A new complex approach to assessment of the stress-strain condition of foundation and earth structures is presented here, which permits limit-state computations. Soil plasticity and dynamic consolidation are discussed in terms of rheological processes due to static and dynamic loading. Results of experiments on soil strength and deformability under static and dynamic loading are discussed. Algorithms are provided for computations of elastoviscoplastic soil deformations, and results of numerical stress-strain experiments employing those algorithms are analyzed for foundations and footings of structures, dykes, dams and other structures.