Modeling transient groundwater flow and piping under dikes and DAMS

Dikes and dams are water mitigating structures that protect the land from floods and high tides. In the Netherlands these structures are often constructed of impervious clays and are built on a sandy aquifer as subsoil. Foundations of such geotechnical structures are vulnerable to an erosion effect called piping that refers to the development of small flow channels that begin at the downstream side of the structure where the seepage pressure is high. The internal erosion process works its way to the upstream side. If the erosion process continues the structure may collapse. This paper presents a new numerical formulation of the piping mechanism based on Poiseuille flow through a piping slit and White's limit equilibrium for particle movement, in combination with a groundwater flow simulator capable of resolving the transient behavior of the groundwater pressure field based on Richard's equation. Simulations demonstrate that the compressibility of the aquifer delays the increase of water pressures in time. This delay hampers the growth of the piping channel.