Drying of filtered tailings in contact with the atmosphere

Abstract

Filtered tailings technology enables the separation and reuse of part of the water from solid waste, before its disposal. The filtered tailings can be piled in a stack, avoiding the need for a dam. The behavior of such deposits depends on the degree of saturation of the tailings at the closure stage. This paper proposes a conceptual model describing the processes and variables determining the evolution of the water content and the degree of saturation throughout the construction of the deposit. We have obtained data from the Casposo mine (San Juan, Argentina) and this has been analysed to study, on the one hand the drying process while the tailings remain exposed to the atmosphere and, on the other hand, the consolidation process under the load imposed by subsequent layers. The concept of target water content at the moment of covering the tailings under the next layers is only useful if its variability is taken into account. This can be characterized, for the case studied, as a normally distributed random variable. The concept of saturation water content is defined as the value that will cause saturation of the tailings when subjected to the maximum vertical stress. This is also a normally distributed variable. By comparing both variables, the probability of reaching saturation in a layer located at a certain depth is computed. This allows us to evaluate if the degree of saturation by the end of the construction will be within the desirable range. It also provides a tool to analyse and adjust the design.