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<p>In deep geological engineering projects, the mechanical response and microcracking behavior of jointed granite under high temperatures remain insufficiently understood, posing major challenges to stability assessment and design. This study employs a grain-based model (GBM) within the two-dimensional Particle Flow Code (PFC2D) to numerically investigate the influence of joint geometric characteristics and grain size heterogeneity on the shear slip behavior and damage evolution of jointed granite under coupled thermo-mechanical conditions. Five granite models with controlled grain size distributions were generated, into which joints of varying angles and roughness levels were incorporated. Results indicate that the failure mode transitions progressively from new fracture intersecting or traversing the preexisting joint to pure shear failure confined almost exclusively to the original joint as the joint angle increases or roughness decreases. Correspondingly, peak shear strength decreases, with the influence of angle being substantially more pronounced. However, grain size heterogeneity exerts a non-monotonic influence on shear behavior. Moderate grain size heterogeneity markedly enhances peak strength relative to the homogeneous case through improved asperity interlocking and increased fracture energy dissipation, whereas excessive heterogeneity leads to strength reduction. Although joint angle and grain size heterogeneity act independently, their effects are superimposed and interact synergistically to produce a nonlinear superposition of structural and material contributions to macroscopic shear strength. The findings in this study will advance the understanding of how macroscopic joints and microscopic mineral heterogeneity jointly control shear mechanism in jointed granite, providing theoretical guidance for stability evaluation and risk assessment in enhanced geothermal systems (EGS) and geological repositories for radioactive nuclear waste.</p>

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Effects of Joint Geometry and Heterogeneity on Granite Joint Shear Behavior under Thermo-Mechanical Coupling Based on Grain-Based Model

  • 期刊论文

  • 发表日期：

    2026年7月17日

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  • Jian Gao,
  • Fanzhen Meng,
  • Qijin Cai,
  • Feili Wang,
  • Junnan Zhang,
  • Yang Wang

摘要

In deep geological engineering projects, the mechanical response and microcracking behavior of jointed granite under high temperatures remain insufficiently understood, posing major challenges to stability assessment and design. This study employs a grain-based model (GBM) within the two-dimensional Particle Flow Code (PFC2D) to numerically investigate the influence of joint geometric characteristics and grain size heterogeneity on the shear slip behavior and damage evolution of jointed granite under coupled thermo-mechanical conditions. Five granite models with controlled grain size distributions were generated, into which joints of varying angles and roughness levels were incorporated. Results indicate that the failure mode transitions progressively from new fracture intersecting or traversing the preexisting joint to pure shear failure confined almost exclusively to the original joint as the joint angle increases or roughness decreases. Correspondingly, peak shear strength decreases, with the influence of angle being substantially more pronounced. However, grain size heterogeneity exerts a non-monotonic influence on shear behavior. Moderate grain size heterogeneity markedly enhances peak strength relative to the homogeneous case through improved asperity interlocking and increased fracture energy dissipation, whereas excessive heterogeneity leads to strength reduction. Although joint angle and grain size heterogeneity act independently, their effects are superimposed and interact synergistically to produce a nonlinear superposition of structural and material contributions to macroscopic shear strength. The findings in this study will advance the understanding of how macroscopic joints and microscopic mineral heterogeneity jointly control shear mechanism in jointed granite, providing theoretical guidance for stability evaluation and risk assessment in enhanced geothermal systems (EGS) and geological repositories for radioactive nuclear waste.