A new acoustic emission characteristic parameter can be utilized to evaluate the failure of cemented paste backfill and rock combination

In backfill mining, there is a phenomenon of the joint bearing of cemented paste backfill and rock, so it is essential to study the destabilization damage mechanism of cemented paste backfill and rock combination (BRC). This study aimed to improve the evaluation system for the instability failure of BRC. A new evaluation index, Dr, based on acoustic emission (AE) characteristic parameters was proposed for predicting BRC instability failure caused by the load. This index comprehensively considers the time dependence and interaction of the AE rise time, amplitude, and average frequency during BRC failure. The study conducted uniaxial compression and simultaneous AE experiments for various ratio combinations of BRC to obtain the AE rise time/amplitude (RA) and average frequency (AF) values of BRC. Then, the RA/AF values were numerically calculated with fractal theory to obtain the Dr index, and the intrinsic relationship between Dr and BRC instability failure was further discussed. Finally, the index was validated through comparison with the statistical index b-value based on AE amplitude, and a discrimination criterion for BRC instability failure was proposed. The results show that: After reaching the yield stress, the number of AE events of the rock gradually decreases. In contrast, the number of AE events of the CPB fluctuates in the high-level range. The cement-tailings ratio significantly affects the BRC AE frequency and amplitude distribution. The decrease of the cement-tailings ratio enhanced the high-frequency amplitude signal of CPB, while weakening the medium and high-frequency amplitude signal of rock. The sudden drop of Dr in the near-failure stage can be used as a criterion for BRC failure determination. Compared with the b-value, using Dr as an evaluation index to predict BRC failure can obtain a slightly conservative result. The research provides a new and effective method for evaluating BRC instability failure, which can be used for realtime prediction of BRC instability failure in mining engineering practice.