Evolution mechanism of fracture failure and zonal support strategy for roadway surrounding rock under non-isobaric stress conditions

• A failure criterion for roadway rock under non-isobaric stress was established. • A MATLAB program extracts fractal dimension D and damage ratio n . • Fracture evolution under non-isobaric stress was quantitatively revealed. • A zonal support strategy for different stress regimes was proposed. To address the complex fracturing behavior and poor support adaptability of roadway surrounding rock under non-isobaric stress, this study combines theoretical analysis, numerical simulation, MATLAB programming, and field practice to investigate fracture evolution and control methods. A non-isobaric unloading failure criterion F is established, revealing the coupled control of K h , K v , and joint dip angle θ: dominance shifts from K h to K v as θ increases from 0° to 45°, and K v dominates when θ = 45°∼90°. The non-isobaric ratio I significantly enhances the sensitivity of F to the principal stress direction, and high I can trigger instability even at low stress levels. Fractal dimension D and damaged zone ratio n are used to quantify fracture evolution. As I increase from 5% to 60%, fractures evolve from local initiation to a complex “X-shaped” network. Under high non-isobaric conditions ( σ h = 8.0 MPa, σ v = 19.3 MPa, I = 60%), n increases from 0.86% to 16.58% and D rises from 1.0098 to about 1.46, with failure evolving through four stages: local initiation, directional expansion, deep penetration, and stabilization. A zonal control strategy of “strong support in high-stress, high- I zones and conventional support in low-stress, near-isobaric zones” is proposed and verified by field application, showing a significant improvement in roadway stability and support performance.