Non-linear behaviour in the deformation and localization analysis of unsaturated soil

Deformation and localization analysis is a crucial issue and has thus been intensively investigated in the last decades. In particular, geotechnical applications do not only concern a single solid material but they also affect the interaction with the pore-fluids, water and air. As a result, both the deformation and the localization analysis must be applied to a triphasic material consisting of a materially incompressible elasto-plastic or elasto-viscoplastic skeleton saturated by two viscous pore-fluids, a materially incompressible pore-liquid and a materially compressible pore-gas. Based on a continuum mechanical approach, unsaturated soil can be described within the well-founded framework of the Theory of Porous Media (TPM). The numerical computations proceed from weak formulations of the momentum balance of the overall triphasic material together with the mass balance equations of the pore-fluids. The resulting system of strongly coupled differential-algebraic equations (DAE) is solved by use of the finite element tool PANDAS. Furthermore, several initial boundary-value problems are presented demonstrating the efficiency of the overall formulation.