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Glossary of Terms

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ADVANCE Distance excavated during a given time (shift or day).
ADVANCE PATH 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.
ANNULAR FILLER Material for grouting the annular space between the existing pipeline and the lining system.
AUGER BORING Method of forming a bore, usually from a drive pit, by means of a rotating cutting head. Spoil is removed back to the drive pit by helically wound auger flights rotating in a steel casing. The equipment may have limited steering capability.
AUGER TBM Tunnel boring machine (TBM) in which the excavated soil is removed to the drive shaft by auger flights passing through the product pipeline pushed in behind the TBM.
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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.
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.
BLIND SHIELD Non-mechanical shield which has a controlled and partly sealed face.
BORE Void which is created to receive a pipe, conduit or cable.
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CAN Principal module which is part of a shield machine as in microtunnelling or of a TBM. Two or more may be used, depending on the installation dimensions required and the presence of an articulated joint to facilitate steering.
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 Pipe to support a bore. Usually not a product pipe.
CASING PIPE METHOD Method in which a casing, generally steel, is pipe jacked into place, within which a product pipe is later inserted.
CAULKING General term which, in trenchless technology, refers to methods by which joints may be closed within a pipeline or between lining segments.
CCTV Closed circuit television used to carry out internal inspection and survey of pipelines.
CHEMICAL GROUTING Method for the treatment of the ground around a shaft or pipeline, using non-cementitious compounds, in order to facilitate or make possible the installation of an underground structure.

Renovation method in which a length of pipeline between two access points is sealed by the introduction of one or more compounds in solution into the pipe and surrounding ground and, where appropriate, producing a chemical reaction. Such systems may perform a variety of functions such as the sealing of cracks and cavities, the provision of a new wall surface with improved hydraulic characteristics or ground stabilisation.

COMPRESSED AIR METHOD General term which, in trenchless technology, refers to the use of compressed air within a tunnel or shaft in order to balance ground water pressure and to prevent ingress into an excavation open to the atmosphere.
CONVENTIONAL TRENCHING Method in which access is gained by excavation from ground level to the required level underground for the installation, maintenance or inspection of a pipe, conduit or cable. The excavation is then backfilled and the surface reinstated.
CONVENTIONAL TUNNELLING Method of tunnel construction ranging from manual excavation to the use of self-propelled tunnel boring machines. Where a lining is required, bolted segmental rings are frequently used.
CUTTING/CUTTER HEAD Tool or system of tools on a common support which excavates at the face of a bore. Usually applies to mechanical methods of excavation.
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DIRECTIONAL DRILLING Steerable method for the installation of pipes, conduits and cables in a shallow arc using a surface launched drilling rig. In particular, the term applies to large scale crossings in which a fluid filled pilot bore is drilled without rotating the drill string, and this is then enlarged by a washover pipe and back reamer to the size required for the product pipe. The required deviation during pilot boring is provided by the positioning of a bent sub
DRILL BIT/HEAD Tool which cuts the ground at the head of a drill string, usually by mechanical means.
DRILL STRING/STEM The total length of drill rods/pipe, bit, swivel joint etc. in a bore.
DRILLING FLUID/MUD Mixture of water and, usually, bentonite or polymer continuously pumped to the cutting head or drill bit to facilitate the removal cuttings, stabilise the bore, cool the head and lubricate the passage of the product pipe. In suitable ground conditions water alone may be used.
DRIVE/ENTRY/SHAFT/PIT Excavation from which trenchless technology equipment is launched for the installation or renovation of a pipeline, conduit or cable. It may incorporate a thrust wall to spread reaction loads to the ground.
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.
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EARTH PIERCING Term commonly used in North America as an alternative to Impact Moling.
EARTH PRESSURE BALANCE (EPB) MACHINE 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 in order 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.
EARTH PRESSURE BALANCE (EPB) SHIELD Mechanical tunnelling shield which utilises a full face to support the ground in front of the shield and usually employs an auger flight to extract the material in a controlled manner.
ENTRY/EXIT ANGLE Angle to the ground surface at which the drill string enters or exits in forming the pilot bore in a directional drilling/guided drilling system.
EPB Abbreviation for Earth Pressure Balance.
EXPANDER A tool which enlarges a pilot bore during a pull-back operation by compression of the surrounding ground rather than by excavation. Sometimes used during a thrusting process as well as during pull-back.
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FACE STABILITY Stability of the excavated face of a tunnel or pipe jack.
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.
FLUID ASSISTED Method of guided drilling using a combination of mechanical drilling and BORING/DRILLING pressurised fluid jets to provide the soil cutting action.
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.
FREE BORING Method of auger boring without a casing.
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GROUTING Method of filling voids, usually with cementitious grout.
GUIDE RAIL Device used to support or guide, first the shield and then the pipe within the drive shaft during a pipe jacking operation.
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.
GUIDED DRILLING Method for the installation of pipes, conduits and cables using a surface- launched drilling rig. A pilot bore is drilled using a rotating drill string and is then enlarged by a back reamer to the size required for the product pipe. The necessary deviation during the pilot boring is provided by a slanted face to the drill head, eccentric fluid jets or a combination of these, usually in conjunction with a locator.
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HEAVING Process in which the ground may be displaced causing a lifting of the ground surface.
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IMPACT MOLING Method of creating a bore using a pneumatic or hydraulic hammer within a casing, generally of torpedo shape. The term is usually associated with non- steered or limited steering devices without rigid attachment to the launch pit, relying upon the resistance of the ground for forward movement. During the operation the soil is displaced, not removed. An unsupported bore may be formed in suitable ground, or a pipe drawn in or pushed in behind the impact moling tool. Cables may also be drawn in.
INFILTRATION Water from the surrounding ground which enters through defects in pipes or joints in a pipeline or through the lateral connections, manholes or inspection chambers.
INFILTRATION/INFLOW (I/I) The total quantity of water from both infiltration and inflow without distinguishing the source.
INFLOW Water discharged into a sewerage system and service connections from sources on the surface.
INTERJACK PIPES Pipes specially designed for use with an intermediate jacking station.
INTERMEDIATE JACKING METHOD Pipe jacking method which redistributes the jacking force by the use of intermediate jacking stations.
INTERMEDIATE STATION JACKING (IJS) A fabricated steel shield incorporating hydraulic jacks designed to operate between interjack pipes to provide incremental thrust or to redistribute thrust on long pipe jacking drives.
INTERNAL INSPECTION Means of ascertaining the condition of pipelines, either by visual inspection for man-entry size or by the use of remote control instrumentation.
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JACKING FORCE Force applied to pipes in a pipe jacking operation.
JACKING PIPES Pipes designed for use in a pipe jacking operation.
JACKING SHIELD Fabricated steel cylinder from within which excavation is carried out, either manually or by mechanical means. Incorporated within the shield are facilities for controlling the line and level.
JET CUTTING Guided boring method using pressurised fluid jets for soil cutting.
JOINT SEALING Method in which an inflatable packer is inserted into a pipeline to span a leaking joint, resin or grout being injected until the joint is sealed and the packer then removed.
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LAUNCH PIT As for drive pit but more usually associated with launching an impact moling or similar tool.
LEAD PIPE The leading pipe designed to fit the rear of a jacking shield and over which the trailing end of the shield is fitted.
LINING WITH CLOSE-FIT PIPES 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.
LINING WITH CONTINUOUS PIPE 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.
LINING WITH CURED-IN-PLACE PIPES Method of lining with a flexible tube impregnated with a thermosetting resin which produces a pipe after resin cure.
LINING WITH DISCRETE PIPES 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.
LINING WITH INSERTED HOSE Method of lining with a loose fit reinforced hose to provide a pipe lining such that fluids may be conveyed under pressure.
LINING WITH PIPE SEGMENTS Method of lining with pipe sections made of at least two pieces with both longitudinal and circumferential joints.
LINING WITH SPIRALLY WOUND PIPES Method of lining with a profiled strip, spirally wound to form a continuous pipe after installation.
LIVE INSERTION Method of installation of a liner whilst the product pipe remains in service.
LOCALISED REPAIR Repair work on a pipe, particularly sewerage, for lengths less than the run between two adjacent access points.
LOCATOR An electronic instrument used to determine the position and strength of electro- magnetic signals emitted from a transmitter sonde in the pilot head of a boring system, in an impact moling tool or from existing underground services which have been energised. Sometimes referred to as a Walkover System.
LOW LOAD METHOD A pipe jacking method in which separate provision is made to carry the jacking load, the pipe being installed carrying little or none of the jacking force.
LUBRICATION Means of reducing friction either around a pipe being jacked or a shaft being sunk into the ground.
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MAN-ENTRY Description of any operation which requires an operative to enter a pipe, duct or bore. The minimum size and other conditions for which this is permissible may be defined under health and safety legislation.
MANUAL MECHANICAL SHIELD Open shield in which manpower is used to excavate the material but which has some steering capability.
MEASUREMENT WHILE DRILLING (MWD) Instrumentation in a bore that provides continuous data simultaneously with drilling operations, usually transmitting to a display at or near the drilling rig.
MICROTUNNELLING Method of steerable remote control pipe jacking to install pipes of internal diameter less than that permissible for man-entry. In North America the term is used to describe remote control continuous pipe jacking in all diameters.
MIDI-RIG Steerable surfaced launched drilling equipment for the installation of pipes, conduits and cables. Applied to intermediate sized drilling rigs used as either a small directional drilling machine or a large guided boring machine. Tracking of the drill string may be achieved by either a downhole survey tool or a locator.
MINI-HORIZONTAL DIRECTIONAL DRILLING An alternative term for Guided Drilling.
MOLE PLOUGHING Method of installing a pipeline by pulling a plough through the ground whilst a continuous length of pipe is fed into the top of the plough whilst a continuous length of pipe is fed into the top of the plough and buried from the tail.
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NOMINAL SIZE Size of pipe or shaft used to define the internal working diameter.
NON-MAN ENTRY Size of pipe, duct or bore less than that for man-entry.
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OPEN FACE SHIELD Shield in which manual excavation is carried out from within a steel tube at the front of a pipe jack.
OVALITY The difference between the maximum and minimum diameter divided by the mean diameter at any one cross section of a pipe, generally expressed as a percentage.
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PILOT BORE First, usually steerable, pass of any boring operation which later required back- reaming or other enlargement. Most commonly applied to guided drilling, directional drilling and 2-pass microtunnelling systems.
PIPE BURSTING Replacement method in which an existing pipe is broken by brittle fracture, using mechanically applied force from within. The pipe fragments are forced into the surrounding ground. At the same time a new pipe, of the same or larger diameter, is drawn in.
PIPE DISPLACEMENT Term used in North America.
PIPE EATING Replacement method, usually based on microtunnelling, in which a defective pipe is excavated together with the surrounding ground and a new pipe installed. The microtunnelling shield machine will usually need some crushing capability. The defective pipe may be filled with grout to improve steering performance. Alternatively, a proboscis device to seal the pipe in front of the shield may be used.
PIPE JACKING Method for directly installing pipes behind a shield machine by hydraulic or other jacking from a drive shaft such that the pipes form a continuous string in the ground.
PIPE PULLING Method of replacing small diameter pipes where a new product pipe is attached to the existing pipe which is then pulled out of the ground.
Non-steerable method of forming a bore by driving a steel casing, usually open-ended, with a percussive hammer from a drive pit. The soil may be removed by augering, jetting or compressed air. In appropriate ground conditions a closed casing may be used.
PIPE SPLITTING Replacement method for breaking an existing pipe by longitudinal slitting. At the same time a new pipe of the same or larger diameter may be drawn in behind the splitting tool.
PIPELINE SYSTEM Interconnecting pipe network for the conveyance of fluids.
POINTING Method of repairing a brick sewer or manhole by the application of cement mortar where loss has occurred.
PRECONDITIONING WORK That part of a project, usually before renovation work, which includes preparatory cleaning and internal inspection.
PREPARATORY CLEANING Internal cleaning of pipelines, particularly sewers, prior to inspection, usually with water jetting and removal of material where appropriate.
PRODUCT PIPE Permanent pipeline for operational use.
PULL-BACK That part of a guided boring or directional drilling operation in which the drill string is pulled back through the bore to the entry pit or surface rig, usually installing the product pipe at the same time.
PULL-BACK FORCE Tensile load applied to a drill string during pull-back. Guided boring and directional drilling rigs are generally rated by their maximum pull-back force.
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RECEPTION/EXIT SHAFT/PIT Excavation into which trenchless technology equipment is driven and may be recovered during the installation or renovation of a product pipe, conduit or cable.
REHABILITATION All methods for restoring or upgrading the performance of an existing pipeline system.
REINSTATEMENT Method of backfilling, compaction and re-surfacing of any excavation order to restore the surface and underlying structure to enable it to perform its original function.
RENOVATION Methods of rehabilitation in which all or part of the original fabric of a pipeline is incorporated and its current performance improved.
REPAIR Rectification of local damage.
REPLACEMENT Methods of rehabilitation of an existing pipeline system by the installation of a new system, either on or off the existing line, without incorporating the original fabric.
REROUNDING Preparatory operation in which an expansion device is inserted into a distorted pipe to return it to a circular cross section. It is usually carried out prior to the insertion of a permanent liner or supporting band.
RESIN INJECTION Method used in the localised repair of pipes, usually sewers, by injection into cracks, defects or cavities of a resin formulation which subsequently cures to prevent leakage and further deterioration.
ROBOT Remote control device with closed circuit television (CCTV) monitoring, used mainly in localised repair work, such as cutting away obstructions, re-opening lateral connections, grinding and re-filling defective areas and injecting resin into cracks and cavities.
ROD PUSHING Method of forming a pilot bore by driving a closed pipe head with rigid attachment from a launch pit into the soil which is displaced. Limited steering and monitoring capability may be provided, usually in conjunction with a locator.
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SHIELD TUNNELLING METHOD Method of excavation in the front of a tunnel or pipe jack using a shield.
SLEEVE PIPE Pipe installed as external protection to a product pipe.
SLIME SHIELD Earth pressure balance shield with soil conditioning additives to facilitate the excavation of the ground.
SLIPLINING General term used to describe methods of lining with continuous pipes and lining with discrete pipes.
SLURRY SHIELD METHOD Method using a mechanical tunnelling shield with closed face which employs hydraulic means for removing the excavated material and balances the ground water pressure.
SPACER BLOCK Device used to extend the distance that the hydraulic rams within a jacking system can propel the pipeline.
SPRAY LINING Method for applying a lining, usually of cement mortar or resin, by a rotating spray head which is winched through an existing pipeline.
SSES Sewer system evaluation survey of tributary sewer systems with levels of infiltration and inflow.
STANDARD DIMENSIONAL RATIO (SDR) The ratio of minimum outside diameter of a pipe to wall thickness.
STEERABLE MOLING Method similar to impact moling with a limited steering capability.
SUBSIDENCE Process in which the ground may be displaced causing a settlement at the surface.
SURVEY TOOLS Downhole equipment and instruments used to determine the position of a bore in directional drilling or in site investigation.
SWAGELINING Method of lining with close-fit pipes in which a temporary reduction in diameter is achieved by passing it through one or more dies which may be heated. This is a Registered Trade Mark of BG plc.
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THRUST Force applied to a pipeline or drill string to propel it through the ground.
THRUST BORING Unpreferred term, loosely applied to various trenchless installation 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 RING Load spreading device to transfer force from the hydraulic rams on to the pipeline in a pipe jacking operation.
TRENCHLESS TECHNOLOGY Methods for utility and other line installation, rehabilitation, replacement, renovation, repair, inspection, location and leak detection, with minimum excavation from the ground surface.
TUNNEL BORING MACHINE (TBM) A machine that excavates a tunnel by drilling out the face to full size in one operation. It may be controlled from within the shield or remotely.
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UNCASED BORE Self supporting bore without a lining or inserted pipe, whether temporary or permanent.
UPSIZING Method in which the cross sectional area of an existing pipeline is increased by replacing it with a larger diameter pipe.
UTILITY CORRIDOR Duct in which two or more different utility services are installed with access for maintenance. Also referred to as a Common Utility Tunnel, Common Duct or Utilidor.
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WASHOVER PIPE Rotating drill pipe of larger diameter than the pilot drill and placed around it with its leading edge less far advanced. Its purpose is to provide stiffness to the drilling pipe in order to maintain steering control over long bores, to reduce friction between the drill string and the soil and to facilitate mud circulation. See Directional Drilling.
WATER JETTING Method for the internal cleansing of pipelines using high pressure water jets.

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