Backfilling is an essential engineering practice in underground mining with the objective of stabilizing mined-out voids, also known as stopes, with the ultimate goal of improving ground control and environmental sustainability (Feng et al., 2023). The contemporary methods of backfilling can be grouped into three main types based on the composition and application approach, which include rock backfill, hydraulic backfill, and paste backfill (Oke & Hashemi, 2021).
Rock backfill (RF)
Rock fill is the oldest method and involves the application of waste rock extracted from the mine development tunnel or quarried from the surface (Oke & Hashemi, 2021). The waste rock can be used as is or blended with cement and referred to as Cemented Rock Fill (CRF) with the objective of providing support to the mining activities (Oke & Hashemi, 2021).
Hydraulic backfill (HB)
Hydraulic fill is a slurry with low solids content, which is normally constituted by classified mill tailings and sand (Zhao et al., 2020). The fill has low density due to the high content of water, which demands the application of adequate drainage and porous barricades to enable the escape of the fill’s water content after application, with the ultimate goal of achieving the required fill strength (Oke & Hashemi, 2021).
Paste backfill (PB)
Cemented Paste Backfill (CPB) has gained significant popularity and acceptance in the mining industry due to its efficiency and environmental benefits (Oke & Hashemi, 2021). CPB is normally constituted by full-stream mill tailings, water, and a cement binder, with the latter being the most common type, which is Portland cement (Zhao et al., 2020). The application of CPB is advantageous over hydraulic fill since it generates minimal bleed water, which eliminates the need for underground drainage infrastructure and facilitates faster mining rates (Oke & Hashemi, 2021).
References
Feng, J., Zhang, Z., Guan, W., Wang, W., Xu, X., Song, Y., Liu, H., Su, H., Zhao, B., & Hou, D. (2023). Review of the backfill materials in Chinese underground coal mining. Minerals, 13(4), 473. https://doi.org/10.3390/min13040473
Oke, J., & Hashemi, A. (2021). In situ backfilll monitoring database. Proceedings of the International Seminar on Paste and Thickened Tailings, 353–368. https://doi.org/10.36487/acg_repo/2115_29
Zhao, X., Fourie, A., & Qi, C. (2020). Mechanics and safety issues in tailing-based backfill: A review. International Journal of Minerals, Metallurgy and Materials, 27, 1165–1178. https://doi.org/10.1007/s12613-020-2004-5
