Mechanism and technology of pressure relief by roof cutting for gob-side entry retention with small coal pillars in thick hard roof

• A short cantilever beam mechanical model is established, revealing the three-stage evolution (“pressure relief–dynamic pressure–compaction”) of thick hard roof fracture and movement. • Roof cutting reduces the load on the coal pillar by 33 % and eliminates the risk of rock burst by controlling the lateral cantilever structure. • A technical system of “large-diameter borehole roof cutting + synergistic cable support” is proposed, with optimized parameters: cutting height = 10 m, angle = 15°, pillar width = 10 m. This study addresses the challenges of surrounding rock instability in gob-side entries with small coal pillars under a thick hard roof. Using the 16,202 working face of Wuhua Mining as a case study, we investigated the pressure relief mechanism and optimized roof cutting parameters through theoretical analysis, numerical simulation, and industrial trials. A mechanical model of a short cantilever beam for the roof under pressure relief via roof cutting was established, revealing the three-stage characteristics (pressure relief–dynamic pressure–compaction) of thick hard roof fracture and movement. The mechanical mechanism by which roof cutting reduces the load on the coal pillar by 33 % was elucidated. A technical system of "large-diameter borehole roof cutting combined with synergistic cable support" was proposed, which innovatively optimizes the roof cutting height, angle, and coal pillar width. Numerical simulations indicated that the stress concentration factor and surrounding rock deformation for a 10 m coal pillar are significantly superior to those of the 6–9 m schemes. Industrial trials verified that the maximum roof subsidence was only 112 mm (a reduction of 31.67 %), with no floor heave observed. The cable bolts experienced stable loads between 138.8–163.8 kN, and the stability of the support structure was improved by 40 %. The results demonstrate that this technology effectively controls the lateral cantilever structure of the hard roof, eliminates the risk of rock burst, achieves an entry cross-section integrity exceeding 95 %, and provides technical support for the safe and efficient mining of working faces with thick hard roofs.