A new path for pressure relief surrounding rock control of thick and hard roof combined blasting

Abstract Roof stability remains a critical challenge restricting safe and efficient coal mine production, particularly under thick and hard roof conditions where delayed caving of the goaf roof results in large suspended areas behind supports and pronounced dynamic pressure effects. Taking Jinjiazhuang Coal Mine as the engineering background, this study establishes a coal-body bearing stress equation for the mining process based on mining compensation theory, thereby elucidating the migration characteristics of roadway roof strata. On this basis, a combined blasting pressure-relief control method is proposed, integrating deep directional top-cut blasting, shallow directional top-cut blasting, and shallow non-directional blasting, supported by theoretical analysis and numerical simulation.Field application results indicate that this method markedly enhances roadway surrounding rock stability: the average roof subsidence is reduced to 58.8 mm, representing a 93.2% decrease; the average floor heave decreases to 409.9 mm, a reduction of 73.1%; and the stress influence range ahead of the working face narrows to 57.9 mm, decreasing by 58.4%. The proposed method effectively mitigates coal-body stress both ahead of the working face and within the roadway coal pillar, thereby optimizing the roadway stress environment and achieving roadway protection. This study provides new technical insights and an effective approach for surrounding rock control under complex roof conditions in coal mining.