Nuclear energy offers advantages and disadvantages, with waste management being a significant concern. To address this issue, the Deep Geological Repository (DGR) concept in India relies on multi-barrier containment strategies, where bentonite was chosen as an optimal engineering barrier material due to its advantageous attributes. Understanding the long-term Thermo-Hydro-Mechanical (THM) interactions within bentonite is crucial for secure waste disposal. The main purpose of this study was to comprehensively understand the intricate mechanisms occurring within bentonite, particularly in the context of nuclear waste disposal, through numerical analysis. To achieve this objective, a two-stage exploration into the thermo-hydro-mechanical behaviour of bentonite was conducted, subjected to thermal loading for 161 h and thermo-hydraulic loading for 1224 h, resulting in a cumulative simulation duration of 1385 h. These were performed for the FEBEX bentonite material, with boundary conditions, duration and device geometry adopted from experimental conditions at the Indian Institute of Technology Patna. In a 1385-h simulation, temperature and stress equilibrium were achieved, with persistent unsaturation attributed to low permeability. Key findings include significant variations in porosity, permeability and dry density, with dynamic equilibrium achieved after approximately 210 h. The study provides valuable insights into the complex THM interactions within bentonite and provides a solid foundation for future research in computational analysis for the long-term safety of nuclear waste disposal.