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This dissertation, Digital Image Processing-based Numerical Methods for Mechanics of Heterogeneous Geomaterials by Sha, Chen, 陳沙, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled Digital Image Processing-Based Numerical Methods for Mechanics of Heterogeneous Geomaterials Submitted by Chen Sha for the degree of Doctor of Philosophy at the University of Hong Kong in November 2005 Geomaterials, such as soil, rock, asphalt concrete and cement concrete, are either natural materials or man-made composites from natural materials. In their formations, geomaterials are heterogeneous and consist of different individual materials or components including minerals, fines, sands, gravel, core-stones, voids and cracks. Each individual material component usually has distinctive physical properties and mechanical responses under external loading. The present literature review reveals that (1) it is generally recognized the heterogeneity of geomaterials plays a significant role in determining the failure behavior of geomaterials under loading; and (2) most relevant investigations have used either the phenomenological approach for homogeneous geomaterials at the meso-level or the statistical approach, considering the meso-level geomaterial heterogeneity at the statistics sense. To incorporate the actual material heterogeneity into mechanical analyses, the present work has developed the digital image processing (DIP)-based numerical methods. The proposed methods incorporate together the DIP, the vector data transformation, and the conventional numerical methods. The region segmentation method and the edge detection method are utilized to identify or separate individual material components from images of geomaterials. The generated material heterogeneity is the digital mesostructure that contains material spatial distribution. Vector transformation algorithms for transformation of image mesostructures into vector square data or vector polygon data are developed for the two-dimensional (2D) numerical analysis. An iterative milling and scanning system is developed to establish the three- dimensional (3D) actual mesostructures of geomaterials from 2D images at different geomaterial sections. The data are further incorporated into existing numerical software packages for further 2D or 3D mechanical analyses. Both the finite element method (FEM) and the finite difference method (FDM) are employed for numerical investigations. Stress analysis, seepage analysis, crack propagation simulation, fracture patterns analysis and mechanical properties prediction are conducted. Conventional laboratory tests including the Brazilian tensile test and the compression test are simulated. The effect of material heterogeneity in determining overall material properties and the properties at failure is studied in detail. This study demonstrates that material heterogeneity greatly influences the stress distribution and the stress variation in the material domain. Consequently, failure properties, including the crack propagation process and fracture patterns, are affected by the material heterogeneity. Mechanical performance such as tensile strength and uniaxial compressive strength is also strongly controlled by the material heterogeneity. Uniaxial compression tests on thin granite plate specimens have been conducted to elucidate the fracture behavior of granitic rock and to verify DIP-based numerical methods. The cracking processes of the granite plate specimens are recorded. Based on the actual materia

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