Coupled Thermo–Hydro–Mechanical Characteristics of Compacted GMZ Bentonite: Parameters Identification and Validation: Fid-Bau Portal

Coupled Thermo–Hydro–Mechanical Characteristics of Compacted GMZ Bentonite: Parameters Identification and Validation

Wang, Qiong / Su, Wei / Ye, Weimin / Zhang, Yawei / Chen, Yonggui

Compacted Gaomiaozi (GMZ) bentonite has been considered as the first choice of buffer materials in the deep geological disposal of high-level radioactive wastes (HLW) in China. During the long-term lifespan of the repository, the bentonite barriers will simultaneously undergo a coupled thermohydromechanical (T-H-M) process, which induces complex volume changes. In this study, the constitutive model of GMZ bentonite with consideration of THM coupling was established, using the framework of the BExM model along with a thermal volume change model for unsaturated soils. New formulations for the interaction between micro and macrostructures ( $f_{I}$ and $f_{D}$ ) and the thermal loading yield surface (TY curve) were adopted. Emphasis was placed on the identification and validation of the material parameters based on a series of experimental results. A comparison between the simulated and measured values show that the improved model with parameters calibrated successfully represents the main features of volume changes observed in the laboratory and during wetting-drying cycles, elastic thermal expansion, and plastic thermal contraction under various suctions and stresses, as well as compressibility under various suctions and temperatures.