Drilling

Drilling is the most important process in a mining. This minimizes the risk of damage or injury as a result of an old working opening up under a machine. Void officers design a series of probe holes, generally ranging from 16 to 25m deep. These are pegged by surveyors. Probe drills then work along the zones, drilling these holes until they reach the old workings. By knowing where a hole was drilled; what angle it was drilled at and what depth it hit the old workings, void officers can adjust the danger zones, either shrinking them where the old workings have been satisfactorily filled or by expanding them where the old workings have expanded through self-mining. This process may be repeated until the exact locations of the old workings are known.

Drills aren't just exposed to harsh elements - they literally operate within them, enduring a constant mix of water and large amounts of drilling waste. Vibration, shock loads and high operating temperatures make conditions even worse. Once the pattern has been drilled, its holes are checked for depth and the presence of water. This “quality control” ensures that blasts are as effective as possible and reduces poor blasting practices that may result in toe or oversize in the blast.