Behaviour of copper tailings after isotropic and K₀ consolidation: A critical state approach

Tailings dams are often constructed using tailings themselves. Every year, 2–5 catastrophic tailings dam failures are reported globally, highlighting the need for improved understanding of tailings behaviour. This study presents a series of drained and undrained triaxial tests conducted on isotopically and $K0$ consolidated specimens of copper tailings. Their characteristic behaviour, for example, the instability, phase transformation (PT), and characteristic state (Ch) were evaluated within the critical state soil mechanics framework. $K0$ showed a linear relationship with the post-consolidation void ratio. For isotropically consolidated specimens, static liquefaction/instability was triggered at excess pore water pressure ratios (⁠$Δu/p′0$⁠) between 0·45 and 0·70, whereas for $K0$ specimens, this ranged between 0·15 and 0·45. A unique critical state line was observed regardless of the consolidation conditions. The relationships between the normalised stress ratio at instability (⁠$η$_IS/M) and pre-shearing state parameter (ψ₀) were different in isotropic and K₀ consolidated specimens at higher ψ₀ values. A unique relationship between flow potential and the state parameter at PT was observed, irrespective of consolidation conditions. The normalised stress ratio at PT (⁠$η$_PT/M) in undrained shearing and Ch in drained shearing (⁠$η$_Ch/M) showed a unique relationship with ψ_0, that is a bounding surface constitutive model may be adaptable for copper tailings.