复杂应力状态下三维弯折裂纹扩展规律及力学特性的研究

Three-dimensional kinked fissures are widely exists in rock mass. Under external load and ground stress, kinked fissures may propagate and coalesce, resulting into failure of rock mass. Due to the geometric complexity of three-dimensional kinked fissures and the heterogeneity of rock materials, this failure mechanism is not well understood by applied conventional fracture mechanics. This proposal adopts 3D printing technique and produces three-dimensional kinked fissure specimens based on transparent resin materials. Low temperature treatments are considered for enhance the brittleness of the specimen. Moreover, based on a triaxial loading test system, the crack propagation, coalescence and failure modes of the rock mass are investigated for revealing the failure mechanism of the rock mass with three-dimensional kinked fissures and concluding the instability patterns. Furthermore, numerical investigations are conducted for verifying the summarized test results and assisting to build failure criteria of the three-dimensional kinked fissures. The mechanical properties of the rock mass with different three-dimensional kinked fissures are discussed. It has important guiding significance for understanding the deformations, strengths and failure properties of jointed rock mass.

三维弯折裂纹广泛存在于岩体中，在外载荷或地应力作用下，弯折裂纹可能扩展、贯通，进而造成岩体破坏。由于三维弯折裂纹的几何复杂性及岩石材料的不均质性，传统断裂力学方法无法提供足够三维理论支持，其破坏模式和断裂机理不明确。本项目采用3D打印技术，基于透明光敏树脂材料制备含三维弯折裂纹类岩石试件。对打印后的透明光敏树脂试件进行低温处理以提高其脆性，进而研究它的力学特性；通过真三轴加载室内模型试验，研究三维弯折裂纹的起裂扩展、贯通和破坏模式，揭示复杂应力状态下三维弯折裂纹失稳破坏的力学机制，总结典型的失稳模式；运用试验模型验证数值计算结果，并对试验数据进行拟合，建立参数空间下的三维弯折裂纹开裂判断准则。项目成果探讨不同几何形态下三维弯折裂纹的力学特性，所获得的试验现象和结果对研究节理岩石的变形、强度和破坏特性具有重要的指导意义。

地下深部工程中潜在的失稳和破坏威胁与潜在的大量直/非直裂缝、裂缝和/或其他缺陷有关。裂隙的类型和程度对整个场地的力学行为和变形有重要影响，裂隙通常在荷载作用下由裂隙合并而成。因此，本文研究了s形裂纹的起裂和贯通行为及机理，揭示了非直缝的破坏特征。通过三维打印试样的单轴拉伸试验和数值模拟，研究了不同几何参数(倾角β和有效曲率A/ c)对s形裂纹的影响。s形裂纹的裂纹合并只发生在拉伸裂纹中，而s形裂纹的尖端裂纹和非尖端裂纹模式可以根据裂纹的起裂位置来识别。研究发现，斜角和有效曲率对s形裂隙的破坏模式有重要影响。基于实验结果，进行了大量的数值模拟来预测裂纹模式，如尖端裂纹/非尖端裂纹。在大量数值计算的基础上，提出了一种合理有效、快速识别单轴拉伸下s形裂隙A/ c - β参数的开裂模式的判据准则。本研究为非直裂纹的理论研究提供有价值的实验参考和依据。