2nd prize of the year 2024
A combined laboratory and microstructural investigation of the coupled hydro-mechanical failure behavior of Opalinus Clay
Dr. Lisa Winhausen
RWTH Aachen, Chair of Engineering Geology and Hydrogeology
In her work, Dr Lisa Winhausen comprehensively investigated the behaviour of Opalinus Clay, a potential host rock for the safe disposal of radioactive waste in Switzerland. The research focussed on the hydro-mechanical properties of this rock, particularly under short-term loads.
An innovative approach combining various laboratory experiments and high-resolution scanning electron microscopy provided new insights. Methods for precisely quantifying the geomechanical properties of the Opalinus Clay were developed and evaluated. The aim was to understand the elastoplastic behaviour of the rock on different scales, from sub-microscopic deformations to macroscopic failure mechanisms.
The results show that the failure of Opalinus Clay under compressive loading depends on various factors: the state of saturation and consolidation, the effective mean stress and the direction of loading. Important indicators for brittle and ductile deformations were identified and integrated into a comprehensive model.
A remarkable finding is the non-linear change in hydromechanical properties as a function of stress. These changes are related to the transition from brittle to ductile behaviour at the microscopic level. In addition, the transverse isotropy of the Opalinus Clay decisively influences its shear and tensile strength as well as the poromechanical coupling, which is responsible for compaction or dilatancy.
Overall, these micro- and macro-scale findings contribute to the development of a new material model. This model can be used to simulate the behaviour of the rock during tunnel construction, which has important implications for the safe storage of radioactive waste. This study thus provides valuable insights into the geomechanical properties of Opalinus Clay and its potential as a safe host rock.
