A Reduced-Order Model for Coupled THM Problems and Its Application in the Inverse Analysis of an in situ Heating Test for Deep Geological Nuclear Waste Repositories

In this study, a proper orthogonal decomposition–based reduced-order model (ROM) is developed for coupled thermo-hydromechanical (THM) problems using LiveLink for MATLAB, which provides integration between the MATLAB scripting environment and COMSOL Multiphysics. The MATLAB-COMSOL LiveLink significantly streamlines the ROM development process by enabling the efficient generation of snapshot solutions and discretization details from the full-order model (FOM) through the computational capabilities of COMSOL Multiphysics. The developed ROM substantially reduces computational cost while maintaining excellent agreement with the FOM, thereby enabling extensive repeated simulations. The proposed framework is applied to the inverse analysis of an in situ TED heating test in Callovo-Oxfordian claystone in the context of a deep geological disposal of nuclear waste repository, where thousands of three-dimensional coupled THM simulations are performed using the ROM. Based on the inverse analysis, feasible ranges of THM parameters are identified.