Influence of Mesoscopic Defects on the Mechanical Behaviour of Granites Based on a Three-Dimensional Multilevel Force Chain Network

In this paper, a novel three-dimensional grain-based model based on particle flow code (PFC3D-GBM) is used to reconstruct the crystalline structure of granite, which enables the grouping and filling of minerals. Some contacts in the numerical sample are grouped separately and then calibrated with lower microparameters, which represent mesoscopic defects within natural granites. In addition, considering the heterogeneity of the levels of force chain networks in different structures of granites, a multilevel classification of the entire force chain network is accomplished. A uniaxial compression test is conducted to quantify the effect of the microtensile strength σD and volume proportion VD of mesoscopic defects on the macroscopic mechanical behaviour of granites at various points of the force chains. Both the strength and modulus of the sample increase as σD increases. The mean, sum and maximum of the general force chains of the intact structures and defect structures increase with increasing σD. The bearing capacity of various structures also increases. Both the strength and modulus of the sample decrease as VD increases, and the strength of the overall force chain network decreases. The mean, sum and maximum values of the general force chains of the intact structures decrease. Although the number of force chains in the corresponding defect structures greatly increases, the average level of the force chain network decreases. The bearing capacity of the various structures decreases as VD increases.