The Full-Scale In-Situ System Test (FISST) constitutes one of the most comprehensive and large-scale experimental investigation s to date, aimed at advancing the design and understanding of engineered barrier systems (EBS) within the framework of nuclear waste repository development. Initiated in 2018, the FISST involves the placement of two test canisters within designated deposition holes in the ONKALO® underground research facility's demonstration area, located in a tunnel approximately 50 meters in length. FISST represents a full-scale implementation of the KBS-3V disposal design concept, the reference methodology adopted in Finland and Sweden for the final disposal of nuclear waste. A laboratory testing campaign was undertaken to calibrate the thermo-hydro-mechanical (THM) model parameters for the deposition hole buffer and tunnel backfill materials used in FISST. These materials consisted of Wyoming-type bentonite utilized for blocks and pellets within the deposition hole, along with Italian and Bulgarian bentonites employed in the form of blocks and pellets as tunnel backfill materials. Blocks and pellets were produced with these three types of bentonites. This study focuses on the calibration of key material properties associated with the components of FISST, including thermal conductivity, water retention characteristics, permeability, and mechanical parameters. The Barcelona Basic Model (BBM) was used to represent the block materials, while model with double porosities was employed for the pellets. Additionally, a methodology was developed to linearize the BBM for improving computational efficiency in the simulations that followed. Subsequently, the linearized Barcelona Basic Model (BBM) was employed in thermo-hydro-mechanical (THM) calculations. Following the calibration of the material models, a large-scale 3D thermo-hydraulic (TH) simulation, was performed to define TH boundary conditions for a 3D THM model on a reduced scale. This approach validated the feasibility of 3D modeling under defined TH boundary conditions with accurately calibrated THM parameters. All simulations were conducted using CODE_BRIGHT, a finite element method (FEM) program specifically tailored for advanced THM modeling of complex systems.
Previous studies on the modelling of coupled thermo-hydro-mechanical (THM) processes in bentonite-based engineered barrier systems (EBSs) showed the sensitivity of the output quantities to changes in the input parameters. To investigate the effects of uncertainties on the modelling results, to improve the understanding of the coupled processes active in the repository near field and to gain in-depth understanding of model uncertainties of different codes, a sensitivity analysis and code comparison of EBS simulations was performed within the Task Force on Engineered Barrier Systems. The analysis included variations in material parameter values, boundary and initial conditions, considered physical processes and model geometries, amounting to 60 different cases. This in-depth analysis helped evaluate the influence of parameter and conceptual uncertainties on the results of coupled THM simulations and to identify key parameters and processes. The cross-code comparison encouraged a fruitful exchange among modelling teams and led to very good agreements between the results of the different codes. Serving as a benchmark example for THM-coupled simulations of bentonite-based EBSs, the study helped increase the confidence in the modelling capabilities of several codes used for safety evaluations of repositories for spent fuel and high-level radioactive waste.
Abstract In tunnel construction in the city area, NATM method is adopted for construction by the limitation of the construction condition. When classifies roughly in supporting method of construction, there are against the spring water, face stability, ground surface subsidence, cement, water glass and urethane are usually used for grouting material against the spring water, but there is the concern, such as expensive and high load on the environment because of artificial materials. On the other hand, Kaolinite is a natural material, there is less load on the environment, and many merits in the processing of the excavated muck. Therefore, we focused a pressurized clay injection method by using the above-mentioned characteristics and applied this to the construction of the underground. In this paper, the availability of the injection a fluid with a dispersion of kaolinite was discussed to summarize the applicability for controlling groundwater of the saturated sand layer. Specifically, a one-dimensional column test was conducted under the high hydraulic gradient. As a result, it was shown the possibility of effecting of decreasing hydraulic conductivity at less than one-order. Consequently, it is concluded hydraulic conductivity of sand layer was able to be reduced by Kaoline clay suspension.
. The requirement to reduce operational energy use in the built environment has driven a rise in the level of building envelope airtightness. An unintentional consequence of this can be a reduction in the indoor environment quality with respect to hygrothermal comfort. Some aspects of this may be addressed through correctly commissioned active ventilation systems. However, there is also a need to consider the passive role that building materials have in maximising the quality of the indoor environment. There has been growing interest in the use of exposed clay surfaces for the passive regulation of indoor temperature and humidity levels. This is largely due to the exposed thermal mass and hygroscopic properties that help buffer the temperature and relative humidity of the internal environment. There is also scope for the inclusion of mineral and organic aggregates to help improve these hygrothermal properties. This paper presents results from preliminary testing on a range of novel clay coatings, which incorporate different mineral and organic aggregate contents. Two novel mixes were prepared with an enhanced level of mineral and organic aggregate exchange. Both mixes showed a reduction in thermal conductivity compared to control clay mixes. The moisture buffering of the plaster was improved by the increased organic aggregate content while no significant change was observed for the mineral aggregates. The results of this paper will inform future developments of clay plasters, which will support the development of airtight buildings with improved indoor environment quality.
