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LAYNE MINERAL EXPLORATION – ROTARY AIR BLAST (RAB) DRILLING
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Layne Christensen is able to offer the exploration professional the option of using a rapid economic
drilling technique for the early stages of a "greenfields" project where an inexpensive method of
evaluation of the ground is required rather than more expensive resource drilling.
RAB drilling is a standard rotary drilling technique using compressed air as a drilling circulation
medium. The drill string and bit are rotated continuously as axial force is applied to the string.
Compressed air or a mixture of compressed air and water is pumped down the hole through the drill
pipe. The cuttings are blown up the hole along the annulus between the drill pipe and the wall of
the hole.
RAB drilling can employ a drag or blade bit, a roller bit, or a downhole hammer, depending on the
ground conditions. Drilling can be achieved to a depth of 120 meters using 3-1/2” drill pipe,
should suitable ground conditions apply.
The sample is a chip sample that can be directed through a cyclone to the splitter and sample bag.
Advantages of a Rotary Air Blast System
Low cost, versatile and mobile, RAB is mainly useful on alluvial deposits where inexpensive samples
are required before committing the project to expensive, more accurate drilling. The RAB drilling
technique can also be used for blast holes; however, more specialized equipment is normally used on
larger projects.
RAB can be used on test ground that cannot easily be tested by soil geochemical sampling due to
problems with transported overburden.
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