Finite element and experimental study of soil-structure interfaces

Many geotechnical engineering problems, such as building-foundation systems, depend on the interaction between soil and structure. Most current stress analyses of such problems neglect the effect of the soil-structure interfaces. For more realistic stress-strain predictions, soil-structure interfaces need to be incorporated into the analysis utilizing advanced elasto-plastic constitutive laws for both soil and interfaces.; An integrated nonlinear finite element program that combines elasto-plastic soil and interface elements is developed to realistically model soil-structure interaction problems. A formulation of Plesha's zero thickness interface element is employed to represent the soil-structure interfaces. The elasto-plastic Hierarchical Single Surface (HiSS) constitutive law is adopted to model the soil. Modification of the HiSS model for discontinuities is needed to model the soil-structure interfaces.; Experiments on laboratory surface-sand interfaces and small scale pile tests are performed to verify the performance of the finite element model. A modified direct shear device is developed for the laboratory surface-sand interface tests. This device is used to obtain the soil and interface constitutive parameters used for all finite element modeling. Tests with rough and smooth surfaces under constant stress and constant volume conditions are performed with both the modified direct shear device and the small scale pile test equipment. The performance of the interface model is verified by numerically back predicting the results of these constant stress and constant volume surface-sand interface tests of both devices. These back predictions demonstrate that the adopted interface model is capable of modeling rough and smooth surface-sand interfaces for constant stress and constant volume conditions.; Finite element analysis of modified direct shear and small scale pile tests demonstrates the capabilities of the developed finite element program to model soil-structure interaction problems. The analysis also shows that the interface elements play an important role in realistically modeling the response of the soil-structural system. The use of interface elements, while essential to accurately model smooth surface-sand interfaces, also yields better results when used to model rough surface-sand interfaces compared to analysis without interface elements.