The current scientific and technical co-operation between Graz University of Technology and Hohai University is motivated by the joint interest of both universities in gaining further insight into the properties of unsaturated soils. The activities are experimental investigations with artificial soil specimens in the laboratory, the evaluation of in situ measurements and the preparation of a database, the mathematical modelling of saturated and unsaturated soil behaviour, the calibration of the mathematical model to real soil materials and the application of the model to earth dams and to other engineering problems with a similar physical background. For the practical application of the model appropriate calibration procedures have to be worked out. Furthermore the construction of dams in horizontally compacted layers may lead to initial anisotropy. For the practical relevance of the joint project it is necessary that each of the aspects mentioned above is treated in an appropriate way by the corresponding disciplines, i.e. a multilateral co-operation between the disciplines of Mechanics of Granular Materials, Geotechnics and Hydraulic Structures.