Study on the Influence of the Location of Dirt Band on Top Coal Caving Property in Extra-Thick Coal Seam

The influence of dirt band on the top coal caving property is usually analyzed from the thickness and hardness of the dirt band. For the extra-thick coal seam with a thickness of more than 20 m, the location of the dirt band also has a huge impact on the top coal caving property. In this paper, No. 19 coal seam of Tanyaoyu coal mine is took as the research object, the influence of the location of dirt band on the top coal caving property is analyzed, and the calculation formula of the limit span and thickness of the dirt band is derived. The results show that, when the dirt band located in the upper part of the extra-thick coal seam, the bridge structure is more to form in the mining process, when the dirt band located in the middle part of the extra-thick coal seam, the arch structure is more to form, when the dirt band located in the lower part of the extra-thick coal seam, the dirt band is to release in the form of a loose media. The upper dirt band and lower dirt band have little influence on the top coal caving property, while the middle part dirt band has the greatest influence on the top coal caving property.