Experimental study of elastic properties of different constituents of partially saturated argillite using nano-indentation tests

Callovo-Oxfordian argillite, obtained from the ANDRA underground research laboratory in Meuse/Haute-Marne (France), is characterized as a multiphase material. The argillite is composed of carbonate inclusions (10–50μm) embedded in an argillaceous matrix (representing expanding clay minerals, such as smectites). The matrix itself is also multiphase, composed of clay aggregates of 1μm-size carbonate and quartz inclusions. The high sensitivity of the mechanical behaviour of argillite to saturation is an important characteristic of this material as it has been previously demonstrated in macro-scale mechanical experiments performed under varying degrees of humidity.