Recording of ultra-low frequency electromagnetic emission during loading of a rock sample

The review of publications devoted to the study and features of the registration of electromagnetic emission observed during the loading of samples of rocks, metals, composite materials in laboratory conditions, as well as in areas of disintegration of rock massifs at mining sites is given. Electromagnetic emission observed during the destruction of rock samples in laboratory experiments and field conditions can appear itself not only in the high and low frequency ranges (1000–3·10⁶ Hz and 500–1000 Hz, respectively), but also in the very low and ultra-low frequency (200–500 Hz and 0.01–200.00 Hz, respectively) ranges. However, the overwhelming majority of experimental studies of rock samples under the influence of a destructive load in laboratory conditions are aimed at measuring electromagnetic emission of the high frequency range. An instrumentation and measurement complex is described that allows recording electromagnetic emission in the ultra-low frequency range. The composition of the instrumentation and measurement complex includes magnetic modulation transducers of magnetic induction as magnetic field sensors. The methodology of laboratory experiments on recording electromagnetic signals arising from the influence of an external load on rock samples using an instrumentation and measuring complex is presented. An example of uniaxial loading of a basalt sample is given. When loading the sample under consideration, the amplitude of the electromagnetic emission pulses exceeds the background values of technogenic magnetic noise by two orders of magnitude. The high sensitivity of the magnetic modulation transducer of magnetic induction allows it to be used to register the components of magnetic induction in the process of destruction of rock samples in conditions of interference from technogenic magnetic noise. The results obtained are important for monitoring and forecasting the process of cracking before mining impacts, as well as for studying the geological environment and processes that generate low-frequency electromagnetic emission in the mining areas.

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