Comparison of Shear Stress in Erosion Function Apparatus and Portable Scouring Testing Device

Soil erosion is critical in assessing bridge pier scours. To minimize the uncertainty in soil erosion analysis, the Federal Highway Administration (FHWA) introduced the portable scour test device (PSTD) to measure soil resistance by in situ testing in the field. The PSTD is a new erosion testing device that has a lot of similarities with the in situ scour testing device (ISTD) in mechanism and data acquisition. The fluid condition in PSTD is radial, and the recorded data in PSTD include flow rate, depth of eroding soil sample, and the eroding time. Shear stress induced by the fluid is an important parameter, which plays a load role in the soil erosion process. PSTD in its current setup lacks a sensor to measure shear stress at the soil-water interface. A computational fluid dynamics (CFD) method is used to simulate the shear stress imposing on the soil sample in a PSTD test. Also, a set of six controlled erosion function apparatus (EFA) and PSTD lab tests have been performed to compare the shear stress obtained from these two tests. The comparison allows for identifying a correlation of shear stress obtained from EFA and PSTD.