Abstract Cubic specimens of granite, marble, and sandstone, with side lengths of 50 mm, were prepared in the laboratory. True triaxial compression tests were conducted on each rock type with minor principal stress (σ3) magnitudes of 10, 20, 30, 50, and 100 MPa and the intermediate principal stress (σ2) varying from σ2 = σ3 to σ2 = σ1 (where σ1 represents the major principal stress). The experimental results demonstrated that the failure strength, fracture dip angle, non-linear behavior and failure mode of these rocks under true triaxial conditions were affected by both σ2 and σ3, as well as by the rock lithology. When σ3 was kept constant and σ2 increased, failure strength showed an initial increase followed by a decrease, whereas the fracture dip angle increased monotonically. The non-linear behavior before the peak strength point of granite became more apparent by the increase of σ3, whereas σ2 had an opposite effect on the non-linear behavior of granite under high σ3 (e.g. 100 MPa). The non-linear behavior before the peak strength point was always found in marble and sandstone for all of the stress state conditions. Analyses of fracture dip angle and failure mode showed that when σ3 = 10, 20, and 30 MPa and σ2/σ3 ≥ 5, 7.5, and 10, respectively, the failure mode of granite changed from shear to slabbing, whereas marble and sandstone always fractured in the shear direction. This study confirms that rocks may experience slabbing failure under true triaxial stress, and slabbing failure mode is likely to be induced in high-strength and brittle rocks under low σ3 with the stress ratio of σ2/σ3 exceeding a particular threshold value.

中文翻译：

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真三轴应力下立方花岗岩、大理石和砂岩试样的破坏特性

摘要 在实验室中制备了边长为50 mm的花岗岩、大理石和砂岩立方体试样。对每种岩石类型进行了真三轴压缩试验，小主应力 (σ3) 为 10、20、30、50 和 100 MPa，中间主应力 (σ2) 从 σ2 = σ3 到 σ2 = σ1（其中 σ1代表主要的主应力）。实验结果表明，这些岩石在真三轴条件下的破坏强度、裂缝倾角、非线性行为和破坏模式受σ2和σ3以及岩石岩性的影响。当σ3保持不变，σ2增加时，破坏强度呈现先增后减的趋势，而裂缝倾角则单调增加。随着σ3的增加，花岗岩峰值强度点之前的非线性行为变得更加明显，而σ2对高σ3（例如100MPa）下花岗岩的非线性行为有相反的影响。在所有应力状态条件下，在大理石和砂岩中总是发现峰值强度点之前的非线性行为。裂缝倾角和破坏模式分析表明，当σ3 = 10、20和30 MPa，σ2/σ3 ≥ 5、7.5和10时，花岗岩的破坏模式由剪切变为板坯，而大理石和砂岩总是沿剪切方向断裂。这项研究证实，岩石可能会在真正的三轴应力下经历板坯破坏，