Obtaining complete rock cores is exceptionally challenging in certain extreme environments, such as deep earth and deep space; consequently, it is difficult to obtain the macro strengths of rock, which are the key indexes for engineering design, via standard rock mechanical tests. This research indicates that by determining and leveraging the mechanical properties of grains and grain-to-grain interfaces, the rock macro strength can be effectively estimated. Nanoindentation tests were first conducted to determine the elastic modulus of the mineral grains and their interfaces. Subsequently, symmetrical and anti-symmetrical four-point bending tests were executed to establish the statistical law governing interfacial tensile and shear fracture toughnesses. Furthermore, by employing the Dugdale–Barenblatt model and considering the oblique angular distribution of interfacial cracks, the corresponding tensile strength, shear strength, and friction parameter were derived. These meso‑mechanical parameters were then inputted into the 3D Finite-Discrete Element Method to estimate rock macro strength. And the numerical results were then compared with the results of standard uniaxial compression, direct tension, Brazilian splitting, and direct shear tests. The consistency observed between the predictions and experimental results attests to the validity of the proposed method.

中文翻译：

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根据确定的颗粒和颗粒间界面的力学特性估计岩石的宏观强度

在某些极端环境下，例如地球深处和深空，获得完整的岩心是非常具有挑战性的；因此，通过标准的岩石力学试验很难获得作为工程设计关键指标的岩石宏观强度。这项研究表明，通过确定和利用颗粒和颗粒间界面的力学特性，可以有效地估计岩石的宏观强度。首先进行纳米压痕测试以确定矿物颗粒及其界面的弹性模量。随后，进行对称和反对称四点弯曲试验，建立界面拉伸和剪切断裂韧性的统计规律。此外，采用Dugdale-Barenblatt模型并考虑界面裂纹的斜角分布，推导了相应的拉伸强度、剪切强度和摩擦参数。然后将这些细观力学参数输入到 3D 有限离散元方法中，以估计岩石宏观强度。然后将数值结果与标准单轴压缩、直接拉伸、巴西劈裂和直接剪切试验的结果进行比较。预测与实验结果之间的一致性证明了所提出方法的有效性。