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

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.