Work package #3

Model development


A strong driver for the project is the current limitations in the predictive capability in the numerical models. The issue of homogenisation and swelling of the barrier is challenging both from a conceptual and a numerical point of view. Thus both the conceptual and the numerical approaches need to be significantly advanced.  The final goal is to develop enhanced, robust and practical numerical tools, firmly grounded on a good understanding of the phenomena involved.  The numerical tools should have the required predictive capabilities concerning the behaviour of engineered barriers and seals especially in relation to their final state.

Description of work

In this context, a key component of the numerical tool that requires especial attention is the mechanical (stress-strain) constitutive model because the final state of the barrier (including its heterogeneity) is directly dependent on its features and capabilities. Issues such as irreversibility and long-term behaviour are bound to play a critical role in relation to a satisfactory prediction of the final state of the barrier or seal. Long term behaviour may also involve the consideration of chemo-osmotic effects. This focus on mechanical behaviour is in contrast with previous projects where thermal behaviour and, especially, hydraulic behaviour were the primary focus of constitutive development.

Due to the wide range of situations for which those developments can be applied to, the following areas of work are envisaged:

  • Saturated and unsaturated materials
  • Blocks and pellet-based materials
  • Isothermal and  non-isothermal conditions

Generally, different teams will address only a partial number of those areas of work.

The resulting constitutive models will be implemented into suitable computer codes capable of performing coupled HM and THM analyses so that they can be applied to real repository situations. Those codes may also require additional developments to address properly the problems under consideration (e.g. gap elements, large displacements).

Finally, the constitutive models and numerical implementations will be verified through the analysis of proposed benchmarks. The full verification, validation and application of the models are performed in WP5. In WP3, only simple exercises are envisaged devoted to the identification, demonstration and comparison of the basic features of the developed models.