The coalescence of flaws provides valuable insights into the failure behaviors of rock masses, which is a critical issue in rock engineering. In this study, a series of compressive-shear tests were conducted on sandstone specimens containing double flaws. The failure and cracking behaviors of specimens with different geometric configurations under various loading conditions were analyzed using the digital image correlation (DIC) technique. The strain and displacement fields effectively demonstrate crack propagation and coalescence, accompanied by the axial load–displacement curve. The results revealed the effect of eccentric and overlapping distance of double flaws on the compressive-shear bearing capacity. The relative displacement method (RDM) was applied to analyze the crack characteristics in this study. Based on the relative displacement behaviors of the cracks, five typical types of crack modes were identified, including tensile mode, shear mode, mixed-I mode, mixed-II mode, and mixed-III mode. Both wing cracks initiated from flaw outer tips and anti-wing cracks generated from flaw inner tips were classified as a tensile mode or mode-I, dominated by normal relative displacement. In contrast, the secondary cracks were categorized as either shear mode or mode-III, which are dominated by tangential relative displacement. The geometry configurations of flaws affected both the coalescent mode and cracking path, which in turn influenced the failure mode of specimens. This study identified and summarized eight types of coalescent modes between double flaws. The findings presented in this paper contribute to a better understanding of the failure behavior of rock masses containing flaws subjected to compressive-shear loads.

缺陷的合并为岩体的破坏行为提供了有价值的见解，这是岩石工程中的一个关键问题。在这项研究中，对含有双缺陷的砂岩样本进行了一系列压剪试验。使用数字图像相关（DIC）技术分析了不同几何构型的试件在不同载荷条件下的失效和开裂行为。应变和位移场有效地展示了裂纹扩展和合并，并附有轴向载荷-位移曲线。结果揭示了双缺陷偏心和重叠距离对压剪承载力的影响。本研究采用相对位移法（RDM）来分析裂纹特征。根据裂纹的相对位移行为，识别出五种典型的裂纹模式，包括拉伸模式、剪切模式、混合I型、混合II型和混合III型。从缺陷外尖端引发的翼形裂纹和从缺陷内尖端产生的反翼裂纹都被归类为拉伸模式或 I 型，以法向相对位移为主。相比之下，二次裂纹被分类为剪切模式或 III 型，以切向相对位移为主。缺陷的几何形状既影响聚结模式又影响裂纹路径，进而影响试件的破坏模式。本研究识别并总结了双缺陷之间的八种聚结模式。本文提出的研究结果有助于更好地理解含有缺陷的岩体在压剪载荷作用下的破坏行为。