A Primary Study on Buckle-folding of Multilayer Strata
Date Issued
2009
Date
2009
Author(s)
Lin, Wei-Sheng
Abstract
Folds occur on all scales from the microscopic to the regional. Buckling is defined as the flexing or folding of a surface or series of parallel surface by a compressive stress directed along that surface or layer. Surfaces, either primary, such as bedding, or tectonically induced, such as cleavage, are common features in many rocks and are often buckled during formation. During the formation of folds, it usually accompanies with other small scale geological structure. These features record the property of rock mechanics and geological conditions. Therefore, It is significant to understand the influence of layers in a region and the history of geological structure by folds research.he primary factors forming multilayer folds are thickness of layer, competence ratio and thickness of matrix between layers. A general discussion of the reasons for the great variation in folded multilayered rocks is initialed by considering the way that folds in single layers can interact with each other to produce disharmonic, harmonic or polyharmonic association. So, the classifications of multilayer folds are 1) disharmonic fold: each layer would have its own characteristic wavelength depending upon its thickness and layer-matrix competence contrast. 2) harmonic fold: despite differences in thickness and mechanical properties of individual layers, all the layers have buckled with the same wavelength and amplitude. 3) two competent layers are of markedly differing thickness or show markedly different competent-incompetent layer ductility contrasts each competent layer is likely to induce its own characteristic wavelength in to the overall fold pattern. his research is based on theoretical solution of single layer. And, it uses the finite element method, ABAQUS, to simulate the formation of multilayer folds. Besides, we compare the numerical solution with the theoretical solution deriving by this study.he primary results of the study are:. the formula derivation of matrix reaction and verification of numerical simulation.. derivation the theoretical solution of multilayer fold with matrix between layers by force equilibrium method.. derivation the theoretical solution of multilayer fold with extreme thin matrix between layers by force equilibrium method.. the influence of facts (material property, section property, and matrix thickness) to multilayer fold wavelength.. numerical simulation of disharmonic fold, harmonic fold, and poly-harmonic fold.
Subjects
single layer fold
multilayer fold
elastic material
buckle
disharmonic fold
harmonic fold
polyharmonic fold
Type
thesis
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