Four series of cyclic direct-shear experiments were conducted on several replicas of three natural fractures and a tensile fracture of welded tuff from Yucca Mountain. The objective of the tests was to examine the effect of cyclic shear loading on joint shear behavior under different boundary conditions. The shear tests were performed under either different levels of constant normal load ranging between 2.7 and 113.9 kN or constant normal stiffness ranging between 25.9 and 328.1 kN/cm. Each test in the two categories consisted of five cycles of forward and reverse shear. Normal compression tests were also performed before and after each shear experiment to measure changes in joint normal deformability. In order to quantify fracture surface damage during shear, fracture-surface fractal dimensions were obtained from profile measurements before and after shear.; Based on the results of the shear tests conducted on several joint replicas under different levels of constant normal load, the shear behavior of joint replicas under constant normal stiffness was predicted by using the graphical method proposed by Saeb (1989) and Amadei and Saeb (1990). The predictions were compared to the results of actual shear tests conducted for the same range of constant normal stiffness. In general, a good agreement was found between predicted and observed shear behavior.; The results of the constant normal load shear experiments were analyzed using several constitutive models proposed in the rock mechanics literature for joint shear strength, dilatancy, and joint surface damage. Some of the existing models appear to have limitations. New constitutive models are proposed and are included in a mathematical analysis tool that can be used to predict joint behavior under various boundary conditions.; Separate from the direct shear experiments, rotary shear tests were also conducted to re-evaluate Barton's empirical failure criterion. Eleven rotary shear tests were performed on replicas of three hollow cylinders of natural fractures with Joint Roughness Coefficient (JRC) values of 7.7, 9.4 and 12.0. The replicas were made from gypsum. By varying the water-to-gypsum cement ratios from 30 to 45%, fracture replicas with different values of Joint Wall Compressive Strength (JCS) could be created. The rotary shear experiments were performed under constant normal (nominal) stresses ranging between 0.2 and 1.6 MPa. The rotary shear test results were compared with predictions using Barton's empirical peak shear strength equation. Observations during the experiments indicated that only certain parts of the fracture profiles influence fracture shear strength and dilatancy. Under relatively low applied normal stresses, the JCS does not seem to have a significant effect. As an alternative, a new procedure for predicting the rotary shear behavior of the hollow cylinder fractures was developed. The approach is based on basic fracture properties such as fracture surface profile data and the compressive strength, modulus of elasticity, and Poisson's ratio of the fracture walls. Comparison between predictions and actual shear test results shows that the alternative procedure is a reliable method.
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机译：对来自丝兰山的三个自然裂缝和焊接凝灰岩的拉伸裂缝的几个副本进行了四个系列的循环直接剪切实验。测试的目的是研究循环剪切载荷对不同边界条件下的联合剪切行为的影响。剪切试验是在2.7至113.9 kN的恒定法向载荷或25.9至328.1 kN / cm的恒定法向刚度的不同水平下进行的。这两个类别中的每个测试都包含五个正向和反向剪切循环。在每个剪切实验之前和之后也进行了正常的压缩测试，以测量关节正常变形能力的变化。为了量化剪切过程中的断裂表面破坏，从剪切前后的剖面测量中获得了断裂表面的分形维数。基于在不同水平的法向恒定载荷下对多个关节复制品进行的剪切试验结果，使用Saeb（1989）和Amadei and Saeb（1990）提出的图形方法预测了在恒定法向刚度下关节复制品的剪切行为。 ）。将该预测结果与在相同范围的恒定法向刚度下进行的实际剪切测试的结果进行了比较。通常，在预测和观察到的剪切行为之间找到了很好的一致性。使用岩石力学文献中提出的几种本构模型对节理抗剪强度，剪胀性和节理面损伤进行了分析，分析了恒定法向荷载剪切试验的结果。一些现有模型似乎有局限性。提出了新的本构模型，并将其包含在数学分析工具中，该模型可用于预测各种边界条件下的接头行为。与直接剪切试验不同，还进行了旋转剪切试验以重新评估Barton的经验破坏准则。对三个天然裂缝的空心圆柱体进行了十一次旋转剪切试验，其接头粗糙度系数（JRC）值为7.7、9.4和12.0。复制品由石膏制成。通过将水石膏水泥比从30％更改为45％，可以创建具有不同墙面抗压强度（JCS）值的裂缝副本。旋转剪切实验是在0.2到1.6 MPa的恒定法向（名义）应力下进行的。使用Barton经验峰值剪切强度方程将旋转剪切测试结果与预测值进行了比较。实验过程中的观察结果表明，仅某些断面轮廓会影响断裂剪切强度和剪胀性。在相对较低的法向应力下，JCS似乎没有明显的作用。作为替代方案，开发了一种预测空心圆柱体断裂的旋转剪切行为的新方法。该方法基于基本的断裂特性，例如断裂表面轮廓数据以及断裂壁的抗压强度，弹性模量和泊松比。预测结果与实际剪切试验结果之间的比较表明，替代程序是一种可靠的方法。
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