Influence of Mining Speed on Stope Energy in Deep Mines

Enhancing the mining speed of a working face has become the primary approach to achieve high production and efficiency in coal mines, thereby further improving the production capacity. However, the problem of rock bursts resulting from this approach has become increasingly serious. Therefore, to implement coal mine safety and efficient extraction, the impact of deformation pressure caused by different mining speeds should be considered, and a reasonable mining speed of the working face should be determined. The influence of mining speed on overlying rock breaking in the stope is analyzed by establishing a key layer block rotation and subsidence model. Results show that with the increasing mining speed, the compression amount of gangue in the goaf decreases, and the rotation and subsidence amount of rock block B above goaf decreases, forcing the rotation and subsidence amount of rock block A above roadway to increase. Consequently, the contact mode between rock block A and rock block B changes from line contact to point contact, and the horizontal thrust and shear force between blocks increase. The increase in rotation and subsidence of rock block A intensifies the compression degree of coal and rock mass below the key layer, thereby increasing the stress concentration degree of coal and rock mass as well as the total energy accumulation. In addition, due to the insufficient compression of gangue in the goaf, the bending and subsidence space of the far-field key layer are limited, the length of the suspended roof increases, and the influence range of mining stress and the energy accumulation range expand. Numerical test results and underground microseismic monitoring results verify the correlation between mining speed and stope energy, and high-energy events generally appear 1-2 d after the change in mining speed. On this basis, the statistical principle confirms that the maximum mining speed of the working face at 6 m/d is reasonable.