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Longwall top coal caving (LTCC) mining is the most efficient method to extract thick or extra-thick coal seam and extensively used in western China. [1][2][3][4][5] With high productivity and efficiency, LTCC mining plays an ultimate important role in the development and reform of the traditional coal mining method. The prototype of LTCC could date back to the 1960s and 1970s, when some European countries, especially the French and Yugoslavia, used the total soutirage method to extract thick and irregular coal seams. 6 The poor recovery has been a major problem for the early soutirage longwall caving mining. 7 In the early 1980s, LTCC mining was first introduced in China. 5,8,9 Since then, with significant modifications and improvements, the LTCC mining method has experienced rapid development and achieved great success in China. 8 In addition, the past few years have witnessed a series of successful applications of LTCC mining in Australia, India, Russia and so on. 2,[10][11][12] In LTCC mining, the recovery ratio and the mining efficiency depend on fragmentation and caving of the top

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