Insights into mine tailings mechanical response under plane-strain compression and stress path testing

Abstract

Mine tailings storage facilities (TSFs) are commonly analyzed under plane-strain assumptions, yet experimental data on tailings behavior under this condition are absent from the literature. This study uses a plane-strain apparatus capable of measuring intermediate stress to investigate drained and undrained compression and constant shear drained (CSD) responses of a non-plastic mine tailing. The critical state line (CSL) from plane-strain testing is shown to be identical to that from triaxial testing on the same material, supporting CSL uniqueness in e–p' space. The critical stress ratio under plane strain falls within Mohr-Coulomb and Matsuoka-Nakai bounds, consistent with prior findings on sands. Intermediate stress ratios (b) range from 0.25–0.30 under drained loading and 0.30–0.48 under undrained loading. Under CSD loading, all specimens exhibit Type-I instability at the transition from volumetric expansion to contraction, with onset near the lower bound of the expected critical state stress ratio range. The intermediate stress development is stress-path dependent, producing a distinct CSD response relative to compression loading. These findings represent the first known experimental investigation of mine tailings under zero-lateral strain conditions (plane-strain) that tracks intermediate stresses and provides a basis for improving TSF stability assessments.