The Article considers methodology of foundation calculation, providing safety of urban construction in difficult engineering - geological conditions of St.-Petersburg. Object of research is waterlogged argillous adjournment of various genesis and age of small and average degree. The article analyzes most widespread mathematical models of soil. The article gives the results of research: - the analysis of a situation in underground building of the St.-Petersburg region; - the analysis of nonlinear soil models, applied in most popular programs of calculation (model of Coulomb-Mohr, models of Cam Clay, EDP Cap Model, models with double hardening); - the analysis of soil in the conditions of a weighting and discharge; - the analysis of soil model combined by clayey grounds.