Early-warning signal recognition methods in flawed sandstone subjected to uniaxial compression

To investigate the precursor information related to rock fracturing, a series of indoor uniaxial compression tests are conducted on flawed sandstone. Four methods of identifying potential precursors to rock catastrophic failure, namely, cumulative acoustic emission (AE) activity, AE b-value, inter-event time function, and critical slowing down, are discussed. The results show that the four precursory identification methods can reasonably identify the early-warning signal, subcritical failure, and final catastrophic failure of flawed sandstone involving the whole loading process. The minimum b-value is correspondingly obtained when the specimen approaches failure. The inter-event rate of AE multi-parameters shows a significant increase, following a power law distribution. By comparison with the other three precursor identification methods, the time intervals of AE parameters-based variance between the precursory signal and its corresponding tripping points become increasingly shortened. Additionally, the precursory characteristics of variance of AE multi-parameters are more accurate and reliable than that of autocorrelation coefficient.