A state-of-the-art review of active-thermometry techniques for bridge and pipeline scour monitoring, and exploratory passive thermometry studies

ABSTRACT This paper reviews the application of active thermometry techniques for bridge and pipeline scour monitoring, and explores the potential for passive thermometry through outdoor bucket-type static scour experiments. Active thermometry uses a device to supply heat and then monitors temperature loss. The heat generation is typically through resistive (joule) heating, and temperature is measured using digital temperature sensors, fiber optic temperature sensors, and thermistors. All laboratory studies in the literature were conducted in static conditions, in which the onset and progression of scour are detected by monitoring the changes in thermal properties using sensors placed along the bridge pier (or pipeline). The passive thermometry option explored in this study involved using DS18b20 digital temperature sensors to measure temperature variations in water and in three sediment types: clay, sand, and gravel. The results demonstrated larger diurnal variations in water than in the sediments. Sensors located in the sediment were distinguished from those in water by examining a combination of decrement ratios and phase shifts among the different temperature waveforms obtained for a finite number of diurnal cycles.