With the aim to overcome the difficulty of determining the reasonable cutting height, the influence factors of determining the cutting height were analyzed in detail. Combined with the Panel 30101 of some mine, the stability of coal wall, the working resistance of support, the top-coal migration and recovery at different cutting height are studied by using numerical simulation and field practice. The result shows that the stability of coal wall, the support working resistance, top-coal migration positively correlate with the cutting height, which is not a linear relation, with the increase of cutting height, the top-coal recovery shows a trend of increases first and then decrease. Overall considering that the stability of coal wall, the working resistance of support, the top-coal migration and recovery, the determination a cutting height of 5 m for the Panel 30101 is reasonable.
With the development of the large cutting height mining and top-coal caving theory and techniques, as well as the improvement of fully-mechanized equipment, the extremely-thick coal seam is increasingly considered to be mined by top-coal caving with great mining height. And this mining method positively combines the advantages of large cutting height mining and top-coal caving. To be exact, it is relatively lower-cost, more efficient and more productive. As a result, it is the best choice for extremely-thick coal seam (Cao 2008). However, the development of top-coal caving with great mining height is restricted because of low top coal recovery rate, rib spalling, adaptability of support and great amount of gas emission, and all these factors have something to do with cutting height (Wang 2005, Yan & Yin 2008, Yan & Yin 2008). The cutting height is therefore the key to achieve safety, high productivity and efficiency for top-coal caving with great mining height. Many studies have been done to obtain a appropriate cutting height in the past few years. Article (Liu 2011) investigated the relationship between cutting height and gas emission through numerical simulation, indicating that the gas density decreases as the cutting height increases. Article (Xia & Kang 2008) studied the influence of cutting height on rib stability, demonstrate the increase of cutting height results in the deterioration of rib spalling.
