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A introduction to the five most common drilling methods
Costeaning (also called trench sampling) involves digging a costean or trench using a backhoe or similar equipment. The edges of the trench are normally mapped and sampled for analysis. This technique is cost effective and applicable for large, near surface targets.
Auger drilling process involves a helical screw which is driven into the ground with rotation. Earth is lifted up to the surface by the screw and collected for sampling. Auger drilling is normally used at depths up to 25m.
Uses a three bladed steel or tungsten drill bit to penetrate soil and rock. The drill rods are hollow and compressed air pumped down the outside wall to flush rock chip samples up the inner rod and to surface. It is a cost-effective drilling method for soft ground of up to 300m.
RC drilling uses a similar technique as aircore drilling except the drilling mechanism is a hammer. Because of the hammer, RC drilling can penetrate harder rock and can achieve depths of 500m+.
Diamond coring uses an annual diamond impregnated drill bit at the end of hollow drill rods to produce cylindrical cores of solid rock. The product of solid cores over rock chips (from RC/Aircore) yields greater information about the geology and rock formations. Although this is the most expensive form of drilling, it is the most informative and can commonly drill hard rock to depths of 1800m+.