Backfilling techniques in underground mining refer to methods used to fill and stabilize voids created by mining activities. These techniques help support surrounding rock, enhance mine safety, reduce surface subsidence, prevent wasteful ore dilution, and manage mining waste environmentally by placing it underground.
Common backfilling techniques and materials include [1]:
Cemented backfilling: Tailings or waste rock are mixed with cement to bind the material into a solid mass, providing strong support. This method is especially useful where only small amounts of cement are feasible due to cost.
Dry rock backfilling: Uses dry materials such as gravel or dried tailings, often applied in cut and fill mining methods to fill mined-out areas.
Hydraulic sand backfilling: Coarser sand separated from tailings is hydraulically pumped into underground voids, sometimes mixed with binders like cement to improve strength and reduce water-related issues.
Paste backfilling: A slurry of solid tailings, water, cement, and sometimes fly ash is created into a paste-like mixture that can be pumped underground. This method is especially common in coal mines for stable fill with controlled rheology and strength.
These techniques serve multiple purposes: they stabilize the mine by filling voids, enable safer working conditions, allow extraction of ore from pillars that would otherwise be left for support (due to the support being provided by the backfill), and minimize environmental impact by reducing surface waste storage and mitigating groundwater contamination through cementitious sealing properties.
Backfilling materials are often derived from mining by-products like tailings or waste rock, which can be treated or mixed with cementitious materials to optimize their mechanical properties and stability. Advanced backfilling operations utilize surface plants for mixing materials with binders and then transport them underground via pipelines, declines, or shafts.
Overall, backfilling is a critical and evolving technique in underground mining, balancing technical, safety, environmental, and economic factors to optimize mining operations.
Reference
[1] “Essential Guide to Backfilling in Mining Operations.” Accessed: May 13, 2025. [Online]. Available: https://www.flyability.com/fr/blog/backfilling
