Acoustic emission and crack evolution characteristics of cemented tailings backfill under different loading rates

To investigate the dynamic regulation mechanism of loading rate on crack evolution in cemented tailings backfill (CTB), uniaxial compression tests with acoustic emission (AE) monitoring were conducted at loading rates v of 0.002, 0.004, 0.008, and 0.010 mm/s. By analyzing the time-varying characteristics of AE parameters, including ring count, average frequency AF, rise time–amplitude ratio RA, and r-value (RA/AF), and applying unsupervised clustering to RA–AF datasets using Gaussian Mixture Model (GMM) combined with a moving average filter, crack types and their evolution patterns were identified. The results indicate that: ① Near peak stress, AE ring counts of CTB exhibit interval oscillations. With increasing loading rate, the fluctuation amplitude of ring counts during elastic and plastic yield stages decreases. ② As the loading rate increases from 0.002 to 0.010 mm/s, the concentrated range of AF distribution exhibited a progressive compression from 0 − 150 kHz to 0 − 100 kHz, while the RA distribution range expanded from 0 − 5 ms/V to 0 − 10 ms/V, with high-RA signals concentrated in the narrow band of AF < 80 kHz. ③ The increase in loading rate significantly affects the post-peak failure mode: the proportion of shear cracks rises sharply from 19.11% (v=0.002 mm/s) to 64.23% (0.010 mm/s), indicating a shift in failure mechanism from tensile-dominated to tensile–shear composite failure. ④ Based on stress stages, GMM clustering divides crack evolution into four phases: tensile crack dominance (0 − 20%σ_f), tensile–shear crack transition (20%σ_f − 80%σ_f), rapid shear crack growth (80%σ_f − 100%σ_f), and tensile–shear co-dominance (post-peak failure). Among them, the rapid increase in shear cracks at 80% – 100% of peak stress is identified as a precursor to localized instability. This study provides theoretical support for stability analysis and failure prediction of CTB.