Large Deformation Finite Element Analysis Of Engineering Behaviors Of Some Geotechnical Problems

Progressive failure of soil is one of the key issues in geotechnical engineering such as slope, excavation, embankment and composite foundation engineering. It is necessary to develop further studies and explain more clearly on the progressive failure mechanism of soil. The stability and failure behaviors of slope, excavation and embankment engineering are analyzed by using arbitrary Lagrangian-Eulerian (ALE) finite element method, which is an efficient method for large deformation problems. Combined with field testing, the engineering behavior of the stone column anchor and the single-piled composite foundation is also studied by using finite element method. The research work done includes as following:1. Based on the fundamental principle of arbitrary Lagrangian-Eulerian (ALE) method, the computer program is developed by large deformation FEM that can be used for two-dimensional, three-dimensional, plane strain and axi-symmetric conditions, in which, the elastic, visco-elastic and elasto-plastic models of soil and complex boundary conditions can be taken into consideration. Firstly, the program was verified by some examples.2. Progressive failure behavior and stability of soil slope were analyzed by using the large deformation finite element program developed. Combined with some strain localization methods and the onset condition of strain localization, the progressive failure processes of a homogeneous soil slope were analyzed by using bifurcation theory and criterion of strain localization. The main influencing factors on stability of soil slope were discussed. The homogeneous soil slope, the undrained clay slope with a weak foundation layer and the undrained clay slope with a thin weak layer were discussed in detail by using shear strength reduction method. Finally, an engineering example of slope failure was analyzed by using finite element method. The numerical analysis results were consistent with the observational ones in practice.3. The process and the behavior of cut slopes failure in excavationengineering on soft soil foundation were analyzed by using large deformation finite element method, with non-softening and softening model of Mohr-Coulomb respectively. The effect on computing results was studied, which was resulted in by the coefficient of earth pressure at rest. And an engineering example of cut slopes failure in excavation engineering on soft soil foundation was analyzed by using non-softening, softening model and finite element method respectively. The results show that the analysis by using softening model is close to the observation in field.4. The filling process of embankment on soft clay foundation, especially to simulate the fast filling process and failure behavior of embankment on monolayer and two-layer foundation, was analyzed by using large deformation finite element method. And the influencing factors on limited height of embankment were also studied. Referring to the field testing results of Lianyungang testing embankment, the limit height and failure behavior of that embankment were studied by using Mohr-Coulomb model, the numerical calculating results were compared carefully with those of the field test.5. Finally the stone column anchor and the single-piled composite foundation were introduced. The field testing results of vertical ultimate pull-out bearing capacity of stone column anchor single-piled composite foundation were analyzed, and those of bearing capacity behavior under compression-tension and tension repeated loading of were also studied. The behaviors of single-piled composite foundation of stone column anchor and stone column were analyzed by using finite element method (FEM) under the compression loading condition.The work presented herein not only studies the progressive failure and failure behavior of soil slope, cut slope in excavation engineering and embankment, but also analyzes the engineering behavior of stone column anchor and its single-piled composite foundation, and reveals the progressive failure process and failure behavior of some issues in geotechnical engineering. The work will enrich the research of geotechnical failure problems and provide some helpful references to engineering practice.