Abstract
Numerical models are often used to describe flow and deformation processes occurring in dikes during flood events. Modeling of such phenomena is a challenging task, due to the complexity of the system, consisting of three material phases: soil skeleton, pore water and pore air. Additional difficulties are transient loading caused by variable in time water levels, heterogeneity of the soil or air trapping. This paper presents a brief review of the influence of the air phase in soil on water flow and pore pressure generation, with focus on applications related to stability of dikes, earth dams and similar structures. Numerical simulations are carried out to investigate the differences between the Richards equation and the two-phase flow model, using an in-house code based on the finite volume method. A variety of boundary problems are considered, including seepage through flood dikes, dike overtopping and water level fluctuations. Special attention is paid to the problem of air trapping, which occurs when water flows over the top of a dike. Such a phenomenon occurred during experiments on model dikes reported in the literature, ultimately leading to development of cracks and damages in dike structure.
Highlights
When considering water movement in soil, it is often assumed that the air present in the soil is connected with the atmospheric air, which has approximately constant pressure
Most of the available software for modeling unsaturated zone flow is based on the Richards equation, which does not account for the air flow
* Corresponding author: wittisle@pg.gda.pl applications focusing on the water flow, a sufficient accuracy can be achieved with a simplified model, where both air and water are considered as immiscible and the deformation of the solid skeleton is treated in a simplified manner [2, 11]
Summary
When considering water movement in soil, it is often assumed that the air present in the soil is connected with the atmospheric air, which has approximately constant pressure. There is an increasing evidence that in some situations air flow must be taken into account: heterogeneous soils [1,2,3], rapid downward infiltration [4], water table fluctuations [5], seismic events [6] or overtopping of dikes [7,8,9,10]. In such cases the two phase flow model should be taken into account. We compare solutions obtained using the full two phase model with the solutions of the Richards equation, which neglects the air flow
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