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<p>The closure behavior of rock fractures is a critical factor influencing the stability and seepage properties of rock masses, governed by multiple parameters such as fracture surface morphology and dip angle. While the significant influence of dip angle on the macroscopic mechanical behavior of fractures is recognized, the mesoscale evolution of contact pressure and its theoretical description for low to moderate dip angles (0°–30°) remain poorly understood. This study integrates 3D laser scanning and pressure-sensitive film experiments with theoretical analysis to systematically investigate the closure mechanisms and contact characteristics of granite fractures with various dip angles under normal stresses of 1–4&#xa0;MPa. Results show that as the dip angle increases, the contact pressure distribution evolves from a symmetrical circular pattern to a strip-like pattern. The average contact stress decreases significantly (from 7 to 8.5&#xa0;MPa to 1–1.8&#xa0;MPa), while the contact ratio increases exponentially (from 6% to 70%). By incorporating a dip angle cosine term into the Bandis model and modifying the equivalent curvature radius and contact force formulas in Hertzian contact theory, this study quantifies the control of geometric asymmetry and anisotropy on contact stress distribution, revealing how the dip angle regulates mesoscopic contact evolution through normal stress decomposition and geometric asymmetry. At different stress levels, the fracture aperture maintains a Gaussian distribution, with smaller apertures closing preferentially as stress increases. The mesoscopic contact mechanics framework established in this study, which explicitly accounts for dip angle effects, provides a theoretical basis for accurately predicting the mechanical behavior of non-orthogonal fracture systems. This work holds significant theoretical value and offers practical guidance for the stability assessment of engineering rock masses, the optimization of hydraulic fracturing, and the safe development of underground resources.</p>

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Mesoscopic mechanisms of fracture closure in granite: experimental and theoretical insights into dip angle effects

  • 期刊论文

  • 发表日期：

    2026年8月5日

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  • Haichun Ma,
  • Jian Wang,
  • Jiazhong Qian

摘要

The closure behavior of rock fractures is a critical factor influencing the stability and seepage properties of rock masses, governed by multiple parameters such as fracture surface morphology and dip angle. While the significant influence of dip angle on the macroscopic mechanical behavior of fractures is recognized, the mesoscale evolution of contact pressure and its theoretical description for low to moderate dip angles (0°–30°) remain poorly understood. This study integrates 3D laser scanning and pressure-sensitive film experiments with theoretical analysis to systematically investigate the closure mechanisms and contact characteristics of granite fractures with various dip angles under normal stresses of 1–4 MPa. Results show that as the dip angle increases, the contact pressure distribution evolves from a symmetrical circular pattern to a strip-like pattern. The average contact stress decreases significantly (from 7 to 8.5 MPa to 1–1.8 MPa), while the contact ratio increases exponentially (from 6% to 70%). By incorporating a dip angle cosine term into the Bandis model and modifying the equivalent curvature radius and contact force formulas in Hertzian contact theory, this study quantifies the control of geometric asymmetry and anisotropy on contact stress distribution, revealing how the dip angle regulates mesoscopic contact evolution through normal stress decomposition and geometric asymmetry. At different stress levels, the fracture aperture maintains a Gaussian distribution, with smaller apertures closing preferentially as stress increases. The mesoscopic contact mechanics framework established in this study, which explicitly accounts for dip angle effects, provides a theoretical basis for accurately predicting the mechanical behavior of non-orthogonal fracture systems. This work holds significant theoretical value and offers practical guidance for the stability assessment of engineering rock masses, the optimization of hydraulic fracturing, and the safe development of underground resources.