A temperature gradient test system for investigating thermo-mechanical responses of containment materials of underground storage facilities

Underground energy storage is a promising option for the global ambition of moving towards carbon neutrality. To achieve safe and reliable energy storage in underground caverns, it is essential to understand the contributions of thermal and mechanical loads to the deformation of containment materials (e.g., concrete and geomaterials) and to forecast potential risks related to unexpected failure of these materials. A temperature gradient test system is developed to investigate the thermo-mechanical responses of containment materials under simulated temperature gradient and earth pressure conditions. The test system has advantages of establishing a temperature gradient of over 400 ​°C/m across a large-scale specimen and examining the resulting strain based on the digital image correlation analysis. This study sheds light on 3 typical applications of the test system to examine the thermal and mechanical responses of intact limestone, flawed limestone, and fractured concrete. The results demonstrate that the mechanical load mainly controls the strain evolution of the intact limestone, while the thermal load strongly affects the strain evolution around the circular hole. The failure pattern of concrete primarily influences the mechanically induced strain, and the thermally induced strain is insensitive to the concrete failure. This test system can be modified and upgraded to study various research topics related to underground energy storage.