Numerical Modelling of Backward Erosion Piping: Methodological Approach and Preliminary Results

Backward erosion piping (BEP) is an internal erosion mechanism that leads to the formation of shallow erosion channels within the sandy foundation of river embankments, typically at the interface with an overlying, finer and less permeable layer. Triggered by underseepage, this process increases the likelihood of river embankment structural failures and, consequently, affects the hydraulic vulnerability of the surrounding territory. Numerical modelling of BEP is an important challenge due to the complex, different and highly localized physical processes involved, making it still an open research issue within the scientific community and highlighting the need for further investigations. This contribution first introduces backward erosion piping from a physical perspective and then presents a methodological approach to numerically simulate such process by means of finite element analysis, starting with a detailed study of the groundwater flow through a saturated porous medium. To simulate the time-dependent evolution of the erosion process, the proposed numerical algorithm combines a laminar flow transport equation with Exner’s sediment mass conservation equation. In the end, the paper discusses the promising results of preliminary analysis on groundwater flow, underscoring the complementary role of finite element analysis and physical modelling in understanding and mitigating internal erosion mechanisms beneath river embankments.