Numerical Study on the Vibratory Compaction Mechanism of the Sand-Gabion Backfills in Underground Coal Mines

Coal mine backfilling can effectively prevent large-scale movement of rock formations, not only improving the overall production capacity of the mine but also protecting the surface from destruction and maintaining the original ecological environment. Backfilling extent and backfills compactness are two factors determining the supporting effect on the overburdens in underground coal mines. To make full use of the aeolian sand as the backfill materials in underground coal mines in the desertification areas, Northwest China. Then, vibratory compaction was proposed to enlarge the compactness of these sand-gabion backfills by considering the limited working space. After that, the movement law of the sand particles during vibratory compaction, the influencing law of the vibratory parameters, and the gabion constraint on the ultimate compactness of the sand-gabion backfills were studied using the discrete element software PFC3D from the microscopic point of view. It was found that the aeolian sand particles are more likely to inter-squeeze under vibration than under static load. Furthermore, there are a series of optimal vibratory compaction parameters to the inner aeolian sand for each external gabion constraint strength. The optimal vibration parameters were frequency 50 HZ, excitation force 0.3 MPa, amplitude 40 KPa, and vibration time 4 s. Conclusions of this study can provide references for enlarging the compactness of the sand-gabion backfills in the underground goaf in the desertification area of Northwest China.