Shear mechanism of rock joints under pre-peak cyclic loading condition
Shear mechanism of rock joints under pre-peak cyclic loading condition
复制标题
DOI：
10.1016/j.ijrmms.2016.01.009
复制
发表时间：
2016-03-01
影响因子：
7.2
通讯作者：
Ballivy, Gerard
中科院分区：
文献类型：
--
作者：
Fathi, Ali;Moradian, Zabihallah;Ballivy, Gerard
用天然未风化花岗岩节理制作了13个砂浆复型试件。剪切试验通过两个连续的步骤进行：载荷控制和位移控制。在5、10、20、100、500和1000次预峰值载荷循环下进行载荷控制剪切试验，振幅为最大单调剪切强度的30%和50%。然后以位移控制的方式继续测试直到10 mm的剪切位移。通过定义“微小窗口”的概念，重建了关节面的几何模型，确定了关节面接触区、接触损伤区和非接触区的分布和大小。在剪切峰前阶段定义了两个阈值角：“接触阈值角”和“损伤阈值角”，“接触阈值角”是指非接触区和接触区的分界线，“损伤阈值角”是指接触区和损伤区的分界线。在不同阶段的剪切接触面积的分布和几何特性进行了鉴定和退化的一阶和二阶粗糙度进行了评估。将峰前循环加载试验的结果与单调试验的结果进行了比较，以阐明循环加载对节点剪切机制和剪切强度参数的影响。有人发现，最陡峭的凸体，面向剪切方向接触剪切峰之前，在单调测试。在低循环次数期间发生收缩，因此接触面积和剪切强度参数略有增加。在较大的循环次数下，二阶粗糙体发生降解，因此剪切强度参数缓慢下降。还发现，增加或减少在峰前循环载荷的循环次数不会有显着影响的剩余剪切强度参数的测试样本。(C)2016爱思唯尔有限公司版权所有
Thirteen mortar replica specimens were made from natural unweathered granite joint. Shear tests were conducted through two consecutive steps; load-controlled and displacement-controlled. Load controlled shear tests were conducted under 5, 10, 20, 100, 500, and 1000 cycles of pre-peak loading with amplitudes of 30% and 50% of the maximum monotonic shear strength. Then tests were continued up to 10 mm shear displacement in the displacement-controlled manner. By defining a concept named 'tiny window', the geometric models of the joint surfaces were reconstructed and the distribution and size of just in-contact areas, in-contact damaged zones and not in-contact areas were identified. Two threshold angles were defined in the pre-peak stage of shearing: "in-contact threshold angle" as the boundary between not in-contact areas and just in-contact areas and "damaged threshold angle" as the boundary between just in-contact areas and in-contact damaged zones. The distribution and the geometric properties of contact areas in different stages of shearing were identified and degradation of the first and second order asperities was evaluated. The results of the pre-peak cyclic loading tests are compared with the results of a monotonic test to clarify the effect of the cyclic loading on the joint shear mechanism and the shear strength parameters. It was found that the steepest asperities that are facing the shear direction came into contact in shearing before peak in the monotonic test. Contraction occurred during low number of cycles and consequently the contact area and the shear strength parameters slightly increased. During larger number of cycles, degradation occurred on the second order asperities, therefore the shear strength parameters slowly decreased. It was also found that increasing or decreasing the number of cycles during pre-peak cyclic loading does not have a significant effect on the residual shear strength parameters of the tested specimens. (C) 2016 Elsevier Ltd. All rights reserved.