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Relationship between Micro and Macro Mechanical Properties of Cemented Artificial Conglomerate
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- Author / Creator
- Li, Yuan
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Micromechanics modeling is becoming more popular in geotechnical analysis. It allows engineers to understand the deformation and failure processes at the microscopic level. Due to the advancement of computer capacities and numerical methods for micromechanics analysis, engineers are able to perform micromechanics analysis on more practical problems. In order to perform these analysis, it is necessary to determine the micro mechanical parameters of the material. This research is focused on the theoretical and experimental development to determine the micro mechanical parameters of cemented granular material. In the theoretical analysis, the micro mechanical properties of geomaterials consist of several components. The contribution of each of these components to the overall macro behavior is dependent on the characteristics of each component. The strength of a cemented granular material consists of frictional strength between the grains, the bonding strength between the grains and the cement, and the bonding strength of the cement. It is assumed that the voids in a cemented granular material are occupied by cement, and the overall strength of the material can be calculated from the strength of each individual component. In this study, the theoretical relationship that relates the strength of each component to the overall macro mechanical strength of the cemented granular material has been developed. Experiments were conducted to measure the micro and macro mechanical parameters in the theoretical relationship for cemented granular material. Artificial conglomerate made up of steel balls and Portland cement was used to minimize the variation of grains and cementation properties in natural materials, and the possibility of crushing of grains under high stress. Direct shear, uniaxial/triaxial and Brazilian tensile tests were conducted to study the mechanical behavior and measure the macro parameters of artificial conglomerates. Microscopy analysis, 3D scanning and post-failure analysis were carried out to obtain the micro properties. In addition, an innovation approach was developed to measure the inter-particle friction angle of steel balls. Numerical simulation was performed to study the micro mechanical behavior of cemented granular material and it was further used to examine the theoretical relationship that relates the micro and macro mechanical parameters. Using calibrated micro properties, the numerical results show good agreement between theoretical calculations and laboratory measurements under different normal stresses. However, different micro parameters are required for modelling tests with samples of different particle sizes. This is due to the size dependent progressive failure mechanism in the micro model. Using measured micro properties as inputs, the calculated cohesions from the theoretical relationship are about 0.84 to 1.05 times of the measured values from direct shear tests. The calculated peak friction angles are about 10% to 15% higher than the measured values from direct shear tests. Since it is practically impossible to arrange particles in the experiment that is assumed in the theoretical relationship, this could be the reason that accounts for the differences between the calculated and measured values. The calculated cohesion and friction agree with the measured values in the laboratory, which supports the existence of a relationship between the micro and macro mechanical properties. The macro parameters of cemented granular material can be calculated with measured micro properties using the derived theoretical relationship. In addition, this study also provides the laboratory procedures to measure the macro and micro properties of cemented granular material.
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- Graduation date
- Fall 2017
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- Type of Item
- Thesis
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- Degree
- Doctor of Philosophy
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- License
- This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.