Abstract: The energy release of brittle rock has critical characteristics under stress, In order to understand the statistical distribution law of acoustic emission(AE) avalanche energies and waiting-times in rock loading process before and after critical point, uniaxial compression tests were carried out in the laboratory. The AE characteristics of the loading stage before and after the critical point are obtained; and then the distributions of the functions in the loading states are analyzed, The results show that: (1) It is found that the process of rock samples from the uniform random expansion to the strip concentration until the final penetration through the evolution of AE centers, the cumulative energy(2.8×108 aJ) and the cumulative counts(6.68×105) of AE had mutations before crack coalescence, marking reach the critical point. (2) The probability density function(PDF) of AE energies conforms to be the power-law distribution in 4 magnitudes of the loading stage before and after the critical point. (3) The waiting-time follows the two-power law within any energy interval; each energy region follows the same power-law distribution in a small waiting-time interval( <0.1 s); different energy region will have different power-law characteristics in a large waiting-time interval( > 0.1 s); (4) Combining statistical distributions law of energy with waiting-time, the distribution law of AE signals in the critical state is consistent with the whole process; and the energy signals of the whole process distribution mainly concentrates on the loading process after the critical point.

Key words: sandstone, acoustic emission, uniaxial compression(AE), critical point, energy, waiting-time