1.1 This test method covers the laboratory determination of the erosion function of a soil under horizontally flowing water over the surface of a vertical soil sample in an Erosion Function Apparatus (EFA).2 The erosion function is the site-specific relationships between the erosion rate of the soil and either the mean flow velocity or the hydraulic shear stress at the water-soil interface. The erosion function of the soil has applications in earthworks impacted by scour and erosion.

1.2 The results obtained from this procedure are applicable to both coarse-grained and fine-grained soils.

1.3 The principle underlying this method is to collect a specimen from the site where erosion is being investigated and to test the specimen in the laboratory by flowing water laterally over it in a closed channel under a pressure flow condition and measuring its erosion rate. The sampling tube with the specimen is placed through the bottom of the rectangular flow channel where water is set to flow at a constant, specified velocity. The soil is pushed out of the sampling tube by a piston only as fast as the soil is eroded by the water flowing over it. For each specified water velocity, an erosion rate is measured, and a shear stress is calculated based on the Moody chart.3 The conversion from velocity to shear stress using the Moody chart requires the hydraulic diameter of the flow channel, the kinematic viscosity and mass density of the water, and the average roughness of the specimen surface after each specified velocity.

1.4 As a result of this test, a point-by-point erosion function is obtained for the tested specimen. The erosion function can be plotted as erosion rate-velocity and erosion rate-shear stress.

1.5 The critical velocity and critical shear stress of the specimen are determined as the point in the erosion function corresponding to an erosion rate of 0.1 mm/h.

1.6 Units—The values stated in SI units are to be regarded as standard. Reporting of test results in units other than SI shall not be regarded as nonconformance with this standard.

1.7 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice D6026.

1.8 The procedures used do not consider material or environmental variations, purpose(s) for obtaining the data, specialized studies, or any unique considerations for the user’s objectives; and it is common practice to increase or reduce significant digits of reported data to be commensurate with these considerations provided they are conforming to Practice D6026. It is beyond the scope of this standard to consider significant digits used in analysis methods for design.

1.9 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.10 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.