Conventional Tunneling: Methods of tunnel construction ranging from manual excavation to the use of self-propelled tunnel boring machines. Where an initial lining is required, bolted segmental rings are frequently used. The tunnel boring machine supports the ground during excavation and provides a place to erect the tunnel support. (If the tunnel support is not the final liner then it is considered two-pass tunneling)

Earth Pressure Balance Machine (EPBM): Type of microtunneling or tunneling machine with a closed face and pressurized muck 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 pressurized drilling fluid.

Pipe Jacking: Installation of pipe into the ground behind the tunneling machine using hydraulic jacks located in the jacking pit. The tunnel boring machine and jacking pipes are jacked into place from a jacking shaft to a receiving shaft on opposite ends to the drive such that the pipes form a continuous string in the ground. When the machine reaches the receiving shaft, it is retrieved and removed.

Microtunneling: A trenchless construction method for installing pipelines. Microtunneling is remotely controlled and guided pipe jacking that provides positive control of the tunnel face.

Drilling Fluid or Mud: A mixture of water and usually bentonite and/or polymer continuously pumped to the cutting head to facilitate cutting, reduce required torque, facilitate the removal of cuttings, stabilize the borehole, cool the head and lubricate the installation of the product pipe. In suitable soil conditions, water alone may be used.

Jacking Shaft: Excavation from which trenchless technology equipment is launched for the installation or renewal of a pipeline.

Manhole: A structure that allows access to the sewer system.

Reception Shaft: Excavation into which trenchless technology equipment is driven and recovered following the installation of the product pipe, conduit or cable.

Slurry: A fluid, mainly water mixed with bentonite and sometimes polymers, used in a closed loop system for the removal of spoil and for the balance of groundwater pressure during tunneling and microtunneling operations.

Spoil (Muck): Earth, rock and other materials displaced by a tunnel, pipe or casing and removed as the tunnel, pipe or casing is installed. In some cases, it is used to mean only the material that has no further user.

Tunnel Boring Machine (TBM):
1) A full-face circular mechanized shield machine, usually of worker-entry diameter, steerable and with a rotary cutting head. For pipe jacking installation it leads a string of pipes. It may be controlled from within the shield or remotely such as in microtunneling.
2) A mechanical excavator used in a tunnel to excavate the front face of the tunnel.