This article was originally written by (Ram Chandar et al., 2022).
Waste rock and mine tailings are extensively used in the backfilling of underground mined out areas; this could help in decreasing the amount of land used for mining activity and reduce the environmental impact (Lu & Cai, 2012).
The process of back filling involves deposition of tailings and waste rock with required amount of water and binders into the empty stopes. After few months of curing, the backfill will be able to provide adequate support to the adjacent stopes allowing further mining operation. In most cases, about 40% to 60% of the tailings produced in a mine can be reused as backfill, thereby reducing the environmental footprint left behind by the surface impoundment of tailings (Wills & Finch, 2016).
Three most widely applied backfills are hydraulic fill, rock fill and CPB. Hydraulic f ills are produced using de-slimed tailings and use binders to acquire mechanical strength after the curing period. Usually, waste rock is used for dry back filling and tailings for hydraulic (Lu & Cai, 2012).
However, the paste – backfill had to be optimized for each site as the properties of tailings and water had significant effect on the strength acquisition of backfill. However, the back filling is an unproductive work which incurs additional cost.
Back filling is very useful in case of weak host rock where cut and fill method of stoping is adopted; in case of sublevel stoping, the host rock is generally very hard and does not need any additional support; in that case, the dried tailings or crushed waste rock can be dumped in stopes.
Sun et al. (2018) used waste rock-tailing paste to control subsidence in earthquake-prone areas and secondary disasters, like as down-hole debris flow and groundwater contamination at Tong Cheng mine, China.
Among the three backfill methods adopted (All non-cemented backfill, All-cemented backfill and cemented non-cemented joint backfill), the cemented–non-cemented combination was selected after their comparison.
A backfilling strategy of vertical stratification and horizontal partition was developed for the subsidence area. The backfilling paste had a mass concentration of 81%–83%, 25%–30% of waste rock and 2%–5% of cement.
The paste showed satisfactory anti-disintegration property and attained a compressive strength of about 1.5 to 3 MPa in 28 days. When the coefficient of permeability of the backfill ranged between 10−4 cm/s and 10−3 cm/s, a moderate level of permeability was achieved, and this was suitable for the control of subsidence.
Reference
Lu, Z., & Cai, M. (2012). Disposal Methods on Solid Wastes from Mines in Transition from Open-Pit to Underground Mining. Procedia Environmental Sciences, 16, 715–721. https://doi.org/10.1016/j.proenv.2012.10.098
Ram Chandar, K., Gayana, B. C., & Shubhananda Rao, P. (2022, May 27). Mine Waste Utilization. https://doi.org/10.1201/9781003268499
Sun, W., Wang, H., & Hou, K. (2018). Control of waste rock-tailings paste backfill for active mining subsidence areas. Journal of Cleaner Production, 171, 567–579. https://doi.org/10.1016/j.jclepro.2017.09.253
Wills, B. A., & Finch, J. A. (2016). Chapter 16—Tailings Disposal. In B. A. Wills & J. A. Finch (Eds.), Wills’ Mineral Processing Technology (Eighth Edition) (pp. 439–448). Butterworth-Heinemann. https://doi.org/10.1016/B978-0-08-097053-0.00016-9
