Spannungsfeldmodellierung Schweiz

Stress Field Modelling Switzerland

Modelling of the stress field in the subsurface of possible siting areas for a radioactive waste repository in Switzerland

Geomechanical model (top) for a siting area with dimension of 14 x 14 x 3 km, comprised of a number of slightly dipping units which are characterised by their densities and mechanical properties and are intersected by tectonic faults. Gravity and far-field forces act on the model. The model volume is discretised into linear hexahedron elements in order to compute the equilibrium of forces by applying the finite element method. In a vertical cross section (bottom) the resulting differential stress is shown. Distinct contrasts between the individual units appear, with the far-field forces being accommodated primarily by the stiff units.
Geomechanical model (top) for a siting area with dimension of 14 x 14 x 3 km, comprised of a number of slightly dipping units which are characterised by their densities and mechanical properties and are intersected by tectonic faults. Gravity and far-field forces act on the model. The model volume is discretised into linear hexahedron elements in order to compute the equilibrium of forces by applying the finite element method. In a vertical cross section (bottom) the resulting differential stress is shown. Distinct contrasts between the individual units appear, with the far-field forces being accommodated primarily by the stiff units.

Knowledge of the state of stress in the subsurface is indispensable at the planning of large-scale excavations in view of the engineering feasibility, design and stability of the excavations. In the context of a repository for radioactive waste the state of stress is of importance in numerous further aspects. In Switzerland several geological siting areas have been designated as possible locations for such kind of repository.

In cooperation with Nagra (National Cooperative for the Disposal of Radioactive Waste) geomechanical models are being built for individual siting areas in order to assess the impact of tectonic faults, topography and spatial variability of mechanical rock properties on the state of stress in the subsurface. At the same time this conduces to an improved understanding of available data and to identification of the need of additional data to be acquired by measurements.

Publications

Reiter, K., Hergert, T., Heidbach,O., 2016. Stress field sensitivity analysis within Mesozoic successions in the Swiss Alpine foreland using 3-D-geomechanical-numerical models, EGU General Assembly, 17-22 April 2016, Vienna, Austria.

Hergert, T., Heidbach, O., Reiter, K., Giger, S. B., and Marschall, P., (2015). Stress field sensitivity analysis in a sedimentary sequence of the Alpine foreland, northern Switzerland, Solid Earth, 6, 2, 533-552, doi: 10.5194/se-6-533-2015.

Heidbach, O., Hergert, T., Reiter, K., Giger, S.B., Marschall, P., 2015. 3D stress field sensitivity analysis on the scale of geological siting regions in Northern Switzerland with focus on Opalinus Clay, 6th International Clay Conference – Clays in natural and engineered barriers for radioactive waste confinement, March 23-26 2015, Brussels, Belgium, (oral presentation).

Hergert, T., Heidbach, O., Reiter, K. & Giger, S.B. , 2015. Stress Field Sensitivity Analysis at a Reservoir Scale (Northern Switzerland) Using Numerical Geomechanical Modelling, 2nd EAGE Workshop on Geomechanics and Energy – The Ground as Energy Source and Storage, 13-15 October 2015, Celle, Germany (oral presentation).

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