层状岩体力学特性及PFC模拟研究进展

Advances in the Study of Mechanical Properties and PFC Simulation of Layered Rock Masses

摘要: 非常规油气资源的高效开发依赖水力压裂形成复杂裂缝网络，然而层状岩体的强各向异性导致裂缝扩展行为复杂、井壁失稳频发。文章首先系统综述了岩石断裂韧性理论、层状岩体力学特性及PFC数值模拟的研究进展。回顾了经典断裂准则(最大周向应力/应变准则、能量类准则)及I型断裂韧性测试方法，指出现有准则主要面向均质材料，对层理各向异性考虑不足。其次，总结了层状岩体强度、变形与破坏模式的倾角依赖性，分析了岩层厚度比、围压、界面性质等关键影响因素及各向异性强度准则。再次，阐述了PFC离散元方法在岩石宏细观力学行为模拟中的应用优势与局限性，对比了不同接触模型的适用性。最后，指出当前研究在层状岩体各向异性断裂准则、方向性断裂韧性测试、细观穿层机理等方面存在的不足，并展望了建立考虑层理真实形态的数值模型、闭环研究流程的未来方向。

Abstract: The efficient development of unconventional oil and gas resources relies on hydraulic fracturing to create complex fracture networks. However, the strong anisotropy of layered rock masses leads to complex fracture propagation behavior and frequent borehole instability. This paper first systematically reviews the research progress on rock fracture toughness theory, the mechanical properties of layered rock masses, and PFC numerical simulation. Classical fracture criteria (maximum tangential stress/strain criteria, energy-based criteria) and mode I fracture toughness testing methods are reviewed. It is pointed out that existing criteria are mainly oriented to homogeneous materials and insufficiently consider bedding anisotropy. Secondly, the dip-angle dependence of strength, deformation, and failure modes of layered rock masses is summarized, and key influencing factors such as rock layer thickness ratio, confining pressure, interface properties, as well as anisotropic strength criteria are analyzed. Thirdly, the application advantages and limitations of the PFC discrete element method in simulating macro- and micro-mechanical behaviors of rocks are elaborated, and the applicability of different contact models is compared. Finally, the deficiencies in current research regarding anisotropic fracture criteria for layered rock masses, directional fracture toughness testing, and meso-scale cross-layer mechanisms are identified, and future directions are proposed, including the establishment of numerical models considering the true morphology of bedding and closed-loop research workflows.