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<p>Stick–slip is the predominant fault movement mode during earthquakes, wherein the frictional weakening effect driven by stress-rate coupling serves as the principal mechanism causing instability at frictional interfaces. Through a series of frictional tests, this study investigated the stick–slip characteristics and stability evolution of granite fractures under stress-rate coupled conditions. By introducing the stick–slip index (SSI), the transition criterion between stable slip and stick–slip behavior was quantitatively determined. Furthermore, the damage morphologies of fracture surfaces under different levels of stick–slip release intensity were systematically examined. The results indicate the shear strength of fractures significantly increases with rising normal stress (maximum increase of 74.03%) but progressively decreases as slip rate increases (maximum decrease of 39.2%). Although fractures inevitably undergo stable slip deformation in the initial slip stage, the transition to stick–slip is jointly governed by normal stress and slip rate. The optimal slip rate range for stick–slip behavior is approximately 0.0005–0.001&#xa0;mm/s, with fracture movement becoming increasingly stable slip-dominated as the slip rate deviates further from this interval. Elevated normal stress suppresses stick–slip initiation, yet, once stick–slip occurs, it induces a more severe instability response, demonstrated by the velocity-state friction parameter (<i>a–b</i>) reaching minimum values during slip-rate perturbations between 0.001&#xa0;mm/s and 0.005&#xa0;mm/s, and decreasing progressively with increasing normal stress. Fracture surface damage correlates directly with the intensity of stick–slip release, macroscopically exhibiting linear abrasion bands varying in number and size, and microscopically presenting milky-white arcuate scratches (with arc convexities oriented toward the slip direction) and secondary fractures induced by the concentrated of shear debris. These damage morphologies provide important geological markers for identifying the transition between stable slip and stick–slip in fault zones.</p>

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Evaluation Criterion for Stable Sliding to Stick–Slip Transition and Surface Damage Evolution of Granite Fractures Under Coupled Stress–Rate Conditions

  • 期刊论文

  • 发表日期：

    2026年7月25日

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  • Peng Zhao,
  • Zijun Feng,
  • Hanmo Nan,
  • Peihua Jin,
  • Chunsheng Deng

摘要

Stick–slip is the predominant fault movement mode during earthquakes, wherein the frictional weakening effect driven by stress-rate coupling serves as the principal mechanism causing instability at frictional interfaces. Through a series of frictional tests, this study investigated the stick–slip characteristics and stability evolution of granite fractures under stress-rate coupled conditions. By introducing the stick–slip index (SSI), the transition criterion between stable slip and stick–slip behavior was quantitatively determined. Furthermore, the damage morphologies of fracture surfaces under different levels of stick–slip release intensity were systematically examined. The results indicate the shear strength of fractures significantly increases with rising normal stress (maximum increase of 74.03%) but progressively decreases as slip rate increases (maximum decrease of 39.2%). Although fractures inevitably undergo stable slip deformation in the initial slip stage, the transition to stick–slip is jointly governed by normal stress and slip rate. The optimal slip rate range for stick–slip behavior is approximately 0.0005–0.001 mm/s, with fracture movement becoming increasingly stable slip-dominated as the slip rate deviates further from this interval. Elevated normal stress suppresses stick–slip initiation, yet, once stick–slip occurs, it induces a more severe instability response, demonstrated by the velocity-state friction parameter (a–b) reaching minimum values during slip-rate perturbations between 0.001 mm/s and 0.005 mm/s, and decreasing progressively with increasing normal stress. Fracture surface damage correlates directly with the intensity of stick–slip release, macroscopically exhibiting linear abrasion bands varying in number and size, and microscopically presenting milky-white arcuate scratches (with arc convexities oriented toward the slip direction) and secondary fractures induced by the concentrated of shear debris. These damage morphologies provide important geological markers for identifying the transition between stable slip and stick–slip in fault zones.