Fracture propagation in rocks is a complex thermal-hydro-mechanical (THM) phenomenon present in geotechnics, such as enhanced geothermal systems, CO₂ sequestration, and shale gas exploitation. Numerical simulation is an essential way to study its mechanism. In this study, a pore-scale model combined with the lattice Boltzmann method (LBM) and the discrete element method (DEM) is developed, in which the comprehensive THM coupling phenomena are considered, consisting of convective heat transport, conjugate heat transfer, hydrodynamic force, and thermal strain. In addition, to couple the temperature and anisotropic thermal expansion of rock in LBM-DEM, a novel method based on the deformation of sphero-triangle particle is presented, where the deformation is calculated using the principle of minimum potential energy. The main features of the proposed THM model are that it can accurately calculate the fluid flow in fractures and the temperature in both fractures and DEM particles, and it takes full consideration of multiple anisotropic properties in rock. After validations, the THM fracturing mechanism is preliminarily investigated using the proposed model.

岩石中的裂缝扩展是岩土工程中存在的一种复杂的热-水-机械 (THM) 现象，例如增强型地热系统、CO ₂封存和页岩气开采。数值模拟是研究其机理的重要途径。在这项研究中，开发了一种结合格子 Boltzmann 方法 (LBM) 和离散元方法 (DEM) 的孔隙尺度模型，其中考虑了综合 THM 耦合现象，包括对流传热、共轭传热、流体动力学力和热应变。此外，为了在LBM-DEM中耦合岩石的温度和各向异性热膨胀，提出了一种基于球三角形粒子变形的新方法，该方法利用最小势能原理计算变形。提出的THM模型的主要特点是可以准确计算裂缝中的流体流动以及裂缝和DEM颗粒中的温度，充分考虑了岩石的多种各向异性特性。经过验证，利用所提出的模型对THM压裂机理进行了初步研究。