The presence of cracks and fractures in geomaterials makes their mechanical behaviour difficult to predict, this is particularly true for fluid saturated rocks [1]. Fluids spread through pores and cracks of rocks and have significant effects on the rock mechanics. The continuous interest in this hydromechanical coupling in geomaterials reflects the need to rationalize empirical practices in fields of applications as diverse as earthquake forecasting or mine pit stability. The description of the fluid transport and hydromechanical coupling in fractured rocks is a non-trivial physics problem encountered in many research fields. Our ability to overcome current challenges in the domain relies on a better fundamental and experimental understanding of the behaviour of rocks having heterogeneous pore structures and complex interconnected fracture morphologies (see picture).

Recent advances in X-ray micro-computed tomography (micro-CT) enable 3D observations of the inner structure of rocks and offer new avenues to carry out mechanical studies on fractured geomaterials at the laboratory scale. The two groups at the Australian National University and Ghent University have developed world-class in-situ (e.g., inside the scanner) micro-mechanical instruments that enable 3D study of the hydromechanical coupling and fluid transport in a rock as it deforms, fails or even fragments [2-5]. The PhD student will join this collaborative research activity tackling difficult questions such as: 

How does the failure and fracturing of a rock depend on its level of fluid saturation? Can we quantify the impact of different loading paths and fragmentation level on pores connectivity to better predict fractured rock permeability? Can we characterise the 3D structure of hydraulically cracked rocks at different description level from local fracture morphology to the connectivity of the fracture network? What is the response of a fracture with a complex morphology to cyclic changes in fluid pressure?

Those questions will be explored by carrying out tomography-based experiments on actual rock cores and on model synthetic solids to try rationalising key factors and mechanisms underlying our observations; an important aspect of the work will be the frequent interactions with geotechnical engineers with expertise in empirical field practices. 

[1] Gueguen Y. and Bouteca M., Mechanics of Fluid-saturated Rocks (Elsevier Academic Press, 2004). [2] Francois, N., et al., Review of Scientific Instruments, 93(8): p. 083704 (2022). [3] Bultreys, T., et al. 34, 042008 Phys. Fluids (2022). [4] Bultreys, T., et al. 121 (12) PNAS (2024). [5] Francois, N., et al. arXiv:2206.12763, (2022).

Candidate profile

We are looking for candidates having a curious mind, creative thinking, some grit and determination. He/She will help developing a set of advanced experimental set-ups to explore the hydromechanical coupling in geomaterials.

• PhD applicants must hold a master's degree or equivalent education in physics, engineering or relevant fields. Knowledge of / Experience with the fundamentals of rock mechanics and/or 3D imaging would be a plus. Strong analytical and critical thinking skills are expected, a basic knowledge of Python/Matlab or other programming languages is needed.
• Applicants must be able to work independently, have a taste for collaborative work, and demonstrate good communication skills.
• Applicants must be proficient in both written and oral English.

Work environment

•  The home institute for this 3 year-long PhD project is the Australian National University (ANU). Over the project course, there will be a 12-month-long exchange to Ghent University.
•  The work will be carried out in two experimental research groups (see links section):
  •  the Experimental Mechanics group at ANU which is part of the ANU CT-lab.
  •   the Centre for X-ray Tomography (UGCT), Ghent University, Belgium
• Though the project is built upon a strong experimental component, the work will involve quantitative 3D image analysis, numerical modelling and/or theoretical analysis depending on the candidate’s taste and skills.
• The candidate will also be a member of a large research program (Ore AI) on geomaterials characterisation undertaken at the ANU. The program, with embedded industry experts, gathers 20 researchers with a broad spectrum of competences (physicists, geologists, chemists, applied mathematicians…).
• The candidate will thus work in a highly multidisciplinary and strongly collaborative environment.

What we offer

• A dual PhD degree in two world leading groups for research and applications of X-ray micro-computed tomography in geoscience.
• Extended work periods (>12 months) in both institutions with support for several travels between Australia and Belgium.
• A conducive and intellectually stimulating work environment between two research groups with a tradition to work at the interface of Academia and Industry.
• Australian funding: while working in Australia, the PhD research fellow will earn a stipend of 42000 AUD/year (standard 36650AUD/year as ANU PhD student + 5350 AUD/year top-up from our industrial partner)
• Belgium funding: While working in Belgium, the stipend will be topped up to be similar to PhD scholarship at Ghent University.

To Apply

To be considered for this position, please apply online via:

https://docs.google.com/forms/d/1qmy6touHyw8vvy4ocPl6kiSWft_4jhAjNr0A22hczx0/edit?ts=66dee5a0

Applications by email will NOT be processed. Applications close on 1st March 2025 and will be evaluated on a bi-weekly rolling basis. The starting date of the position will be in 2025 and is to be determined together with the selected candidate.

Questions can be directed to A/Prof. Nicolas Francois (nicolas.francois@anu.edu.au) Experimental Mechanics Lab at ANU and Prof. Tom Bultreys (Tom.Bultreys@UGent.be) at Centre for X-ray Tomography (UGCT), Ghent University.

Links to our labs

Experimental Mechanics Lab is part of the M3D Training centre (https://m3d.edu.au/) and ANU CT-Lab (https://ctlab.anu.edu.au/). Geomaterials research group at Ghent University, Belgium (PProgress, https://pprogress.ugent.be/ and https://www.youtube.com/watch?v=SZo-StQtAYs )