Hydraulic conductivity optimisation of bentonite-modified tailings using response surface methodology

Le résumé fourni par la source

The environmental management of mine tailings continues to pose significant technical challenges due to inherent geotechnical deficiencies that limit their direct application in engineering works. In this study, gold mine tailings were stabilised with bentonite and evaluated for unconfined compressive strength (UCS), hydraulic conductivity and desiccation cracking characteristics to transform tailings into a viable construction resource. The tailings were sourced from the Soweto mining belt and oven-dried at 110 °C prior to treatment with 0–20% sodium bentonite. Response surface methodology (RSM) was used as an application-oriented optimisation framework to model the effect of bentonite content, UCS and crack intensity on hydraulic conductivity to establish optimal performance conditions. The study found an optimum bentonite content of 14.7%, corresponding to a UCS of 487 kPa and a crack intensity of 1.93%, which satisfied the regulatory 1 × 10−7 cm/s criterion for compacted liner systems. An increase in bentonite content reduces hydraulic conductivity and crack intensity while improving strength. Scanning electron microscopy and energy-dispersive X-ray spectroscopy results revealed that the layered aluminosilicate structure of bentonite contributed to pore filling and matrix densification, which were responsible for the observed reduction in hydraulic conductivity. Although the models demonstrated strong predictive performance against the laboratory results, the findings should be interpreted within the investigated parameter range because of the limited experimental dataset. The study suggests that bentonite-modified tailings can be repurposed for geoenvironmental containment systems.

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