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Abstract To decrease the loss of coal pillar for thick coal seam，a new technique with preset packing body for thick coal seam without coal pillars is put forward based on the analysis of reasonable model of surrounding rock structure. The actual steps for mining are：(1) the entry-in packing should be preset ahead of the coalface，which is nearby the coal wall of the next coalface；and (2) the gob-side entry of the next coalface is driven along the packing body without coal pillars. If the new technique is applied for an old entry，which is excavated with normal cross-sections，the coal wall of the next coalface should be enlarged and supported also by cablet ahead of the coalface. The key technique is the materials chosen and their mixture ratios of the packing body to guarantee the stability of packing body，and also the entry surrounding rock under the premise of minimizing the width of packing body. The selected filling material is mainly supported by a small amount of waste rock slag cement，sand cement mixture of water body，cement，sand，slag waste rock according to the weight in proportion to the ratio 1∶1∶4.7. The results of industrial test and field measurement show that the technique is successful；and it can be applied to thick coal seam with similar conditions. Meantime，it can enhance the recovery rate of coal resources and the economic efficiency.
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Received: 24 October 2009
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