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تسجيل مستخدم جديدStability assessment of a tailings storage facility using a non-local constitutive model accounting for anisotropic strain-softening
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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.
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The interest of the mining industry on the assessment of tailings static liquefaction has exacerbated after recent failures of upstream-raised tailings storage facilities (TSF). Standard practices to evaluate global stability of TSFs entail the use o
f limit equilibrium analyses considering peak and residual undrained shear strengths; thus, neglecting the work input required to drive the softening process that leads to progressive failure of susceptible tailings. This paper presents a simplified procedure to evaluate the static liquefaction triggering of upstream-raised TSFs by means of finite element models employing the well-known Hardening Soil model with small-strain stiffness (HSS). A calibration methodology is proposed to overcome the model limitation of not being implemented in a critical state framework, focusing on the stiffness parameters that control the rate of shear-induced plastic volumetric strains. A real TSF is modelled in Plaxis 2D to evaluate its vulnerability to liquefy due to an undrained lateral spreading at the foundation. Results show that minor movements near the toe induce the material into a strain-softening regime that leads to a progressive failure towards the structure crest.
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