Abstract Previous 2D studies and tests have mainly focused on the discontinuity of fracture structures along the flaw-inclination direction, and there has been little research into the discontinuity or concealment characteristics of flaws along the flaw-strike direction. To this end, hard brittle rock-like gypsum specimens containing two parallel flaws with three types of flaw-concealment conditions (with proportions of 3D internal flaws of 0%, 50%, and 100%) were prepared. Uniaxial compression tests, accompanied by digital image correlation and acoustic emission monitoring, revealed the following. 1) The concealment conditions of the parallel flaws mainly influenced the uniaxial compression strength of the samples, while the existence of fracture structures was the main factor affecting their elastic modulus. 2) The flaw-concealment conditions had a significant effect on the distributions of the external and internal secondary failure structures. 3) When the proportion of 3D internal flaws was 50%, local failures occurred around the internal flaws and remained hidden, never showing on the outside surface of the specimen; when the proportion of 3D internal flaws was 100%, this kind of 3D sample had greater strength, a faster failure process, more severe damage behaviors, and a more concealed process of destruction than the corresponding 2D sample. 4) The higher strength and concealed failure process of samples containing 3D internal flaws explains why the conclusions of previous 2D research have been found to be not applicable to real 3D conditions.

中文翻译：

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平行双裂纹不同隐蔽条件对脆性岩石单轴压缩力学性能及破坏特征的影响

摘要 以往的二维研究和试验主要集中在裂纹结构沿裂纹倾斜方向的不连续性，对裂纹沿裂纹走向方向的不连续性或隐蔽性的研究较少。为此，制备了包含两个平行缺陷的硬脆性类岩石膏试样，具有三种缺陷隐藏条件（3D 内部缺陷的比例为 0%、50% 和 100%）。单轴压缩测试，伴随着数字图像相关性和声发射监测，揭示了以下内容。1)平行缺陷的隐蔽条件主要影响试样的单轴抗压强度，断裂结构的存在是影响其弹性模量的主要因素。2）缺陷隐藏条件对外部和内部二次破坏结构的分布有显着影响。3）当3D内部缺陷比例为50%时，内部缺陷周围发生局部失效并保持隐蔽，从未在试件外表面显现；当3D内部缺陷比例为100%时，这种3D样品比相应的2D样品具有更大的强度、更快的破坏过程、更严重的损伤行为和更隐蔽的破坏过程。4）含有3D内部缺陷的样品的更高强度和隐藏的破坏过程解释了为什么之前2D研究的结论被发现不适用于真实的3D条件。3）当3D内部缺陷比例为50%时，内部缺陷周围发生局部失效并保持隐蔽，从未在试件外表面显现；当3D内部缺陷比例为100%时，这种3D样品比相应的2D样品具有更大的强度、更快的破坏过程、更严重的损伤行为和更隐蔽的破坏过程。4）含有3D内部缺陷的样品的更高强度和隐藏的破坏过程解释了为什么之前2D研究的结论被发现不适用于真实的3D条件。3）当3D内部缺陷比例为50%时，内部缺陷周围发生局部失效并保持隐蔽，从未在试件外表面显现；当3D内部缺陷比例为100%时，这种3D样品比相应的2D样品具有更大的强度、更快的破坏过程、更严重的损伤行为和更隐蔽的破坏过程。4) 含有3D内部缺陷的样品具有更高的强度和隐藏的破坏过程，这解释了为什么之前2D研究的结论被发现不适用于真实的3D条件。这种3D样品比相应的2D样品具有更大的强度、更快的破坏过程、更严重的损伤行为和更隐蔽的破坏过程。4）含有3D内部缺陷的样品的更高强度和隐藏的破坏过程解释了为什么之前2D研究的结论被发现不适用于真实的3D条件。这种3D样品比相应的2D样品具有更大的强度、更快的破坏过程、更严重的损伤行为和更隐蔽的破坏过程。4) 含有3D内部缺陷的样品具有更高的强度和隐藏的破坏过程，这解释了为什么之前2D研究的结论被发现不适用于真实的3D条件。