| Summary: | In order to evaluate the coal pillar stability in recovery of residual room pillars under different mining rates, this paper studies the influence of loading rate on the mechanical properties of the coal body. The uniaxial compression tests of coal samples in Yangcheng area at different loading rates were carried out with the MTS815 electrohydraulic servo rock mechanics test system. The stress-strain curves and the evolution characteristics of AE signals were analyzed. At same time, the mechanism of damage and failure of specimens are also discussed. The results show the following. (1) With the increase in loading rate, the ultimate stress and ultimate strain of specimens decrease first and then increase. (2) Loading rate has a significant effect on the stability adjustment of specimens. With the decrease in loading rate, the earlier the stress adjustment is, the larger the adjustment range is, and the failure mode changes from shear failure to tensile failure. (3) In addition, when the loading rate increases, the AE evolves from continuous dense to discrete catastrophe, which indicates that the failure of the sample at a larger loading rate is sudden, which is not conducive to the maintenance of the stability of the coal pillar. (4) Finally, the failure mechanism of the specimen structure under different loading rates is obtained, and the improvement measures for the effect of mining velocity of working face on the stability of coal pillar are put forward. The results reveal the loading rate effect of mechanical properties of coal and provide a reference for controlling the stability of the residual coal pillar.
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