THESIS
2008
154 p. : ill. ; 30 cm
Abstract
Today, majority of the embankment dam stability and deformation analyses approaches empirically or semi-empirically. These analyses overlook the anisotropic effect on granular materials using either approach. Although an anisotropic analysis can simulates the soil responses with anisotropic effect, but it is practically too complicated. Current practice relies on isotropic analysis and inherent fabric anisotropy and simplified by lowering the critical state line obtained from simple compression test based on experience....[
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Today, majority of the embankment dam stability and deformation analyses approaches empirically or semi-empirically. These analyses overlook the anisotropic effect on granular materials using either approach. Although an anisotropic analysis can simulates the soil responses with anisotropic effect, but it is practically too complicated. Current practice relies on isotropic analysis and inherent fabric anisotropy and simplified by lowering the critical state line obtained from simple compression test based on experience.
To enhance the analyses, a simplified method was proposed to implement the inherent fabric anisotropy into the isotropic procedure using an objective measurement, A. The objective measurement, A, captures the anisotropic state of an element. This parameter reflects the orientation influence between the material fabric and the stress state on soil responses. Therefore, the inherent fabric anisotropy is apparently implemented into the isotropic analysis by obtaining a suitable value of A.
To study the anisotropy effect and the effectiveness of the proposed method, two two-dimensional fully-coupled dynamic finite element procedures, SUMDESitAN and SUMDES2D, are used in this research. Both procedures are developed based on the physic laws on balance of momentum and conservation of mass, and the separately defined constitutive laws for soil skeleton, pore fluid, and the interaction between the phases. The most important difference between two procedures is the constitutive laws for soil skeletons: SUMDESitAN uses an anisotropic model and SUMDES2D uses an isotropic model. The two models lead to the estimating procedures for flow liquefaction and cyclic mobility responses in a unified manner.
A series of fully-coupled analyses have been conducted on the Upper San Fernando Dam by other scholars and are reviewed in this paper. The effect of the anisotropy of the dam on the deformation and stresses distribution are addressed in details. Also, the performance of the proposed simplified method is discussed and is tested with the Lower San Fernando Dam.
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