Feasibility Study on Use of Drone-Based Infrared Thermography for Soil Moisture Detection in Highway Embankment and Dam Inspections

This research explored the capabilities of drone-based infrared thermography technology for soil moisture detection on embankment/dam soils. FLIR Vue Pro R, a radiometric thermal camera, was evaluated in both laboratory and field settings on embankment/dam soils for their accuracy, repeatability, and dependability. Field testing was first carried out at the Pavement Research Facility (PRF) of the Louisiana Transportation Research Center (LTRC) to assess the camera's capabilities and limitations. Subsequently, field data were collected at one embankment and two dam sites. The laboratory tests showed that the decreasing trend in measured apparent temperature is obvious when the moisture content is low. After that, the relationship curve got flatter. Meanwhile, the field results showed that drier soil is associated with higher the measured apparent temperature. The correlation between the soil moisture content and apparent temperature reading from the thermal camera is very complicated and only has a relative value for spatial comparison when the ambient environment is not considered. The index combining the land surface temperature and vegetation within the normalized difference vegetation index (NDVI)-land surface temperature (LST) space showed promising results for detecting false wet soil results in thermal sensing due to vegetation. The failure areas or seepage issues with abnormal moisture conditions at the field-testing sites were successfully identified within regions exhibiting low measured apparent temperatures. The findings of this study demonstrate that the drone-mounted thermal camera is capable of distinguishing various moisture zones. Hence, drone-based infrared thermography technology proves to be a promising tool for rapidly mapping earth embankment and dam slope surface moisture conditions, indicating potential stability risks. Its application can enhance the information available to inspectors and dam owners, facilitating targeted ground inspections focused on areas identified as potential concerns by drone-based thermal inspection.