<p>Frequent failures of roadway anchor bolts in the roof-dripping zones of the Tashan coal mine endanger roadway stability and safety. To clarify the stress-corrosion cracking (SCC) mechanism and identify mitigation strategies, we combined water-chemistry analysis, multi-scale fractography, slow strain-rate tensile (SSRT) testing, and on-site anti-corrosion trials. Mine water showed weak alkalinity (pH 7.06–7.82), high mineralization (970–1980 mg L<sup>− 1</sup>), and elevated Cl<sup>⁻</sup>/SO<sub>4</sub><sup>2−</sup> suggesting strong pitting tendencies. Failed field bolts displayed limited necking, step-like fracture sections, and dendritic crack networks initiated at pits. SSRT tests in simulated solution revealed marked reductions in plasticity and strength compared to air; the SCC susceptibility index (ISCC), based on elongation, rose from 15.76% at 10<sup>− 3</sup> s<sup>− 1</sup> to 59.23% at 10<sup>− 7</sup> s<sup>− 1</sup>, demonstrating greater SCC sensitivity at lower strain rates. SEM confirmed reduced dimples, deep pits, and reticulated cracking. A four-stage mechanism was proposed: pit initiation, crack nucleation via anodic dissolution under stress, occluded-cell-assisted propagation, and unstable fracture, often intergranular. Field trials with hot-dip-galvanized bolts showed intact surfaces and stable axial-force responses for over 30 days in dripping zones, confirming both barrier and sacrificial-anode protection. These results provide mechanistic insights and may offer practical guidance for improving corrosion-resistant anchor bolt design in aggressive underground environments, while recognizing that long-term monitoring and broader protective strategies remain necessary.</p>

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Multi-scale analysis of stress-corrosion failure and anti-corrosion strategies for anchor bolts in Tashan coal mine

  • Lei Wang,
  • Zhongwei Li,
  • Yukai Fu,
  • Xiang Xu,
  • Xiaowei Chu

摘要

Frequent failures of roadway anchor bolts in the roof-dripping zones of the Tashan coal mine endanger roadway stability and safety. To clarify the stress-corrosion cracking (SCC) mechanism and identify mitigation strategies, we combined water-chemistry analysis, multi-scale fractography, slow strain-rate tensile (SSRT) testing, and on-site anti-corrosion trials. Mine water showed weak alkalinity (pH 7.06–7.82), high mineralization (970–1980 mg L− 1), and elevated Cl/SO42− suggesting strong pitting tendencies. Failed field bolts displayed limited necking, step-like fracture sections, and dendritic crack networks initiated at pits. SSRT tests in simulated solution revealed marked reductions in plasticity and strength compared to air; the SCC susceptibility index (ISCC), based on elongation, rose from 15.76% at 10− 3 s− 1 to 59.23% at 10− 7 s− 1, demonstrating greater SCC sensitivity at lower strain rates. SEM confirmed reduced dimples, deep pits, and reticulated cracking. A four-stage mechanism was proposed: pit initiation, crack nucleation via anodic dissolution under stress, occluded-cell-assisted propagation, and unstable fracture, often intergranular. Field trials with hot-dip-galvanized bolts showed intact surfaces and stable axial-force responses for over 30 days in dripping zones, confirming both barrier and sacrificial-anode protection. These results provide mechanistic insights and may offer practical guidance for improving corrosion-resistant anchor bolt design in aggressive underground environments, while recognizing that long-term monitoring and broader protective strategies remain necessary.