An understanding of crack propagation is critical for the development of rock mechanic models. To study the propagation of internal cracks in situ and determine their formation mechanism, a series of uniaxial compression tests on shale specimens were conducted using a novel setup that combines X-ray micro-computed tomography (X-ray micro-CT) with a uniaxial loading apparatus, which allows CT scans to be performed during compression. Macro- and micro-scale internal cracks were extracted from CT images collected after various stages of deformation through image thresholding segmentation, providing a record of the evolution of damage within the specimens, characterized by crack closure, generation, growth, and penetration. In addition, macroscopic cracks with two distinct orientations were observed and their formation mechanism was further determined. Furthermore, test results show that the distribution of pyrite grains influences the formation of cracks at the meso- and macro-scales. These results are significant for understanding crack propagation and the failure of shale.
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This work was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant no. XDB10030302). We thank Jin Hao for experimental support.
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Conflict of interest
The authors have no conflicts of interest to declare.
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