Abstract Rock masses consist of various discontinuities that significantly affect the crack development patterns which dominates the ultimate failure of geostructures. The interaction of the pre-existing flaws with each other and with the newly formed cracks is complicated and demands a comprehensive investigation. This paper couples the 3D printing technology with the digital image correlation (DIC) and the bonded particle model (BPM) to study failure of rock-like specimens with pre-existing flaws. Systematic flaws configurations are considered including single, coplanar, partially overlapped and fully overlapped arrangements. The flaws are considered to be unfilled and filled with a weak material. The DIC strain and BPM displacement vectors analysis indicate the strong effects of the filling material on the deformation behaviour of the 3D printed specimens. The failure pattern of the single filled flaws is transformation from compressive failure (0°) to shear failure (15°-60°) and to tensile failure (75°-90°). However, in the coplanar flaws failure is transformation from compressive (0°) to mixed-mode compressive shear (15°-30°), then to shear (45°), to mixed-mode tensile-shear (60°-75°) and then to pure tensile (90°). However, the partially coplanar filled flaws all (except 0° which is compressive failure) exhibit mixed-mode failure in the order of compressive-shear (15°-30°) and transformation to the tensile-shear (45°-90°). BPM displacement vectors revealed five crack types in the specimens by the analysis of the relative movement of the vectors in some critical locations such as flaws tips, rock bridge and coalescence zone. Moreover, a new coalescence type was identified in the 15° flaw (either unfilled or filed) which is named Type X and is a mixed-mode shear tensile crack with a coplanar secondary shear crack. Furthermore, it is observed that the peak load of the filled specimens are much higher than that of the unfilled ones because the filling material requires extra energy to fracture and thus the filled specimens can carry larger load before fail.

中文翻译：

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含未填充和填充缺陷类岩石试样裂纹发展的比较研究

摘要 岩体由各种不连续性组成，这些不连续性显着影响裂缝发展模式，裂缝发展模式主导着地质结构的最终破坏。预先存在的缺陷彼此之间以及与新形成的裂纹之间的相互作用很复杂，需要进行全面的调查。本文将 3D 打印技术与数字图像相关 (DIC) 和结合粒子模型 (BPM) 相结合，研究具有预先存在缺陷的类岩石试样的失效。系统缺陷配置被认为包括单一、共面、部分重叠和完全重叠的布置。缺陷被认为是未填充的并填充了弱材料。DIC 应变和 BPM 位移矢量分析表明填充材料对 3D 打印试样的变形行为有很强的影响。单个填充缺陷的破坏模式是从压缩破坏 (0°) 到剪切破坏 (15°-60°) 和拉伸破坏 (75°-90°) 的转变。然而，在共面缺陷中，破坏是从压缩（0°）到混合模式压缩剪切（15°-30°），然后到剪切（45°），再到混合模式拉伸剪切（60°-75°）的转变)，然后达到纯拉伸 (90°)。然而，部分共面填充缺陷（0°除外，即压缩破坏）表现出按压缩剪切（15°-30°）和向拉伸剪切（45°-90°）转变的顺序的混合模式破坏. BPM位移矢量通过分析裂纹尖端、岩桥和聚结带等关键位置矢量的相对运动，揭示了试样中的五种裂纹类型。此外，在 15° 缺陷（未填充或填充）中发现了一种新的聚结类型，称为 X 型，是一种混合模式剪切拉伸裂纹，具有共面的二次剪切裂纹。此外，观察到填充试样的峰值载荷远高于未填充试样的峰值载荷，因为填充材料需要额外的能量才能断裂，因此填充试样在失效前可以承受更大的载荷。在 15° 缺陷（未填充或填充）中发现了一种新的聚结类型，称为 X 型，是一种混合模式剪切拉伸裂纹，带有共面的二次剪切裂纹。此外，观察到填充试样的峰值载荷远高于未填充试样的峰值载荷，因为填充材料需要额外的能量才能断裂，因此填充试样在失效前可以承受更大的载荷。在 15° 缺陷（未填充或填充）中发现了一种新的聚结类型，称为 X 型，是一种混合模式剪切拉伸裂纹，带有共面的二次剪切裂纹。此外，观察到填充试样的峰值载荷远高于未填充试样的峰值载荷，因为填充材料需要额外的能量才能断裂，因此填充试样在失效前可以承受更大的载荷。