Numerical modeling of coupled thermal-hydro-mechanical behavior of GMZ bentonite in the China-Mock-up test

• China-Mock-up test to study the performance of GMZ bentonite for disposal purpose is presented.
• Coupled THM processes of the GMZ bentonite in the test are simulated with a proposed model.
• Effect of the fluctuant room temperature on the test is considered in the numerical study.
• Comparison between predicted results and experimental data in first three years were conducted.
• Overall satisfactory agreement of the thermal, hydraulic and mechanical behavior is observed.

Gaomiaozi (GMZ) bentonite is currently considered as the most suitable buffer material for high-level radioactive waste geological repository in China. To investigate the long-term performance of GMZ bentonite under repository conditions, a large scale mock-up test has been carried out since 2011. In the test, a hydration system and an electrical heater were employed to simulate the Thermal-Hydro-Mechanical (THM) coupled conditions near a repository. In this work, a numerical study is performed to reproduce the experimental data obtained in the first three years of the China-Mock-up experiment. The principle THM characteristics and parameters of the bentonite are presented. On this basis, a THM coupled constitutive model is introduced. With the proposed model, numerical simulations of the China-Mock-up test are carried out using LAGAMINE. The numerical data of temperature, relative humidity, and swelling pressure of the GMZ compacted bentonite are compared with the experimental ones. We discuss the effect of the balance between the drying effect and water penetration process on the THM behavior of the GMZ bentonite. The good agreement between the predicted and experimental results suggests that the proposed model can reproduce the fundamental behavior of GMZ compacted bentonite under coupled THM conditions.