Ultra-Close Range Photogrammetry for Imaging Rock Surfaces
Abstract
It is well known that microscopic or macroscopic porosity controls the strength of rock specimens. Many researchers have presented relationships between porosity and tensile strength based on the assumption that the porosity on the failure plane is representative of the porosity of the entire specimen. Our goal was to investigate and compare the relationship between total specimen macroporosity and tensile strength and failure plane macroporosity porosity and tensile strength. Indirect tension testing was conducted on twenty-two cylindrical mortar specimens to determine tensile strength. Styrofoam balls were mixed into the mortar mix to simulate macroporosity, and any uneven surfaces were ground using prior to testing. A load cell measured the compressive force applied by the loading frame; the maximum force was recorded and used to calculate the tensile strength of the specimen. The total specimen porosity was determined using the mass, diameter, and thickness of the specimens. The failure plane macroporosity was determined by taking overlapping pictures of the failure plane and stitching them together to create a high-definition digital image of the failure plane. Digital measurements of the styrofoam balls were taken and used to calculate the failure plane macroporosity. The results of this study concluded that specimens with higher porosities have lower tensile strengths. However, the failure plane macroporosity and total specimens macroporosity of some specimens were vastly different for the same tensile strength. This demonstrates that while failure plane porosity can be generally representative of the total specimen macroporosity, one must be careful when creating a direct correlation between the two.
Ultra-Close Range Photogrammetry for Imaging Rock Surfaces
It is well known that microscopic or macroscopic porosity controls the strength of rock specimens. Many researchers have presented relationships between porosity and tensile strength based on the assumption that the porosity on the failure plane is representative of the porosity of the entire specimen. Our goal was to investigate and compare the relationship between total specimen macroporosity and tensile strength and failure plane macroporosity porosity and tensile strength. Indirect tension testing was conducted on twenty-two cylindrical mortar specimens to determine tensile strength. Styrofoam balls were mixed into the mortar mix to simulate macroporosity, and any uneven surfaces were ground using prior to testing. A load cell measured the compressive force applied by the loading frame; the maximum force was recorded and used to calculate the tensile strength of the specimen. The total specimen porosity was determined using the mass, diameter, and thickness of the specimens. The failure plane macroporosity was determined by taking overlapping pictures of the failure plane and stitching them together to create a high-definition digital image of the failure plane. Digital measurements of the styrofoam balls were taken and used to calculate the failure plane macroporosity. The results of this study concluded that specimens with higher porosities have lower tensile strengths. However, the failure plane macroporosity and total specimens macroporosity of some specimens were vastly different for the same tensile strength. This demonstrates that while failure plane porosity can be generally representative of the total specimen macroporosity, one must be careful when creating a direct correlation between the two.