In order to increase the mining rate of underground coal resources, an innovative nonpillar underground coal mining approach (fracturing roofs to maintain entry (FRME)) has been widely applied in China. The effect of roof fracturing determines whether the entry can be retained successfully or not. In this work, the tail entry of 21304 panel in Chengjiao Coal Mine (China) has been considered as the test site. The coal mine is located approximately 900 m underground. A numerical investigation on the relationship between the entry stability and roof fracturing angle was conducted. In order to investigate the reasonable scope of roof fracturing angle under static and dynamic loadings, the double‐yield model was employed to simulate the gob materials, and the input parameters of the model were calibrated meticulously using the method of inversion analysis. Furthermore, dynamic loading was applied to research the influence of fracture of hard rock strata on the entry stability. The global model was validated with the field data. The simulation results demonstrate that the reasonable scope of the roof fracturing angle is 10–20°, in which case the distributions of vertical stress are favorable to the stability of gob‐side entry. Additionally, the dynamic responses were found to be relatively moderate. The numerical method could provide a significant reference for the design of FRME approach.

The effect of conventional bolt support is not ideal due to the large deformation character of soft rock. As an innovative bolt, constant resistance large deformation (CRLD) bolt has been successfully applied to swelling soft rock...

Gob-side entry retaining by roof cutting and pressure relief (CRRE) eliminates coal pillar waste and mitigates mining-induced stress concentration. Although widely applied in mines shallower than 1000 m, systematic research on asymmetric deformation mechanisms and matched control technologies under ultra-deep conditions (>1000 m, σH > 60 MPa) remains limited. This study investigates the 5307 working face of Anju Coal Mine (burial depth: 1127–1195 m) using theoretical analysis, FLAC3D numerical simulation, and 480 m of field monitoring. The stress evolution, deviatoric stress field response, and asymmetric deformation mechanisms of the surrounding rock under ultra-deep mining conditions are systematically analyzed, based on which a targeted collaborative control technology is proposed. The key findings indicate that (1) CRRE significantly attenuates advanced abutment pressure compared with conventional pillar retention, with an average stress reduction of 20.1 ± 1.2% (95% CI: 17.8–22.4%, p < 0.01). (2) During the advanced mining stage, the second invariant of deviatoric stress exhibits a saddle-shaped distribution with a pronounced concentration at the mid-rib, identifying this as the dominant zone for rib bulging failure. (3) In the post-mining entry-forming stage, the roof deviatoric stress field demonstrates marked asymmetric evolution, with the distortion energy on the solid-coal side substantially exceeding that on the gob side; moreover, the low-position roof strata exhibit high distortion and poor stability, rendering them prone to bending fractures. Grounded in these mechanisms, a full-cycle differentiated surrounding rock control technology is developed, integrating pre-mining directional roof pre-splitting, active tough support reinforcement, post-mining temporary roof control and pressure relief, and gangue retaining with rib collaborative protection. The key parameters include a roof cutting height of 7 m, a cutting angle of 15°, NPR constant-resistance anchor cables with W-steel belts, and temporary support extending 300 m behind the working face. Field monitoring reveals staged deformation evolution, with stabilization achieved 250 m behind the working face. Maximum roof subsidence, floor heave, and total roof-floor convergence were 180 mm, 329 mm, and 422 mm, respectively, below the 500 mm allowable threshold for ultra-deep retained entries.