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Influence of grain size and basic element size on rock mechanical characteristics: insights from grain-based numerical analysis
Bulletin of Engineering Geology and the Environment ( IF 4.2 ) Pub Date : 2022-08-04 , DOI: 10.1007/s10064-022-02856-z
Tao Zhang, Liyuan Yu, Yuxuan Peng, Minghe Ju, Qian Yin, Jiangbo Wei, Shiping Jia

The mechanical properties of rock materials are closely related to their heterogeneous internal structure. It is necessary to reproduce the internal structure of rock materials in more realistic models to learn more about their mechanical properties. In this paper, using the three-dimensional particle flow code (PFC) developed by Itasca, a novel grain-based model (GBM) is proposed to group and fill mineral grains. Then, the GBM is used in numerical simulations of uniaxial compression tests to investigate the influence of grain size and basic element size on the distributions of contacts and microcracks and the mechanical behaviour of numerical samples. The numerical results show that based on the proposed GBM, the heterogeneous structure of granite can be reproduced in a more realistic way by the multilevel division of contacts and microscale cracks. The stress–strain curves of the numerical samples with different grain sizes and basic element sizes can be divided into three stages during loading, including the elastic deformation, nonlinear deformation and post-peak softening stages. As the grain size increases, the number of basic elements contained within a single mineral grain increases. As a result, the number of intragranular contacts increases with increasing bond micro-strength. The external load required to cause macroscopic failure of a sample increases as the number of intragranular cracks increases. As the basic element size increases, the number of basic elements contained within a single mineral grain decreases, and the contact distribution density is significantly smaller. The number of contacts to be fractured decreases when macroscale fracturing of a sample occurs, which leads to a decrease in the value of the external load.



中文翻译:

晶粒尺寸和基本元素尺寸对岩石力学特性的影响:基于晶粒的数值分析的见解

岩石材料的力学性能与其异质的内部结构密切相关。有必要在更真实的模型中重现岩石材料的内部结构,以了解更多关于其力学性能的信息。本文利用Itasca开发的三维粒子流代码(PFC),提出了一种新的基于颗粒的模型(GBM)对矿物颗粒进行分组和填充。然后,将GBM用于单轴压缩试验的数值模拟,研究晶粒尺寸和基本元素尺寸对接触和微裂纹分布以及数值样品力学行为的影响。数值结果表明,基于所提出的 GBM,花岗岩的异质结构可以通过接触和微观裂缝的多级划分以更真实的方式再现。不同晶粒尺寸和基本单元尺寸的数值试样的应力-应变曲线在加载过程中可分为弹性变形、非线性变形和峰后软化三个阶段。随着晶粒尺寸的增加,单个矿物颗粒中所含的基本元素的数量也会增加。结果,晶内接触的数量随着键合微观强度的增加而增加。导致样品宏观失效所需的外部载荷随着晶内裂纹数量的增加而增加。随着基本元素尺寸的增加,单个矿物颗粒中包含的基本元素数量减少,并且接触分布密度明显更小。当样品发生宏观断裂时,要断裂的触点数量减少,这导致外部载荷值下降。

更新日期:2022-08-05
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