InfFroSoil - Thermohydraulic processes during water infiltration in frozen ground with implications for geohazards under climate change


Project management:        Dr.-Ing. Ivo Baselt

Project engineer:                  Julian Bauer M.Sc.

                                                      E-Mail: ivo.baselt@unibw.de, Tel.: 089/6004-3844

Running time:                       01.07.2023 – 01.05.2027

Promotion:                              Deutsche Forschungsgemeinschaft (DFG)

Project number:                    518478532

Project partner:                    Ruhr-Universität Bochum,

                                                      Institute of Geology, Mineralogy and Geophysics, Dr. Thomas Heinze

Project description:   

Climate change has a particular impact on hydrology in Alpine regions due to rising temperatures, more and more intense rainfall events, including during the winter months. These changes lead to an increase in natural hazards such as excessive surface runoff and mudslides. One of the reasons for such events is a reduced infiltration capacity of the (partially) frozen ground. If rainwater or meltwater cannot infiltrate sufficiently, surface runoff induces soil erosion, which can lead to mudslides. If water infiltrates into deeper layers along preferential flow paths and pore pressure increases between frozen layers, this can lead to mechanical failure of the slope. Significant surface runoff means that hardly any groundwater recharge takes place and the buffering effect of the groundwater body is lost. This is particularly important for regions where snow and mountain water contribute significantly to the groundwater balance. This project investigates the thermo-hydraulic interaction between infiltrating water and soil at temperatures below freezing. Sophisticated modeling approaches, numerical simulation tools and laboratory and field experiments are used for this purpose. Preferential flow paths, e.g. macropores through root growth or wormholes, in the soil are essential because they enable faster infiltration of water into the soil and also have a different freezing and thawing behavior than small pores in the soil matrix. Understanding the influence of macropores on the freezing and melting of water during infiltration is therefore essential for any further analysis. Water infiltration is determined by the temperature of the phases involved. The infiltrating water is warmer than the freezing point, while the soil is frozen. The temperature development of the individual phases depends on the heat transfer between the phases. Since heat transfer and hydraulic flow are strongly coupled and also very dynamic around the freezing point, special care is required in the theoretical description of the thermohydraulic behavior. With an in-depth understanding of the influence of preferential flow paths and the heat transfer between the phases involved, specific geological and meteorological conditions can be identified that cause either extreme surface runoff or slope failure. This knowledge can be applied in precautionary measures as well as in groundwater management in alpine areas.

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