Applications of Passive Infrared Thermal Imaging for Detecting Delaminated Areas of Ancient Rock-cut Tunnel

Delaminations are generally developed in construction works due to numerous factors, including cyclic loading, water flow, and weather conditions. A conventional non-destructive method, such as tapping or chain dragging, is commonly used to predict subsurface delaminations. However, tapping tests may require more precision, especially for minor subsurface defects. Passive Infrared Thermal Imaging or Passive Infrared Thermography (PIRT) effectively detects sizable delaminated areas of a structure quickly. However, the inspected structural components are recommended to be exposed to direct sunlight. In this study, PIRT was used to investigate an operating ancient rock-cut tunnel and to detect potentially dangerous locations where delamination and spalling have occurred. The results prove that PIRT can effectively detect delaminated areas, even when there is only a 1-2°C atmospheric temperature difference nine hours before testing.