基于多级力链网络分析的花岗岩压缩特性的矿物尺寸效应研究

Investigation on the grain size effect of the compression characteristics of granites based on the multi-level force chain network

为定量分析花岗岩受载时压缩特性的矿物尺寸效应,利用基于颗粒流思想的三维等效晶质模型还原花岗岩内部结构。试样整体力链网络实现了多级划分,各种晶内结构及晶间结构内力链的值、数量、倾向被定量分析。从力链角度分析试样单轴抗压强度、微裂纹特征、各类结构的承载能力及抗破裂能力的矿物尺寸效应。研究结果表明:当接触数量基本不变的情况下,加载过程中的一般力链数量下降量与微裂纹的上升量有较好地相关性。各类一般力链的倾向分布较为均匀。力链网络整体水平随矿物尺寸的上升呈上升趋势。强力链的主要倾向与加载方向一致,且与裂纹主要倾向呈明显地正交关系。强力链的数量可以很好地表征试样的宏观力学特性。完整矿物及晶间结构的承载能力均随矿物尺寸的上升而提高,且变化范围与接触的微观拉伸强度呈正比。完整矿物结构产生单个裂纹所需的强力链数量随矿物尺寸的上升而上升,即抗破裂能力上升,但晶间结构的抗破裂能力并无明显变化。

To quantitatively analyze the grain size effect of the compression characteristics of granites under loading,a three-dimensional grain-based model based on particle flow code is used to restore the internal structure of granites.The whole force chain network of the sample is divided into multiple levels.The value,number and orientation distribution of force chains in intragranular structures and intergranular structures are quantitatively explored.The grain size effect on uniaxial compressive strength,micro-cracking behavior,load-bearing capacity and fracture resistance of various structures is quantized in force chain point of view.The results show that when the number of contacts is basically unchanged,the decrease in the general force chain(GF)number and the increase in the microcrack number have a good correlation.The orientation distributions of various GFs are relatively uniform.The overall level of the force chain network increases with the increase of RG.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.The load-bearing capacity of intact minerals and intergranular structures increases with the increase of RG,and the variation range is proportional to the micro-tension strength of internal contacts.The number of HF required to produce a single crack in intact mineral structures increases as RG increases,that is,the fracture resistance increases,but the fracture resistance of intergranular structures do not change significantly versus RG.