Influencing factors of rib spalling in deep buried working face with large mining height

Rib spalling is a highly severe issue during mining in deep-buried large-mining-height working faces. This study takes Zhaogu No.2 Coal Mine in Jiaozuo Coalfield, China, as the research background and carries out three focused works to address this problem. Firstly, field measurements were conducted to clarify rib spalling characteristics: the coal wall is dominated by shear failure, internal cracks are mainly distributed 3–6 m above the coal wall surface, and the maximum depth of crack development reaches 3 m. Secondly, Universal Distinct Element Code (UDEC) numerical simulation software was used to build a rib spalling model, with the Trigon model adopted to divide the coal wall into blocks. Analysis of four key factors shows that increased buried depth and mining height significantly raise the total length of coal wall internal cracks, increasing rib spalling risk, while higher coal body strength and support strength effectively alleviate this phenomenon. Finally, an orthogonal experiment was designed to quantitatively determine the influence degree of the four factors on rib spalling. Results show that coal body strength has the greatest impact, followed by support strength, mining height, and mining depth in order of influence. This study provides valuable theoretical guidance for on-site prevention and control of coal wall rib spalling.