Detection of Top of Coal During Overburden Blast Hole Drilling

This report summarises work on stage 1 and 2 of a program to develop a system to detect the top of coal during overburden blast hole drilling. The benefits of such a system are seen to be the attainment of a reliable and accurate stand off from the bottom of the drill hole to the top of coal. If this can be achieved, then a reduction in blast damage to the top of the coal seam should result in increased coal recovery.

The Coffey/GEC Marconi initiative is directed to the development of an acoustic device for top of coal detection.

Modeling of the drill noise/coal overburden strata suggested that a suitable indicator should be the reflection of drill noise from the coal seam. Field trials at Ravensworth have confirmed that such an effect is indeed present and that standard geophones can be shielded from electromagnetic noise to make a suitable sensor. At this stage some intensive signal processing is required to resolve the interference effect from the noise.

ACARP will support work on the next stage of research and development to encompass the following:

• Enhancement of the sensor to improve the signal noise ratio
• Development of a data processing algorithm to allow faster and better information display
• Confirmation of the applicability of the interference effect in different geologies and rock types.