Electrical Resistivity Changes During Heating Experiments Unravel Heterogeneous Thermal‐Hydrological‐Mechanical Processes in Salt Formations

• Published in: Geophysical research letters Vol. 51; no. 14
• Main Authors: Chen, Hang, Wang, Jiannan, Luo, Linqing, Otto, Shawn, Davis, Jon, Kuhlman, Kristopher L., Wu, Yuxin
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 28.07.2024; American Geophysical Union (AGU); Wiley
• Subjects: Cluster analysis; Clustering; Dredging; Electrical resistivity; electrical resistivity tomography; Excavation; Heat; Heating; Heterogeneity; hydrogeophysics; Hydrologic processes; Hydrology; Parameterization; Performance assessment; Performance testing; Prediction models; Properties; Radiation damage; radioactive waste; Radioactive waste disposal; Radioactive wastes; Rock; rock salt; Rocks; Salt; Salts; THM processes; Time measurement; Tomography; Waste disposal; Water flow
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2024GL109836

Rock salt is considered a suitable medium for the permanent disposal of heat‐generating radioactive waste due to its isolation properties. However, excavation damage and heating induce complex and heterogeneous thermal‐hydrological‐mechanical (THM) processes across different zones. Quantifying this heterogeneity is crucial for accurate long‐term performance assessment models, but traditional methods lack the necessary resolution. This study employs 4D electrical resistivity tomography (ERT) monitoring during controlled heating experiments in a salt formation to unravel the spatiotemporal dynamics of THM processes. Advanced time‐lapse inversion and clustering analysis quantify subsurface properties and map the heterogeneity of THM dynamics. The ERT results can estimate subsurface properties and delineate the damaged and intact zones, enabling appropriate parameterization and representation of processes for long‐term modeling. This approach may be used in further improving the predictive models and ensuring the safe long‐term disposal of radioactive waste in rock salt. Plain Language Summary Rock salt is great for the disposal of heat‐generating radioactive waste because it prevents releasing harmful radiation into the environment. However, mining and heating can cause complex changes in temperature, water flow, and pressure, affecting rock salt in various ways. It is important to understand these changes accurately for planning how the disposal will affect the rock salt, but the traditional ways of studying them are not detailed enough. In this study, we used a special technique called 4D ERT while heating up the rock salt to see how these changes happen over time and space. We analyzed the data in advanced ways to measure the underground properties and understand the complex changes. The information can improve how we model and plan the disposal of heat‐generating waste. This new insight makes it easier to ensure that storing heat‐generating radioactive waste in rock salt is safe for a long time. Key Points We employ 4D electrical resistivity tomography (ERT) monitoring during a controlled heating experiment in salt formations The resistivity data exhibits contrasting trends throughout and post‐heating, indicating the heterogeneous thermal‐hydrological‐mechanical processes in rock salt are likely linked to the different levels of excavation damages Employing time‐series clustering technology enables quantification and spatial distributions of excavation damage/disturbed zones within the salt formations which may help further improve the parameterization of long‐term predictive models