Assessment of porosity-permeability variation on the response of sandy soils via hypoplasticity model

Bayraktaroğlu, Hilmi.
Hydro-mechanical characteristic of the saturated sands is highly influenced by their porosity and permeability. During loading, unloading and reloading compaction of sands, loosening and re-compaction take place, which leads to changes in pore volume and permeability. In order to accurately simulate these real-life conditions, new variables and phenomena should be investigated using sophisticated numerical tools and equipment. In this study, the behavior of water saturated sands subjected to cyclic and dynamic loading is analyzed numerically and experimentally. For the finite element analyses, a three-dimensional fully coupled two-phase finite element is developed and implemented on the basis of a two-phase model in order to consider the pore water pressure development in saturated sands. In addition, an extended hypoplastic constitutive model is used to describe the material behavior of sandy soils. The porosity-permeability variation is taken into account by implementation of Kozeny-Carman relationship. Using the experimental test results both performed in laboratory and documented in the literature, the influence of porosity-permeability variation on the mechanical behavior of sandy soils is investigated by comparing the strain and pore pressure accumulations. The necessity of the consideration of porosity-permeability variation for realistic modeling of the cyclic and dynamic behavior of saturated sandy soils is assessed. The laboratory experiments and numerical methods required to determine thirteen parameters of the hypoplastic constitutive model are explained systematically. The hypoplastic material parameters of a sandy soil is determined and then compared with the recommended parameters available in the literature for the same type of soil. In addition, hypoplastic model parameters of various sands that are commonly used in the modeling of the soil under dynamic loading are presented. This thesis will contribute to researchers working on the numerical modeling of material behavior using finite element method in geotechnical engineering.
Citation Formats
H. Bayraktaroğlu, “Assessment of porosity-permeability variation on the response of sandy soils via hypoplasticity model,” Thesis (M.S.) -- Graduate School of Natural and Applied Sciences. Civil Engineering., Middle East Technical University, 2019.