PhD candidate position: Scaling friction from single grain to aggregate grain (fault-gouge) contacts.

The Department Mechanics of Solids, Surfaces & Systems (MS3), part of the faculty of Engineering Technology (ET) is currently seeking a PhD candidate in the area of modelling friction in crushed rock grains (gouge) in reservoir faults. The work will be done in the Surface Technology and Maintenance (SEM) group, where we work on topics related to surfaces and interfaces, damage and failure mechanisms, e.g. frictional failure in faults leading to earthquakes.

Earthquakes reflect the phenomenon of sudden slip when the frictional strength of faults in the Earth's crust is overcome. This project seeks to understand the physical processes controlling this sudden failure through numerical modelling and lab experiments and applying the results to acquire large-scale models for earthquakes caused by gas extraction, geothermal energy production and subsurface storage. Gaining deeper knowledge of frictional mechanisms in faults at different length scales will help improve forecasting of earthquakes and other subsurface phenomena, caused by growing human intervention.

Fractures and discontinuities in rocks, i.e. faults in natural gas reservoirs are typically filled with crushed rocks grains called gouges. In a depleting gas reservoir, stresses on pre-existing faults result in fault reactivation and slip, thereby inducing seismicity. Understanding the friction between the gouge-grains in key to modelling fault slip. Frictional phenomena in individual gouge-grain contact can be experimentally simulated at the microscale as the relevant scale where physical frictional interactions take place. Using results from single grain experiments, a physical basis will be formulated for friction phenomena in microphysical and numerical granular models for fault-gouges.

The aim of the project is to develop physics-based friction models for fault contacts following a bottom-up approach and use these models to compute fault slip resulting in induced seismicity due to subsurface activities. The objectives of the PhD research, to accomplish the main aim will be:

O1. To develop friction laws for single-grain contacts in crushed fault-rock "gouges" using microscale sliding experiments and numerical models.

O2. To implement these micro-scale friction laws in numerical models developed to compute friction in fault-gouges (dm-scale granular-assembly).

Job description

We are looking for a highly motivated PhD candidate to strengthen our research portfolio in the emerging field of 'geo tribology', tribology in the subsurface of earth. Careful experimental analysis, involving single-(rock) grain pre-sliding and sliding experiments, atomic force microscopy, surface force apparatus etc. will be employed to analyze, model and quantify microscale contact and friction forces. A numerical discrete element model (DEM) will be developed/adapted to study friction in granular aggregates under shear loading. Understanding the physical background of friction processes in single-grain contact, friction models will ultimately be implemented in the aggregate grain (dm-) scale DEM model.