Experimental investigation on dynamic evolution characteristics of micro-cracks for sandstone samples under uniaxial compression

The dynamic evolution characteristics of micro-cracks are the important information of rock failure for their significance in analyzing the failure process of rockburst and predicting the rock dynamic hazard. The uniaxial compression tests are conducted on sandstones, while their stress and the intensity characteristics of acoustic emission (AE) are analyzed to study the dynamic evolution process of crack. The results show that the stress variation and the intensity characteristics of AE events have a consistent segmented transformation pattern, which is used to divide the evolution process into three phases. A four-dimensional evolution method is proposed based on the further analysis of the characteristics of crack type. The micro-cracks are mostly tensile. With the increase of time, the micro-cracks change to shear-type cracks, the number of the cracks increases rapidly, and their intensity increases gradually. It is proposed that the AE events occurring with high intensity, high RA and low AF characteristics in the third phase are used as the qualitative prediction of rock failure. By comparing the inversion results of the moment tensors, the dynamic evolution characteristics of the micro-cracks are obtained.