A CT-XRD-based thermo-mechanical coupling DLSM for quantitative analysis of extreme temperature-induced damage in rocks

Abstract

The extreme temperature damage of rocks is critical in various fields such as liquefied natural gas storage, geothermal extraction, and lunar surface exploration. However, efficient analytical methods for such extreme temperature ranges are lacking. To address this challenge, we propose a thermo-mechanical coupling Distinct Lattice Spring Model (DLSM) based on computerized tomography (CT) and X-ray diffraction (XRD) analyses. This approach enables the modeling of rock structures by integrating CT imaging with XRD mineral composition analysis, accounting for factors like pore distribution, porosity, ice saturation, mineral composition, and their corresponding strength distributions. By embedding this model into the thermo-mechanical DLSM, thermal damage simulations can be performed. The proposed method is validated through analytical solutions and experimental results, demonstrating its reliability. Parametric simulations were conducted, leading to several key conclusions. For low-porosity sandstone, the damage variable exhibits minimal change with temperature or saturation. Conversely, for high-porosity sandstone, temperature significantly influences damage. In the early cooling stage, the damage variable decreases sharply, while in later stages, the decrease is more gradual. The damage variable shows slight decreases with saturation and porosity but drops significantly after reaching critical thresholds for both. The study reveals further cooling damage mechanisms, including the effects of mineral shrinkage, ice expansion, temperature, porosity, and saturation. The weakening of damage with decreasing temperature is attributed to stress concentration relief and the reduction in the absolute coefficient of thermal expansion. This method offers a promising analytical tool for assessing thermal damage in rocks under extreme temperature conditions.