The International Society for Trenchless Technology

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There are 211 entries in this glossary.
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Term Definition
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.

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