Evolution of rock heterogeneity under coupled stress-temperature gradient loading and implications for underground cryogenic storage

Abstract

Underground cryogenic storage can be a critical energy infrastructure of urban cities for the survival and recovery of energy supply from severe natural disasters and extreme weather events. The efficiency of underground cryogenic storage is essential to ensure the balance between energy input and output and dependent highly on the thermo-mechanical responses of containment materials. This study investigated the evolution of strain field heterogeneity of Chanceaux limestone under the defect (e.g., circular hole) and stress-temperature gradient effects using a temperature gradient test system. We performed 4 suites of temperature gradient experiments, including the thermo-loading and thermo-unloading experiments on intact and flawed specimens, respectively, under different combinations of axial stress (0.75–3.50 MPa) and temperature gradient (56–298 °C/m), taking underground liquefied natural gas storage as the background. We computed the axial strain in the region of interest for each experiment based on the digital image correlation analysis and derived the coefficients of strain field heterogeneity in the mechanical loading and unloading sequences. The results show that the coefficient of strain field heterogeneity can be amplified with the presence of pre-existing defects, a lower axial stress, and a higher temperature gradient. Our findings highlight that understanding the evolution of rock heterogeneity is important to ensure the integrity of containment materials and the efficiency of underground cryogenic storage.