冲击荷载作用下岩石裂纹扩展的机理分析与FD-PDM数值模拟

This project is focus on the rock crack propagation characteristics under impact loading. Impact compression experiments, as well as FD-PDM (Peridynamics method coupled with finite-difference method) simulation are carried out in order to investigate crack propagation law and dynamic mechanism in rocks containing pre-cracking. First, based on a 50 mm diameter SHPB test platform, impact compression tests of rock specimens containing pre-existing cracks with different lengths, dip angles, and numbers are conducted. The strain signals of rock specimen are recorded by super-dynamic strain gauge, and the crack propagation process is observed in real time using high-speed camera. The effects of crack length, dip angle and number on crack propagation are analyzed. The cracked surface of the damaged specimen will be scanned using scanning electron microscope (SEM), and the crack propagation patterns will be classified microscopically, to reveal the dynamic mechanism of the crack propagation. Secondly, via improving the numerical dispersion properties of Peridynamics, a coupling algorithm of FDM and PDM is established to perform highly efficient simulation of rock crack propagation. In this project, the research of rock crack propagation characteristics is extended from low strain rate to a higher strain rate, which can provide important theoretical basis and high-efficiency numerical algorithm for the study of rock failure characteristics under strong disturbance (rock burst or blasting) conditions.

本项目围绕动载条件下岩石裂纹扩展特性，采用冲击压缩实验研究和有限差分-近场动力学法(FD-PDM)耦合数值模拟，探讨岩石裂纹扩展规律及动力学机理。首先，基于50mm杆径的SHPB试验平台，开展含不同长度、倾角、数目的预制裂纹岩石冲击压缩试验。利用超动态应变仪记录岩石试样应变信号，借助高速摄像机实时观测裂纹扩展过程，分析裂纹长度、倾角、数目对裂纹扩展的影响。对破坏后的试样进行开裂面局部切片电镜扫描，从微观上得到岩石裂纹扩展模式分类，揭示扩展的动力学机制。其次，通过改善近场动力学法数值频散性质，建立FD-PDM耦合算法，对岩石裂纹扩展进行高效模拟。本项目将岩石裂纹扩展特性的研究扩展到更高应变率段，可为强扰动(岩爆或爆破)条件下的岩体破坏特性研究提供重要理论依据和高效数值算法。

岩体作为构建地下空间的主要材料，其变形与破坏机理与地下工程稳定性密切相关。地震、爆破、“岩爆”等动载作用下岩体破坏机制更为复杂，不能完全套用静力学理论进行分析。本研究针对动载条件下岩石裂纹扩展特性，采用冲击压缩实验研究和有限差分-近场动力学法(FD-PDM)耦合数值模拟，探讨岩石裂纹扩展规律及动力学机理。利用傅里叶变换等解析方法分析PDM数值频散特性，考察了影响域尺寸、微弹模形式、空间步长、频率等对PDM数值频散特性的作用规律，研究了减弱数值频散的方法。利用波动理论，研究了FDM与PDM耦合交界面波阻抗差异的机制，编制了FD-PDM耦合计算程序，并对程序进行了验证。发展了传统的圆域PDM（二维），提出了方域PDM，分析了两者模拟结果的异同。利用50mm直径SHPB实验系统开展了含预制裂缝岩石的冲击压缩试验，结合超高速摄影技术和超动态应变测试技术，研究岩石内裂纹扩展路径、扩展模式。利用FD-PDM耦合算法对所开展实验进行模拟，结合超高速摄影观察，对岩石中裂缝扩展特性与力学机理进行综合分析。本研究可为强扰动(岩爆或爆破)条件下的岩体破坏特性研究提供高效数值算法。