Backfill Mining Techniques for Surface Subsidence Control
Summary
Backfill mining techniques offer a suite of methods to control surface subsidence by replacing or supporting the void left by mineral extraction. Techniques range from cemented paste and hydraulic filling to granular waste and raw gangue backfilling. The choice of backfill material and sequence of operations influences the stress distribution in the rock mass and determines the effectiveness of surface control. Recent innovations include the integration of numerical modelling with laboratory testing to optimise filling parameters, the development of low-strength paste fills using industrial by-products, and the application of smart sensors to monitor subsidence in real time. These advances have enabled mining under sensitive infrastructure, beneath aquifers and within urban environments, reducing ecological impact and preserving landscape stability. Globally, backfill mining has become central to sustainable extraction strategies, particularly in regions with shallow overburden, high water tables or strict environmental regulations. The practical impact spans from coal basins in China to hard-rock operations in Europe, highlighting the adaptability of backfill solutions to diverse geological settings.
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Case studies in China have demonstrated the feasibility of using raw gangue—a non-coal waste product—as backfill, emphasising practical considerations for on-site handling, compaction and its influence on subsidence control under construction scenarios. Investigations into strip filling sequences reveal that adopting a “fill-before-mining” approach significantly reduces stress concentrations and surface deformation compared with traditional schemes; this has informed guidelines for optimising the mining-to-filling ratio to prevent isolated pillar formation. Comprehensive analyses of backfill material properties—including granular, cemented and high-water-content mixtures—have led to selection frameworks that balance strength, permeability and cost. Experimental and numerical studies on paste fills composed of fly ash, gypsum and local aggregates have shown that tailoring binder ratios can achieve target mechanical performance while utilising industrial by-products, thus aligning subsidence control with waste-valorisation and environmental objectives.
Backfill Mining Techniques for Surface Subsidence Control publication trend
The graph below shows the total number of articles in backfill mining techniques for surface subsidence control across all publications each year (not limited to Nature Index journals).
Technical terms
Backfill: Material placed into an excavated void to support overlying strata and control surface movement.
Goaf: The void left after the extraction of a mineral seam, often requiring backfilling to prevent collapse.
Paste backfill: A mixture of fine particles and binder, pumped into voids to provide continuous support to the roof and overburden.
Subsidence: The downward movement of the ground surface resulting from underground excavation.
Abutment pressure: Stress transferred to the remaining pillars or backfill material adjacent to the mined area.
Filling ratio: The proportion of void volume occupied by backfill material relative to the total mined space.
Raw gangue: Unprocessed waste rock or mineral by-product used as backfill without prior beneficiation.
References
- Raw Gangue Filling Mining under Construction —A Case Study in China. Engineering (2023).
- Properties and Application of Backfill Materials in Coal Mines in China. Minerals (2019).
- Modeling study on the influence of the strip filling mining sequence on mining‐induced failure. Energy Science & Engineering (2020).
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