PhD: Upscaling pore-scale behaviour of clay-interfaces

The Department of Earth Sciences seeks a highly motivated PhD candidate with an MSc background in Earth Sciences, Hydrogeology, Physics, Environmental Engineering, or related fields. You will work on the project 'Upscaling pore-scale behaviour of clay-interfaces in shallow groundwater systems, enabling sustainable subsurface utilisation’.

Your job
Aquitards (low-permeability clay and peat layers) are among the protection layers for our groundwater systems. They seal and compartmentalise aquifers, protecting drinking-water reservoirs from contamination, separating different groundwater compositions, and confining heat in geothermal and energy-storage systems. In coastal urban areas, these shallow aquitards also interact with foundations, tunnels, and other critical infrastructure. As we increasingly rely on the subsurface to address societal challenges (from sustainable energy storage to climate adaptation), we are putting unprecedented pressure on these aquitards. Understanding their behaviour under changing environmental conditions is essential for sustainable subsurface utilisation.

What you will do
In this four-year study, you will develop an innovative, integrated approach that combines cutting-edge microfluidic experiments with advanced numerical modeling. Your work will enable upscaling from pore- to column-scale clay behaviour under real-world conditions relevant to sustainable subsurface use.

You will design and conduct microfluidic experiments to investigate clay behaviour under environmental stressors, including temperature fluctuations, pressure gradients, salinity changes, and wet-dry cycles. Using state-of-the-art monitoring techniques you will track changes in permeability, particle mobilisation (turbidity), and volume and visualise flow pathways in real time.

By integrating your experimental observations with numerical modeling, you will develop and test constitutive equations that capture fundamental clay behaviour, including the development of leakage paths, micro-fracturing, and internal erosion. Subsequent column-scale experiments and modeling will validate your pore-scale findings and enable extrapolation to field-scale conditions. Experiments will be conducted at the Porous Media Lab facilities, part of the Utrecht GeoLab.

Among the key research questions you will address are:

• How do changing environmental conditions weaken clay-substrate interfaces?
• How do pore-scale processes like swelling and shrinkage generate microfractures and facilitate clay particle movement?
• Can we develop robust upscaling approaches from pore to field scale that enable reliable predictions?

Finding answers to these fundamental questions will directly support decision-making in sustainable subsurface engineering, protect drinking-water resources, enhance subsurface energy storage, and ensure the long-term resilience of coastal and urban infrastructure.

Your development
A personalized training programme will be established, tailored to your training needs and career objectives. Approximately 20% of your time will be dedicated to professional development, including specialised courses and workshops, as well as teaching experience in the department's Bachelor's and Master's programmes. Through interactions with scientists, government, and industry partners, you will be exposed to diverse career paths in both academia and the applied sector, helping you shape your professional future.

You are a motivated team player with strong experimental and/or numerical modeling skills. You have completed (or will complete before the position starts) your MSc degree in Earth Sciences, Hydrogeology, Physics, Environmental Engineering, or a related discipline. Non-Dutch MSc diplomas may be subject to specific approval by the Board for Conferral of Doctoral Degrees before you can be accepted into the PhD programme.

Required qualifications:

• Demonstrated experience with experimental techniques (e.g., flow-through experiments, column studies, material characterization) and/or numerical modeling of flow and transport in porous media;
• Strong analytical skills and ability to integrate experimental observations with computational approaches;
• Proficiency in at least one programming language (Python, MATLAB, or similar) for data analysis and modeling;
• Theoretical background and genuine interest in porous media processes, such as fluid flow, reactive transport, soil-fluid interactions, or geomechanics;
• Excellent communication skills in English, both written and spoken;
• Motivation to work in a multidisciplinary environment that bridges fundamental research with societal applications;
• Willingness to engage with stakeholders from government and industry.

Desirable qualifications:

• Experience with microfluidic techniques or microscale visualization methods;
• Background in clay mineralogy, colloid science, or soil mechanics;
• Familiarity with Discrete Element Modeling (DEM), pore-network modeling, Computational Fluid Dynamics (CFD), or finite element methods;
• Experience with image analysis or particle tracking techniques;
• Previous exposure to interdisciplinary research connecting laboratory experiments with field-scale applications;

Due to the international character of our research and collaboration network, a good command of spoken and written English is essential. We highly encourage applicants from all members of our community and of diverse backgrounds to join us.

We offer:

• a position (1.0 FTE) for 1 year, with an extension to a total of four years upon a successful assessment in the first year, and with the specific intent that it results in a doctorate within this period;
• a working week of 36 - 40 hours and a gross monthly salary between € 3.059 and €3.881 in the case of full-time employment (salary scale P under the Collective Labour Agreement for Dutch Universities (CAO NU));
• 8% holiday pay and 8.3% year-end bonus;
• a pension scheme, partially paid parental leave and flexible terms of employment based on the CAO NU.

In addition to the terms of employment laid down in the CAO NU, Utrecht University also offers a range of its own schemes for employees. This includes arrangements for professional development, various types of leave, and options for sports and cultural activities. You can also tailor your employment conditions through our Terms of Employment Options Model. In this way, we encourage you to keep investing in your personal and professional development. For more information, please visit Working at Utrecht University.

A better future for everyone. This ambition motivates our scientists in executing their leading research and inspiring teaching. At Utrecht University, the various disciplines collaborate intensively towards major strategic themes. Our focus is on Dynamics of Youth, Institutions for Open Societies, Life Sciences and Pathways to Sustainability. Sharing science, shaping tomorrow.

Utrecht University’s Faculty of Geosciences studies the Earth: from the Earth’s core to its surface, including man’s spatial and material utilisation of the Earth – always with a focus on sustainability and innovation. With 3,400 students (BSc and MSc) and 720 staff, the faculty is a strong and challenging organisation. The Faculty of Geosciences is organised in four Departments: Earth Sciences, Human Geography & Spatial Planning, Physical Geography, and Sustainable Development.

The Department of Earth Sciences conducts teaching and research across the full range of the solid Earth and environmental Earth sciences, with activities in almost all areas of geology, geochemistry, geophysics, biogeology and hydrogeology. Our key research themes are Earth & Planetary Processes, Sustainable Use of the Subsurface, Planetary Health & Environment, and Climate & Life. The department hosts a highly international tenured staff of over 50 scientists and more than 110 PhD students and postdoctoral researchers. We house or have access to a wide variety of world-class laboratories, among which are UU’s Electron Microscopy Centre, the Geolab (including the Porous Media Lab), and the Earth Simulation Lab. We also have excellent High- Performance Computing facilities.

About Utrecht
The department and its facilities are located at Utrecht Science Park. Utrecht is the fourth largest city in the Netherlands with a population of nearly 360,000 and forms a hub in the middle of the country. Its historical city centre and its modern central station can easily be reached from the Science Park by public transport or by a 15-minute bicycle ride. Utrecht boasts beautiful canals with extraordinary wharf cellars housing cafés and terraces by the water, as well as a broad variety of shops and boutiques.

For informal information (not for application) about this position, please contact Dr Thomas Sweijen, project leader, at T.Sweijen@uu.nl

Candidates for this vacancy will be recruited by Utrecht University.