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    Volume 46, Issue 4 (July 2018)

    Special Issue Paper

    Fragmentation Evolution and Fractal Characteristics of Deep Rocks by Lab Compression-Shear Tests

    (Received 30 September 2016; accepted 27 February 2017)

    Published Online: 2017

    CODEN: JTEVAB

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    Abstract

    We studied the fragmentation evolution and fractal characteristics of deep coalbed rocks that were subjected to underground pressure. First, 14 rock samples of three lithologic groups were collected from the lower coalbed floor at the first working face in Daizhuang Coal Mine and subjected to a series of laboratory compression-shear tests at variable angles on a WES-D3000 universal electro-hydraulic servo testing machine. Then, based on the Mohr–Coulomb failure criterion and the experimental setup specifics, we theoretically explained the testing principle and determined the linear regression relations between the shear stress and normal stress of rock samples in the three groups. Last, we classified fractured fragments by their shapes, established the relationships between the fractal dimensions and their volumes according to fractal theory, and studied the fragmentation distribution and their fractal characteristics. The results show that (1) the variable angles of the curves of rock load versus load displacement obtained in the compression-shear tests are similar to those of the curves of stress versus strain obtained in the servo-controlled permeability tests; (2) the fractal dimension gradually decreases when the rock shear angle increases; (3) among the three lithologic groups, limestone has the smallest average fractal dimensions, which indicates that it has the highest strength to resist shear failure; (4) there is an obvious negative correlation between the fractal dimensions and the percentage of fragments >10 g, which can be used as an important evaluation index of rock brittleness; and (5) the higher the fractal dimension is, the easier the rock fragmentates or fails.

    Author Information:

    Zhu, Shuyun
    School of Resources and Geosciences, China University of Mining and Technology, Xuzhou, Jiangsu Province

    Wu, Yun
    School of Resources and Geosciences, China University of Mining and Technology, Xuzhou, Jiangsu Province

    Lu, Liangliang
    School of Resources and Geosciences, China University of Mining and Technology, Xuzhou, Jiangsu Province


    Stock #: JTE20160491

    ISSN:0090-3973

    DOI: 10.1520/JTE20160491

    Author
    Title Fragmentation Evolution and Fractal Characteristics of Deep Rocks by Lab Compression-Shear Tests
    Symposium ,
    Committee D18