Speaker
Description
Deep geological disposal of high-level radioactive waste relies on the long-term integrity of bentonite-based engineered barriers. However, predicting their performance remains a challenge due to the complex evolution of the pore structure under different environmental conditions, which directly controls their swelling and sealing capacity. Existing stress-strain constitutive models often neglect the pore structure evolution, as well as the hysteretic nature of water retention behaviour and the distinction between adsorption and capillary mechanisms.
To address these limitations, the existing ACMEG-S model is extended to ACMEG-Ex-S. The new formulation introduces a double-structure water retention model that explicitly distinguishes between adsorption and capillary mechanisms, while retaining the simplicity of a single-structure mechanical formulation. Additionally, it incorporates hysteresis and accounts for the pore structure evolution of the material under both mechanical and hydraulic stress paths. These features allow the use of a single set of parameters across different compaction states and stress paths.
The model has been validated for an MX-80 compacted bentonite, simulating swelling tests, isotropic compression, and oedometric loading. The results show good agreement with experimental data, successfully reproducing the non-linear stress–strain response, the transition between micro- and macropore water retention, and the coupled hydro-mechanical behaviour over a wide suction range. The integration of pore-scale mechanisms into a macroscopic constitutive framework enables the model to capture the complex water retention and mechanical response in bentonite-based engineered barriers.
| Country | Switzerland |
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