隧道衬砌锈蚀钢筋的热效应及红外检测方法

Thermal Effect of Reinforcement Corrosion in Tunnel Lining and Infrared Detection Method

摘要:

隧道衬砌受腐蚀环境、材料劣化以及地下水的影响，衬砌钢筋锈蚀将成为衬砌后期服役的主要病害之一，钢筋锈蚀以及产生的顺筋裂缝直接威胁衬砌的耐久性和安全性，为此，及时检测钢筋锈蚀程度十分重要。目前的检测方法以接触式测量为主，效率低，为探究非接触快速检测的可行性，采用室内试验和数值分析相结合的方法，深入研究了浅层钢筋锈蚀的热传导规律，分析了主动热激励条件下钢筋锈蚀程度和混凝土保护层厚度对衬砌表面温度场的影响规律。结果表明：主动热激励条件下锈蚀产物表面分布区在热像图中表现为高温区；钢筋锈蚀率为4.36 %~23.16 %时，衬砌表面温差为2.3 ℃~4.4 ℃；试件表面温差随钢筋锈蚀程度的增加而增大，呈现三次函数的关系；而混凝土保护层厚度与表面温差呈明显的负相关性，保护层厚度越大，温差越小。夏季时由于衬砌内外温差导致的热传导效应将在钢筋锈蚀位置的衬砌表面产生，通过红外热像仪检测衬砌表面的温度分布，结合衬砌表观特征，可以综合判定钢筋的锈蚀程度，为钢筋锈蚀的快速检测提供了新的方法和技术手段。

Abstract:

As one of the most important diseases of tunnel lining， reinforcement corrosion is a serious threat to the structural durability and safe operation of tunnels in service. The reinforcement corrosion and the resulting cracks directly threaten the durability and safety of the lining. Therefore， it is very important to timely perceive the reinforcement corrosion degree of tunnel lining. The current detection method mainly relies on contact measurement， which is low in efficiency. To explore the feasibility of non-contact rapid detection， a combination of indoor experiments and numerical analysis was used to study， in detail， the heat conduction law of shallow steel corrosion. The influence of the degree of steel corrosion and the thickness of concrete protective layer on the temperature field of the lining surface under active thermal excitation conditions was analyzed. The results show that under the condition of active thermal excitation， the corrosion area of concrete surface is shown as a high temperature area in thermal image， When the corrosion rate of steel bars is 4.36 %–23.16 %， the temperature difference of concrete surface is 2.3 ℃–4.4 ℃. The temperature difference on the surface of the specimen increases with the increase of reinforcement corrosion degree， presenting a cubic function relationship. The thickness of concrete protective layer is negatively correlated with surface temperature difference. The larger the thickness of protective layer is， the smaller the temperature difference is. In summer， the heat conduction effect caused by the temperature difference between the inside and outside of the lining will occur on the lining surface at the position of reinforcement corrosion. By detecting the temperature distribution of the lining surface with infrared thermal image in combination with the apparent characteristics of the lining， the corrosion degree of reinforcement can be determined comprehensively， which provides a new method and technical means for the rapid detection of reinforcement corrosion.