Evolution law and dominant frequency characteristics of acoustic emission sources during red sandstone failure process

The AE source location test of red sandstone under uniaxial compression was carried out by GDS VIS 400 HPTAS triaxial rheometer and PCI-2 AE system, and the moment tensor method was used to analyze shear, tension, and mixed AE sources spatial distribution characteristics, evolution law and their main frequency characteristics.Based on the nonlinear growth characteristics of the cumulative AE source number, and the dominant frequency characteristics of AE sources in the unsteady development stage of micro-cracks, both cracking stress and damage stress estimation methods, and rock failure prediction methods were proposed.The results show that in the micro-cracks compaction stage, the AE source is far away from the axis of the specimen, and mainly distributed near the upper and lower ends of the specimen.From the elastic deformation stage to the micro-crack stable development stage, the AE sources are distributed throughout the specimen and tend to develop in the specimen center.At the unsteady development stage of micro-cracks, the AE sources are mainly concentrated in the upper and lower parts of the specimen.The evolution law of different types of AE sources is related to the loading stress.When the loading stress is greater than the cracking stress but less than the damage stress, the shear source overgrows, and the initial stress of rapid growth of the shear source corresponds well with the cracking stress.When the loading stress is greater than the damage stress, the tensile and mixed sources enter into a relatively rapid growth period, and the initial stress of relatively rapid growth of tensile and mixed sources corresponds well with the damage stress.In the process of red sandstone failure, the main frequency of shear, tension, and mixed AE sources are located in the range of 0-50, 100-150, 250-350 kHz.In the unsteady development stage of micro-cracks, only the shear AE source has 200-250 kHz signals, which can be used as a precursor to the failure of red sandstone under uniaxial compression.The research results verify that different types of AE sources have different main frequency characteristics in the process of rock failure, which can provide a reference for the research of rock failure prediction methods based on acoustic emission monitoring.