scope:

This standard guideline covers the planning, design, pipe materials, and construction of microtunneling. Microtunneling is defined as a trenchless construction method for installing pipelines. The North American definition of microtunneling describes a method and does not impose size limitations on such method; therefore, a tunnel may be considered a microtunnel if all of the following features apply to construction:

Remote controlled: The microtunneling boring machine (MTBM) is operated from a control panel, normally located on the surface. The system simultaneously installs pipe as spoil is excavated and removed. Personnel entry is not required for routine operation.

Guided: The guidance system usually references a laser beam projected onto a target in the MTBM, capable of installing gravity sewers or other types of pipelines to the required tolerance, for line and grade.

Pipe jacked: The pipeline is constructed by consecutively pushing pipes and MTBM through the ground using a jacking system for thrust.

Continuously supported: Continuous pressure is provided to the face of the excavation to balance groundwater and earth pressures.