Mud rotary drilling is used in geological areas that would generally prohibit the use of hollow stem augers. Those areas would include; bedrock, broken rock and sand or gravel formations. Terra Drill can offer this service as an option over hollow stem auger drilling in a variety of sizes.
In the mud rotary drilling method, the drill bit is attached to the drill rod while being rotated and advanced into the borehole while pumping a drill mud consisting of a bentonite or polymer slurry into the borehole. The drilling mud is circulated into a mud pit where the cuttings from the borehole drop out and the mud is reused.
As the drill bit is advanced, the drill mud is pumped down the inside of the drill rods to carry the drill cuttings out of the borehole and cool the drill bit. The rotation and downward pressure of the drill rig along with the flow of the drill mud advances the boring to the desired depth. At the desired depth the drill bit may be removed and the sample can be taken. While utilizing this method of drilling the borehole is not cased. This is the preferred method of drilling in sand and gravel formations during the collection of split spoon samples for Geotechnical purposes.
