CT三维重构下砂岩热损伤机理及数值模拟验证

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

摘要:

在深部等复杂地质环境中,岩石力学特性及损伤特性对高温工程的开展具有决定性影响,为深入探究高温岩石的力学性能及其在受载过程中的损伤机理,以不同温度(25、200、400、600、800 ℃)作用后的黄砂岩为研究对象,基于X射线断层扫描技术(CT)获取黄砂岩内部孔隙数据及三维模型,分析黄砂岩孔隙率随温度变化规律,结合数值模拟探究黄砂岩微裂纹演化规律及损伤机理,从微观层面揭示高温作用下岩石热损伤机理。结果表明:随温度升高,黄砂岩总孔隙率呈二次函数形式增长,面孔隙率均匀度随之降低；黄砂岩产生热损伤的主要因素包括高温脱水、矿物成分热分解、矿物颗粒膨胀；热分解及颗粒膨胀导致的孔隙率增加是造成热损伤的关键因素；25~400 ℃阶段,不同矿物颗粒膨胀挤压,导致局部应力区域出现,黄砂岩内部裂纹以晶间裂纹为主；400~800 ℃阶段,黄砂岩内部矿物成分相变、分解,导致局部应力区域增大,黄砂岩内部裂纹以晶内裂纹为主。以黄砂岩孔隙率定义损伤变量,构建了热作用下黄砂岩损伤演化模型,可为高温岩石力学的损伤机理研究提供理论基础和技术支撑。

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.