Determining the feasibility of a real-time geophysical magnetic and electric measurement system for monitoring strain underground

Abstract

In deep mining environments, rockbursts can occur in areas of high stress. The unpredictable nature, and sometimes fatal consequences of the rockbursts, makes identifying increases in stress that occur prior to failure events, important for mine safety. The piezoelectric, electrokinetic, and seismo-electric/magnetic effects result in rocks that are stressed emitting electric and magnetic fields that can potentially be measured in (or close to) a rock mass. Electric, magnetic and seismic data were collected during a four-day period at Coleman Mine, Sudbury, Ontario, and later analysed. No signals due to strain were evident in the magnetic or electric data, so a more careful three-part experiment was proposed to see if strain related signals could be identified in magnetic data. In the first part of the experiment thirty-two rocks were stressed until failure. Measurable magnetic signals associated with audible cracking sounds were found for most rock samples, as well as consistent signals across all samples prior to failure. The implementation of real-time monitoring of these signals has the potential to significantly improve deep mine safety by mapping the evolution of strain underground and potentially indicating areas susceptible to failure.