Use of double edge-cracked Brazilian disk geometry for compression-shear fracture investigation of rock
来源期刊：中南大学学报(英文版)2003年第3期
论文作者：陈枫 曹平 饶秋华 孙宗颀
文章页码：211 - 215
Key words：rock fracture; stress intensity factor; weight function; cracked Brazilian disk
Abstract: A new specimen geometry-the double edge-cracked Brazilian disk and a relevant fracture analysis by weight function method are proposed for the investigation of rock fracture caused by compression-shear loading. Not only can the mixed mode fracture with any ratio of KⅠ /KⅡ be achieved, but also the pure mode Ⅱ crack extension can be obtained. The combined mode fracture analysis for this geometry shows that diametral compression in the farfield can induce a compression-shear stress state in the singular stress field ahead of crack tips. Experimental investigations conducted on marble specimens show that the pure mode Ⅱ crack extension can be obtained when the dimensionless crack length а＞ 0. 7 and the inclined crack angle 50≤ф≤400. Normalized modeⅠ and mode II stress intensity factors decrease from一0. 45 and 2. 47 atф=50 to一1. 65 and 1. 52 atа=400, respectively. The strains at three points of specimen are also measured in order to investigate the influence of stress singularity on initial crack extension. The results show that the principal orientations of strain at three points are very stable in the loading process.The derived formulae are quite explicit, and the specimen geometry is easy to fabricate and convenient to achieve thepure mode Ⅱ crack extension. Therefore, it can hopefully be used to obtain modeⅡfracture toughness of rock.
