Electromagnetic Emissions Monitoring to Warn of Wind Blasts and Gas Outs

Electromagnetic signals are emitted by rocks as they fracture, in much the same way as acoustic signals, but by different processes and with different characteristics. The object of this project was to evaluate the potential usefulness of the emissions (EME) as warning signals, to complement the acoustic emissions (AE) which are now used in several mines in Australia and overseas. AE have some difficulties as regards cost and flexibility, and are not completely reliable. Three sets of single channel EME measurements were collected between March and July 2001. Results were compared with fracture events in the mine and with the four channel AE records. In one of the three cases there was no response, in another there was a large response beginning before the seismic and lasting for some time. In the third case the EME showed only a small response.

The conclusion is that EME show promise, but that additional measurements, preferably multichannel, are necessary before the true potential can be assessed.