Browsing by Author "Shafaei Bajestani, Mahsa"

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    Development of a new hydro-mechanical model for swelling of bentonite-based sealing materials (BBSM)
    (University of New Brunswick, 2024-08) Shafaei Bajestani, Mahsa; Nasir, Othman
    Bentonite-based sealing material (BBSM) is proposed for use in engineered barrier systems for the disposal of high-level radioactive waste in a deep geological repository (DGR) due to its low permeability and high swelling potential. The performance of BBSM can impact the mechanical stability and environmental performance of the DGR system. Understanding the hydro-mechanical (HM) behavior of BBSM, the ability to model, and predict the behavior are crucial components in ensuring the safety of the system. This research aimed to improve the understanding of the HM behavior of BBSM during hydration and to develop a new modelling tool by integrating experimental and numerical investigations. Experimental investigations on BBSM assessed its swelling properties via swelling experiments and advanced HM column-type tests using a newly developed tool. In the numerical part, a new HM model was developed, calibrated using experimental data from the current study, and validated with the published results for the prediction of BBSM properties, including a multiscale porosity model with a new swell model using FLAC3D and TOUGH3 software. The model was applied to a large-scale hypothetical DGR to check its applicability to a full-scale DGR system. The results of the laboratory experiments confirmed that the newly developed device was capable of measuring the swelling pressure and could be used for the advanced test. The HM column-type experiments provided insights into the wetting front, axial, and radial swelling pressure at different times. The proposed HM model was able to capture the evolution of swelling pressure and saturation profile using a single set of calibrated parameters for small-scale experiments and a large-scale hypothetical DGR. Results of the DGR analysis showed that it may take up to 10,000 years for the engineered barrier system to become fully saturated, which was consistent with other studies. The maximum swelling pressure at the fully saturated condition of the BBSM did not exceed the in-situ minor principal stress of rock formation. The sensitivity analysis of the model parameters highlighted the significant impact of rock formation and bentonite permeability on saturation time. Furthermore, it revealed that the strength-stress ratio was susceptible to variations in model parameters.