83 / 2021-09-22 17:19:50

Study on signal characteristics of burst tendency coal under different loading rates

loading rate; burst tendency; the mechanics, AE and EME signals; block damage; energy release rate; mining speed; rock burst.

In order to study the mechanics, acoustic emission (AE) and electromagnetic emission (EME) response law of burst tendency coal at different loading rates, uniaxial compression tests were carried out on coal mass from Konggu Coal Mine. The corresponding relations among mechanical properties, AE and EME signals in the process of coal failure under loading were analyzed, and the energy evolution law of coal failure with bursting liability under loading rate was discussed. The results show that: (1) within a certain range of loading rate, the higher the loading rate, the higher the compressive strength and peak load of bursting liability coal, and the shorter the time for coal to reach the peak load. When the loading rate reaches a certain value, the experimental results are abnormal. As the loading rate increases, the compressive strength and peak load of the coal begin to decrease. When the loading rate reaches a certain high value, the bursting damage of coal mass appears in a short period of time. (2) Under different loading rates, the mechanics, AE and EME signals of coal samples can be well corresponded. When there is a stress drop, the AE and EME signals have relatively high values. When the stress reaches the peak, the two signals also reach the maximum value. The maximum value and cumulative value of AE count increase with the acceleration of loading rate. On average, the AE signal value of fast loading is greater than that of slow loading. (3) When the loading rate is low, the number of blocks destroyed of coal sample is large and the block size is relatively small, and the blocks are mainly scattered around the test platform. When the loading rate is high, the number of damaged blocks is relatively small and the block size is relatively large, and the blocks are far away from the test bench. When the loading rate is high enough, the coal samples show the characteristics of impact burst and the blocks "eject" out of the test platform. (4) When loading at a low rate, the internal cracks in coal body can be fully developed and connected, and the energy release rate is relatively uniform in the process of loading and failure of coal sample. In the case of high loading rate, the energy release rate of coal sample in the loading process is much smaller than that in the moment of failure. Combining the above test results with the engineering site, it is concluded that ultra-high speed mining and slow speed mining are beneficial to the prevention and control of rock burst, while the energy stored in the relatively fast mining coal is larger, which is easier to induce the rock burst. The research results provide some theoretical guidance for making reasonable mining speed and preventing rock burst in coal mining face.