3D digital core reconstruction and phase-field-based fracture modeling at the representative microstructural domain scale

Abstract

Natural rocks often contain geometrically irregular, multiscale discontinuous pores, which significantly influence their mechanical behavior. Quantitatively assessing the relationship between pore structures and mechanical properties remains challenging for analytical and experimental approaches. This study proposes a microscale numerical approach that integrates a two-dimensional image-based reconstruction method for generating three-dimensional digital rock cores (DRCs) with a phase-field cohesive zone model (PF-CZM) to quantitatively investigate the relationship among digital core microstructure, mechanical responses, and fracture mechanisms at the representative microstructural domain (RMD) scale. The optimal RMD size is determined using the box-scaling method in conjunction with the PF-CZM, by analyzing the porosity evolution and mechanical properties within the 3D DRCs. Subsequently, 3D reconstructions are generated from a single 2D image using a simulated annealing (SA) algorithm at RMD scale. Fracture simulations based on the PF-CZM are then performed to analyze the mechanical response. The accuracy and validity of the reconstructed DRC models are systematically evaluated from both geometric and mechanical perspectives. The geometric parameters, statistical characteristics, and mechanical responses of the reconstructed digital rocks are in close agreement with those of the reference model, demonstrating the reliability of the proposed approach.