Modeling Internal Erosion Processes in Soil Pipes: Capturing Geometry Dynamics

Abstract

Core Ideas Soil pipes are important features contributing to nonuniform flow in the vadose zone. Soil pipe flow and internal erosion is modeled with coupled flow and transport equations. Modeling results compare favorably to experimental measurements. The flow of water in a soil pipe and the resulting erosion of the soil pipe wall is simulated using a numerical solution of the Reynolds‐averaged Navier–Stokes equations coupled with the well‐known linear excess shear stress equation and the governing equation for transport of suspended sediment in turbulent flow. The modeling results are compared with an experiment in which the entrance to the soil pipe constructed in a laboratory flume was subjected to a constant head of water in a reservoir. The modeled pipe discharge was in good agreement with the measured results when roughness was imposed on the pipe wall. The temporal growth of the soil pipe was in good agreement with the experimental results when using a soil erodibility coefficient of 0.0025 s/m. Several assumptions were made in model formulation, the most significant being that the soil pipe grows uniformly along its length and that no sediment deposition occurs. Recommendations for future work regarding these assumptions as well as others are discussed.

A novel analytical model for determining erosion from hole erosion tests

“…Wan and Fell (2004a) proposed laboratory testing method to determine the erosion coefficient in the pre-formed soil pipe. The erosion law is generally employed to explain stressstrain relationship on the soil pipe periphery (Nieber et al 2019). The erosion coefficient reflects the binding force of the inner soil layer to resist wall shear stress.…”

“…Internal erosion progressively erodes geotechnical infrastructures, such as earthen dam, road embankment, and landfill cover through preferential flow or rise in water level (Nieber et al 2019). Internal erosion driven by seepage force would lead to the change of soil properties (i.e., soil stiffness, porosity, permeability), and further trigger the occurrence of piping, settlement, sinkhole, landslide, and even collapse (Cividini and Gioda 2004;Elkholy et al 2015;Sato and Kuwano 2018;Indiketiya et al 2019).…”

“…Generally, the mechanism of internal erosion is idealized as a soil pipe model (Nieber et al 2019). The moving fluid flow acts on the soil boundaries causing the deformation (i.e.…”

“…However, these numerical approaches using the computational fluid dynamics or finite element method had limitation in determining erosion characteristics of soils in the HET (Lachouette et al 2008). Limited studies considered erosion characteristics (especially erosion coefficient) in the theoretical deductions of numerical simulation, in which soil erosion were mostly considered as soil dispersity or diffusion instead of shearing movement of soil particles (Onate et al 2011;Hicher 2013;Nieber et al 2019). Bernatek-Jakiel and Poesen (2018) and Wilson et al (2018) pointed out that the mechanistic mathematical formulations explaining sediment detachment and transport within soil pipes have not been fully established yet.…”

Current Insights into Nonuniform Flow across Scales, Processes, and Applications

“…Nieber et al (2019) developed a numerical approach based on the Reynolds‐averaged Navier–Stokes equation, coupled with suspended sediment transport equations for the modeling of turbulent flow and internal erosion of a uniform diameter soil pipe. Their modeling results were consistent with experimental data, provided that the pipe wall roughness and soil erodibility were properly chosen.…”