Bridging Process Threshold for Sediment Infiltrating into a Coarse Substrate

Abstract

Sand infiltration into gravel frameworks poses significant engineering and ecological difficulties. Ten flume experiments were conducted to quantify a sand bridging threshold in a static gravel bed. The D15 substrate/d85 sand ratio was computed for each of 37 unique sand-substrate pairs and the data were plotted, with previously published flume data, to determine the threshold between bridging and unimpeded static percolation. The process threshold boundary between bridging and unimpeded static percolation fell in the range of 12<D15 substrate/d85 sand<14, substantially higher than predicted by standard geotechnical filter criteria. Plotting the results against the critical constriction size of the substrates provided a more definitive process separation along the line Dc∗/d85=3.