To promote the understanding of the shear behavior of intermittent joints subjected to cyclic shear loads, this paper provides the experimental results of cyclic shear tests in the laboratory. We vary joint configurations and boundary conditions to investigate their effect on the shear behavior and evolution of shear resistance during cyclic shearing. The cyclic shear failure of intermittent joints can be identified as two stages: the cracking of rock bridges (Stage I) and shear slip (Stage II). After ten shear cycles, the shear strength losses generally exceed 50% and reach up to 74.22%. Joint configurations and boundary conditions determine the stress state of intermittent joints during cyclic shearing, thus leading to varied shear zones and evolutions of shear strength. Shear strength is more sensitive to normal stress and joint persistence than joint overlap, spacing, and shear rate. The combination of high joint persistency, moderate joint overlap, small joint spacing, low normal stress level, and high shear rate is most detrimental to the stability of engineering rock masses. Activation of rupture surfaces in different shear directions during cyclic shearing results in a difference in shear strength during positive and negative shearing. Intermittent joints show significant compressibility during cyclic shearing, and the average dilation angle decreases with the cycle number, which also is dependent on joint configurations and boundary conditions. Joint persistence and spacing have a more significant effect on the average dilation angle, while the shear rate is the least significant factor. The combination of high joint persistence, high joint overlap, small joint spacing, high normal stress level, and shear rate during cyclic shearing is the most favorable for compression.

中文翻译：

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间歇接头循环剪切行为的实验研究


为了促进对循环剪切载荷作用下间歇接头剪切行为的理解，本文提供了实验室循环剪切试验的实验结果。我们改变接头配置和边界条件，以研究它们对循环剪切过程中剪切行为和剪切阻力演变的影响。间歇节理的循环剪切破坏可分为两个阶段：岩桥开裂（第一阶段）和剪切滑移（第二阶段）。经过10次剪切循环后，剪切强度损失一般超过50%，最高可达74.22%。接头配置和边界条件决定了循环剪切过程中间歇接头的应力状态，从而导致剪切区域的变化和剪切强度的演变。与接缝重叠、间距和剪切速率相比，剪切强度对法向应力和接缝持久性更敏感。高节理持久性、适度节理重叠、小节理间距、低正应力水平和高剪切率的组合对工程岩体的稳定性最不利。循环剪切过程中不同剪切方向的断裂表面激活导致正剪切和负剪切过程中剪切强度的差异。间歇接头在循环剪切过程中表现出显着的压缩性，平均膨胀角随着循环次数而减小，这也取决于接头配置和边界条件。接缝持久性和间距对平均扩张角有更显着的影响，而剪切速率是最不显着的因素。 高节理持久性、高节理重叠、小节理间距、高法向应力水平和循环剪切期间的剪切速率的组合对于压缩是最有利的。