Layered re-breaking behavior of gangue backfilling materials and inspirations for protecting mined ecological environments

Abstract

Gangue backfilling mining technology plays an important role in relieving environmental problems in mining area. The compression deformation and particle re-breaking properties of backfilling material directly affect gangue backfilling effect. In this study, three-dimensional acoustic emission (AE) positioning for broken particle materials was used to reveal the internal particle re-breaking process for broken backfilling coal gangue. The results can be summarized as follows: the compression deformation stage significantly affected the AE amplitude evolution during compression. In the initial and linear compaction stages, it increased gradually until stabilization at 90–100 dB. After compression to the plastic compaction stage, the AE amplitude gradually decreased, showing a higher decrease at smaller particle size. During the entire compression stage, more than 90 % of the AE amplitude was concentrated around 40–59 dB. According to the AE positioning and particle re-screening results, broken coal gangue exhibited layered re-breaking characteristics, that is, the particle re-breaking first occurred in the middle layer and then gradually shifted to the upper and lower layers with the stress increased. Larger particles were more likely to re-break under the same stress. Increasing the compacting force and reducing particle size of gangue backfilling materials in the middle of the mining goaf are proposed to improve the gangue backfilling effect and protect the ecological environment of mining areas.