Thermal damage mechanism and numerical simulation verification of sandstone by 3D reconstruction on CT images

Abstract:

In complex geological environments such as deep layers, the mechanical and damage characteristics of rocks have a decisive impact on the development of high-temperature engineering. To further explore the mechanical properties of high-temperature rocks and their damage mechanisms under load, this study delves into yellow sandstone samples exposed to varying temperatures (25 ℃, 200 ℃, 400 ℃, 600 ℃, 800 ℃). Based on X-ray tomography (CT) technology, obtain internal pore data and 3D model of yellow sandstone, analyze the variation law of porosity of yellow sandstone with temperature. Additionally, numerical simulations were executed to delve into the evolution of microcracks and the damage mechanisms inherent in yellow sandstone under distinct temperature conditions. This microscopic approach unveils the thermal damage mechanisms of rocks under high temperatures. Key findings include: as temperature rises, the total porosity of yellow sandstone follows a quadratic growth trend, accompanied by a decrease in pore distribution uniformity. The main factors of thermal damage in yellow sandstone include: high-temperature dehydration, thermal decomposition of mineral components, and expansion of mineral particles. The increase in porosity due to thermal decomposition and particle expansion is a key factor in thermal damage. Between 25400 ℃, differential expansion and compression of mineral grains generate localized stress zones, predominantly fostering intergranular cracks within yellow sandstone. In the 400-800 ℃ range, phase transitions and mineral component decomposition within yellow sandstone amplify these stress zones, favoring intragranular crack propagation. A damage evolution model of yellow sandstone under thermal action was constructed by defining the damage variable based on the porosity of yellow sandstone, which can provide theoretical basis and technical support for the study of damage mechanism in high-temperature rock mechanics.