Hydromechanical Behaviour of Rock-Bentonite Interfaces Under Compression

Interfaces between geomaterials may be critical for the long term confinement of the engineered barriers of nuclear waste disposals, particularly if there is water flow. Hydromechanical compression tests have been performed on rock-bentonite interfaces representing the contact between a host rock (toarcian argillite) and an engineered barrier within a nuclear waste repository. The results show that there is no major influence of the bentonite fraction or the nature of the additive as long as the additive is inert (sand or crushed rock): all the interfaces are closed for low values of normal stress (about 4 MPa). On the other hand, the hydromechanical behaviour of the interfaces changes when a high fraction of cement is used. Moreover, it has been shown that bentonite is very sensitive to hydraulic erosion, producing flow channels within the interface zone. A numerical study confirms the importance of erosion for the hydromechanical behaviour of the interface.