Statistical study of acoustic emissions generated during the controlled deformation of migmatite specimens

The present work focuses on a detailed analysis of the seismoacoustic emissions generated in rock specimen during the stepwise increasing deformation during laboratory loading tests. A cylindrical specimen of migmatite was subjected to cyclical and stepwise loading with controlled deformation. The stepwise deformation increase was approximately 0.8 mStrain per one step and deformation rate was cca 8 mStrain/s. This sudden increase of deformation was accompanied by peak stress increase with duration of approximately 2 s. During load testing, seismoacoustic emissions were monitored and time series of acoustic impulses were recorded. It was found that the higher the level of stress, the longer the duration of aftershock sequence. Analysis of the autocorrelation functions of individual sequences showed significant changes in parameters at maximum specimen stress. An increase was found in the values of first autocorrelation coefficients, which can be used to assess the stability of the rock specimen.