Do Electromagnetic Pulses Induce the Relaxation or Activation of Microcracking Rate in Loaded Rocks?

Abstract

The work is devoted to the problem of role of ambient factors (external electromagnetic field, in particular) in the process of ageing of mechanically burden nonmetallic solids (rocks). A specific research point is the effect of temporary activation of Acoustic Emission (AE) of rocks specimens during action of EM field pulses applied externally. Extended experimental studies of responses of AE have been conducted to evince the changes in defects accumulation process in loaded specimens due to external power impacts (EPI). The experiments have been held on noiseless rheological machines available at Bishkek Geodynamic Research Center - RS RAS. We have tested a number of specimens made of different materials and analyzed the temporal dependence of AE activity during exposure in electric field and crossed electric and magnetic fields; the compressive load being constant. The effect of AE stimulation by power pulses (triggering) has been verified. The obtained results allow to distinguish two kinds of AE activation. The first kind involves simultaneous well correlated growth of numbers of minor and major AEs (so-called selfconsistency of temporal plots of activity of different range acoustic events). The second kind represents dissimilar variations: the increment of activity of minor energy AEs, but the decrement of those of major energy. The first kind of solids material responses to EPI is prevailing when the compressive loads is under 0,85 of fracturing value. The episodes of dissimilar AE responses may signify that electromagnetic control of defects accumulation process inside rocks is possible, in principle.