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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.
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.
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.
Articulated Head
A shield of two sections where the front section can be deflected to steer the shield or cutting head.
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.
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.
A mechanical device for excavation within an open shield
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.
A natural clay material having thixotropic properties which is used as a basic ingredient for drilling muds and lubricants.
Void which is created to receive a pipe, conduit or cable.
Breakout Wrench
Manual or hydraulic tool used to connect or break tool joints at access points forward of the drill rig.
Burp Hole
Excavation along the drill path to relieve excess pressure that has created hydrolock.
Term used for square end jacking pipes.
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 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.
A pipe to support the bore. Usually not the product pipe.
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.
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.
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.
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.
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
Pipeline installation in which the primary purpose is to provide one or more passages beneath a surface obstruction.
Crush Lining
See Pipe Eating.
Cured-In-Place Pipe (CIPP)
Method of lining with a flexible tube impregnated with a thermosetting resin which produces a pipe after resin cure.
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.
See Spoil
One of several drilling fluid additives that reduces clay balling and keeps tooling clean.
The variation from line and level to that specified.
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.
Downhole Drilling Assemblies
Mud motors and mechanical downhole motors used primarily to excavate hard soils and rock.
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.
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.
Entrance Seal
See Launch Seal
Entry Ring
See Launch Seal
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
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.
The undisturbed soil immediately ahead of the shield.
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.
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.
See Hydrofracture
Free Boring
Method of auger boring without a casing.
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.
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.
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.
Hand Shield
An open face shield for manual excavation.
Hole Openers
Downhole tool that uses rolling cutters to enlarge a hole in hard soil and rock formations.
Horizontal Directional Drilling (HDD)
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. During the pilot bore the direction of the drill string is controlled by the orientation of a slanted face to the drill head, eccentric fluid jets or a combination of these, usually in conjunction with a locator.
Hose Lining
Lining system for pressure applications where a woven flat fiber reinforced polyethylene hose is pulled into the host pipe and secured by special end fittings. Once inserted, the woven hose liner is inflated to the service pressure expanding the liner until it contacts the wall of the host pipe.
Hydraulic Jacks
High pressure hydraulically operated jacks providing the power to move the pipeline.
The inadvertent loss of drilling fluid from the borehole annulus to the surrounding soil as a result of excess downhole fluid pressure.
A phenomenon that occurs when circulation is lost creating a hydraulic cylinder in front of a reamer with holding pressure greater than the pullback capacity of the drill rig.
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 that rely 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.
The downward movement of water from the atmosphere into soil or porous rock. The unintended ingress of ground water into a drainage system. 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.
Flow which enters the sewer generated by rainfall or an industrial discharge or other particular connection. 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 Station
A fabricated steel cylinder fitted with hydraulic jacks that is incorporated into a pipeline between two pipes segments. Its function is to distribute the jacking load over the pipe string on long drives.
Intersect Method
Horizontial directional drilling method that allows accurate installation over longer distances than can be achieved by conventional means. The Intersect method employs two rigs starting from opposite ends of the project to create pilot bores using conventional drilling tools. A magnetic source is substituted for the conventional steering tool in one of the rigs, which allows the other rig to accurately measure its position relative to the electromagnetic signal. The rig with the magnetic source tool advances toward the other rig until it intersects the bore and continues through the bore to the other side as the conventional tooling is retracted.
Jacking Force
Force applied to pipes in a pipe jacking operation.
Jacking Frame
A structural component that houses the hydraulic cylinders used to propel the microtunneling machine and pipeline. The jacking frame serves to distribute the thrust load to the pipeline and the reaction load to the shaft wall or thrust wall.
Jacking Pipe
A pipe with a flexible joint designed specifically for jacking.
Jacking Shaft
An excavation from which trenchless technology equipment is launched for the installation or removal of a pipeline, conduit, or cable. May include a thrust wall to spread reaction loads to the ground.
Jacking Shield
A fabricated steel cylinderat the front end of which excavation is carried out either by hand or by machine. Incorporated with the shield are facilities to allow it to be adjusted to control line and grade.
Jet Cutting
Guided boring method using pressurised fluid jets for soil cutting.
Flexible sealing and jointing arrangement between two pipes.
Joint Sealing
Method in which an inflatable packer is inserted into a pipeline to span a leaking joint, resin or grout is injected into the annulus between the packer and pipeline until the joint is sealed and the packer then removed.
Launch Pit
Slimliar to drive shaft but more usually associated with launching an impact moling or similar tool.
Launch Seal
A mechanical seal, usually composed of a rubber flange that is mounted to the wall of the drive shaft. The flange seal is distended by the MTBM as it passes through, creating a seal to prevent water or lubrication inflow into the shaft during tunneling operations.
Lead Pipe
The leading pipe manufactured to fit the rear of the jacking shield and over which the trailing end of the shield is fitted.
Leading Interjack Pipe
The pipe immediately ahead of, or attached to, the interjack shield.
Live Insertion
Method of installation of a liner while 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.
Trenchless procedures for identifying the site of underground utilities, infrastructure, obstructions, etc. without excavation or with minimum excavation.
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, or an impact mole 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.
Means of reducing friction either around a pipe being jacked or a shaft being sunk into the ground.
Manual Mechanical Shield
Open shield in which manpower is used to excavate the material but which has some steering capability.
Marsh Funnel
Funnel used to calculate the viscosity of a fluid by measuring the time the funnel filled with liquid empties into a cup.
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.
Mechanical Props Repair
See Rerounding
A remote control method of installing pipes using a fully guided microtunneling machine.
Microtunnel Boring Machine (MTBM)
MTBM has a closed faced shield from which excavated soil is removed using a slurry, which also counterbalances groundwater and earth pressures. The machine is guided by a laser or other survey device mounted in the jacking shaft, which projects a beam onto a target in the articulated steering section of the MTBM. The MTBM is steered by extending or retracting remotely controlled steering jacks.
Microtunnel Shield
See Microtunnel Boring Machine (MTBM)
Mixing Sytem
A system of pumps, hoppers, venturi mixers, hoses and tanks used to create the proper drilling fluid mixture suitable for the local geological conditions.
Modified Sliplining
See Close-Fit Slip lining
See Impact Moling
Mole Ploughing
Method of installing a pipeline by pulling a plough through the ground while a continuous length of pipe is fed into the top of the plough and buried from the tail.
Spoil or removal of same.
Mud Motor
Downhole tool for drilling in rock using pressurized fluid to power rotating cutterheads.
Mud Weight
The weight of the drilling fluid measured against the weight of water used to determine the solids content of the fluid or slurry. Excess solids can adversely affect the efficiency of the drilling system and cause excessive wear on pumps. Mud weight calculations can also be used to measure the effectiveness of recycling solids control equipment.
Narrow Trenching
Method of excavation of a trench up to 100 mm wider than the outside diameter of the service to be installed, usually employing either a rockwheel or chain type trencher.
New Installation
Construction of a new pipe or underground utility to replace or upgrade an existing system or to provide new service.
Non-Structural Renovation
Pipe renovation method that relies on the host pipe to meet the structural integrity requirements of the utility.
Any object or feature that lies completely or partially within the cross-section of a microtunnel or drill that prevents continued forward progress.
Open Cut
Underground construction method involving excavation from ground level to the level required for the installation, maintenance or inspection of a pipe, conduit or cable. Upon completion of the work, the trench is backfilled and the surface restored.
Open Shield
A shield that allows direct access to the soil face.
The annular space between the excavated hole and the outside diameter of the jacking pipe.
See Compression Ring.
Material placed between pipe joints to distribute the jacking loads.
Small-diameter monitoring wells that allow ground water levels or pressures to be monitored.
Pilot Bore
First, usually steerable, pass of any boring operation which later requires back-reaming or other enlargement. Most commonly applied to guided drilling, directional drilling and 2-pass microtunnelling systems
Pilot Tube Method
A multi stage method of accurately installing a product pipe to line and grade by use of a guided pilot tube followed by up-sizing to install the product pipe
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 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
A system of directly installing pipes behind a shield machine by hydraulic jacking from a drive shaft such that pipes form a continuous string in the ground.
Pipe Lubricant
See Lubrication
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.
Pipe Ramming
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 splitting. At the same time a new pipe of the same or larger diameter is pulled in behind the splitting tool.
Point Source Repair
See Localised Repair
Method of repairing a brick sewer or manhole by the application of cement mortar where loss has occurred.
Method using vacuum excavation for obtaining visual confirmation of utilities and underground obstructions near or crossing the planned bore path.
Power Pack
A hydraulic pump unit feeding fluids to activate the hydraulic jacks.
Preconditioning Work
That part of a project, usually before renovation work on a pipeline, that 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.
Pressure Plate
A steel pressure plate located between the rear end of the jacks and the thrust wall to backspread concentrated loadings.
Product Pipe
Pipe used for the conveyance of water, gas, sewage, and other products and services.
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.
Pump Capacity
Measured in gallons per minute or similar measurements of flow; along with thrust/pullback and torque, one of three measurements typically used to describe and classify drill rigs and their suitability to successfully perform an installation.
Push Ring Adapter
Mechanical structure mounted on the thrust ring to prevent the thrust ring from coming into contact with the pipe collar and causing damage to the collar.
A percussive hammer attached to an open end casing is driven through the ground. The spoil within the casing is removed to leave an open casing.
Downhole tools used to enlarge the bore sufficiently to facilitate installation of the product.
Rebated Joint
A joint which is formed within the thickness of a pipe wall.
Reception/Exit Shaft/Pit
Excavated shaft at the end of a jacked section from which the jacking shield is recovered.
All measures for restoring or upgrading the performance of existing utility systems including renovation, replacement or repair to overcome problems related to any aspect of performance.
Method of backfilling, compaction and re-surfacing of any excavation to restore the surface and underlying structure to enable it to perform its original function.
Methods of rehabilitation that incorporates all or part of the original fabric of a host pipe to improve the performance of the pipe
Trenchless construction procedures to restore or improve the structural integrity and / or performance of the utility.
Construction of a new pipe or underground utility located on or off the line of the existing systems, which serves the same function as the old system.
Preparatory operation in which an expansion device is inserted into a distorted pipe to return it to a circular cross section. Rerounding is usually carried out prior to the insertion of a permanent liner or supporting band.
Resin Injection
Localised repair of pipes, usually sewers, by injection into cracks, defects or cavities a resin formulation which subsequently cures to prevent leakage and further deterioration.
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.
Segmental Lining
Method of lining with pipe sections made of at least two pieces with both longitudinal and circumferential joints.
Segmental Sliplining
See Discrete Sliplining
Skin Friction
The resisting force created between pipes and soil when the pipes are jacked forward.
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.
Slurry Chamber
A chamber located behind the cutting head of a slurry microtunneling machine, in which excavated material is mixed with the slurry for transport to the surface.
Slurry Line
A series of hoses and pipes that transport tunnel muck and slurry from the face of a slurry microtunneling machine to the ground surface for separation.
Slurry Separation
A process in which excavated material is separated from the circulation slurry.
Slurry TBM
A microtunnel method that uses tunnel Boring Machine (TBM) or shield with closed face which employs hydraulic means for removing the excavated material and balances the ground water pressure.
Soft Lining
See Cured-In-Place Pipe (CIPP)
Transmitter located near the front of an HDD drill string that sends an electronic signal that provides location and depth of the drill string near the bit. The sonde signal also transmits pitch, roll, temperature, and battery status to the receiver.
Mechanical structure used to connect the jacking thrust ring to the pipe and used to accommodate lengths of pipe that are longer than the stroke length of the jack.
Spiral Lining
Method of lining with a profiled strip, spirally wound to form a continuous pipe after installation.
Earth, rock, and other materials removed during installation.
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.
Standard Dimensional Ratio (SDR)
Numerical designation of a pipe series which is a convenient round number approximately equal to the ratio of the nominal outside diameter and the minimum wall thickness.
Steel Banded Joint
A joint formed with a steel band to locate and join each pipe. Usually used with butt-ended pipes.
Steerable Moling
Method similar to impact moling but with limited steering capability.
Structural Renovation
Pipe renovation methods that do not require the structured-wall (SW) of the host pipe to contribute to the ring stiffness needed to satisfy the integrity of the utility
Survey Tools
Downhole equipment and instruments used to determine the position of a bore in directional drilling or in site investigation.
Devices placed between the reamer and the duct puller or pulling head to eliminate rotation of the product during pullback.
Target Shaft/Pit
See Reception/Exit Shaft/Pit
Force applied to a pipeline or drill string to propel it through the ground.
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
Working shaft at the beginning of the jacked section of pipeline in which the specialist equipment is installed, and from which jacking operations are carried out.
Thrust Ring
A steel ring that is placed against the cross sectional area of the pipe to ensure that the jacking forces are spread around the circumference of the pipe.
Thrust Wall
A wall at the rear of the thrust pit designed to spread the reaction loads to the ground behind the thrust pit.
Measured in pounds or similar measurements of force; along with torque and pump capacity, one of three measurements typically used to describe and classify drill rigs and their suitability to successfully perform an installation.
Measured in Foot-pounds or similar measurements of rotational force; along with thrust/pullback and pump capacity, one of three measurements typically used to describe and classify drill rigs and their suitability to successfully perform an installation.
System for locating and recording progression of a horizontial drilling installation by monitoring an electromanetic signal transmitted from a sonde mounted at the drill head to a receiver (locator) at the surface, or by wireline or wireless non-walkover systems.
Trailing Interjack Pipe
The recessed pipe immediately behind the interjack station which slides into the rear of the shield.
See Sonde
See Open Cut.
Trenchless Technology
Underground construction methods of utility installation, rehabilitation, inspection, location and leak detection, with minimum excavation from the 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.
A construction method of excavating an opening beneath the ground without continuous disturbance of the ground surface and of large enough diameter to allow individuals access and erection of a ground support system at the location of material excavation.
Uncased bore
Any bore without a lining or pipe inserted, i.e., self-supporting, whether temporary or permanent.
Any method that increases the cross-sectional area of an existing pipeline 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.
The resistance of a fluid to flow, which can be estimated by using a Marsh Funnel.
Walkover System
See Locator
Washover pipe
A pipe inserted in the borehole to stabilize the hole when using small diameter drill string, when recovering a stuck drill pipe, or when retracting a drill string to change bits or to re-tool. Washover pipes may also be used to stablilize the bore when drilling in difficult unstable formations.
Water Jetting
Internal cleaning mechanism of the cutterhead in which high-pressure water is sprayed from nozzles to help remove cohesive soils.
Surface system consisting of a grid of energized wire coil, which in combination with a downhole survey probe, tracks the location of the drill string.
Working Shaft
A general term applied to the more specific description of thrust or reception pits.