Failure precursor characteristics of different types of rocks under load: insights from critical slowing down of acoustic emission

In this study, uniaxial compression tests and simultaneous acoustic emission (AE) monitoring were carried out on four rocks (yellow sandstone, white sandstone, marble and limestone). The mechanical properties and AE energy evolution characteristics of different rocks were analysed. With the help of critical slowing down (CSD) theory, the AE precursor characteristics of their failure were investigated. It is pointed out that the AE during rock loading has a CSD phenomenon. A sudden change in the variance of one of the CSD indicators can be regarded as a precursor to failure, and it has the advantage of being more accurate and sensitive to failure than the autocorrelation coefficient. The stress level of a rock's failure precursor is closely related to its brittleness characteristics. The higher the brittleness of the rock, the more backward the failure precursor is, and the more difficult the early warning is. The study aims to provide new indicators and references for the monitoring and early warning of rockbursts and other disasters induced by rock fracture in deep underground engineering.