Development of concepts to generate boundary and initial conditions for a two-phase flow dual-permeability model to simulate the rapid water infiltration into macro-porous soils

The present thesis deals with the investigation of boundary conditions in the simulation of water infiltration into ground with the simulation tool MUFTE-UG. This study is aiming to the application and further development of the software MUFTE-UG, in the frame of the Grosshang project in western Austria, concerning moving landslides. A general description of the study area and the project is given first in the thesis. After that, the related physical principles are described, regarding subsurface flow. Specifically, certain properties of the ground as a porous medium are studied as well as flow consisting of two phases, water and air. Also the special feature of the ground at the studied area, the differently behaving macropores, is discussed, leading to the final form of the mathematical relations used in the program to describe subsurface flow. Apart from these, the existing model types for simulating water flow in a porous medium are presented and the structure and function of MUFTE-UG are explained. As for the applications of the simulation tool, the parameters and assumptions concerning the study in the present thesis are firstly described. The concept and setup of the initial as well as the boundary conditions(BC) at the boundaries of the domain are then presented, namely the Dirichlet and the Neumann BC. The simulations and some representative results are given and discussed. Certain cases of Dirichlet BC and Neumann BC for the water at the top boundary are studied. An extension of the two, the Rainfall BC, is also presented and explained in detail. Conclusions are based on simulations of the development of the infiltration process for the various conditions, in terms of quantity and velocity, as well as the uncertainty of the assumed parameters.