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| Brazilian splitting test study on crack propagation process and macroscopic failure mode of pre-cracked black shale#br# |
| WANG Hui1，2，LI Yong1，2，CAO Shugang1，2，PAN Ruikai1，2，YANG Hongyun1，2，ZHANG Kewen3，LIU Yanbao4#br# |
(1. State Key Laboratory of Coal Mine Disaster Dynamics and Control，Chongqing University，Chongqing 400044，China；2. School of Resources and Safety Engineering，Chongqing University，Chongqing 400044，China；3. Tangjiahe Coal Mine of Guangwang Energy Development(Group) Limited Liability Company of Sichuan Province，Guangyuan，Sichuan 628205，China；4. China Coal Technology and Engineering Group Chongqing Research Institute，Chongqing 400039，China)
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Abstract In order to study the fracture mechanisms of black shale with bedding and prefabricated cracks，Brazilian splitting tests were carried out on pre-cracked disk specimens，and the fracture processes of specimens were monitored by using a high-speed camera and an acoustic emission monitoring system. The results show that the prefabricated cracks can weaken the strength of specimens and the strength of specimens shows significant difference with changing the inclination angles of the bedding and the prefabricated crack. The position of the crack initiation point and the crack initiation angle are also affected by the inclination angles of the bedding and the prefabricated crack. When the prefabricated crack inclination angle is small，the crack initiation point deviates from the prefabricated crack tip and the crack propagates along the middle or the bedding surface of specimens. With increasing the prefabricated crack angle，the crack initiation point gradually transfers to the prefabricated crack tip and the crack propagates from the prefabricated crack tip to the loading direction. Moreover，the effect of the bedding inclination angle on the crack initiation angle decreases gradually with increasing the prefabricated crack inclination angle. According to the morphology and generation mechanism of cracks，the failure mode can be divided into five types and temporal distribution of acoustic emission count can be divided into two types. By combining the results of numerical simulation and theoretical analysis，it can be seen that the black shale shows certain transverse isotropic characteristics，that the bedding effect increases with increasing the bedding inclination angle and decreases with rising the prefabricated crack angle，and that the maximum tangential stress criterion can be used as the criterion for the initiation of prefabricated cracks.
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2020, Vol. 39 
