Effects of intermediate principal stress on strainburst in granite: Insights from true-triaxial unloading experiments and PFC3D-GBM simulations

Abstract

To improve the accuracy of rockburst risk evaluation in mining and tunnelling engineering, the influence of intermediate principal stress σ₂ deserves further consideration, which has been neglected in general prediction frameworks. This study employs an integrated approach that combines true-triaxial unloading experiments with three-dimensional grain-based discrete element modeling (PFC3D-GBM) to examine the effects of σ₂ on strainburst systematically and elucidate the underlying mechanisms. Through this dual experimental–numerical methodology, the strainburst characteristics under varying σ₂ are analyzed in detail regarding mechanical responses, failure evolution and patterns, microscope fracture mechanisms, and energy partitioning. The results indicate that elevated σ₂ can enhance the bearing capacity of rock, thereby necessitating a higher stress condition required for strainburst. However, it also enlarges the potential strainburst intensity, manifesting as deeper rockburst pits and more violent ejection of rock fragments. An increasing σ₂ facilitates the microscope transgranular fractures, inhibits intergranular tensile fractures, and raises the kinetic energy conversion ratio slightly. It affects the intensity of strainburst through the following mechanisms, including the increase of energy storage limit, the intensification of Poisson effect for lateral expansion, and the enhancement of the transgranular fracturing mechanism. In practical engineering, the depth and range of support needs to be ensured under high σ₂ conditions, and it is recommended to use prestressing techniques to control the development of significant slabbing.

Keywords

Rockburst / Intermediate principal stress / True-triaxial experiment / 3D grain-based model

CRediT authorship contribution statement

Hongru Li: Writing – review & editing, Writing – original draft, Software, Investigation, Funding acquisition, Data curation, Conceptualization. Manchao He: Supervision, Project administration. Tai Cheng: Writing – review & editing, Writing – original draft, Visualization, Software, Investigation. Yafei Qiao: Supervision. Dongqiao Liu: Supervision. Jie Hu: Investigation. Yingming Xiao: Investigation.

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

This work was supported by the National Natural Science Foundation of China (No. 42507210), the Fundamental Research Funds for the Central Universities (No. 2025XJSB01), the State Key Laboratory for Tunnel Engineering (No. SKLTEK202421), and the Foundation of Key Laboratory of Deep Coal Resource Mining (China University of Mining and Technology), Ministry of Education (No. KLDCRMMOE24KF11).

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