Mechanics of an Iron Ore Tailings Exhibiting Transitional Behaviour

Abstract

Laboratory critical state line (CSL) testing used in engineering practice to analyse the stability and liquefaction susceptibility of tailings explicitly assumes a unique CSL for a particular tailings. However, there is evidence of non-unique CSLs in some soils, a behaviour commonly referred to as “transitional behaviour”. There is currently limited consensus or understanding of its applicability, what factors contribute to its occurrence, and whether there is a fundamental divergence from critical state theory or an artefact of the strain limitations of laboratory element tests. In this research, normally consolidated samples of an iron ore tailings prepared using the moist tamping and slurry deposition methods were sheared to critical state in triaxial compression tests. The results of these tests showed that a different CSL was apparent for the two specimen preparation methods used. This further emphasises the need to re-evaluate the effects of fabric on the uniqueness of the CSL, which may be a consequence of different sample preparation methods typically used to prepare laboratory element tests.