model.zip from Geometry evolution of mesoscopic mechanical structures during the rock fragmentation process induced by tunnel boring machine (TBM) cutters

We investigated the geometric evolution of mesoscopic mechanical structures in rocks during the rock fragmentation process induced by tunnel boring machine cutters. Numerical models were built using a grain-based discrete element method to accurately represent the mesoscopic structures and macroscopic mechanical behaviours of rocks, and the relationship between the mesoscopic evolution and the macroscopic response of rock was determined. The major results are as follows. First, the crushing and re-compaction of the grains were found to mainly occur in the thin crushed zone immediately beneath the cutter tip. Second, the reduction in the bearing ability of the dense core during cutter indentation was due to the order increment of the contact topological structure at the mesoscopic scale. Third, the area percentages of low-and high-order meso-loops decreased and increased, respectively, during the indentation process, and the volume expansion of the dense core was mainly caused by an increase in the internal pore area of high-order meso-loops that have low internal solid fractions. Fourth, the low-order meso-loops primarily bore and transferred the indentation force. Finally, the distribution contour of the meso-loops was found to be an appropriate and intuitive approach for representing the evolution of cracks on a macroscopic scale.本研究针对隧道掘进机刀具诱导的岩石破碎过程中，岩石内部介观力学结构（mesoscopic mechanical structures）的几何演化规律展开探究。本研究采用基于颗粒的离散元法（grain-based discrete element method）构建数值模型，以精准复现岩石的介观结构与宏观力学行为，并阐明岩石介观演化与宏观响应之间的关联机制。主要研究结果如下：其一，颗粒的破碎与重新压实主要发生在刀具刀尖正下方的薄层破碎带内；其二，刀具压入过程中密实核（dense core）的承载能力衰减，源于介观尺度下接触拓扑结构的阶数提升；其三，压入过程中，低阶介观环（meso-loops）的面积占比逐渐降低，高阶介观环的面积占比则逐步升高，密实核的体积膨胀主要源于内部固相占比较低的高阶介观环的内部孔隙面积增大；其四，低阶介观环主要承担并传递压入载荷；最后，研究发现介观环的分布云图可作为一种直观且恰当的表征手段，用以反映宏观尺度下岩石裂纹的演化过程。