Experimental and Numerical Analysis of Air Trapping in a Porous Medium with Coarse Textured Inclusions

Szymańska, Paulina; Tisler, Witold; Schütz, C.; Szymkiewicz, Adam; Neuweiler, Insa; Helmig, Rainer

doi:10.1515/acgeo-2016-0095

Cited by 7 publications

(8 citation statements)

References 37 publications

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“…Consequently, most of the available software for modeling unsaturated zone flow is based on the Richards equation, which does not account for the air flow. However, 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.…”

Section: Introductionmentioning

confidence: 99%

Influence of the air phase on water flow in dikes

Tisler

Szymkiewicz

2017

E3S Web Conf.

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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.

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Section: Introductionmentioning

confidence: 99%

Influence of the air phase on water flow in dikes

Tisler

Szymkiewicz

2017

E3S Web Conf.

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“…It is generally accepted that comprehensive representations of water flow in the vadose zone can be obtained using the Richards equation (e.g., Healy, 2010), although this approach generally does not account for some processes that may be important at the local scale, such as preferential flow (e.g., Šimůnek et al, 2003) or air entrapment (e.g., Szymańska et al, 2016). An extended form of the Richards equation can be used to describe flow under both unsaturated and saturated conditions, thereby offering a unified three-dimension (3D) description of flow for the entire subsurface domain.…”

Section: Introductionmentioning

confidence: 99%

Simulations of freshwater lens recharge and salt/freshwater interfaces using the HYDRUS and SWI2 packages for MODFLOW

Szymkiewicz

Gumuła-Kawęcka

Šimůnek

et al. 2018

Journal of Hydrology and Hydromechanics

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Abstract:The paper presents an evaluation of the combined use of the HYDRUS and SWI2 packages for MODFLOW as a potential tool for modeling recharge in coastal aquifers subject to saltwater intrusion. The HYDRUS package for MODFLOW solves numerically the one-dimensional form of the Richards equation describing water flow in variablysaturated media. The code computes groundwater recharge to or capillary rise from the groundwater table while considering weather, vegetation, and soil hydraulic property data. The SWI2 package represents in a simplified way variable-density flow associated with saltwater intrusion in coastal aquifers. Combining these two packages within the MODFLOW framework provides a more accurate description of vadose zone processes in subsurface systems with shallow aquifers, which strongly depend upon infiltration. The two packages were applied to a two-dimensional problem of recharge of a freshwater lens in a sandy peninsula, which is a typical geomorphologic form along the Baltic and the North Sea coasts, among other places. Results highlighted the sensitivity of calculated recharge rates to the temporal resolution of weather data. Using daily values of precipitation and potential evapotranspiration produced average recharge rates more than 20% larger than those obtained with weekly or monthly averaged weather data, leading to different trends in the evolution of freshwater-saltwater interfaces. Root water uptake significantly influenced both the recharge rate and the position of the freshwater-saltwater interface. The results were less sensitive to changes in soil hydraulic parameters, which in our study were found to affect average yearly recharge rates by up to 13%.

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“…The air remaining in inclusions cannot escape unless its pressure exceeds the entry pressure of the background material. As a result, local unsaturated zones are formed, with continuous air phase in the pores of coarse inclusion [11,36,40,42].…”

Section: Introductionmentioning

confidence: 99%

Simulations of air and water flow in a model dike during overflow experiments

et al. 2018

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Flow in flood dikes, earth dams, and embankments occurs in variably saturated conditions, with pores of the earth material filled partly with water and partly with air. In routine engineering analysis, the influence of pore air is neglected and the air pressure is assumed equal to atmospheric. In some circumstances, for example, during overtopping of the dike by water, the effect of pore air on water flow and stability of the structure can be important. These features cannot be captured with the commonly used Richards equation. In this paper, we analyze earlier experiments on the overtopping of a model dike made of fine sand. During the experiments, a significant amount of air was trapped near the outer slope of the dike, which later escaped through a fracture formed in wet sand. The observations were compared with numerical simulations using the Richards equation and the two-phase immiscible flow model. The deformation and damage of the dike were not modelled, but the initial evolution of the entrapped air pressure (before damage occurred) was in a good agreement with two-phase flow simulations.

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Experimental and Numerical Analysis of Air Trapping in a Porous Medium with Coarse Textured Inclusions

Cited by 7 publications

References 37 publications

Influence of the air phase on water flow in dikes

Influence of the air phase on water flow in dikes

Simulations of freshwater lens recharge and salt/freshwater interfaces using the HYDRUS and SWI2 packages for MODFLOW

Simulations of air and water flow in a model dike during overflow experiments

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