article dans une revue internationale avec comité de lecture  
2013  
Cariou Sophie; Dormieux Luc; Skoczylas Frédéric  
Applied Clay Science (Appl Clay Sci)  
8081  
18 – 30  
CallovoOxfordian argillite exhibits a mechanical behavior that is not typical for a porous material. Its stiffness for example is found to decrease with an increasing saturation degree. Time to reach strain equilibrium at high mass water content is much longer after a purely hydric loading than after a purely mechanical loading. This behavior is a source of questions and these experimental observations question in particular the interaction between liquid in the pore space and the solid particles of argillite.
Based on the analysis of the microstructure, some pores are revealed inside the solid particles. This paper assumes that these intraparticle pores are in thermodynamical equilibrium with the pores in the interparticular space. Micromechanics integrates the assumption of this connection and leads to an original constitutive law for CallovoOxfordian argillite. Based on micromechanics, an explanation is proposed for the origin of the elasticity tensor of CallovoOxfordian argillite. This state equation is then checked against some experimental data, and the relevance of this original stress state equation is emphasized. In particular, the fact that CallovoOxfordian argillite behaves like a Terzaghi's material at constant saturation degree is consistent with the proposed constitutive law. As in Biot's theory, Biot's tensor in the proposed stress state equation of CallovoOxfordian argillite weighs in a hydromechanical coupling term the pressure variation in the interparticle pores. Because of the particular microstructure of CallovoOxfordian argillite, Biot's tensor cannot be determined by a classic triaxial “change in pore” pressure poromechanical test. An original methodology is proposed to determine this tensor, which uses the monitoring of the length variation of a sample during a freedrying. Biot's tensor is found to be almost isotropic, with a Biot's coefficient equal to 0.84. 

Argillite; Twoscale doubleporosity material; Partiallysaturated media; Biot's tensor  