Speaker
Description
Expansive clays, such as bentonite, are involved in the design of engineered barriers for municipal and nuclear waste disposal. These materials are characterized by very low permeability, high swelling capacity, and self-healing properties, which ensure effective waste isolation and long-term stability under many different environmental conditions. Given the critical nature of their engineering applications, the design and use of these engineered barriers demand an accurate prediction of their behaviour. Although these materials have been employed in such roles for many years, the tools currently available and the physical understanding of the phenomena governing their behaviour remain limited, posing significant challenges to their application. This study introduces a novel stress-strain constitutive framework to simulate the behaviour of compacted bentonite under varying environmental loads, such as changes in relative humidity and mechanical loads at different saturation levels. Based on the physical behaviour of the material, the proposed formulation integrates the Advanced Constitutive Model for Environmental Geomechanics (ACMEG) with a water retention framework that distinguishes between capillary and adsorption mechanisms based on microstructural observations from the literature. Key advancements include a compaction-dependent air entry suction for the Capillary Water Retention Curve (CWRC) and an interaction function that accounts for hydration and compaction states of the material. Furthermore, an innovative effective stress formulation incorporates electrochemical stresses taking place from the interactions between clay particles and pore water molecules. The constitutive model is validated on a single Gauss point through simulations of uniaxial consolidation, isotropic compression under varying suctions, and constant-volume wetting tests at different dry densities on a MX-80 bentonite. Results demonstrate the ability of the model to capture the mechanical behaviour across a wide suction range and accurately predict swelling pressure under different compaction states. This work contributes to providing a robust tool for the analysis and optimization of engineered barriers, addressing critical gaps in current constitutive approaches.
| Country | Switzerland |
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