Lessons Learned Using Laboratory Jet Method to Measure Soil Erodibility of Compacted Soils

Overtopping, internal erosion, and piping are the main causes of accidents and failures of embankments for dams, lagoons, and levees. A key parameter in the failure of these structures is the erodibility of the soil materials used in construction of the embankments. The soil materials are typically constructed based on compaction specifications. The jet erosion test (JET) has been developed to study the erosion characteristics of soil materials. A laboratory version of this apparatus is described in this article and is used in this study to investigate the effects of compaction on erodibility. Two approaches for determining compaction specifications are also compared and discussed. Soil samples, 944 cm3, were prepared at different compaction water contents and compaction efforts, and tested using the JET method. Erodibility was observed to vary by several orders of magnitude dependent on the soil gradation and plasticity, and the compaction effort and water content. The findings indicate the resistance to erosion for a given soil can be improved considering the following: compaction near optimum water content creates a structure most resistant to erosion; higher compaction effort at a given water content increases erosion resistance; and soil properties including, texture and plasticity, influence erosion resistance as much or more than compaction factors. The findings also indicate the usefulness for erodibility testing of embankment materials to aid in determining the optimal compaction specifications for a given soil.