Optimization analysis of protective coal pillar size of dip roadway based on roof cutting and pressure relief

As coal mining depth increases, dip roadway faces encounter challenges like stress concentration and dynamic disturbances, underscoring the importance of designing protective coal pillar dimensions optimally. This research delves into optimizing protective coal pillar dimensions for system roadways through roof-cutting and stress-relief technology, focusing on the 17,191 (1) working face in Huainan, Anhui, China. The study investigated the impact of coal pillar dimensions on roadway stress distribution and stability through theoretical analysis, physical similarity experiments, numerical simulations, and engineering practice. Findings indicate that roof-cutting stress relief notably influences overburden movement and stress evolution, decreasing vertical stress on coal pillars and enhancing the stress conditions of the surrounding rock. Mining-induced stress notably affects an area approximately 175–185 m ahead of the working face. Roadway rock stress conditions are severe when the coal pillar width is below 130 m, with a stress increase rate of under 5% at 170 m width. Pillar widths exceeding 190 m effectively mitigate the stress state in the main roadways. A combined deep-shallow hole blasting roof-cutting and stress-relief scheme was proposed for the mining area based on its geological conditions. This implementation notably decreased the roof-floor convergence of the roadway, extending the terminal line by 20 m and meeting production safety standards. These results offer significant insights into optimizing protective coal pillar dimensions in deep coal mining.