Mud rotary drilling is an open hole, fluid based re-circulatory method of drilling. The bore hole is advanced in rock and/or sediments by rapid rotation of a drill bit mounted at the end of drill rods. NSF approved drilling fluid circulates in the bore-hole as it pumps down through the rod string, where it picks up drill cuttings and carries them to the surface. The drilling fluid also lubricates the drill bit and provides hydro-static pressure in the borehole to keep the hole open and stable for sampling and installations. Mud rotary drilling is used in bedrock, dense sand or tight gravel formations where hollow stem augers would be ineffective.
Applications: Best used in highly saturated silts, muds and in unconsolidated sediments where soil sampling is necessary. Mud rotary is effective up to about 1000’. Not effective in consolidated rock, cobbles or gravels where mud circulation is difficult.