Multiphase flow processes in unsaturated cohesive soils are often affected by deformation due to swelling and shrinking as a result of varying water contents. This paper presents a model concept which is denoted 'phenomenological' in terms of the processes responsible for soil deformation, since the effects of deformation on flow and transport are only considered by constitutive relations that allow an adaptation of the hydraulic properties. This new model is validated in a detailed intercomparison study with two state-of-theart models that are capable of explicitly describing the processes relevant for the deformation. A 'numerical experiment' with a state-of-the-art reference model is used to produce 'measurement data' for an inversemodelling-based estimation of the model input parameters for the phenomenological concept.

Summary. The numerical simulation of flow and transport processes is frequently applied to environmental, technical and even medical problems. In many cases, a deformation of the porous medium occurs which cannot be neglected. Therefore, we present a non-isothermal multiphase multicomponent flow and transport model which also allows for structural alterations of the porous medium phenomenologically. This means that the model accounts for the effects of the structural changes by adapting the hydraulic properties using constitutive relationships.

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