Microscopic characteristics of different fracture modes of brittle rock
来源期刊：中南大学学报(英文版)2001年第3期
论文作者：RAO Qiu-hua SUN Zong-qi WANG Gui-yao XU Ji-cheng ZHANG Jing-yi
文章页码：175 - 179
Key words：microscopic characteristic; ModeⅡfracture; mixed mode fracture; rock; SEM analysis
Abstract: Three types of rock specimens, three-point bending specimen, anti-symmetric four-point bending specimen and direct shearing specimen, were used to achieve ModeⅠ, ModeⅡand mixed modeⅠ-Ⅱfracture, respectively . Microscopic characteristics of the three fracture modes of brittle rockwere studied by SEM technique in order to analyze fracture behaviors and better understand fracture mechanisms of different fracture modes of brittle rock. Test results show that the microscopic characteristics of different fracture modes correspond to different fracture mechanisms. The surface of ModeⅠfracture has agreat number of sparse and steep slip-steps with few tearing ridges and shows strong brittleness. In the surface of ModeⅡfracture there exist many tearing ridges and densely distributed parallel slip-steps and it is attributed to the action of shear stress.The co-action of tensile and shear stresses results in brittle cleavage planes mixed with streamline patterns and tearing ridges in the surface of mixed modeⅠ-Ⅱfracture. The measured ModeⅡfracture toughness KⅡC and mixed modeⅠ-Ⅱfracture toughness Km Care larger than ModeⅠfracture toughnessKⅠC.KⅡC is about 3.5 times KⅠC, and KmC is about 1.2 times KⅠC.
