In the vast and complex world of mining, one of the most critical challenges faced by engineers and environmental scientists alike is the control and management of water-induced hazards, particularly water inrush events in coal mining regions. A recently published study in Environmental Earth Sciences sheds new light on this pressing issue by examining the impact of backfill ratio on the risk of water inrush within goaf areas filled with coal gangue, especially under the precarious conditions posed by overlying aquifers.
Water inrush — an abrupt and devastating inflow of water into mine workings — poses significant risks to mining safety, operational continuity, and environmental stability. Traditional methods of mitigating these risks often involve backfilling goaf spaces, the voids left behind after coal extraction, with various materials to restore structural integrity and reduce water pathways. However, until now, the precise relationship between the amount of backfill material used and the likelihood of water inrush under aquifer conditions has remained insufficiently understood.
Scientists Xing, Li, Wang, and their colleagues approached this challenge through rigorous theoretical analysis combined with experimental validation. Their study meticulously explores how varying the backfill ratio — the proportion of void space in the goaf that is replaced with coal gangue material — can influence the permeability and structural properties of the backfilled zone, ultimately affecting the propensity for water to infiltrate the mine.
Coal gangue, a byproduct of coal mining containing rock fragments and residues, has garnered attention both as a waste management solution and as a practical backfill material due to its availability and compatibility. Understanding how different backfill ratios of this substance modify the hydraulic behavior and mechanical strength of goaf areas under the stress of adjacent aquifers is paramount for designing safer mining operations.
The researchers employed detailed geomechanical modeling to simulate the interplay between backfill compaction, porosity, and the hydrostatic forces exerted by aquifers. Their results indicate that lower backfill ratios, which imply a less dense and more porous filling structure, significantly exacerbate water permeation via the goaf. This elevates the risk of sudden water inrush events owing to weakened resistance against aquifer pressure.
Conversely, increasing the backfill ratio creates a more compact and impermeable barrier. This improvement in mechanical stability and decrease in permeability mitigates the pathways through which water can travel, effectively suppressing the potential for inrush. Yet, this approach is not without caveats, as overly high backfill ratios may involve increased material costs and logistical challenges that need to be balanced against safety gains.
The study also delves into the time-dependent behavior of backfill materials, revealing that the mechanical properties of coal gangue evolve due to consolidation and particle rearrangement, which impact water transport dynamics over extended periods post-backfilling. This insight marks a crucial advancement, highlighting the necessity for ongoing monitoring and adaptive management strategies within mining operations.
Complementing the modeling work, the authors conducted controlled laboratory flow tests and permeability measurements on samples prepared with various backfill ratios. These empirical findings consistently reinforced the theoretical predictions, providing robust validation and practical relevance to the insights generated. The convergence of numerical simulations and physical experimentation underlines the study’s robust scientific rigor.
This research holds profound implications for mine safety protocols, environmental protection, and the sustainable management of post-mining landscapes. Water inrush incidents have historically led to catastrophic mining disasters, and improving predictive capabilities around geological stability can save lives, reduce economic losses, and minimize environmental degradation.
Beyond the immediate scope of mining safety, the study contributes valuable knowledge towards waste management practices within the coal industry. Adopting coal gangue backfilling not only addresses the challenge of managing mining byproducts but also advances circular economy principles by reusing materials that would otherwise accumulate as environmental burdens.
The authors emphasize that optimizing backfill ratios must be integrated with detailed site-specific geological assessments and aquifer characterizations. The heterogeneity of aquifer geology — varying in permeability, pressure, and connectivity — demands customized approaches rather than one-size-fits-all solutions, underscoring the complexity inherent in subsurface engineering.
Importantly, this research promotes a paradigm shift in mining water hazard mitigation, moving away from purely reactive safety interventions toward preemptive, scientifically informed design and operation of backfilling strategies. The integration of multidisciplinary data sets and modeling tools as demonstrated will likely become the standard for future mining safety frameworks.
Furthermore, this study resonates globally, especially in regions where coal remains a dominant energy source and mining activity intersects with vulnerable groundwater systems. The ability to quantitively assess and reduce water inrush risks through backfill ratio management equips mining companies and regulators with actionable insights to safeguard communities and ecosystems.
While this investigation is focused on coal gangue under aquifers, its findings are likely transferable, with adaptations, to other forms of backfill materials and hydrogeological settings. This opens intriguing avenues for future research to refine and expand water hazard prevention methodologies across a variety of mining contexts.
By illuminating the crucial balance between backfill density and water permeability, Xing, Li, Wang, and colleagues have substantially advanced our understanding of underground water risks and provided a roadmap to safer and more sustainable mining practices. Their contribution underscores the vital role that careful engineering, grounded in sound science, plays in protecting both human interests and the natural environment.
In the ongoing battle against mining hazards, this research marks an essential milestone—where traditional backfilling techniques are not just improved but fundamentally reimagined through the lens of modern scientific inquiry. It propels the mining industry towards a future where safety is engineered with precision, and disasters are preemptively averted through knowledge and innovation.
Subject of Research: The impact of backfill ratio on the risk of water inrush in goaf backfilling of coal gangue under aquifers.
Article Title: Effect of backfill ratio on the risk of water inrush in goaf backfilling of coal gangue under aquifer.
Article References:
Xing, S., Li, M., Wang, Y. et al. Effect of backfill ratio on the risk of water inrush in goaf backfilling of coal gangue under aquifer. Environ Earth Sci 84, 542 (2025). https://doi.org/10.1007/s12665-025-12549-x
Image Credits: AI Generated
