A constitutive model for porous rock including effects of bond strength degradation and partial saturation

We present a constitutive model to simulate the geomechanical response of porous rocks including the effect of bond strength degradation (or cementation), and the role of capillary pressure in partially saturated conditions. It is oftentimes difficult to obtain enough experimental data for the proper hydro-mechanical characterization of the rocks. This, for example, is what generally occurs with the geological reservoirs to be used for CO2 storage, located about 600 m below the ground level. Therefore, the model proposed entails a compromise between the ability to reproduce realistic strain–stress paths and the number of parameters. A review and analysis of a wide range of tests show that it is not easy to put forth formulations that are sufficiently general with less than eleven parameters. With this number of parameters, the model proposed has enabled to obtain a satisfactory simulation of brittle/ductile behaviour, pre-peak dilatancy, the bond effect, the effects of chemical degradation on bond strength, and the unsaturated behaviour of porous rocks.