Numerical study of the interaction between adjacent galleries in a high-level radioactive waste repository

In the framework of the feasibility study of high-level radioactive waste geological disposal, the potential interaction between adjacent galleries is an important issue to the layout design of the repository. Based on some experimental investigations by ANDRA, the present work is devoted to provide a preliminary evaluation on this phenomenon by a series of numerical simulations. According to the repository concept in France, the multi-barriers system, composed of geological and engineered barriers, is adopted for the construction of underground repository. The engineered barriers mainly include the canister, the concrete and the clay embankment. In the study, the hydromechancial behaviour of host rock (claystone) and concrete are characterized by a coupled elastoplastic damage model. On long-term scale, the creep of host rock as well as the chemical degradation of concrete is taken into account. A nonlinear elastic model of the classical Cam-clay type is applied to the bentonite plug. The numerical simulations are then performed for adjacent galleries with different inter distances. The evolution of stress distribution, pore pressure, and inelastic zone are analysed which can help the engineers to get a good understanding on the interaction of adjacent galleries. Finally, based on the predictive results, the minimum interdistance between galleries is discussed.