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| Infrared detection method for shallow peeling of tunnel lining |
| LIU Xuezeng1，TANG Jing1，YANG Zhilu2，3，GU Wenchuan1，DUAN Junming1 |
| (1. College of Civil Engineering，Tongji University，Shanghai 200092，China；
2. Shanghai Engineering Research Center of Underground Infrastructure Detection and Maintenance Equipment，Shanghai 200092，China；3. Tongyan Civil Engineering Technology Co.，Ltd.，Shanghai 200092，China) |
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Abstract ：Because of the deterioration of lining materials or corrosion of steel bars, it is easy to cause shallow concrete spalling，which will seriously affect the safety of tunnel operation. It is necessary to find the concrete spalling phenomenon in time through non-destructive testing technology and judge the possibility of spalling. The purpose of this paper is to explore the feasibility of using infrared thermal imaging technology to detect the peeling defects of lining concrete. The methods of numerical analysis，indoor tests and field tests are used to analyze the influence factors on the temperature field of lining inner surface under natural environment and heating conditions. These factors include stripping depth，size and temperature difference between the two sides of the lining. The results show that，the square shallow peeling defects with side length of 80 mm can be detected when the spalling depth is 10 mm and the temperature difference between the two sides of the lining is 8.06 ℃. And when the spalling depth is 50 mm and the temperature difference reaches 11.9 ℃，it is possible to detect the peeling range with side length no less than 150 mm. It is feasible to detect the shallow spalling defects of tunnel lining within 50 mm depth by infrared thermal imager under natural conditions，and the detection feasibility increases with the decrease of defect depth. Moreover，the temperature difference between the stripping position and the intact position on the detection surface is proportional to the temperature difference between the two sides of the lining，and increases linearly with the increase of the side length of the peeling range. Under the heating condition, the effect of infrared detection is obviously improved，but it is still not available for defects with side length less than 20 mm.
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2021, Vol. 40 
