Estimation of characteristic stresses in granite through acoustic emission monitoring of microcrack fracture mode evolution

Abstract

Characteristic stresses are critical indicators for microcrack initiation and propagation in rock, a process intrinsically linked to fracture mode. To investigate fracture mode evolution and its feasibility for estimating characteristic stresses, this study conducted uniaxial compression and cyclic loading-unloading tests on fine- and coarse-grained granite with acoustic emission (AE) monitoring. Cyclic target stresses were set within intervals determined by characteristic stresses. Analysis using the AE parameters AF-RA revealed that fracture mode evolution correlates with damage level, and shear microcrack propagation primarily governs macroscopic failure. A characteristic stress estimation method was developed by mapping key points on the shear crack proportion curve: crack closure stress (transition between fluctuating and stable segments), crack initiation stress (inflection point of curve rise), and crack damage stress (slope change point in ascending segment). Comparative analysis with the crack volumetric strain method validated the proposed method. The influences of fracture mode dividing line and statistical interval were discussed, with practical recommendations provided. Compared to conventional AE parameters, the fracture mode proportion exhibits lower sensitivity to AE parameter variations, enabling more reliable identification of characteristic stress points. Furthermore, it directly reflects microcrack evolution behavior, enhancing interpretability and providing a novel perspective for AE-based characteristic stress determination.

Keywords

Fracture mode / Shear microcrack / Characteristic stress / Stress threshold / Acoustic emission

CRediT authorship contribution statement

Yunge Zhao: Writing – original draft, Validation, Methodology, Conceptualization. Linqi Huang: Writing – review & editing, Project administration, Investigation, Formal analysis. Longjun Dong: Resources, Methodology, Investigation, Formal analysis. Xibing Li: Supervision, Project administration, Funding acquisition, Conceptualization.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

The authors would like to appreciate the financial support from the National Natural Science Foundation of China (Nos. 52434006, 51927808, and 52374151) and Fundamental Research Funds for the Central Universities of Central South University (No. 2024zzts0420). The authors would also like to appreciate the constructive comments from the editors and anonymous reviewers to help improve the paper.

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