Erosion Indices of Soils Used in ARS Piping Breach Tests; Final rept

摘要

Three soils used in a series of embankment dam piping erosion and breach tests at the Agricultural Research Service hydraulics laboratory in Stillwater, Oklahoma were analyzed by the Bureau of Reclamation to determine their erodibility. Erosion indices were determined using the hole erosion test (HET) method and the submerged jet erosion test (JET) method. Tests were performed in the laboratory on three series of remolded specimens, the first compacted at optimum moisture content to approximately 95% of Standard Proctor maximum density (representative conditions), the second compacted to match the real soil conditions from the ARS breach tests, and the third covering a range of compaction moisture contents. Erodibility of the soils varied from specimens so weak that they could not be tested by the HET method (likely HET group 1 or 2) up to specimens in the upper end of HET group 4 (moderately slow erosion rate). For the samples compacted to match field conditions, the two test methods ranked the erodibility of the soils similarly, but erodibility rankings were reversed for the samples compacted to the representative conditions. Jet tests on the samples compacted to match field conditions were relatively consistent with field jet tests conducted in Oklahoma immediately after each breach test. Differences between detachment rate coefficients and critical shear stresses determined by the two methods were significant and consistent with ongoing research being performed to compare these test methods across a broad range of soil types.