Passive Gamma-Ray Emission for Underwater Sediment-Disturbance Detection
ENGINEER RESEARCH AND DEVELOPMENT CENTER HANOVER NH HANOVER United States
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Sediment erosion around physical structures in surface water e.g., bridge footings is an important phenomenon to monitor. Traditional assessment methods rely on divers to make physical observations and measurements. Often, high currents and the high degree of turbidity of the water make these observations difficult. High turbidity can also prevent lowering a camera from a boat to make indirect visual observations. Another possible approach to this problem is the use of gamma-ray spectrometry. This study used a handheld sodium iodide gamma-ray detector to collect in situ gamma-ray spectra of two soils submerged in water. Study results indicate that naturally occurring gamma rays being emitted by the sediment are detectable underwater. Further, the difference in gamma-ray intensity reflects density differences in the sediment due to disturbances such as erosion. A difference between the Potassium 40 40K activity of uncompacted and compacted soil and a comparable rate of 40K signal attenuation as standing water depth increased suggests that underwater detection of in situ 40K gamma-ray emissions is a potentially viable approach to assessing underwater sediment erosion.
- Soil Mechanics
- Nuclear Physics and Elementary Particle Physics