Cable percussion drilling (otherwise known as shell and auger) is utilised where deeper ground conditions need to be assessed alongside in situ strength testing and sample recovery. It is dependent upon access limitations and favourable ground conditions. Boreholes up to 60m depth can be achieved.
Rotary drilling is used to reach depths which could not be recovered using traditional cable percussion or window sampling. This is commonly used for mine working investigations. The drilling method involves a powered rotary cutting head, which rotates as it is driven into the ground. The system requires lubrication (air, water or drilling mud) to keep the cutting head cool and to displace arisings. Water flush is used when drilling is within coal measures and within proximity of residential buildings
This method allows for the easy installations of standpipes / gas monitoring tubes within the borehole.