it up to size.

NOTE: Inflation can be achieved by means of a separate pressurized tube or hose inside the liner which is either withdrawn after resin cure or left in place as a permanent internal membrane

ABBREVIATIONS

b - width of test piece

E0 - short-term flexural modulus

Ex - long-term flexural modulus at x years

Et - flexural creep modulus at time t

F - force applied in flexural test

h - thickness of test piece

hm - mean thickness of test piece

I - moment of inertia (the second moment of area) per unit length of the pipe wall

L - distance between supports in flexural test

L1 - distance between points of contact of curved flexural test piece with supports

L2 - true span of curved flexural test piece

r - radius of support

R2 - radius of curvature of test piece at mid-thickness

V - rise of centre of curved flexural test piece above its points of contact with supports

S0 - initial specific ring stiffness

δt - deflection of flexural test piece at time t

αx, dry - dry creep factor at x years

εf0 - initial flexural strain at zero stress

εfb - flexural strain at first break

εfM - flexural strain at maximum applied load

σ0 - required flexural stress in creep test

σfb - flexural stress at first break

σfM - flexural stress at maximum applied load

σl - ultimate longitudinal tensile stress

CIPP - Cured-in-place pipe

EP- Epoxy resin

GRP - Glass-reinforced thermosetting plastics

PA - Polyamide

PAN - Polyacrylonitrile

PE - Polyethylene

PEN - Poly (ethylene naphthate)

PET - Poly (ethylene terephthalate)

PP - Polypropylene

PUR - Polyurethane

PVC-U - Unplasticized poly (vinyl chloride)

UP - Unsaturated polyester resin

VE - Vinyl ester resin