Application [of] an elasto-plastic models for soils in the analysis of earth retaining structures. [Doctoral dissertation] | Primena elastoplastičnih modela za tlo u proračunu fleksibilnih potpornih konstrukcija. Doktorska disertacija

The subject of the thesis is the analysis of methods for designing flexible retaining structures and in particular the application of an elasto-plastic model for soils finite element method. In terms of analysis, the retaining structures are one of the most complex geotechnical structures. The interaction retaining structure – soil is reflected in the fact that the structure is both subject to the lateral pressures of the soil and is supported by its resistance. The deformations of the structure and soil displacement significantly influence the distribution of pressures onto the structure. The developments in the analysis of the flexible retaining structures include the theory of the limit state soil mechanics, application of the theory of elasticity (subgrade reaction method), the theory of plasticity and the use of elastoplastic models for soils. The latter two methods of analysis were made possible by the developments of computers and numerical methods of structural analysis, and in particular the use of the finite element method. The particular problem with the implementation of the elasto-plastic model for soils in the analysis of geotechnical structures using finite element method is the integration of constitutive relations of the model. The importance of the integration of constitutive relations arises from the fact that basic unknowns in the constitutive equations of the model. There are a number of numerical methods for integration of constitutive relations that successfully deal with this problem, such as method of trapezoid rule, midpoint rule, return mapping algorithm and different implicit methods. The thesis develops the algorithm of the implicit integration of the governing parameter (GPM method) for modified Cam-Clay model and bounding surface model (Mrozz, Norris and Zienkiewicz) as well as the return mapping algorithm for the bounding surface model. Both models have been incorporated into PAK finite element structural analysis software. An example of flexible retaining structure has been produced using PAK, and the results were compared with the other analysis method.