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<p>To investigate quantitatively the influence of stress-induced microcracks on tensile strength anisotropy of granite cores, Brazilian tensile tests were systematically conducted on granite cores from a 138&#xa0;m-deep vertical borehole in Pingtan, southeast China. We characterized the microcracks in granite cores by the Diametrical Core Deformation Analysis (DCDA) tests, <i>P</i>-wave velocity tests, and optical microscopic observations. The Brazilian test on a disc containing microcracks was then conducted using the finite-discrete element method (FDEM) numerical simulation method, and the tensile strength was calculated. The conclusions are as follows: (1) The Brazilian tensile strength (BTS) exhibits significant anisotropy, with the highest and lowest values in the <i>S</i><sub>H</sub> and <i>S</i><sub>h</sub> directions, respectively, and an anisotropy ratio of 11.6–38.1%. (2) BTS varies with loading direction, following a cosine wave trend that correlates with diameter changes and inversely with <i>P</i>-wave velocity. (3) Transgranular microcracks perpendicular to the <i>S</i><sub>H</sub> direction, identified through DCDA, <i>P</i>-wave velocity tests, and microscopic observations, are the primary cause of tensile strength anisotropy. (4) The <i>S</i><sub>H</sub> direction, corresponding to the maximum core diameter, reliably indicates the upper and lower limits of tensile strength. (5) FDEM simulations confirm that loading direction significantly affects tensile strength, with fluctuations of 4.81–13.6%. Strength is highest when loading aligns with the <i>S</i><sub>H</sub> direction and lowest when perpendicular to it, consistent with experimental results. It is thus recommended that the DCDA test be combined with the Brazilian tensile test to quantitatively evaluate the range and anisotropy of the tensile strength of rock cores.</p>

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Experimental Study on Tensile Strength Anisotropy of Granite: Insights from Horizontal Stress-Related Microcracks

  • 期刊论文

  • 发表日期：

    2025年4月24日

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  • Zixuan Gao,
  • Chongyuan Zhang,
  • Yinlin Ji,
  • Zhen Wang,
  • Jiawang Zhan,
  • Manchao He,
  • Shaohui Li,
  • Yonghao Zhang,
  • Yanhong Gou,
  • Yifan Chen,
  • Leihua Yao

摘要

To investigate quantitatively the influence of stress-induced microcracks on tensile strength anisotropy of granite cores, Brazilian tensile tests were systematically conducted on granite cores from a 138 m-deep vertical borehole in Pingtan, southeast China. We characterized the microcracks in granite cores by the Diametrical Core Deformation Analysis (DCDA) tests, P-wave velocity tests, and optical microscopic observations. The Brazilian test on a disc containing microcracks was then conducted using the finite-discrete element method (FDEM) numerical simulation method, and the tensile strength was calculated. The conclusions are as follows: (1) The Brazilian tensile strength (BTS) exhibits significant anisotropy, with the highest and lowest values in the SH and Sh directions, respectively, and an anisotropy ratio of 11.6–38.1%. (2) BTS varies with loading direction, following a cosine wave trend that correlates with diameter changes and inversely with P-wave velocity. (3) Transgranular microcracks perpendicular to the SH direction, identified through DCDA, P-wave velocity tests, and microscopic observations, are the primary cause of tensile strength anisotropy. (4) The SH direction, corresponding to the maximum core diameter, reliably indicates the upper and lower limits of tensile strength. (5) FDEM simulations confirm that loading direction significantly affects tensile strength, with fluctuations of 4.81–13.6%. Strength is highest when loading aligns with the SH direction and lowest when perpendicular to it, consistent with experimental results. It is thus recommended that the DCDA test be combined with the Brazilian tensile test to quantitatively evaluate the range and anisotropy of the tensile strength of rock cores.