Multiscale modelling of coupled problems in porous materials

Abstract

In this paper a multiscale approach for coupled mechanical and transport phenomena in porous media is presented. It is shown that monoscale approaches show different limitations: phenomena like nonlinear elasticity, hysteresis, stiffness recovery in compressive loading, preferential moisture uptake into cracks, changes of the permeability caused by changes in the pore structure due to chemical processes are not taken adequately into account. The multiscale mechanical model is based on a damage and moisture dependent PM model. The PM model is based on the presence of a distribution of hysteretic units in the material, which open and close at different stresses. Changes in moisture content and the occurrence of crystallisation lead to changes in internal pressure in the material causing swelling and shrinkage and changes in stiffness and strength. The multiscale transport model is based on the prediction of the permeability curve from the pore volume distribution using a multiscale network approach. At the mesoscale a hybrid method is proposed modelling transport in cracks as a moving front into discrete features, including the interaction with the porous matrix which is modelled as a continuum. Finally, a strong discontinuity model for cracking is presented, which is based on a discrete formulation of the damage and moisture dependent multiscale model