Thermo-hydro-mechanical model of the Canister Retrieval Test

Abstract

The paper presents a 2-D axisymmetric numerical simulation of the Canister Retrieval Test (CRT). The main objectives of this analysis are the study of the canister–buffer and buffer–host rock interfaces; and the evaluation of the mathematical models used to predict the THM behaviour of the buffer and interface. The THM simulation was performed using the finite element program Code-Bright. The constitutive law adopted to represent the mechanical behaviour of bentonite and pellets is the Barcelona Basic Model (BBM) with a non-linear elastic component accounting for swelling. A joint element with a non-linear elastic mechanical law was implemented in the code for the simulation of the opening–closure of the interface canister–buffer. The formulation of this element also incorporates appropriate thermal and hydraulic laws. The evolution of temperatures, relative humidities and stresses recorded during the test were compared with the simulation results. Comparing the results measured in situ with the results of numerical analysis shows that the formulation used is able to reproduce satisfactorily the phenomena involved in the test as well as their interactions. In addition, the final dry density and degree of saturation measured in samples of bentonite and pellets extracted during the test dismantling were also in agreement with the calculated values.