Research on Roof Weighting Mechanism of Coal Pillar Mining in Shallow Buried Closely Spaced Multi-seams

Abstract In the process of mining, the lower working face through the coal pillar (CP) in shallow-buried closely coal seams (SBCCS), noticeable roof step sinking, and dynamic load effects on the support were observed. In order to reveal the mechanism of strong ground pressure, the theoretical model of roof structure during the period of CP is established, and the calculation formula of the position of strong mine pressure is given. Taking the 22,408 working faces through the overlying concentrated CP of the Bulianta Coal Mine was selected as the research object. Using the methods of field measurement, physical simulation, and theoretical analysis to master the law of movement of the CP and overlying strata while passing the CP, the structural coupling impact of the key strata structure of the interburden and CP was revealed, which was the main reason for the cutting dynamic load effect during the passing of the CP of the working face. The advanced breaking mechanical model of the coupled roof structure of the “key strata structure of the interburden and the coal pillar” is established; the main factors affecting the breakthrough distance of the advanced breaking distance are analyzed; and the mechanism of the strong weighting caused by the cutting roof of the working surface is explained at the stage of CP. At the same time, it is obtained that when the width of the CP is 25 m, the working face is 20 m below the CP, which is the maximum bending moment point of the rock beam, indicating that the position that is prone to break under this width is about 5 m of the CP, which aligns with experimental data. The present study provides a theoretical guideline for the location and control of strong ground pressure during CP mining in SBCCS.