DEVELOPMENT OF A JET INDEX TO CHARACTERIZE EROSION RESISTANCE OF SOILS IN EARTHEN SPILLWAYS

ABSTRACT A soil parameter is developed based on concepts from local scour studies of non-cohesive and cohesive soils and the results of a site-specific submerged jet testing device. Submerged jet test results on four soils with a range of physical conditions are analyzed. The submerged jet had a nozzle diameter of 13 mm, and was set at a jet height of 0.22 m prior to testing the soil. The soils were tested over a range of jet velocities at the nozzle of 166 cm/s to 731 cm/s. The results indicate that erosion, expressed as the depth of scour divided by time, in the site-specific submerged jet testing device may be related to the jet velocity, a time function, and a soil parameter (jet index, Ji). The jet index is intended to provide a common method of expressing erosion resistance, to assist those who work with different soils and soil conditions for measurement and design, and possibly to develop performance and prediction relationships for earthen spillways.