# Numerical Simulation of Thermo-Hydro-Mechanical Coupling of Model Test for Nuclear Waste Disposal
## 5 Conclusions  
In this research, we conducted a numerical simulation using the finite element software COMSOL Multiphysics. The coupling phenomenon of multiple THM fields in the unsaturated medium of the buffer layer of an HLW disposal repository was explored. The suction variation of buffer materials in the Mock-up test was significantly influenced by the hydration process. The suction values continued to decrease over time. The variation of porosity ranged from 0.35 to 0.4. Near the heater, the porosity decreased and the buffer layer shrank. At the hydraulic boundary, the porosity tended to increase. The horizontal displacement slowly increased towards the heating direction. After 360 days, the horizontal displacement value of the buffer layer tended to be consistent. The effect of temperature on the buffer layer was great, especially the generation of water vapor around the heater,  
Figure 9: **(a)** Variation curve of swelling pressure with radial distance; **(b)** variation curve of swelling pressure with time.  
which led to an increase in gas pressure inside the buffer layer and a horizontal increase in temperature from the outside to the inside.  
Some of the coupling parameters in the current theoretical model come from Beijing Research Institute of Uranium Geology (BRIUG). The next step requires a series of indoor experiments, which are needed to complete the determination of relevant parameters. In general, the numerical models in COMSOL Multiphysics were able to reproduce the coupled THM behavior of buffer materials in the Mock-up experiments. The models in COMSOL must be continuously validated using valuable data from Mock-up experiments. In order to improve the applicability and accuracy of numerical models, existing models will be further optimized in the future. The influence of moisture content on the mechanical properties of unsaturated soils will be considered to obtain more realistic simulation results of stress and displacement fields. The proposed model can be modified to include the influence of the microstructure alteration during the hydration process on the mechanical behavior of buffer materials. In addition, the application and development of emerging technologies such as artificial intelligence can be considered in the field to improve the authenticity and effectiveness of simulations.  
[PERSON] and [PERSON] designed the overall framework and conceived the idea for this paper, [PERSON] and [PERSON] analyzed the data, [PERSON] and [PERSON] provided some suggestions on the structure of the paper and [PERSON] wrote the paper. All authors have read and agreed to the published version of the manuscript.  
This work was funded by the university-level scientific research project of Yibin University (No. 2023 QH22), Scientific Research Projects of Decommissioning Nuclear Facilities and Radioactive Waste Treatment of the State Administration of Science, Technology and Industry for National Defense (No. 20181521).  
Not applicable.  
The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.  
The authors would like to thank [PERSON] for their assistance in revising the manuscript.  
The authors declare no conflicts of interest.