Measuring Soil Erodibility Using a Laboratory “Mini” JET

Typically soil erodibility is quantified using an excess shear stress equation, dependent on two major soil parameters: the critical shear stress (τc) and the erodibility coefficient (kd). A submerged jet test (JET, Jet Erosion Test) is one method that has been developed and methodology of use established in the literature for measuring these parameters. In this study, a new miniature version of the JET device (“mini” JET), with the advantage of being easier to use in the field, was used to measure τc and kd for two soils (silty sand and clayey sand), and results were compared to the larger original laboratory JET. The objective of this research was to determine if the “mini” JET measured equivalent values for τc and kd compared to the original JET device. In-order to compare the performance and repeatability of both JET devices, tests were performed on paired samples prepared in the same way and tested at the same time. Samples of the soils tested were prepared at different water contents with a standard compaction effort of 600 kN-m/m3 (ASTM). Some variability in measuring τc and kd was observed between paired samples due to variability in the soil texture of the soil samples and differences in soil moisture levels. The kd values measured by the two JET devices for both soils were not significantly different. The τc values measured by the “mini” JET were consistently lower than those measured by the original JET. This was hypothesized to be due to the structure of the soil sample due to the compaction method and the procedure utilized to determine τc. Adjustment of the equilibrium depth of the “mini” JET resulted in small differences in the estimated τc between both JET devices. Both JET devices also demonstrated consistent performance in measuring τc-kd relationships, which were compared with those observed in previous field research.