Abstract
We studied the pore structure in intact and inelastically compacted Indiana limestone using X-ray microtomography imaging. Guided by detailed microstructural observations and using Otsu’s global thresholding method, the 3D images acquired at voxel side length of 4 μm were segmented into three domains: solid grains, macropores and an intermediate zone dominated by microporosity. The macropores were individually identified by morphological processing and their shape quantified by their sphericity and equivalent diameter. Our new data revealed a significant reduction of the number of macropores in hydrostatically and triaxially compressed samples with respect to the intact material, in agreement with previous microstructural analysis. The intermediate (microporosity) domains remained interconnected in compacted samples. Our data suggest that the inelastic compaction in Indiana limestone is manifested as not only a decrease in the volume fraction of the microporosity backbone but also a corresponding decrease in its thickness.
Highlights
The mechanical and transport behaviors of a rock are sensitively dependent on its pore geometry
Guided by parallel microstructural observations using optical microscopy and Scanning Electron Microscopes (SEM), a first objective of this study is to investigate to what extent X-ray microCT can be used to characterize the macropores and indirectly infer the geometry and spatial distribution of the microporosity
Most investigations of its pore structure have been done on 2D thin-sections, synthesizing observations on different scales using the optical microscope and SEM
Summary
The mechanical and transport behaviors of a rock are sensitively dependent on its pore geometry. Recent advances in 3-dimensional imaging techniques such as X-ray microtomography (microCT) and Laser Scanning Confocal Microscopy (LSCM) have provided enhanced perspective on pore geometry complexity. It has contributed useful insights into the preexisting pore space and how it influences rock physical properties, as well as damage evolution and its relation to the micromechanics of failure. Since microCT is quite effective in identifying the macropores and characterizing their geometric characteristics, a second objective of the present study is to characterize and contrast these characteristics in undeformed and deformed samples of Indiana limestone, so as to gain insights into the damage evolution and micromechanics of inelastic compaction
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