Crack Coalescence in Molded Gypsum and Carrara Marble: Part 1. Macroscopic Observations and Interpretation
Crack Coalescence in Molded Gypsum and Carrara Marble: Part 1. Macroscopic Observations and Interpretation
复制标题
DOI：
10.1007/s00603-008-0002-4
复制
发表时间：
2009-06-01
影响因子：
6.2
通讯作者：
Einstein, H. H.
中科院分区：
文献类型：
--
作者：
Wong, L. N. Y.;Einstein, H. H.
实验研究了含有两个平行的预先存在的开放缺陷的棱柱形石膏和卡拉拉大理岩试件的开裂和粘结行为。这是在宏观和微观两个尺度上完成的，结果分别在两篇论文中公布。本文总结了宏观实验结果，研究了不同缺陷几何形状和材料对裂纹扩展过程的影响。在本文中(也在本期中)，本文中显示的大多数宏观变形和开裂过程都与潜在的微观变化有关。在本研究中，使用了高速摄像系统，使我们能够准确地观察裂纹的产生机理。确定了9种不同裂纹类型和轨迹的裂纹汇聚类型。裂纹倾角(β)、韧带长度(L)，即缺陷之间完整的岩石长度，以及桥接角(α)，即连接两个缺陷之间的内部缺陷尖端的线的倾斜度，对结合模式有不同的影响。在压缩载荷试验中观察到的大理岩和石膏之间的显著区别之一是在大理岩中宏观裂纹萌生之前形成了宏观白斑，而在石膏中则没有。比较两种材料的开裂和粘结行为，对于相同的缺陷对几何形状，大理岩比石膏更容易发生拉伸开裂。
Cracking and coalescence behavior has been studied experimentally with prismatic laboratory-molded gypsum and Carrara marble specimens containing two parallel pre-existing open flaws. This was done at both the macroscopic and the microscopic scales, and the results are presented in two separate papers. This paper (the first of two) summarizes the macroscopic experimental results and investigates the influence of the different flaw geometries and material, on the cracking processes. In the companion paper (also in this issue), most of the macroscopic deformation and cracking processes shown in this present paper will be related to the underlying microscopic changes. In the present study, a high speed video system was used, which allowed us to precisely observe the cracking mechanisms. Nine crack coalescence categories with different crack types and trajectories were identified. The flaw inclination angle (beta), the ligament length (L), that is, intact rock length between the flaws, and the bridging angle (alpha), that is, the inclination of a line linking up the inner flaw tips, between two flaws, had different effects on the coalescence patterns. One of the pronounced differences observed between marble and gypsum during the compression loading test was the development of macroscopic white patches prior to the initiation of macroscopic cracks in marble, but not in gypsum. Comparing the cracking and coalescence behaviors in the two tested materials, tensile cracking generally occurred more often in marble than in gypsum for the same flaw pair geometries.