A new quantitative method to identify the crack damage stress of rock using AE detection parameters

The quantitative determination of crack damage stress is of significant importance for investigating rock deformation and failure. In this study, a new quantitative method for determining the crack damage stress of rock materials was proposed based on acoustic emission (AE) signal detection. Ten rock materials were subjected to uniaxial compression testing, during which real-time AE signals and axial, lateral, and volumetric strain values were recorded. The AE cumulative count curves of the different rock materials were calculated based on the AE counts. These curves were divided into three stages as the axial stress increased: the slowly increasing stage, the steady stage, and the sharply increasing stage. The point where the sharply increasing stage began was defined as the P_R point and could be accurately determined based on a fitting optimization method. Then, the damage stress was calculated by using the crack volumetric strain model. Finally, the relationship between the R stress (axial stress corresponding to the P_R point) and the crack damage stress was investigated for the ten rock materials. The results showed that there was a good correspondence between the R stress and the crack damage stress. Hence, the R stress can be used to determine the crack damage stress and the starting point of the unstable crack growth stage in rock materials.