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Faculty Mentor

Allen Jones, Francis Ting

Abstract

The Erosion Function Apparatus (EFA) test uses site-specific soil samples acquired via thin-walled tubes to generate the erosion rate and shear stress which is plotted to create an erosion plot. The information produced by the test can help an engineer accurately determine the depth of scour as a function of time for bridge design, and thereby determine the depth a foundation system should be constructed. During EFA testing, a data acquisition system records the velocity and amount of soil eroded. This data is used to calculate the Reynolds Number, friction factor, erosion rate, and shear stress. Once the data has been reduced to erosion rate and shear stress, it is plotted to form an EFA plot. The EFA test contains significant uncertainties in selecting the roughness values and timing of the test. Selecting incorrect roughness values can produce a misleading EFA plot by incorrectly calculating the shear stresses, which will not be representative of the erodibility of the soil. Incorrectly timing the test will also lead to an inaccurate representation of the erodibility of the soil by improperly calculating the erosion rate.

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