Fractal Analysis of Mesoscale Failure Evolution and Microstructure Characterization for Sandstone Using DIP, SEM-EDS, and Micro-CT

Abstract

Joints with different angles in rocks have significant impacts on their fracture mechanisms. In this study, scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), and microcomputed tomography (Micro-CT) were used to study the microstructure characterization of sandstone, and digital image processing (DIP) technology has been applied for the characterization of sandstone mesostructures. DIP technology has been combined with RFPA2D to numerically investigate the mesoscale fracture behaviors of jointed sandstone with different dip angles. On the basis of the box dimension theory and digital image storage principle, Matlab was applied to develop a mesoscale fracture box dimension algorithm based on digital imaging, and therefore, an analysis method was established for the evaluation of mesoscale fracture damage degree based on fractal dimensions. Previous studies have revealed that the elastic modulus and compressive strength of the sandstone had significant anisotropy, and the compressive strength of sandstone had an approximately power exponential relationship with fractal dimensions; therefore, fractal dimensions could be applied to describe sandstone compressive strength. There were found to be five final failure modes in joint specimens with various inclination angles. Failure mode and damage degree could be determined by fractal dimensions and mesoscale fracture damage degree, respectively. As the fractal dimension became greater, failure mode became more complicated and mesoscale fracture damage was enhanced, resulting in more serious damage. This study is helpful in understanding the mechanical properties of sandstone in complex structural areas and provides a novel method for studying the evolution law of mesoscale failure in rocks.