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<p>Tensile failure is a fundamental and critical issue in rock mechanics, with also profound engineering significance for shale formations fracturing. Current studies on shale tensile failure are mostly restricted to quasi-static loading conditions and conventional Brazilian disc (BD) tests, leaving the high-strain-rate direct tensile (DT) failure mechanism of shale still challenging and ambiguous. In this work, dynamic DT tests on transversely isotropic shale are conducted across high strain rates using a split Hopkinson tension bar (SHTB) for the first time. By virtue of the special-designed screwed joints and optimized pulse-shaping technique, dynamic DT failure and dynamic force equilibrium are successfully achieved, ensuring rigorous experimental reliability. The effects of strain rate and anisotropy on shale’s dynamic tensile deformation and failure properties are then systematically investigated. Experimental results reveal that the dynamic tensile modulus is rate-insensitive, while dynamic tensile strength exhibits a strong strain rate dependence. Both dynamic tensile modulus and strength increase nonlinearly with bedding angle. Dynamic failure angles decrease with increasing strain rate, and first increase then decrease with increasing bedding angle. Further, we extend the quasi-static tensorial Nova–Zaninetti (NZ) tensile strength criterion to dynamic loading condition by incorporating the strain rate effects. The newly developed dynamic NZ criterion accurately predicts the dynamic anisotropic tensile strength and failure angles, showing good consistency with experimental data. For comprehensive comparison analysis, our dynamic DT testing results are quantitatively discussed with dynamic uniaxial compression and dynamic BD tests, revealing pronounced dynamic tension–compression asymmetry and significant BD–DT discrepancies. This work provides the first systematic experimental and theoretical insights into layered shale’s dynamic DT behaviors under high strain rates, offering critical guidance for dynamic fracturing in shale reservoirs.</p>

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Dynamic Direct Tensile Failure of Shale via Split Hopkinson Tension Bar: Experimental Insights and Theoretical Criterion

  • 期刊论文

  • 发表日期：

    2026年7月27日

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  • Zelin Yan,
  • Feng Dai,
  • Yi Liu,
  • Mingdong Wei,
  • Lei Zhou

摘要

Tensile failure is a fundamental and critical issue in rock mechanics, with also profound engineering significance for shale formations fracturing. Current studies on shale tensile failure are mostly restricted to quasi-static loading conditions and conventional Brazilian disc (BD) tests, leaving the high-strain-rate direct tensile (DT) failure mechanism of shale still challenging and ambiguous. In this work, dynamic DT tests on transversely isotropic shale are conducted across high strain rates using a split Hopkinson tension bar (SHTB) for the first time. By virtue of the special-designed screwed joints and optimized pulse-shaping technique, dynamic DT failure and dynamic force equilibrium are successfully achieved, ensuring rigorous experimental reliability. The effects of strain rate and anisotropy on shale’s dynamic tensile deformation and failure properties are then systematically investigated. Experimental results reveal that the dynamic tensile modulus is rate-insensitive, while dynamic tensile strength exhibits a strong strain rate dependence. Both dynamic tensile modulus and strength increase nonlinearly with bedding angle. Dynamic failure angles decrease with increasing strain rate, and first increase then decrease with increasing bedding angle. Further, we extend the quasi-static tensorial Nova–Zaninetti (NZ) tensile strength criterion to dynamic loading condition by incorporating the strain rate effects. The newly developed dynamic NZ criterion accurately predicts the dynamic anisotropic tensile strength and failure angles, showing good consistency with experimental data. For comprehensive comparison analysis, our dynamic DT testing results are quantitatively discussed with dynamic uniaxial compression and dynamic BD tests, revealing pronounced dynamic tension–compression asymmetry and significant BD–DT discrepancies. This work provides the first systematic experimental and theoretical insights into layered shale’s dynamic DT behaviors under high strain rates, offering critical guidance for dynamic fracturing in shale reservoirs.