Guided Boring Machine (GBM)
Definition - What does Guided Boring Machine (GBM) mean?
Guided boring machines (GBM) are systems designed for accurate boring, having extended drive lengths for use in multiple geologic compositions. They are used with 40 to 48 inch (100 to 120 centimeter) outside diameter (OD) pipe and larger diameters under a guided auger boring application. The cutting tool on the drill string steers the bore, and is accurate to within 25 millimeters over 120 meters. This maneuverability is facilitated by a slanted drill bit head, drill bits that are asymmetrical, or movable fluid jets on the drill bit. Guided boring machines may also be used in auger drilling and pipe ramming projects where accuracy is crucial.
Trenchlesspedia explains Guided Boring Machine (GBM)
Guided boring machines are preferred for projects that cover a long distance. Though the rig is surface based, an entrance pit needs to be dug so the drill string can be inserted diagonally into position. After drilling is complete, the hole is reamed or back reamed to the desired diameter before a casing is inserted to ensure structural integrity of the bore. Finally, the product pipe is inserted, guided by the casing in the bore.