Electric charge induction monitoring of deformation and failure behavior of igneous rock: Laboratory test and field application

To advance the theoretical understanding, technological development, and field application of electric charge induction for monitoring rock deformation and failure, this study investigates the induced electric charge generated during the deformation and failure of igneous rocks. The charge originates mainly from a combination of electrical polarization and triboelectric effects. Through laboratory experiments, we analyzed the time-frequency evolution of induced electric charge signals and identified relevant monitoring parameters. An online downhole electric charge induction monitoring system was developed and validated in the field. Experimental results show that the dominant frequency range of induced electric charge signals generated during igneous rock deformation and failure lies between 0 and 23 Hz, and a low-pass finite impulse response (FIR) filter effectively suppresses noise. Optimal sensor distances for monitoring cubic and cylindrical specimens were determined to be 17 mm and 13 mm, respectively. We proposed early warning indicators, including the maximum absolute value of the induced electric charge, the arithmetic mean value, the distribution dispersion coefficient, and the cumulative sum value. In field application, time-domain curves and spatial distribution charts of these warning indicators correspond well with changes in abutment stress ahead of the mining face, offering indirect insights into local stress evolution. This research provides technical and equipment support for the application of electric charge induction technology to monitoring and early warning of coal bursts. • A low-pass filter is designed to denoise and filter the electric charge signal. • The mechanism by which the electric charge is generated during the failure of igneous rocks is described. • Electric charge induction monitoring and warning indexes are then proposed. • An online downhole electric charge induction monitoring system was developed. • The warning indicators can indirectly invert stress levels in the coal body.