多尺度内聚颗粒模型破碎过程研究

岩石破碎过程涉及到多个变量（应力、应变和孔隙率等）变化和裂纹的产生、拓展和聚集，是研究岩石破碎机制的重要途径。为了克服现有研究中岩石颗粒模型未考虑岩石内部特征问题，针对岩石内部颗粒非均匀分布、聚集的特点，开展了岩石轴压破碎试验和岩石岩相分析试验，并在此基础上，构建符合真实岩石内部特征的多尺度内聚颗粒模型。根据离散元的颗粒黏结模型（BPM）理论，求解了多尺度内聚颗粒模型不同粒级颗粒间黏结键的力学关系，发现与二级颗粒形成的黏结键断裂判据为 ≥ 2 GPa，三级颗粒之间形成的黏结键断裂判据为 ≥ 6 GPa，并基于该判据建立了用于模拟颗粒模型破碎的演化模型。通过模拟轴压破碎试验，破碎演化模型可以从细观角度得到颗粒模型各颗粒间黏结键承受力的实时变化和岩石破碎过程中黏结键从外而内的断裂顺序；从宏观角度得到岩石内部裂纹呈V形从上表面两端延伸并相交于岩石中部。通过与岩石轴压破碎试验结果对比发现，模拟试验得到的岩石裂纹特征与岩石轴压破碎试验结果相似，验证模型的可靠性，实现了从细观和宏观角度分析岩石破碎过程。

Investigation into the crushing process in multi-scale cohesive particle model

The rock crushing process involves the variation of multiple variables (stress, strain, porosity, etc.) and generation, expansion and accumulation of cracks. It is an effective way to study the mechanism of rock consumption. In order to improve the rock granule model in the existing literature, the internal characteristics of rock materials should be considered. In order to characterize non-uniform distribution and accumulation of particles inside the studied rock, rock axial crushing experiment and rock lithofacies analysis were carried out. On this basis, a multi-scale cohesive particle model conforming to the internal characteristics of the real rock was constructed. According to the BPM theory of discrete elements, the mechanical relationship between the bonds of particles with different grain sizes in the multi-scale cohesive particle model was solved. It is found that the bond breaking criterion formed by the secondary particles is ≥ 2 GPa, and this criterion formed between the tertiary particles is ≥ 6 GPa. On this basis, an evolution model for simulating fragmentation of the particle model is established. By simulating the axial crushing experiment, the fracture evolution model can predict (i) the real-time changes of the bearing force on bond between the particles in the particle model from the mesoscopic point of view and (ii) the fracture sequence of the bond from the outside to the inside during the rock crushing process. It has a V shape extending from both ends of the upper surface and intersecting the middle of the rock. The rock crack characteristics simulated by the proposed method are found to be in a good agreement with the experimental results from rock axial crushing tests. The reliability of the model is verified, and the rock crushing process is analyzed from the microscopic and macroscopic perspectives.