Modeling self-compaction and static stability of a copper filtered tailings pile under unsaturated conditions

Abstract

Filtered tailings piles have better mechanical stability than other tailings disposal alternatives because they operate in an unsaturated condition. However, very few studies have quantitatively assessed the contribution of partial saturation for both self-compaction and mechanical stability. In this article, we evaluate the mechanical stability of a filtered tailing pile, based on an analysis of self-consolidation by material deposition under unsaturated conditions, considering rates of 1 h, 1 day and 4 days. For this purpose, an experimental study was carried out which included oedometric and triaxial consolidation tests in both, saturated and unsaturated conditions. Based on these results, a constitutive soil model was calibrated using the Bishop’s effective stress concept, considering the evolution of the effective saturation and including soil-water characteristic curve (SWCC) as a function of volumetric strains. The results show that the proposed modeling strategy provides a reasonable approximation of laboratory paths with a single set of parameters. Additionally, the same approach was applied to model the pile’s construction process. In this case, it was observed that the potential failure surface is triggered when the soil reaches a saturation degree of about 65-70%. At and this value, the soil behavior is practically independent of deposition rates, slope inclination and pile height. However, the factor of safety (FoS) decreases for faster deposition rates compared to slower ones.