The spatiotemporal distribution of temperature fields serves as a critical basis for the thermal design and safety assessment of high-level radioactive waste repositories. Based on the multi-barrier concept of disposal systems, a two-dimensional axisymmetric three-layer thermal model was developed. The governing heat transfer equations were solved using the Laplace transform, Fourier transform, and their corresponding inverse transforms, yielding semi-analytical expressions for temperature distributions in the bentonite block layer, pellet layer, and host rock. Comparative analyses with numerical simulations and two-layer analytical solutions demonstrated the validity and superior capability of the three-layer model in addressing complex heat conduction phenomena. Utilizing the derived semi-analytical solutions, parametric studies were conducted to investigate the influence of geometric and thermal properties on buffer layer temperature maxima. Furthermore, the model was applied to determine optimal disposal container spacing for various nuclear waste types and to simulate the thermal response in Sweden􀆳s prototype repository. The results indicate: (1) inclusion of the bentonite pellet layer increases buffer peak temperature by 14.84 ℃ compared to its exclusion; (2) pellet layer thickness significantly affects temperature maxima due to its relatively low thermal conductivity; (3) buffer temperature variations become negligible when container spacing exceeds 20 m; (4) the proposed solution accurately predicts thermal behavior in prototype repository heating experiments.

To explore the variation of water retention capacity of expansive soil at different temperatures, the calibration curves of Whatman No.42 filter paper were measured by vapor equilibrium method at 5, 25, 40 ℃ and 60 ℃, and the bilinear calibration equation considering temperature effect was established. The results show that the water retention capacity of the filter paper decreases with the increase of temperature, and the effect on the high suction section of calibration curve is weaker than the low suction section. On this basis, Nanning expansive soil is taken as the research object, and the soil-water characteristic curves of Nanning expansive soil at different temperatures are measured by filter paper method. It is found that the water retention capacity of Nanning expansive soil decreases with the increase of temperature, but the influence of temperature depends on matric suction, especially when it is above 40 MPa, the water-retention capacity of Nanning expansive soil remains unchanged with temperatures. To probe into the microscopic mechanism of the change of water retention capacity of Nanning expansive soil under temperature, some samples were selected for mercury intrusion porosimetry test and bound water adsorption test. Based on the test results, the microscopic mechanism of water retention capacity change of Nanning expansive soil was analyzed from the physical mechanism of the interaction between each phase and each phase interface.