Development and Validation of a Constitutive Model for Opalinus Clay

 

ENSI

Funding Agency: Swiss Federal Nuclear Safety Inspectorate (ENSI)

Project duration: 2018 - 2022

  ENSI Copyright: © © LIH

Development and Validation of a Constitutive Model for Opalinus Clay

Opalinus clay, a Mesozoic shale formation, has been selected as the potential host rock for disposal of high- and low-level nuclear waste in Switzerland. Some of the beneficial characteristics of this formation are the low hydraulic conductivity, the high radionuclide retention potential, and the potential of self-sealing of open cracks and fissures.

The aim of this project is to develop a fully coupled hydro-mechanical (HM) constitutive model to predict the physical behaviour of Opalinus (OPA) clay under various loading and unloading conditions. The key aspect is to integrate existing HM-coupled models supported by laboratory tests, field experiments and numerical simulations, and develop, implement and validate a new constitutive model.

Experimental investigations

We perform HM-coupled experiments using our state-of-the-art laboratory machines. Therefore, we use our in-house technology to prepare, store, monitor and perform, for instance, drained or undrained triaxial compression tests under various configurations considering the material anisotropy. Post-failure analysis is carried out by analyzing the deformation structures using electron microscopy.

Numerical investigations

We model the physical rock behavior and pore pressure response at changing stress conditions. We develop and implement a 3D numerical code that couples hydro-mechanical balance and constitutive equations to simulate the rock behavior. On-going laboratory and existing field experiments are used to calibrate, verify, and validate the developed constitutive model.

Project team:

Florian Amann

Mohammadreza Jalali

Lisa Winhausen

Kavan Khaledi

Pooya Hamdi

Publications and conference contributions

  • Winhausen, L., Amann-Hildenbrand, A., Fink, R., Jalali, M.R., Khaledi, K., Hamdi, P., Urai, J.L., Schmatz, J., Amann , A. (2020) A comparative study on methods for determining the hydraulic properties of a clay shale, Geophysical Journal International . https://doi.org/10.1093/gji/ggaa532

  • Khaledi, K., Hamdi, P., Winhausen, L., Jalali, M.R., Amann, F. (2020) Short-Term Pore Pressure Evolution around Tunnels in Opalinus Clay: Lessons Learned from an Overcoring Experiment (Kurzfristige Porendruckentwicklung um Tunnel im Opalinuston: Lehren aus einem Überbohrungsexperiment), Geomechanik Kolloquium 2020. Freiberg, Germany.

  • Khaledi, K., Hamdi, P., Jalali, M.R., Amann , F. (2020) Hydro-mechanical analysis of an overcoring experiment in Opalinus clay: experimental and numerical results. Mont Terri Consortium, Annual Technical Meeting (TM-38) . Porrentury, Switzerland.

  • Winhausen, L., Jalali, M.R., Amann-Hildenbrand , A., Amann, F. (2020) HM-C experiment: Lessons learned from hydraulic testing and microstructural investigation – Implications for HM-coupled experiments of OPA. Mont Terri Consortium, Annual Technical Meeting (TM-38) . Porrentury, Switzerland.

  • Winhausen, L., Jalali, M.R., Amann-Hildenbrand , A., Amann, F. (2019) Water permeability of Opalinus Clay determined by different methods – A comparative experimental study. “Tage der Standortauswahl” at Bundesgesellschaft für Endlagerung (BGE). Braunschweig, Germany.

  • Winhausen, L., Jalali, M.R., Amann-Hildenbrand , A., Amann, F. (2019) Water permeability estimation of the Opalinus Clay via different methods – Insights into a comparative experimental study. Geophysical Research Abstracts. EGU General Assembly . Vienna, Austria.

  • Winhausen,L., Jalali, M.R., Amann-Hildenbrand , A., Amann, F. (2019) Water permeability experiments on OPA. Comparison of three different methods - first results. Mont Terri Consortium, Annual Technical Meeting (TM-37) . Porrentury, Switzerland.

Funding Agency