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<p>Accurate characterization of the mechanical strength and fracture evolution of anisotropic shale is essential for constructing complex fracture networks during hydraulic stimulation of shale gas reservoirs. In this study, a discrete element method (DEM)-based thin-layer numerical model is established to reproduce the laminated mineral fabric of shale. The inherent structural anisotropy of shale is reflected by its stratified architecture, while mechanical anisotropy is captured via differentiated mesoscopic parameters for matrix and bedding layer particle bonds. Numerical Brazilian tests results indicate that: The maximum principal stress concentrates mainly around the specimen center, and its spatial distribution is strongly governed by bedding layer orientation. Mesoscopically, cracks propagate along stepped trajectories, which arise from breakage of weaker matrix and bedding layer and ultimately produce distinct macro-fracture morphologies. To quantitatively characterize bedding layer weakening effects, an interface strength weakening coefficient (ISWC) is proposed. A series of parametric simulations demonstrate that both tensile fracture patterns and normalized tensile strength are highly sensitive to ISWC and bedding layer orientation. Moreover, the coupling relationship between failure mode, ISWC and bedding angle is clarified under Brazilian indirect tension loading. The study deepens the fundamental understanding of fracture mechanisms in laminated shale and provides quantitative references for optimizing hydraulic fracturing schemes in shale gas engineering.</p>

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Fracture Morphologies of Shale in Brazilian Tests Based on A Thin-Layer Model

  • 期刊论文

  • 发表日期：

    2026年7月23日

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  • Yuxin Ban,
  • Jun Duan,
  • Yushan Jiang,
  • Houzhi Tang,
  • Qiang Xie,
  • Baoyun Zhao,
  • Weichen Sun,
  • Xiang Fu,
  • Dalang Tian

摘要

Accurate characterization of the mechanical strength and fracture evolution of anisotropic shale is essential for constructing complex fracture networks during hydraulic stimulation of shale gas reservoirs. In this study, a discrete element method (DEM)-based thin-layer numerical model is established to reproduce the laminated mineral fabric of shale. The inherent structural anisotropy of shale is reflected by its stratified architecture, while mechanical anisotropy is captured via differentiated mesoscopic parameters for matrix and bedding layer particle bonds. Numerical Brazilian tests results indicate that: The maximum principal stress concentrates mainly around the specimen center, and its spatial distribution is strongly governed by bedding layer orientation. Mesoscopically, cracks propagate along stepped trajectories, which arise from breakage of weaker matrix and bedding layer and ultimately produce distinct macro-fracture morphologies. To quantitatively characterize bedding layer weakening effects, an interface strength weakening coefficient (ISWC) is proposed. A series of parametric simulations demonstrate that both tensile fracture patterns and normalized tensile strength are highly sensitive to ISWC and bedding layer orientation. Moreover, the coupling relationship between failure mode, ISWC and bedding angle is clarified under Brazilian indirect tension loading. The study deepens the fundamental understanding of fracture mechanisms in laminated shale and provides quantitative references for optimizing hydraulic fracturing schemes in shale gas engineering.