Detection of the top of coal prior to blasting

Accurately detecting the approaching top of a coal seam prior to blasting


Accurately detecting the approaching top of a coal seam prior to blasting is fundamental to efficient coal recovery. Previous investigations reported a reduction in coal dilution through disciplined and detailed overburden drilling and blasting practices.

Mining3 has developed a novel concept for detecting approaching Top of Coal whilst drilling in Rotary Air Blast over-burden blast-hole drilling.

The detection system uses resistance measurements ahead of the drill bit to detect approaching coal in real-time whilst drilling. This system can also be retro fitted to a standard rotary air blast drill rig.

Technology Overview

The research and development of a system that measures and monitors strata information during the drill and blast process on a rotary air blast drill rig. This system monitors the resistivity of the formation ahead of the drill bit and alerts the drill rig operator of the approaching coal seam.

Once the drill bit is a certain distance off the coal seam an alarm is given to the operator to stop the drilling process. This in turn leaves a standoff above the coal seam as a protection barrier during the blasting process. The ultimate goal of this project is to limit coal loss and dilution during routine drill and blast operations due to over drilling.


  • Increased production by reducing damage to coal from blasting
  • Strata recognition and mapping during routine blast hole drilling
  • Enabling other coal dilution technologies such as blast-hole slotting
  • Increase production by reducing damage and dilution to coal from blasting
  • Increase knowledge of overburden strata to inform better blast design
  • Improved productivity, time savings and expense of drilling and/or logging holes solely to map the top of coal if the same or better information is produced during production drilling.
  • Provides information that will assist with drill automation


The project has made significant progress by demonstrating the effectiveness of the MWD Top of Coal detection system at mine sites. Preliminary field trials have shown that even with a compromised hardware component, the system is capable of measuring ground resistance while drilling.

The results from the field trial at Jellinbah mine have also shown that the system was capable of measuring the change in resistance when the drill bit hit coal.

A second field trial is currently being planned with a revised system that addresses the technical issues experienced during the first field trial.


The project was guided by a steering committee, including appointed industry monitors Kirk Henderson (Peabody Coal), Vishwa Bhushan (RTCA) and Steve Simmons (AAMC). The enthusiastic and generous contribution of both Hughes Drilling and Jellinbah mine which provided assistance, support, equipment and a site for a field trial is acknowledged and greatly appreciated.

With support from the Australian Coal Association Research Program (ACARP).