Transport mechanism and control technology of heavy metal ions in gangue backfill materials in short-wall block backfill mining

Yun Zhang; Yongzi Liu; Xingping Lai; Shenggen Cao; Yanbin Yang; Baoxu Yan; Licheng Bai; Liang Tong; Wei He

doi:10.1016/j.scitotenv.2023.165139

Transport mechanism and control technology of heavy metal ions in gangue backfill materials in short-wall block backfill mining

Sci Total Environ. 2023 Oct 15:895:165139. doi: 10.1016/j.scitotenv.2023.165139. Epub 2023 Jun 26.

Authors

Yun Zhang¹, Yongzi Liu², Xingping Lai², Shenggen Cao³, Yanbin Yang², Baoxu Yan², Licheng Bai², Liang Tong², Wei He²

Affiliations

¹ College of Energy Engineering, Xi'an University of Science and Technology, Xi'an 710054, China. Electronic address: zhangyun@cumt.edu.cn.
² College of Energy Engineering, Xi'an University of Science and Technology, Xi'an 710054, China.
³ State Key Laboratory of Coal Resources and Safe Mining, China University of Mining & Technology, Xuzhou, Jiangsu 221116, China.

PMID: 37379916
DOI: 10.1016/j.scitotenv.2023.165139

Abstract

Short-wall block backfill mining can effectively control the movement of overlying strata, prevent water loss and utilize waste gangue materials. However, heavy metal ions (HMI) of gangue backfill materials in the mined-out area can be released and transported to the underlying aquifer, causing pollution of water resources in the mine. Accordingly, with short-wall block backfill mining technology, this study analyzed the sensitivity of gangue backfill materials to the environment. The pollution mechanism of gangue backfill materials to water resources was revealed, and the transport rules of HMI were explored. The regulation and control methods of water pollution in the mine were then concluded. The design method of backfill ratio for comprehensive protection of overlying and underlying aquifers was proposed. The results show that the release concentration of HMI, the gangue particle size, the floor lithology, the burial depth of the coal seam, and the depth of the floor fractures were the main factors that affected the transport behaviors of HMI. After long-term immersion, HMI of gangue backfill materials underwent hydrolysis and were released constantly. HMI were subjected to the coupled action of seepage, concentration, and stress and then driven by water head pressure and gravitational potential energy to transported downward along the pore and fracture channels in the floor with mine water as the carrier. Meanwhile, the transport distance of HMI increased with increasing release concentration of HMI, the permeability of the floor stratum, and the depth of floor fractures. Still, it decreased with increasing gangue particle size and the burial depth of the coal seam. On that basis, external-internal cooperative control methods were proposed to prevent the pollution of gangue backfill materials to mine water. Furthermore, the design method of the backfill ratio for comprehensive protection of overlying and underlying aquifers was proposed.

Keywords: Design of backfill ratio; Gangue backfill materials; Pollution of water resources; Short-wall block backfill mining; Transport of heavy metal ions.