In this study, a 3D coupled FEM-DEM method was adopted to study the influence of thermal-induced damage on the mechanical properties of fractured rock mass. In this method, the rock matrix was discretized into bulk elements bridged by cohesive elements, and the preexisting fractures were represented by cohesive elements. The thermal-induced damage process was modeled through two parts, i.e., thermal conduction and thermal-mechanical coupling. For thermal conduction process, a proposed 3D thermal-cohesive coupled model with a fracture aperture-dependent interfacial thermal conductivity was adopted to simulate the thermal conduction across the fractures, which make it possible to more precisely predict the temperature distribution. Then, the thermal stress induced by temperature variation was coupled to perform the mechanical-failure calculation. Validation simulations indicated that the proposed model is capable of dealing with the thermal-induced damage problems. Then, the influences of fracture aperture on thermal-induced damage in highly fractured rock mass were numerically investigated by the Brazilian disc tests with multiple randomly distributed fractures. The results indicated that as the fracture aperture increases, the area of thermal-induced damage zone increases and the Brazilian tensile strength (BTS) decreases nonlinearly.

在这项研究中，采用3D耦合FEM-DEM方法来研究热损伤对裂隙岩体力学性能的影响。在这种方法中，将岩石基质离散为由内聚力单元桥接的块体单元，并以内聚力单元表示先前存在的裂缝。通过两个部分对热致破坏过程进行建模，即热传导和热机械耦合。对于热传导过程，采用了建议的3D热固耦合模型，该模型具有与裂缝孔径有关的界面热传导率，以模拟跨裂缝的热传导，从而可以更精确地预测温度分布。然后，耦合由温度变化引起的热应力，以执行机械故障计算。验证仿真表明，所提出的模型能够处理热致损伤问题。然后，通过巴西圆盘试验对多个随机分布的裂缝进行数值研究，研究了裂隙孔径对高裂隙岩体中热致破坏的影响。结果表明，随着断裂孔径的增大，热损伤区域的面积增大，巴西拉伸强度（BTS）非线性减小。