Stability assessment of a tailings storage facility using a non-local constitutive model accounting for anisotropic strain-softening

TL;DR

This paper introduces a novel non-local constitutive model that accounts for anisotropic strain-softening to assess the stability of tailings storage facilities, providing a more accurate and resilient evaluation method.

Contribution

It develops and calibrates a new constitutive model incorporating anisotropic strain-softening for stability analysis of tailings dams, improving upon traditional methods.

Findings

The model accurately captures strain-softening behavior.

Calibration with laboratory tests validates the model.

Application indicates improved stability assessment.

Abstract

Recent failures of upstream-raised tailings storage facilities (TSF) raised con-cerns on the future use of these dams. While being cost-effective, they entail higher risks than conventional dams, as stability largely relies on the strength of tailings, which are loose and normally-consolidated materials that may exhibit strain-softening during un-drained loading. Current design practice involves limit equilibrium analyses adopting a fully-softened shear strength; while being conservative, this practice neglects the work input required to start the softening process that leads to progressive failure. This paper describes the calibration and application of the NGI-ADPSoft constitutive model to evaluate the potential of static liquefaction of an upstream-raised TSF and provides an indirect measure of resilience. The constitutive model incorporates undrained shear strength anisotropy and a mesh-independent anisotropic post-peak strain softening. The calibration is performed using laboratory testing, including anisotropically-consolidated triaxial compression tests and direct simple shear tests. The peak and residual undrained shear strengths are validated by statistical interpretation of the available CPTu data. It is shown that this numerical exercise is useful to verify the robustness of the TSF design.