Behavioral Comparison of Fluorescent Tracer Sediment to Lightweight Polystyrene Sediment of the Lower Mississippi River Physical Model (LMRPM)
Semester of Graduation
Master of Civil Engineering (MCE)
Civil and Environmental Engineering
A lightweight, unexpanded polystyrene sediment with a specific gravity of 1.05 and a D10, D50 and D90 of 0.250 mm, 0.425mm, and 0.800 mm, respectively, is utilized in the Lower Mississippi River Physical Model (LMRPM) at Louisiana State University to mimic the sand transport of the Lower Mississippi River. While the black model sediment is easily visible against the stark white of the LMRPM, the relative homogeneity of the sediment particles and the opaqueness of the model channel make it difficult to closely study sediment dynamics during an experiment. For this reason, a tracer sediment that is marked with fluorescence and magnetic properties was tested to allow for more quantitative tracking of particles, and therefore an enhanced understanding of sediment transport and dynamics in the LMRPM. While these particles share similar density and relative grain sizes, parameters such as their angularity, settling velocities, and threshold for incipient motion are unknown. Angle of repose, settling velocity, and incipient motion tests are conducted to estimate these parameters and compare the tracer sediment behavior to that of the model sediment to determine how the tracer sediment can eventually be employed in the LMRPM. While differences do exist between the sediments’ settling velocities and angles of repose, incipient motion tests that combine the two sediments reveal surprisingly similar thresholds for motion, suggesting that the tracer sediment can be implemented in the LMRPM to study punctuated sand transport and the evolution of sand bars around sediment diversions. A pilot study where tracer sediment was seeded in the sand bars upstream of the Mid-Breton and Mid-Barataria Sediment Diversions produced positive results, bolstering the use of the tracer sediment in the LMRPM.
Mudd, Julia C., "Behavioral Comparison of Fluorescent Tracer Sediment to Lightweight Polystyrene Sediment of the Lower Mississippi River Physical Model (LMRPM)" (2023). LSU Master's Theses. 5787.