Abstract

This dissertation focuses on the modeling of two-phase flow processes including the water and gas phase in porous media with fault zones which consist of fractures or macropores. The aim of the thesis is to make applications and comparisons of different model concepts in order to improve the process understanding and to reveal possibilities and limitations of the different approaches as well as to provide knowledge related to the potential for investigations of two-phase flow modeling in porous media with fault zones. Here, three different model concepts were investigated: 2D fracture model concept, 1D fracture model concept and fracture with pipe model concept.

Generally, the choice of model concept is strongly depending on the characteristics of the problems being considered, for example, the scales of the problem. The modeling of two-phase flow processes in porous media with fault zones has been applied to domains with different scales (small scale (<1m), laboratory scale (1-10m) and small field scale (10-100m)).

The first application is carried out in a small scale domain. Water infiltration processes in a single vertical fracture are analyzed. The numerical simulation results show an overall very good agreement between two model concepts: 2D fracture model concept and 1D fracture model concept. The pipe model concept is not suitable in this case.

The second application is carried in a laboratory scale domain. Seepage processes through a dike are investigated for systems with one horizontal fault zone on different locations ont the land or sea side. To check the model concepts, experiments from the laboratory were compared to the numerical simulations. The 2D fracture model concept and 1D fracture model concept are suitable for numerical model in this case, as a good agreement between the experimental and numerical results was obtained. However, the results show an over-estimation of the seepage processes for the pipe model concept. Therefore, this model concept is not further recommended.

The last application is carried out in a small field scale domain. A slope which is idealized from a natural hillslope in Vorarlberg Alps is chosen as a case study for the simulation. The results show considerable influences of the preferential flow in macropores on the water infiltration processes in the slope. Due to the property of macropores, the infiltration is strongly speeded up. However, the maximum water pressure in the system is somewhat smaller due to the macropores. The fast pressure increase in lower parts of a layered hillslope is one main factor influencing the slope stability. The numerical results are in principal agreement with observations in the field. For investigation the influences of small-scale heterogeneities, geostatistical methods are used to generate permeability fields. Comparative studies have been carried out and analyzed for cases with different parameters like correlation lengths, variances, and anisotropies. The simulation results illustrate a more or less strong influence of smallscale heterogeneities on the saturation and pressure