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.

本研究围绕隧道掘进机（Tunnel Boring Machine, TBM）滚刀破岩过程中岩石内部细观力学结构的几何演化规律展开系统探究。为精准复现岩石的细观结构与宏观力学行为，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，明确了岩石细观演化与宏观力学响应之间的内在关联。主要研究结果如下：其一，颗粒的破碎与重新压实主要集中于滚刀刀尖正下方的薄层破碎带内；其二，滚刀压入过程中密实核承载能力的衰减，源于细观尺度下接触拓扑结构的阶数提升；其三，压入过程中，低阶与高阶细观环（meso-loops）的面积占比分别呈下降与上升趋势，密实核的体积膨胀主要由内部固相分数较低的高阶细观环的内部孔隙面积增大所引发；其四，低阶细观环主要承担并传递压入载荷；最后，细观环的分布轮廓可作为一种精准且直观的表征手段，用于反映宏观尺度下裂纹的演化进程。