Abstract: In order to improve the prediction of rock burst with charge induction, the charge monitoring test was carried out on fractured coal samples under uniaxial compression by the self-developed charge monitoring system in the laboratory. The failure types, mechanical properties of coal samples and the law of the charge time-frequency domain signals under different damage types were analyzed emphatically. Moreover, the test results were verified in practice. The results show that the deformation and failure characteristics of coal samples can be divided into single shearing type, conjugated shearing type, and shattered type. The charge time-domain signals of coal samples with single shearing occur only in the early stage of post peak failure, and the stress falls to about 97% . Since the signal characterizes a single burst with higher amplitude, discrete charge frequency distribution and the main frequency of 250 Hz, it is difficult to capture the precursory information. Those characteristics of charge signal indicate that the corresponding engineering coal body may occur a localized failure with releasing the accumulated energy instantly, which leads to significant impact hazard. The charge time-domain signals of coal samples with conjugated shearing are produced in the later period of intensified damage, and the stress reaches (85%~100%) . The signal has an interval burst, and the main frequency is 150 Hz. This indicates that the partitioned rupture occurs with accumulated energy released gradually, and the impact hazard degree is the second. The charge time-domain signals of shattered coal samples are generated in the early stage of intensified damage, and the stress reaches (70%~85%) . The premonitory information is easy to capture because the signals burst continuously with low amplitude and the main frequency of 0 Hz. These results indicate that the coal body may be homogeneously broken with accumulated energy released slowly, and the impact hazard degree is lower. The field monitoring results show that characteristics of charge signals both in crushing area of working face and the occurrence of coal firing gun are highly similar to those charge signals which are produced by coal samples in homogeneous shattered type and single shearing type in the laboratory. These results verify the reliability of the results obtained from the laboratory.

Key words: coal sample, failure characteristic, charge induction, rock burst, prediction