Determination of equivalent mining height based on the minimum compression rate of gangue filling materials

The equivalent mining height theory is an effective means of analyzing the degree of control over the impact of solid filling mining. By analyzing the proportion of each component of equivalent mining height, it is believed that reducing the compression rate of gangue filling materials is an important way to reduce equivalent mining height, and obtaining the optimal particle size distribution of gangue is the most critical. The gangue with a particle size of less than 100mm was divided into 5 grades (100~75mm, 75~50mm, 50~25mm, 25~13mm, and 13~0mm). Based on the Taibo theory, 5 different particle size gangue grading schemes were designed according to the grading index n=0.3~0.7. A steel container with an inner diameter of 380mm was used to load gangue solid filling material with a height of 240mm. The stress conditions of the overlying rock at a burial depth of 400m were simulated, and compression experiments were conducted. The results show that the strain of the solid filling material of gangue increases with the increase of axial stress, and the rate of strain increase decreases with the increase of axial stress. The scheme with a gradation index of n=0.5 has the smallest strain. The minimum equivalent mining height expression was obtained based on the strain stress fitting relationship. And the experimental results were applied to Xingdong Coal Mine, combined with the actual observation of surface deformation after filling mining of the eastern wing of the 1200 mining area. It was found that there was no obvious roof pressure during the filling mining with gangue, and the surface buildings were not affected, and filling scheme of gangue in the east wing of the 1200 mining area was feasible.