Fracture evolution of fiber-reinforced backfill based on acoustic emission fractal dimension and b-value

To investigate the fracture evolution of fiber-reinforced backfill, uniaxial compression tests were conducted on different fiber types of reinforced backfills, and the fracture process of fiber-reinforced backfill was monitored using an acoustic emission (AE) system. The fracture evolution characteristics of the fiber-reinforced backfill were explored by analyzing the trend of the amplitude correlation dimension, RA (rise time/maximum amplitude) correlation dimension, and b-value of AE with time during the fracture of the backfill. The results show that both the amplitude time series and RA time series have good fractal characteristics, but the amplitude time series has better fractal characteristics compared to the RA time series. The fitting coefficient of the amplitude correlation dimension is greater than 0.93, while that of the RA correlation dimension is greater than 0.88. The RA correlation dimension is overall smaller than the amplitude correlation dimension, but the fluctuation of the RA correlation dimension is larger than the amplitude correlation dimension when the AE major event occurs. Compared with the fiber-free backfill, the amplitude and RA correlation dimension curves of the fiber-reinforced backfill have a more pronounced symmetry and a denser distribution after the peak, and the AE b-value of the fiber-reinforced backfill is between 0.4 and 1.2. Both the correlation dimension and b-value show a rapid decrease at the peak stress, which can be used as precursor information for fracture prediction of fiber-reinforced backfill. The results of the study can provide a reference for stability monitoring and fracture prediction of filling materials in mines.