Implementation of DSC model for dynamic analysis of soil-structure interaction problems

Abstract

The Disturbed State Concepts (DSC) model, with simplified unloading/reloading formulation, is implemented in a nonlinear dynamic finite element program for porous media named DSC-DYN2D. It can perform static, two phase dynamic and consolidation analysis of soils and soil-structure interaction problems with the DSC model. The model and the computer procedure are verified by back predictions of laboratory tests of clay, steel-clay interfaces as well as a simulation of pile-soil interaction problem. The Disturbed State Concepts have been developed recently as a constitutive modeling approach. In the DSC, the material is assumed to transform continuously and randomly from the relatively intact state to the fully adjusted state under loading. Hence, the observed response of the material is expressed in terms of the response of relatively intact and fully adjusted states. In this dissertation, the Disturbed State Concept constitutive model is developed by using the HiSS model for the relative intact part and the critical state model for the fully adjusted part in the material. The general formulation for implementation is developed. New and simplified unloading/reloading schemes are proposed for cyclic loading. Then the DSC model with the unloading/reloading scheme are implemented in the dynamic finite element program based on the generalized Biot's theory. The procedure for determining the parameters of the DSC model and the unloading/reloading is discussed. The parameters for the steel-clay interface are found from the tests and used for the prediction of the tests. Consolidation and cyclic loading tests from the field load tests on a pile segment were numerically simulated using the finite element program DSC-DYN2D and compared with field measurements and those from the previous analysis with the HiSS model. The DSC predictions show improved agreement with the field behavior of the pile compared to those from the HiSS model. The unloading/reloading models proposed in the study are simple yet give the realistic prediction of unloading and reloading behavior of the geomaterials under cyclic loading. Overall, the computer procedure with the DSC allows improved and realistic simulation of the complex dynamic soil-structure interaction problems.