Experimental investigation and poroplastic modelling of saturated porous geomaterials

This paper is devoted to experimental investigation of saturated porous geomaterials in view of poroplastic modelling using the effective stress concept. A white chalk is considered as a representative example of porous geomaterials. The emphasis is put on the experimental characterization and validation of effective stress concept in the description of plastic behaviour of cohesive porous materials. A general experimental methodology is proposed, including hydrostatic and triaxial compression tests with particular loading paths combining variations of stress and interstitial pressure, in order to characterize interstitial pressure effects on plastic yield condition of the porous material. The existence of an effective stress tensor for plastic yield function is verified by this methodology for some specific loading conditions. Based on the general poroplasticity theory for saturated porous media, the concept of effective stress for plastic deformation is revisited and discussed. And the validity of such a concept is experimentally verified for the case of porous chalk. Based on this concept, an example of poroplastic model with two yield surfaces is formulated. The proposed model is validated through comparisons between model’s simulations and experimental data in undrained triaxial compression tests with variation of interstitial pressure.