Damage mechanism of rock induced by microcrack evolution: A multi-dimensional perspective

Abstract

This paper investigated the multi-dimensional and multi-scale damage mechanisms of rocks employing Discrete Element Method (DEM) numerical tests, macroscopic damage models, microscopic damage models, and Acoustic Emission (AE) tests. The study analyzed the correlation between the number of microcracks and AE accumulative ring-down count, established a macroscopic damage evolution equation representing rock volume strain, and explored the mechanisms of microscopic damage evolution. The impact of confining pressure and initial microcracks on rock damage characteristics, the relationship between crack volume strain and macroscopic damage evolution, and the effects of different crack types on microscopic damage evolution were discussed. Key findings include: 1) The DEM incorporating gapped contacts can effectively assess the impact of initial microcrack volume on compaction deformation. Concurrently, the consistency observed between the number of microcracks in DEM and the AE accumulative ring-down count aptly characterizes the failure trend. 2) Macroscopic damage is quantitatively derivable through microcrack enumeration, with the noteworthy observation that microcracks undergo substantial development preceding the volumetric expansion of the rock. Consequently, the evolution of macroscopic damage can be aptly described as a piecewise exponential function relative to rock volume strain. 3) Microcracks manifest in two forms: tension and shear, and the evolution of microscopic damage is intricately linked to the type of microcracks, thus prompting a comprehensive consideration of the microscopic damage induced by different microcrack types. This multi-dimensional exploration enhances our understanding of the dynamic processes underlying rock damage at both macroscopic and microscopic levels.