Geological energy storage using subsurface porous rock is a feasible alternative that could satisfy the needs of future large-scale seasonal energy storage, where the petrophysical and mechanical properties of cap rock is vital to ensure safe and sustainable storage of energy. Shale rock is a typical cap rock for geological storage, but its failure behaviors have not been fully understood due to its severe heterogeneity and anisotropy. Numerical simulation methods have been widely acknowledged as an accurate and effective approach to investigate the mechanical and failure behaviors of different materials. For this purpose, this paper developed a numerical model to simulate the failure process of shale specimen when subjected to triaxial compression stresses. The deformation and strength features, progressive failure processes and corresponding acoustic emission (AE) response are obtained by numerical simulation. The performance of the numerical model is validated by experimental data. Simulation results suggest that the failure events which are accompanied by forming micro-fissures are randomly distributed on the specimen at the initial fracture stage. The failure patterns of shale can be summarized into three types, including shear failure, slip failure and splitting failure. The local fractures resulting from the growth of micro-cracks are the sources of shear failure. But high confining pressure has an inhibitory effect on the extension of parts of macroscopic fractures and may induce the contact between fracture surfaces to be rebuilt. While slip failure is caused by the structural surface destruction and the failure plane follows an irregular path that jumps between the bedding plane and the matrix. The propagation of micro-cracks parallel to the bedding plane is the governing factor of tensile failure. That means numerical modeling can be able to reproduce the triaxial test results to a large extent and reflect the rock failure process in detail, and it can help us to understand the macro- and meso‑properties of cap rock for geological energy storage.

使用地下多孔岩石进行地质储能是一种可行的替代方案，可以满足未来大规模季节性储能的需求，盖层的岩石物理和力学特性对于确保安全可持续地储能至关重要。页岩是典型的地质储层盖层岩，但由于其严重的非均质性和各向异性，其破坏行为尚未得到充分的认识。数值模拟方法已被广泛认为是研究不同材料的机械和失效行为的准确有效的方法。为此，本文建立了一个数值模型来模拟页岩试样在三轴压缩应力作用下的破坏过程。变形和强度特征 通过数值模拟获得了渐进式破坏过程和相应的声发射（AE）响应。通过实验数据验证了数值模型的性能。仿真结果表明，在断裂初期，伴随着微裂纹形成的破坏事件是随机分布在试样上的。页岩的破坏模式可以归纳为三种类型，包括剪切破坏，滑动破坏和劈裂破坏。由微裂纹的增长引起的局部裂缝是剪切破坏的根源。但是，高围压对宏观裂缝的部分扩展具有抑制作用，并且可能导致裂缝表面之间的接触被重建。虽然滑移破坏是由结构表面破坏引起的，但破坏平面遵循的不规则路径会在垫层平面和基体之间跳跃。平行于顺层平面的微裂纹的传播是拉伸破坏的决定因素。这意味着数值建模可以在很大程度上再现三轴测试结果并详细反映岩石破坏过程，并且可以帮助我们了解用于地质储能的盖层岩的宏观和细观性质。