Finite deformation dynamic analysis and constitutive modeling of non-cohesive soils for liquefaction problems

It is widely accepted that effective stress based procedures which utilize plasticity models are potentially capable of replicating most of the observed behavior of the soil systems under static or dynamic loading. Performance of these procedures, however, is highly dependent on their underlying constitutive equations and the assumptions related to kinematics. Most of the available effective stress based procedures are formulated on the assumption of infinitesimal strain which in many cases is not realistic. On the other hand, most of the available constitutive models are very complex and often involve many parameters that need to be calibrated for a particular soil.; Motivated by the above mentioned deficiencies in the available methods, an attempt is made to develop a comprehensive methodology for analysis of geotechnical structures consisting of saturated granular soils. In order to achieve this goal, the mechanics of saturated granular soils is studied from three different angles. First, the equations governing the motion of saturated soil as a two phase medium are established in a general continuum mechanics framework considering finite deformation effects. Secondly, a finite element procedure is established in order to solve these governing equations. Finally, mechanics of granular soils is studied from a macroscopic constitutive modeling point of view and a two surface plasticity constitutive model is proposed to represent the average stress-strain behavior of granular soils in the usually encountered stress paths in geotechnical engineering problems. The model is particularly simple and convenient for numerical implementation.; A series of validation studies is conducted in order to evaluate the performance of the methodology developed in this study. First, a few simple quasi-static problems are solved to demonstrate the validity of the special finite element and the finite deformation formulation developed in chapters 3 and 2. Consequently, results of a few centrifuge tests are compared to the numerical simulations made by the proposed methodology. It is shown that the general trend observed in a liquefaction problem is captured by the method. In addition, the finite deformation formulation helps to find a more realistic picture of permanent deformations in a flow failure problem.