This is a joint PhD position within the Earth Systems Science Computational Centre (ESSCC) and the Centre for Mined Land Rehabilitation (CMLR) which is part of the Sustainable Minerals Institute (SMI), collocated in the same building within the University of Queensland, Australia. Various scenarios exist for a modeller to study porous media flows using the finite element software escript/Finley, which is an advanced 3D FEM implementation which is continuously developed within ESSCC, UQ.
The understanding and calculation of flow of water or liquids through porous systems require an understanding of the distribution of pore sizes. Porous systems of soil and or loose rocky material are often considered as stable over time independent of processes taking place. However, the permeation of the pores can affect material properties, which may have an effect on the pore size distribution and the functioning of pores mainly caused by a change of volume and the distribution of pores. Main reasons for volume change are:
- Swelling and shrinking as a result of wetting and drying:
Materials, which contain clay, exhibit the phenomenon of swelling and shrinking as as result of bonding of water molecules onto clay particles. Clay particles expand, increase their volume and in most cases reduce the pore space to a mechanical confinement of the material. Repeated wetting and drying events can alter the pore systems due to a development of a secondary pore system on top of the initial primary pore system, which has different functional properties. Investigation of surface and subsurface hydrology requires a good understanding of theses processes as they are vital for a correct modelling of water flows through e.g. soils. Above all in newly formed landscapes (e.g. rehabilitation sites in mining) or in agriculture, the possibility of predicting the behaviour of soils regarding volume change is important to better understand not only the water balance of soils but also transport of nutrients or contaminants within the soils.
- Mechanical compaction
Overcoming mechanical stresses, which keep an arrangement of a particles in a stable condition cause the collapse of the pore system. In natural environments compaction can have a severe impact on the stability of e.g. soils. Reduced infiltration of water into the pores as a result of compaction, increases runoff and hence erosion. In semi-arid environments compaction reduces the replenishment of soil with water and reduces the possibility for plants to survive droughts or to allow deep drainage into the groundwater.
- chemical reaction (dissolution; precipitation)
In chemically active environments, e.g. mine sites, water management can be heavily influenced by chemical reactions which can alter the pore system. E.g. sulfate containing tailings material is often buffered by lime. In long-term infiltration rain water will dissolve the lime and change the pore system within the tailings. The attempt to buffer acid containing rock with lime stone causes the precipitation of gypsum which is clogging pores in which this reaction takes place and changes the overall hydrology of this system.
There are many project possibilities for potential Honours, Masters and PhD students. Applicants are invited to share their interests to tailor their projects to suit their individual needs and background.
The aims of this project are to:
- develop a mathematical model for the application of interest in Mining and Mined Land Rehabilitation,
- apply the model in different scenarios,
- develop software based on the escript/Finley and VTK python interface
- interpret the results in a meaningful and relevant manner
escript/Finley has already been applied by researchers in Perth to several problems in reactive transport. This project is part of a collaborative project to establish computational porous media modeling with ESSCC and SMI.
The ideal candidate will have some of:
- knowledge of computational methods
- continuum mechanics / porous flow modeling
- relevant mathematical, engineering and/or physics qualifications
- background or interest in Geophysics / Geo-ecology / Mining theory and or applications
You will be supervised by Prof Hans Muhlhaus (Theoretical/Computational Geophysicist) and Dr Thomas Baumgartl (Hydrogeology, Soil Hydrology and Soil Mechanics) with advice from Mr Matt Davies (Computational Software). For further information please contact Prof Hans Muhlhaus.