Poromechanics of partially saturated COx argillite

Our experimental study aimed originally at: 1) measuring argillite Biotʹs coefficient; 2) identifying the main drained poro-elastic parameters in the stabilized partially-saturated state. In doing this, we showed that the current isotropic poro-elastic Biotʹs model used for COx argillite might be improved. rk was based on two experimental set-ups: one for drained uniaxial compression, and the second for triaxial “change in pore pressure” poromechanical measurement. The latter was developed to measure poro-elastic parameters for saturated and partially-saturated material using gas as the fluid injected within the porous network. ms of stiffness, COx argillite was observed to be transverse isotropic. This was not the case as regards Biotʹs tensor which was found isotropic. The apparent Biotʹs coefficient was measured equal to 1, whatever the mass water content w(%). Biotʹs coefficient was labeled apparent because it was measured at stabilized w(%) (no transient water saturation regime during the tests). This allowed the use of the Terzaghiʹs definition of effective stress tensor, as the sum of the external hydrostatic stress tensor and of the pore pressure (times the identity tensor). The impact of w(%) on argillite stiffness was also observed.