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<p>The acoustic emission (AE) characteristics of rocks under stress paths associated with rockbursts is crucial for understanding the underlying mechanisms of rockburst events. This study presents an investigation using granite from the site of a rockburst in the Lalin Railway Tunnel as a case study. A three-dimensional particle flow model was developed using the Particle Flow Code (PFC) to simulate the rockburst stress path, with wall movement used to replicate the stress evolution. The micromechanical parameters of the rock were calibrated based on results from uniaxial compression tests. To assess the effects of unloading, the unloading rate was varied, dividing the unloading process into three distinct types: instantaneous unloading (infinite unloading rate), fast unloading (0.2&#xa0;m/s), and slow unloading (0.1&#xa0;m/s). The AE characteristics during rock deformation and failure under these unloading conditions were then analyzed. Results indicated that rock unloading was accompanied by significant dilatational deformation, with the likelihood of rockburst occurrence increasing as the unloading rate accelerated. The failure mode was found to be a combination of tensile and shear fractures, with tensile cracks comprising approximately 70% of the total fractures. Additionally, the AE rupture strength at the point of failure was higher for instantaneous and slow unloading rates compared to fast unloading. The maximum AE rupture strength was predominantly observed in the upper and middle sections of the specimen. The ranking of AE rupture strength, from highest to lowest, was slow unloading, instantaneous unloading, and fast unloading. These findings offer valuable insights into the mechanisms of rockburst initiation and can inform the development of effective prevention strategies for deep-buried tunnels.</p>

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Acoustic Emission Characteristics of Granite Under Unloading Rates: Insights for Rockburst in Deep Tunnels

  • 期刊论文

  • 发表日期：

    2025年9月19日

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  • Yalei Wang,
  • Shiyu Shang,
  • Jinming Xu,
  • Zhenyi Wang

摘要

The acoustic emission (AE) characteristics of rocks under stress paths associated with rockbursts is crucial for understanding the underlying mechanisms of rockburst events. This study presents an investigation using granite from the site of a rockburst in the Lalin Railway Tunnel as a case study. A three-dimensional particle flow model was developed using the Particle Flow Code (PFC) to simulate the rockburst stress path, with wall movement used to replicate the stress evolution. The micromechanical parameters of the rock were calibrated based on results from uniaxial compression tests. To assess the effects of unloading, the unloading rate was varied, dividing the unloading process into three distinct types: instantaneous unloading (infinite unloading rate), fast unloading (0.2 m/s), and slow unloading (0.1 m/s). The AE characteristics during rock deformation and failure under these unloading conditions were then analyzed. Results indicated that rock unloading was accompanied by significant dilatational deformation, with the likelihood of rockburst occurrence increasing as the unloading rate accelerated. The failure mode was found to be a combination of tensile and shear fractures, with tensile cracks comprising approximately 70% of the total fractures. Additionally, the AE rupture strength at the point of failure was higher for instantaneous and slow unloading rates compared to fast unloading. The maximum AE rupture strength was predominantly observed in the upper and middle sections of the specimen. The ranking of AE rupture strength, from highest to lowest, was slow unloading, instantaneous unloading, and fast unloading. These findings offer valuable insights into the mechanisms of rockburst initiation and can inform the development of effective prevention strategies for deep-buried tunnels.