Study on the height of overburden strata in two zones of “two soft and one hard”unstable coal seam working face

In Yungaishan No.2 Coal Mine in southwest Yuzhou Coalfield, in order to study the height of caving zone and water-conducting fault zone of unstable coal seam that with soft coal, soft bottom and hard top (abbreviated as "two soft and one hard") and the thickness of coal seam varies greatly, the height of roof overburden caving zone and water-conducting fault zone of 23301 coal mining face were analyzed by using in-situ borehole imaging technology, empirical formula analogy analysis and numerical simulation, two belts.quantitative values were obtained for the working face under the non-full mining caving and fully mining caving, the maximum height of caving is 14.4 m, the maximum height of water flowing fractured zone is 50.0 m, find the borehole imaging technology can be used in the mining strata height calculation of two belts.The results of this study have important reference value for the prevention and control of roof water damage and roof support.