Based on multi-level force chain network analysis: investigation on the mineral volume proportion effect of granite subjected to uniaxial compression

To quantitatively analyze the mineral volume proportion effect of the compression characteristics of granites under loading, a novel three-dimensional grain-based model based on particle flow code is proposed to restore the internal structure of granites. The whole force chain network of the sample is divided into multiple levels, and the value, number and orientation distribution of force chains in intragranular/intergranular structures are quantitatively explored. The variation rules of uniaxial compressive strength and micro-cracking behavior of numerical samples with different volume proportion of quartz (V_Q) are analyzed in force chain point of view, and the mineral volume proportion effect on load-bearing capacity and fracture resistance of various structures is quantized. The results show that when the number of contacts is basically unchanged, the decrease in the general force chain (GF) number can characterize the increase in the microcrack number. The orientation distribution of GF is relatively uniform. The overall level of the force chain network increases with the increase of V_Q. The main orientation distribution of the high-strength force chain (HF) is consistent with the loading direction and is orthogonal to that of cracks. The number of HF can well characterize the macroscopic mechanical properties of the sample. This study defines a load-bearing capacity index (P_HF/GF). It is found that P_HF/GF increases with the increase of V_Q, that is, the higher the load-bearing capacity. The relationship between micro-tension strength (σ_micro) and P_HF/GF value is also discussed.