Juha Antikainen

Modelling of the bedrock response to glacial loading at the Olkiluoto site, Finland

The Olkiluoto Island is situated in Baltic Sea, near the southwestern coast of Finland. The most abundant rock type is migmatic mica gneiss, intruded by tonalites, granodiorites and granites. Response of bedrock at Olkiluoto site was modelled with 3DEC program considering four future ice age scenarios. Each scenario produces shear displacements of fractures with different time of occurrence and varying recovery rate. Generally, the larger the maximum ice load, the larger the permanent shear displacements will be. For basic case, the maximum shear displacements were few centimeters at suggested nuclear waste repository level. The sensitivity study performed showed that shear stiffness and joint friction angle of bedrock structures are the most critical parameters for bedrock displacements.

A method to downscale joint surface roughness and to create replica series using 3D printed molds

In order to determine the in-situ shear strength of rock joints, large scale testing is required. However, this is both expensive and difficult to execute. One possible method to overcome this may ...

Thermo-Mechanical Effects on Hydraulic Conductivity in a Nuclear Waste Repository Setting

Abstract Understanding hydrogeological conditions around a future repository is crucial for safe nuclear waste disposal. Strong heterogeneity, even for in-situ fractured media, makes hydraulic conductivity predictions challenging. Furthermore, thermo-mechanical changes from repository excavation and waste heat emission will alter near-field hydrogeological conditions. This study estimates the magnitude of thermo-mechanical effects on performance of a hypothetical nuclear repository. First, complex 3D fracture networks are probabilistically analysed by traditional hydrological upscaling with fracture transmissivity based on in-situ hydraulic data. The resulting effective conductivity distribution is used as input for large scale stochastic continuum models. Next, separate thermo-mechanical modelling evaluates stress field changes due to repository excavation, bentonite swelling and heat emission. Obtained stress field changes, which are related to fracture aperture and transmissivity changes, alter near-field upscaled effective conductivity. Finally, applying the latter to the large scale model estimates the significance of thermo-mechanical effects on particle transport in relation to hydraulic in-situ uncertainty.