矿井水影响下锚索应力腐蚀行为与机理

Stress corrosion behavior and mechanism of cable bolts under the influence of mine water

  • 摘要: 锚索是煤矿巷道围岩控制的主要支护材料。锚索在服役过程中不仅承受高应力荷载,而且受井下苛刻腐蚀环境的影响,应力与腐蚀耦合作用下导致的锚索应力腐蚀开裂失效问题凸显,已严重威胁煤矿锚索服役安全,其中矿井水是诱发锚索腐蚀的关键因素。为了研究不同类型矿井水对锚索应力腐蚀行为的影响规律,采用电化学阻抗谱、电化学极化技术、室内浸泡加速腐蚀试验和微观形貌扫描等方法,分析矿井水中不同的pH、SO42−和Cl浓度影响下锚索的电化学行为与腐蚀演化特征,揭示锚索应力腐蚀开裂机理,阐明锚索应力腐蚀断裂模式。研究结果表明:矿井水pH在2~10范围内,随着pH增加,锚索腐蚀速率先减小后增大,不同的pH改变锚索的腐蚀反应类型,在酸性条件下更容易导致应力腐蚀裂纹形核。矿井水中SO42−和Cl对锚索腐蚀的影响规律类似,均是随着浓度的增加,腐蚀速率逐渐增大,更容易诱发应力腐蚀裂纹萌生;不同的离子浓度范围,应力腐蚀速率增加幅度具有差异性。阳极溶解和氢致开裂是锚索应力腐蚀开裂的2种主要机理,锚索应力腐蚀裂纹萌生经历点蚀、点蚀生长和裂纹形核3个阶段;锚索应力腐蚀断口为台阶式破坏,具有典型的3区,即裂纹萌生区、扩展区和终断区。最后,从“材料、环境和应力”3个维度,提出了防止锚索应力腐蚀开裂的控制对策。

     

    Abstract: Cable bolts are the primary support material for controlling the surrounding rock in underground coal mine roadways. During their service life, cable bolts not only bear high stress loads but are also affected by the harsh corrosive environment. Consequently, stress corrosion cracking (SCC) resulting from the coupling effect of stress and corrosion poses a significant threat to their service reliability in underground coal mines. Among various factors, mine water is a key factor that induces cable bolt corrosion. To investigate the influence of different types of mine water on the stress corrosion behavior of cable bolts, electrochemical impedance spectroscopy (EIS), electrochemical polarization technology, laboratory immersion accelerated corrosion tests and microscopic morphology scanning methods were used to characterize the electrochemical behavior and corrosion evolution characteristics of cable bolts under varying pH levels, SO42− and Cl concentrations in mine water. Overall, the study revealed the SCC mechanism of cable bolts and elucidated the fracture modes of SCC. The results indicate that within the pH range of 2 to 10, the corrosion rate of the cable bolts initially decreases and then increases as the pH increases. Furthermore, pH influences the type of corrosion reactions on the cable bolts. Under acidic conditions, the nucleation of SCC cracks is more likely to occur. The influence of SO42− and Cl concentrations in mine water on cable bolt corrosion follows a similar pattern: as the ion concentrations increase, the corrosion rate gradually increases, facilitating SCC crack initiation. However, the sensitivity of the SCC rate to concentration changes varies across different ion concentration ranges. Anodic dissolution and hydrogen-induced cracking are the two primary mechanisms for cable bolt SCC. The initiation of SCC cracks in cable bolts occurs through three stages: pit initiation, pit growth, and crack nucleation. The fracture surface of the SCC failure of cable bolts exhibits a stepped failure mode, with three typical regions: the crack initiation zone, propagation zone, and final fracture zone. Finally, based on the three dimensions of "material, environment, and stress," control strategies are proposed to prevent cable bolt SCC.

     

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