Coupled hydromechanical (H-M) performance of in situ shaft sealing components for nuclear waste disposal

Abstract

Decommissioning and closure of Canada’s Underground Research Laboratory (URL) involved installing a full-scale 5 m diameter by 12 m long seal in the main access shaft. The seal consisted of clay and concrete components spanning a major water-bearing fracture zone (FZ2) located at a depth of around 275 m that isolates two hydrogeochemical regimes. This paper presents results of coupled hydromechanical (H-M) numerical modelling that simulated measured performance of the seal. Parameters for the H-M modeling were determined from previously measured laboratory test data. Results from the modelling were compared with field data for water uptake and total pressures in the system. They show that hydration of the clay seal was dominated by the groundwater flow from FZ2. The simulations showed good agreement with field readings and provide an improved understanding of various interrelated physical processes that take place during hydration.