The coupled hydro-mechanical behaviours of compacted crushed Callovo-Oxfordian argillite

Callovo-Oxfordian (COx) argillite obtained from the excavation of high-level radioactive waste geological disposal has been evaluated as an alternative sealing/backfill material in France. This paper presents an experimental investigation into the hydro-mechanical behaviour of compacted crushed COx argillite. A series of oedometer compressive tests including various loading-unloading cycles were conducted on COx argillite powders at different initial water contents. After reaching the desired dry density (2.0 Mg/m3), the vertical stress was reduced to different levels (7.0 and 0.5 MPa) and the compacted sample was then flooded under constant volume conditions while measuring the changes in the vertical stress. It was found that the initial water content significantly affects the compressive behaviour. The measured saturated hydraulic conductivity is less than 1×10−10 m/s.