Key Takeaways & Executive Findings
- •• • Optimized iron tailings sand-bentonite mixture: permeability coefficient k decreases exponentially with bentonite content (CB), from 10^-4 cm/s at CB=0% to 10^-8 cm/s at CB=9%, meeting the engineering standard k≤10^-7 cm/s; beyond 9%, marginal benefit diminishes, guiding cost-effective material selection. • • Three-dimensional anti-seepage system with 'pre-embedded pipe + expansion bolt' technique: enhances structural integrity at critical nodes, reducing leakage risk; enables performance-based design over compliance-based design, improving long-term reliability. • • Environmental remediation efficacy: after implementation, heavy metal concentrations in farmland soil decreased by 11.14%–72.41%, all below risk screening values; Fe and Cr interception rates reached 97.17% and 96.76%, respectively, demonstrating effective containment of contaminant migration. • • Integrated design-construction-evaluation framework: achieved 2.78% increase in tailings resource utilization and 4.71% reduction in engineering cost, while reducing Nemerow index from 2.39 (moderate) to 0.62 (none) and potential ecological risk index from 288.50 (moderate) to 148.73 (slight), validating the approach's technical and economic viability.
Abstract
This study addresses the deficiencies in material and structural stability and the singular evaluation system in iron tailings pond pollution remediation. Based on an integrated design-construction-evaluation concept, we developed a three-dimensional anti-seepage system incorporating iron tailings sand-bentonite mixtures and a composite liner structure. The system was applied to an actual remediation project in Qichun County, Hubei Province, China, covering an area of 18.72×10^4 m^2 with 43.42×10^4 m^3 of tailings. Theoretical calculations of leachate generation, material testing, and structural optimization were performed. The optimized mixture achieved a permeability coefficient (k) reduction from 10^-4 cm/s to 10^-8 cm/s as bentonite content increased from 0% to 9%, meeting the engineering standard of k≤10^-7 cm/s. A novel 'pre-embedded pipe + expansion bolt' technique enhanced sealing at structural nodes. Post-remediation monitoring showed significant reductions in heavy metal concentrations in surrounding farmland soil (11.14%–72.41% decrease), all below risk screening values. Iron (Fe) and chromium (Cr) interception rates reached 97.17% and 96.76%, respectively. The Nemerow comprehensive pollution index dropped from 2.39 (moderate pollution) to 0.62 (no pollution), and the potential ecological risk index decreased from 288.50 (moderate risk) to 148.73 (slight risk), representing a reduction of 1–3 pollution levels. The project achieved a 2.78% increase in tailings resource utilization and a 4.71% reduction in engineering cost. This integrated technical system provides a viable approach for tailings pollution control and sustainable waste management.
1. Introduction
Iron tailings ponds pose significant environmental threats due to the migration of heavy metals through surface water, groundwater, and atmospheric pathways. Conventional anti-seepage systems often rely on bentonite geosynthetics, which suffer from desiccation cracking and structural degradation under seasonal wet-dry cycles, leading to permeability increases up to 10^-4 cm/s after 2–6 cycles. Moreover, existing remediation strategies typically treat tailings as waste for disposal, overlooking their potential for resource utilization, and lack rigorous theoretical basis for material selection and structural design. These bottlenecks result in suboptimal performance and high costs, hindering effective long-term containment.
This study introduces an integrated design-construction-evaluation framework that addresses these gaps by incorporating iron tailings sand as a component of the anti-seepage layer, thereby achieving 'waste control by waste'. Through systematic material testing and structural optimization, we developed a three-dimensional anti-seepage system with a tailings sand-bentonite mixture that meets permeability standards while utilizing on-site waste. The inclusion of a novel anchoring technique for critical joints enhances system integrity. Post-project environmental monitoring provides quantitative evidence of pollution reduction, offering a replicable model for tailings pond remediation that balances technical efficacy, economic feasibility, and sustainability.
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XIAO Rui, CHEN Ming (2026). Integrated Barrier and Anti-Seepage Technology for Iron Tailings Pond: Application and Environmental Evaluation. Chinese Journal of Environmental Engineering. https://doi.org/10.12030/j.cjee.202507036
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Frequently Asked Questions
What is the optimal bentonite content in the iron tailings sand-bentonite mixture to achieve the required permeability while minimizing cost?
The permeability coefficient k decreases exponentially with bentonite content (CB). At CB=9%, k reaches 10^-8 cm/s, which is below the engineering standard of 10^-7 cm/s. Increasing CB beyond 9% yields negligible further reduction in k (no order-of-magnitude change), indicating a performance plateau. Therefore, the optimal CB is approximately 9%, balancing permeability performance and material cost.
How does the three-dimensional anti-seepage system perform under long-term field conditions, particularly regarding structural integrity and contaminant containment?
Post-remediation monitoring over the project period demonstrated that the system effectively blocks contaminant migration. Heavy metal concentrations in surrounding farmland soil decreased by 11.14%–72.41%, all below risk screening values. Fe and Cr interception rates were 97.17% and 96.76%, respectively. The Nemerow index dropped from 2.39 (moderate pollution) to 0.62 (no pollution), and the potential ecological risk index decreased from 288.50 (moderate risk) to 148.73 (slight risk), confirming long-term reliability.
What are the scalability and applicability of this technology to other types of tailings, such as lead-zinc or copper tailings?
The technology is adaptable, but the optimal bentonite content must be determined experimentally for each tailings type, with a recommended gradient of 3%–15%. Additionally, the valence state of heavy metals (e.g., Cr6+ vs. Cr3+) can affect material performance and must be considered. The integrated framework is transferable, but site-specific conditions require tailored design and testing.
How does the 'pre-embedded pipe + expansion bolt' technique improve the anti-seepage system's performance compared to conventional methods?
This technique reinforces structural nodes, such as pipe penetrations and liner connections, which are common leakage points. By securely anchoring the liner and creating a tight seal, it reduces the risk of detachment and subsequent seepage. This innovation enhances the overall integrity and durability of the anti-seepage system, contributing to the observed high interception rates and long-term stability.
What are the economic benefits of using iron tailings sand as a component of the anti-seepage layer?
Utilizing on-site tailings reduces the need for imported materials, leading to a 4.71% reduction in engineering cost. Additionally, it increases tailings resource utilization by 2.78%, aligning with the 'waste control by waste' principle. This dual benefit of cost savings and environmental sustainability makes the approach economically attractive for large-scale remediation projects.
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