Blast hole drilling is a method used in mining to break up ground and facilitate further mining activities. It involves drilling a pattern of holes into the ground surface and packing them with explosives. When the explosive is detonated it forms cracks in the underlying geology, breaks up the ground, and thus makes it easier to dig and remove rocks and soil from the mining area. It is primarily used to break up rock and hard minerals to make it easier to reach the resources being mined. The hole into which explosives are placed is called a ‘blast hole’, hence the name of this method, and is one of the primary surface mining techniques employed in mining operations.

Blast hole drilling is typically used when a mining operation wishes to check the mineral composition of a mining lease area and the presence of specific minerals within it but can also be used during mineral extraction. It is a fundamental process in exploratory mining and can also be used in underground mining and in quarries.

Before blast hole drilling can commence, a site must be inspected with an initial site survey. This survey analyses the goals of the mining operation and the composition of the underlying ground to determine how drilling will proceed. For example, this can determine the size or diameter of the hole used in blasting, the depth of the hole, the types of drills that will be required to drill the holes and the amount of explosives that need to be used.

The survey also determines the potential effects of vibration caused by the blast, how rocks and debris will be distributed across the mining area and any impact on other mining operations. Sometimes controlled blasting is used to reduce overbreak and the extent of ground vibrations and can include pre-splitting, contour blasting and muffle blasting, among other techniques.

Often blasting needs to be performed several times to achieve desired outcomes. This is called ‘secondary blasting’ and its purpose is to reduce rocks to a size that is small enough so that they can be handled be mining equipment such as, for example, excavators, rock trucks or crushers.

Once the blast has done its work the debris is removed in what is called the clean up process where appropriate mining equipment is used to gather the rocks and soil freed by the blast, and transport it to a processing area and where, finally, the minerals within are extracted.