Other Methods of Drilling

The process of reverse circulation drilling is successfully being used in locations where rocks are deeply weathered, as is the case of many tropical locales, or when drilling in glacial overburden. A dual-tube drill pipe and a tri-cone bit are employed in this method. Drilling air or fluid, or a combination of both, is pumped down between the dual tubing and then returned up the inner tube, bringing cuttings from the bit up to the surface.

A device which can be used for soil investigation is sonic drilling, this is a sonic vibration device which pushes the rod of the drill into the ground.

There are cases where explorers do not need a core sample, as when an open hole permits instruments to be lowered. A standard rotary drill which is equipped with the necessary compressors and drill pipe is all that one needs for this kind of drilling.

Cost reduction is significant together with greatly improved productivity where applicable. This method, however, is not as reliable as collecting the entire core by diamond drilling.

Underground Drilling
To an established mine, diamond drilling is also important. It is used to:

• Explore for new outline or ore and to map orebodies which are known;
• Investigate rock types and their structure;
• Find location of orebodies displaced by folds and faults;
• Put out pilot holes to direct stopes and drifts to the appropriate location;
• Establish drain holes, ventilation and grouting holes;
• Drill undistured holes to permit placement of rock mechanics instrumentation for measuring stresses in the rock.

Underground diamond drills are lighter and smaller than surface drills, besides, they normally run on electricity, not diesel fuel.

The typical modern underground drills have features which make the extraction of rods from the hole very quick.

While presently, most underground drills are the hydraulic types which are powered by electric motors, there are a variety of sizes available which are powered by diesel or air for when electricity is not available. However, diesel-powered drills need extra ventilation and diesel exhaust scrubbers.

What is very advantageous to the mine geologist is having a drill underground which allows the drilling of holes at any angle desired.