SpannEnD

SpannEnD Project

PhD thesis S. Ahlers

Geomechanical numerical modelling for characterisation of the tectonic stress field for the disposal of radioactive waste in Germany

The disposal of nuclear waste in Germany targets deep rock formations acting as barriers over geological periods. The long-term protective effect of the geological barrier(s) depends on many factors, above all on geological processes. These processes often depend on the tectonic stress field, which is relevant not only to long-term stability but also for the construction of the underground repository. However, a reliable prognosis in the run-up to exploration measures is hindered by the fact that only few data are available and that the stress field is not uniform in its orientation and magnitude. In fact, significant local deviations from the supra-regionally known stress distribution can occur depending on the subsurface structure (lithologies, faults).

In order to improve the understanding of this spatial variability of the stress field, a geomechanical-numerical 3D stress model for Germany will be created in the SpannEnD project. This model will be generated by joining basement units (subproject TU Darmstadt) and overburden units (subproject KIT). It will be calibrated on in-situ measured stress data and allows forecasts for areas without stress data on the basis of continuum mechanical approaches. Furthermore, all six independent components of the stress tensor can be derived from the model. Since there is currently no database for stress magnitudes, such a database will be developed for Germany within the framework of the project.

In addition, modelling tools for models overlapping spatial scales will be developed. This allows a consistent transfer between the Germany model to partial models which are about three orders of magnitude smaller. All of these works provide necessary modelling tools for future geomechanical site models.

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Funding

Subproject A “3D-stress model and upscaling” within the joint project “Geomechanical numerical modelling for characterisation of the tectonic stress field for the disposal of radioactive waste in Germany (SpannEnD)” is funded by the Federal Ministry of Economics and Energy (BMWi) in the funding program “Research for the disposal of radioactive waste; Funding concept of BMWi (2015-2018)” under grant 02E11637A.

Publications

Reiter, K., Henk, A., Heidbach, O., Müller, B., Hergert, T., Schilling, F., 2018. The SpannEnD project – crustal stress data, stress modelling and modelling tools for the site selection process of a deep geological repository of radioactive waste in Germany, GeoBonn 2018, 2-6 September 2018, Bonn, Germany.

Henk, A., Heidbach, O., Müller, B., Reiter, K., Hergert, T., Schilling, F., 2016. The role of stress and geomechanical modelling BEFORE site selection, 2nd Conference on Key topics in deep geological disposal: Challenges of a Site Selection Process: Society – Procedures – Safety, 26-28 Sept. 2016, Cologne, Germany.

Heidbach, O., Henk., A., Müller, B., Reiter, K., Hergert, T., Schilling, F., 2016. SpannEnD – providing stress data and geomechanical modelling tools for the site selection process in Germany, 2nd Conference on Key topics in deep geological disposal: Challenges of a Site Selection Process: Society – Procedures – Safety, 26-28 Sept. 2016, Cologne, Germany.

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