Numerical models concerning the deformation behavior of rigid bodies in a plastic matrix

The presented research project is aimed to simulate with simplistic, generic, numerical 2D models the linear elastic deformation of waste canisters in a rock salt matrix. It is based on own analogue models and an analytical solution (Mandal und Chakraborty 1990) for the linear elastic deformation behavior of pre- to syntectonic granitoid plutons intruding a schistose orogen. For this purpose, a numerical model consisting of a strong body in a weak matrix was deformed linear elastically in 2D under plain strain conditions. During deformation the Young’s modulus of the canister materials steel and copper was lowered and the Poisson’s ratio raised to simulate mechanical weakening of the canister while the rock salt matrix remained mechanically unchanged. Consequently, the canister became with time weaker than the surrounding rock salt matrix. The canisters were either empty or filled with steel in the model. Our results show clearly, that

• deformation gets more pronounced with increased mechanical weakening of the canisters,
• a copper canister develops a higher ellipticity than a steel canister and
• a strong, competent body in a weak, incompetent matrix shows different deformation patterns than a weak, incompetent body in a strong, competent matrix.
  • In the first case (strong body in a weak matrix) concave strain and stress trajectories are observed plus material displacement towards the model margins.
  • In the second case (incompetent body in competent matrix) material displacement from the model rims towards its center is observed and convex strain and stress trajectories occur.

Our simplistic, generic, numerical 2D models will help to strengthen our general comprehension of deformation processes in nuclear waste disposal systems.

References

Mandal, Nibir; Chakraborty, Chandan (1990): Strain fields and foliation trajecto-ries around pre-, syn-, and post-tectonic plutons in coaxially deformed terranes. In: Geol. J. 25 (1), S. 19–33. DOI: 10.1002/gj.3350250103.