Abstract This paper studies the influence of the grain size and the notch effect on the fracture of U-shaped notched rock beams through the variation of the apparent fracture toughness. The research is based on an exhaustive campaign that comprises numerical simulations of 300 four-point bending tests, 30 uniaxial compression tests and 60 tensile splitting (Brazilian) tests. Non-porous, isotropic ideal and equivalent rocks with 5 different uniform grain sizes are modelled using the distinct element method, where the rocks are modelled as a discontinuous material, defining explicitly the grains and the boundary conditions. Several notch radii are simulated and the corresponding variation in the apparent fracture toughness is observed. The notch effect is interpreted using the Theory of Critical Distances (TCD), which uses a material intrinsic property called the critical distance ( L ) to evaluate the stress field around the notch tip. The paper shows the variation of the fundamental rock properties with the grain size, the applicability of the TCD to evaluate the notch effect and the correlation between the critical distance and the grain size.

中文翻译：

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粒度对缺口岩梁断裂影响的离散数值分析

摘要 本文通过表观断裂韧度的变化研究了晶粒尺寸和缺口效应对U形缺口岩梁断裂的影响。该研究基于一项详尽的活动，包括 300 次四点弯曲试验、30 次单轴压缩试验和 60 次拉伸劈裂（巴西）试验的数值模拟。使用不同元素方法对具有 5 种不同均匀粒度的无孔、各向同性理想和等效岩石进行建模，其中将岩石建模为不连续材料，明确定义晶粒和边界条件。模拟了几个缺口半径，并观察到表观断裂韧性的相应变化。使用临界距离理论 (TCD) 解释缺口效应，它使用称为临界距离 (L) 的材料固有特性来评估缺口尖端周围的应力场。本文展示了基本岩石性质随粒度的变化、TCD 评估缺口效应的适用性以及临界距离与粒度之间的相关性。