Commonly Used Terminology

Auger Boring
Casing is jacked into the ground as a rotating auger works simultaneously to remove the excavated soil. It is commonly used in applications where settlement is a concern: under highways, railways and levies. Also known as a dry bore.

A natural clay material used as a basic ingredient for drilling muds and lubricants to facilitate ease of installation.

A horizontal hole created underground: primarily used to accommodate cables, pipe or conduit. Bores are created using a horizontal directional drilling (HDD) rig, boring machine or microtunneling boring machine.

A pipe installed to support the bore, typically using a pipe jacking or pipe ramming technique. The casing is usually not the product line, but serves as a housing. Casing is used in conjunction with numerous trenchless methodologies.

A pipeline installation designed to pass beneath a surface obstruction. Examples of crossings include roads, railway tracks, water bodies, pipeline corridors and utilities.

See spoil.

A term used to describe the process of exposing subsurface pipeline, utilities or infrastructure using hydrovac.

Down the Hole Hammer (DTH)
Pipe or casing is installed using a pneumatic hammer attached to the inside leading edge of the casing. It breaks rock down into pebbles or dust. The spoil travels through the hammer and into the casing, and is removed by airway augers.

Drill Rig
A trenchless machine that installs pipes and cables by drilling a pilot hole which can be enlarged (if necessary), and then pulling the product line.

Entry Point
The starting location of the crossing where the drill enters the ground.

Exit Point
The end location of the crossing.

Guided Boring Machine (GBM)
GBM’s are used in Auger Boring and Pipe Ramming applications to provide precise accuracy to distances up to 120 m (394 ft). The process involves a pilot hole and an LED targeting devices which is monitored onscreen to maintain accurate line and grade.

Heavy HDD Rig
A horizontal directional drilling rig weighing over 82 tons. Used for longer crossings ranging up to 3,000 m (9,843 ft). Used on projects up to 1,524 mm (60 in) in diameter.

Horizontal Directional Drilling (HDD)
A surface-based trenchless technology that involves a horizontal bore under the surface along a planned pathway. Once the HDD creates a bore of suitable size – which may require one or multiple passes by the drilling apparatus – the conduit or pipe is pulled into the bore and connections are made to the appropriate utilities.

Live Lines
Active product lines that are carrying product (eg. water, waste, electricity, oil, gas, etc.).

A proprietary hydraulic pipe ramming technology of The Tunneling Company that is used to install large diameter steel pipe from 914 mm to 4.9 m (36 in to 192 in) in diameter where other boring or tunneling methods are not feasible: beneath crossings in wet, granular, unstable or shallow ground conditions.

Light HDD Rig
A horizontal directional drilling rig weighing less than 82 tons. Used for crossings ranging from 300 m to 500 m (984 ft to 1.640 ft) and diameters between 51 mm and 914 mm (2 in and 36 in). Light rigs are employed for shorter installations and can operate in tighter confines than heavy rigs.

A method for installing pipes using a remote-guided microtunneling machine, which bores the hole and places the pipe. Boring and installation occurs simultaneously. The microtunneling machine is operated remotely from a control panel, usually located on the surface.

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. Backhoe excavation is an example of open cut construction.

Pilot Bore
The initial guide hole that is drilled, spanning the entire path of the hole. Once the pilot hole is complete, it is usually enlarged to accommodate casing or product line.

Pipe Jacking
A method of tunnel construction where hydraulic jacks are used to push specially made pipes through the ground behind a tunnel boring machine or shield. This technique is commonly used to create tunnels under existing structures, such as roads or railways.

Pipe Ramming
A trenchless method where a large pneumatic pipe ramming hammer pushes the pipe or casing horizontally into the ground at the crossing point. Once a section of pipe is installed, spoil is removed by an Auger Boring Machine (ABM). The process is repeated with each new section of pipe or casing until complete.

Pipe Pulling
Method used to replace small diameter pipes by attaching new product pipe to the existing pipe, which is then pulled out of the ground.

Product Pipe
Pipe used for transporting water, gas, sewage, and other products and services.

Ream Size
The diameter of the drill hole into which the product is inserted.

Downhole tools used to enlarge the bore sufficiently to facilitate installation of the product.

The process of restoring or upgrading the performance of existing utility systems. It encompasses renovation, replacement or repair.

Sound Attenuation Walls
Engineered acoustical solutions that are strategically placed at the entry and/or exit points to reduce noise caused by the drilling. Used to minimize the impact of drilling on the public.

Earth, rock, and other materials removed during installation. Also referred to as “cuttings.”

Trenchless Construction
A non-disruptive form of underground construction that requires few trenches and no continuous trenching. It is used for the installation or rehabilitation of underground infrastructure with minimal disruption to surface traffic, business, and other activities. There are several available methodologies, including: horizontal directional drilling, augering, boring, tunneling and hydrovac services.

Tunnel Boring Machine (TBM)
A piece of equipment designed to bore circular tunnels through dense, hard rock, relatively soft sand or any substrate of any hardness between the two.

Utility Corridor
Duct in which two or more different utility services are installed with access for maintenance.

Walkover Line
A transmitter/ receiver system that allows operators to locate a horizontal drilling path. An operator standing on the surface uses a receiver to determine where the drill bit is situated and follow the drill path in real time. Also referred to as a “Walkover System” or “locator”.

Wire Line
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.


Tunnel Boring and Pipe Jacking Systems are used to hydraulically install underground pipelines up to 4.2 m (168 in) in OD range within strict alignment and grade tolerances. The likelihood of settling or sloughing is very low. Wheel machines are equipped with various cutter heads and sand shelves. A closed-face attachment is available for boring in unstable ground conditions. This versatile system can be easily adapted to work with any jacking pipe, in any pipe joint length. It can accommodate a wide range of pipe diameters.

Tunnel Boring Machines are used to excavate tunnels with a circular cross section through a variety of soil and rock strata. They can bore through hard rock, sand, and almost anything in between. Tunnel diameters can range from 1 m and exceed 15 m (3 ft to 49 ft).

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A boring technique commonly used for installing oil & gas pipelines ranging from 51 mm to 1067 mm (2 in to 42 in) in diameter without leaving casing in the ground. Product pipe is welded to steel casings and either pushed or pulled through the ground in sections. The casing is cut off and removed, leaving just the product pipe. Maximum installation length is 150 m (492 ft).

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A pneumatic hammer is attached to the inside edge of the casing. The front of the DTH breaks cobles, boulders and even solid rock into small pebbles or dust. The spoil makes its way through the hammer and into the casing, where it is removed by airway augers.

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A Guided Boring Machine (GBM) is used to install 305 mm to 3.6 m diameter pipe (12 in to 144 in) with grade and alignment precision. It is commonly used for installations 50 m to 150 m in length (164 ft to 492 ft) or when line and grade accuracy is critical in displaceable soil. Our GBM is extremely versatile and our customers continually approach us with new applications.

The pipe installation involves a two-step process where launch and reception shafts are strategically located to minimize surface disruption. A pilot tube with a theodolite guidance system is then pushed through the ground at the precise grade and alignment specified in the design into the reception shaft. A reaming head is welded to the pilot tube and the casing and the pilot tube is used as a guide to install casing. The GBM can be used in conjunction with auger boring or pipe ramming methodologies.

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Pipe Ramming is used in a wide variety of soil types including gravel, cobble or sand. A pneumatic hammer is attached to the back of the casing pipe and driven through the material at any angle: from horizontal to vertical. The material is cleaned out of the pipe using an auger boring machine. Pipe Ramming methods are used for pipe diameters of 305 mm to 3.6 m (12 in to 144 in).

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