Geotechnical characterisation and numerical modelling of tailings

12/05/2024

This dissertation explores the elasto-plastic model NorSand, analysing its behaviour, and comparing it with traditional models, such as the simple elasto-plastic, and two Cam Clay models. It addresses the critical state concept, and its relevance to granular materials like sand and tailings, examining essential elements of an elasto-plastic model, such as elastic properties, yield surfaces, plastic potential, and hardening law. A critical literature review on the mechanical behaviour of tailings was endeavoured, with a particular focus on the applicability of critical state soil mechanics, establishing them as a distinct geotechnical material influenced by grading, and fabric. The state parameter's physical meaning and mathematical derivation is revisited through a literature review. A parametric analysis of NorSand within Plaxis – Soil Test demonstrated its ability to replicate under triaxial compression the usual behaviour of tailings, despite some numerical instabilities and incoherence with empirical data. Key parameters affecting NorSand's response were identified, and seen to be relevant across all granular soils in spite of constitutive model. Additionally, a numerical back-analysis of a centrifuge test simulating slope behaviour was conducted. The results indicated that the Mohr-Coulomb criterion predicted slope failure more conservatively than NorSand, when placed under identical conditions. This raises questions about the practicality of NorSand in geotechnical engineering, when compared to the simpler Mohr-Coulomb model. The findings suggest that, given its complexities and laboratory demands, NorSand's future utility in tailings structure design remains uncertain, warranting further investigation into its applicability in real-world scenarios.

Authors in the community:

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  D

  Diogo Filipe Estêvão Cordeiro

  ist196007

Supervisors of this institution:

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  T

  Teresa Maria Bodas de Araújo Freitas

  ist24958

civil-engineering - Civil engineering

por - Portuguese

Instituto Superior Técnico