Impact of non-linear elastic behavior on bentonite density evolution at the FEBEX

It is necessary to apply reliable numerical simulation techniques to assess the mechanical behavior of repositories for the long-term geological disposal of radioactive waste. Having a constitutive model that can describe the mechanical behavior of bentonite is key to such numerical simulations. In this study, the applicability of a linear elastic constitutive model with a swelling term is examined, focusing on density heterogeneity of the in-situ fullscale engineered barrier experiment (FEBEX) in Grimsel. It was found that the constitutive model underestimates the density change. Therefore, the mechanical behavior was re-simulated with an unsaturated elasto-plastic constitutive model using the changes in degree of saturation as input data. Two-dimensional stress and dry density was reproduced.