特厚煤层卸压综放开采技术原理的实验研究

Technical principle and experimental study on fully mechanized top-coal caving mining after extracting the middle slice in extremely thick coal seam

我国西部地区发现存有大量20 m以上特厚煤层,大部分无法实现露天开采,国内外均没有成熟的理论与技术可以借鉴,为了实现20 m以上特厚煤层的安全高效开采,创造性地提出了特厚煤层卸压综放开采技术。采用60∶1的大比例相似模拟试验方法,研究20 m以上特厚煤层卸压综放开采顶煤垮落破碎的块体分布特征、顶煤位移场分布特征、支架阻力及其对顶煤垮落破碎的影响等。结果表明:当卸压工作面推进75 cm时,500 cm^3以内的顶煤块体较密集,块体比例约为94%,块体数量约为860个;当卸压工作面推进135 cm时,体积为500 cm^3以内的顶煤块体所占累计比例约为96%,块体数量约为1 700个,与卸压工作面推进75 cm时相比,块体比例增加了2%,块体数量增加了840个;当综放工作面推进17 cm时,累计体积达到500 cm^3时几乎包含全部顶煤块体,块体比例约为99.9%,块体数量约为4 810个,与卸压工作面推进135 cm时相比,块体比例增加了3.9%,块体数量增加了3 110个,二次破碎效果显著,能保证顶煤的顺利放出。卸压开采阶段上位顶煤位移>中位顶煤位移>下位顶煤位移。二次综放阶段下位顶煤位移最大,垮落破碎程度最好。由于支架的支撑作用,下位顶煤中产生多条明显的竖直裂隙,受支架影响的顶煤厚度约为10 cm,支架的反复支撑作用明显促进了顶煤的破碎效果。

A large number of extra-thick coal seams with a thickness of more than 20 m have been found in western China.Most of them cannot be mined by using open-pit mining.No mature theories and technologies can be referenced in the world.The fully mechanized caving mining with pressure relief for extra-thick coal seams was proposed for achieving a safe and efficient mining of extra-thick coal seams with a thickness of over 20 m.The large-scale of 60∶1 physical analogue test was used to study the distribution characteristics of the top coal caving and broken blocks,and the distribution characteristics of top coal displacement field.In addition,the test studied the support resistance and its effect on the top coal braking in the fully mechanized caving mining with pressure relief for extra-thick coal seams with a thickness of over 20 m.The results show that the number of top-coal blocks is denser within 500 cm 3,the block ratio is about 94% and the number of blocks is about 860 when the pressure relief working surface is extracted to 75 cm.The cumulative proportion of top-coal blocks is about 96% within 500 cm 3 and the number of blocks is about 1 700 when the pressure relief working surface is extracted to 135 cm.The proportion of the top-coal blocks increased by 2% and the number of blocks increased by 840 when compared with that of pressure relief working face at 75 cm.It contains almost all the top-coal blocks when the cumulative volume reaches 500 cm 3,the block ratio is about 99.9% and the number of blocks is about 4 810 when the top-coal working face is extracted to 17 cm.The top-coal blocks within 500 cm 3 is the most densest,the proportion of the blocks increased by 3.9% and the number of blocks increased by 3 110 when compared with that at 135 cm.The effect of secondary crushing is remarkable,which can ensure the smooth release of the top coal.In the stage of pressure relief mining,the displacement of upper top-coal is larger than that of the median top-coal and the displacement of the lower top-coal is the smallest.In the secondary fully mechanized top-coal caving mining stage,the lower top-coal displacement is the largest,and the effect of the top-coal collapse and fracture is the best.Many obvious vertical cracks were generated in the lower top-coal for the supporting effect of the support,and the thickness of the top-coal which affected by the support is approximately 10 cm.The repeated supporting effect of the support significantly promoted the broken effect of the top-coal.