Study on fissure development law of surrounding rock in horizontal section stope of steeply dipping coal seam group

Utilizing research methods such as physical simulation experiments with similar materials, numerical calculations, and theoretical analysis, the law governing the development of fissures in the horizontal section stope of steeply dipping coal seam groups has been systematically studied. The findings indicate that when interlayer fissures are undeveloped and not penetrated, the extent and quantity of surrounding rock fissures in the alternate mining of each section are influenced by the degree of section advancement and the subsequent mining. The overlying rock fissures ultimately form a stepped distribution pattern, with a higher tendency above and a lower tendency below. As the section advance reaches the sixth degree, the fissure distribution in the inclined direction of the 4# coal seam consistently exhibits a stepped shape, with a narrow upper and wide lower portion. The strike direction changes from an asymmetric stepped fissure distribution with a lower front and higher rear to a rectangular symmetrical distribution. Upon advancing to 30 m, the fissures between the 2# coal and 4# coal develop and penetrate. The height of the 2# coal fissure zone, as determined by theoretical analysis, aligns with the results of numerical simulation, with a maximum relative error of 2.38%.