预应力锚杆因出色的维稳能力及巨大的经济效益,在岩土锚固工程中扮演着重要角色。然而,预应力锚杆的长期性能常因周围恶劣岩土环境的腐蚀而不断退化。为了探究预应力锚杆在模拟岩土环境中的锈蚀机制,通过开展室内加速腐蚀试验,基于电化学阻抗谱及电化学极化曲线分析了处于弱酸、通氧条件下的预应力锚杆腐蚀损伤时变行为,以及该环境下预应力锚杆锚固力与腐蚀速率的关系。结果发现,试验过程中预应力锚杆均未出现明显钝化,浸泡前期处于未通氧环境下预应力锚杆的电化学阻抗谱为一半径很大的容抗弧,预应力锚杆腐蚀不明显,锈蚀受电荷传递控制,中后期阻抗逐渐减小;低通氧速率下预应力锚杆腐蚀由电荷传递与扩散过程联合控制;高通氧速率下预应力锚杆腐蚀受扩散控制作用随通氧速率增大稍有提前。预应力锚杆的耐蚀性随通氧速率增大并非一直降低,本次试验中锚固力损失与腐蚀速率相关性较小。
Abstract
Prestressed rock bolt plays a crucial role in geotechnical anchoring engineering thanks to its excellent stability and huge economic benefits. The long-term performance of prestressed rock bolt, however, has been degrading due to the aggressive corrosion environment of surrounding rock and soil. To investigate into the corrosion mechanism of prestressed rock bolts in simulated geotechnical environments, we examined the time-varying behaviors of corrosion damage of prestressed rock bolts under weak acid and oxygen-ventilated conditions based on electrochemical impedance spectrum and electrochemical polarization curve via indoor accelerated corrosion test, and further analyzed the relationship between anchoring force and corrosion rate of prestressed rock bolts. Results revealed no evident passivation of prestressed rock bolts during the experiment. In pre-immersion stage with no oxygen, the electrochemical impedance spectrum of prestressed rock bolt was a large tolerance arc; controlled by charge transfer, the corrosion of prestressed rock bolt was not obvious, and the impedance decreased gradually with time. With oxygen ventilated at low rate, the corrosion of prestressed rock bolt was controlled by both charge transfer and diffusion process; at high-rate of oxygen ventilation, corrosion was controlled merely by diffusion process and appeared earlier with the growth of oxygen flow rate. In conclusion, the corrosion resistance of prestressed rock bolt did not always attenuate with the increase of oxygen flow rate, and the correlation between loss of anchoring force and corrosion rate was weak in the present test.
关键词
预应力锚杆 /
腐蚀损伤 /
电化学阻抗谱 /
极化曲线 /
通氧环境 /
锚固力损失
Key words
prestressed rock bolts /
corrosion damage /
electrochemical impedance spectroscopy /
polarization curve /
oxygen-ventilated environment /
anchoring force loss
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基金
江苏省研究生科研创新计划项目(KYCX18_0565);中央高校基本科研业务费专项(2018B663X14);国家自然科学基金项目(41877280,41672320)
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