Saturated hydraulic conductivity of uncemented and lightly cemented high-density tailings for surface disposal

Abstract

In recent decades, innovative approaches to tailings management, such as thickened tailings and paste tailings technologies, have emerged as effective disposal techniques for high-density tailings (HDTs). Environmental performance remains a crucial design criterion for HDT structures; however, there is a notable lack of comprehensive data on key performance properties and design parameters for uncemented HDT (UCHDT) and lightly cemented HDT (LCHDT). Many of these characteristics, including leachability and susceptibility to acid mine drainage, significantly influence environmental impact and are closely linked to hydraulic conductivity. In response, this study presents novel experimental insights into the saturated hydraulic conductivity of HDTs, specifically focusing on UCHDT and LCHDT with a Portland Cement content (PCI) ≤ 2%, under various curing conditions and HDT compositions. The findings underscore a time-dependent nature of hydraulic conductivity in HDT (UCHDT, LCHDT), with a discernible decrease observed as curing time progresses. Moreover, the composition of the mix exerts a notable impact on permeability. A reduction in permeability is discernible with higher solid content and binder content, with this decrease being particularly pronounced in the initial stages (≤ 7 days). Additionally, the initial sulfate content present in the pore water of the tailings significantly influences the permeability of LCHDT. Furthermore, under drained curing conditions, a significant decrease in hydraulic conductivity is observed, particularly accentuated in LCHDTs. Moreover, experimental results indicate that the permeability of specimens subjected to rewetting after the first day of curing remains largely unaffected, while for samples rewetted after being cured for 7 days, hydraulic conductivity exhibits a significant increase. Lastly, consolidation is shown to lead to a decrease in hydraulic conductivity, especially notable at early ages (≤ 7 days), as highlighted by the results of this study.