Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/16/2006
Publication Date: 6/1/2007
Citation: Hanson, G.J., Hunt, S. 2007. Lessons learned using laboratory jet test method to measure soil erodibility of compacted soils. Applied Engineering in Agriculture. 23(3):305-312. Interpretive Summary: Due to recent events there has been significant interest in the impact of embankment failures. Overtopping, internal erosion, and piping are the main causes of accidents and failures of embankments for dams, lagoons, and levees. Soil type and construction practices used in embankment dams and levees play a key role in both the process and rate of failure, which ultimately affects flooding. Laboratory erosion tests were conducted in this study on two soils, a sandy soil and a clay soil. The results from these tests showed that: 1) the proportions of sand, silt, and clay; 2) the compaction water content; and 3) the compaction effort all have an important impact on the rate of erosion. Even at optimum conditions the rate of erosion of the clay soil tested was observed to be 100 times less than the sandy soil. The water content of a soil at compaction was also observed to affect the soil more than 100 times. Compaction effort also impacted the erosion rate. The laboratory results were consistent with results from embankment erosion tests in the field for the same two soils. These findings indicate that erosion sensitive construction practices of embankments can impact erosion resistance and potentially flooding.
Technical Abstract: 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 paper and is used in this study to investigate the effects of compaction on erodibility. Two approaches for determining compaction specifications are 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 that resistance to erosion for a given soil can be improved by considering compaction water content, compaction effort, and soil properties. The findings indicate the usefulness of testing the erodibility of embankment materials to aid in determining the optimal compaction specifications for a given soil.