Speaker
Description
Reliable repository engineering requires experimental systems that can reproduce coupled thermal, hydraulic, and mechanical boundary conditions at a scale far beyond standard laboratory testing. This contribution presents the development, qualification, and strategic re-use of a large-scale triaxial test system developed at Clausthal University of Technology (TUC) – Chair for Geomechanics and Multiphysics Systems (GEMS). The facility was originally conceived within a multi-phase research program on shaft sealing elements made of salt cut bricks (SSB), where the central objective was to establish a technically robust platform for investigating engineered sealing systems made of SSB under controlled multiphysics loading conditions.
This paper focuses primarily on the testing facility itself. Its development included the design of dedicated hydraulic and thermal components, EMC devices for controlling gas and confining pressure, and a heating device for temperature control. In parallel, specimen concepts had to be developed specifically for the apparatus, including brick geometries, joint configurations, and manufacturing procedures. CNC-based fabrication enabled reliable production of salt cut bricks with planar and curved surfaces. The realization phase further comprised construction of the facility, calibration with a steel dummy, and manufacturing as well as assembly of several full-scale test specimen made of 375 salt cut bricks each, demonstrating that highly controlled large-scale triaxial testing of engineered SSB-based systems is technically feasible.
Beyond the experimental infrastructure, the facility is embedded in a workflow combining multiphysics measurements with predictive TH2M-coupled numerical simulations and retrospective analyses. In the SSB projects, numerical analyses were used both to interpret measured behaviour and to retrospectively assess test results and boundary effects.
Following completion of the salt cut brick investigations, the same triaxial apparatus is intended to be upgraded and re-used for a highly instrumented large-scale test on claystone-bentonite interaction, including optical fibers, humidity and pressure sensors, radial wetting, and thermal loading. Predictive simulations will support the definition of relevant time scales, admissible stress and pore-pressure levels, and feasible specimen dimensions for this new large-scale claystone-bentonite experiment. The resulting platform is expected to provide a unique large-scale multiphysics dataset for repository engineering and for benchmarking advanced numerical simulators.