The Law Of Infiuence On Thick Coal Seam Mining Of Collapsing Interlayer Rock Under Goaf

With the rapid development of coal industry,the working face of shallow buried depth has gradually shrunk.With the increase of mining depth,the mining of a single coal seam with thickness of 6-25 m is carried out in one after another.Taking Datong mining area as an example,the main ore-bearing strata are Jurassic and carboniferous dual system thick coal seam.The movement and destruction of the overlying strata after the mining of the special thick coal seam has caused the stable goaf in the Jurassic system to move again.When the interlayer rock between the lower layer thick coal seam and the overlying gob is 30-80 m,for normal working face,the downward mining will not have obvious security problems,but for the fault zone of more than 14 m in the gob,the fault zone will directly through the mined-out area,belonging to the thin bedrock close coal seam mining.The overlying stope out rock mass in the overlying gob is excavated at the bottom of the coal seam,and its self-supporting ability is not strong,passing load and acting on the underlying bedrock in some form of fragmentation structure.When the bedrock is not enough to form the structure,the upper goaf and the lower gob are fully penetrated,the working face will appear the full thickness falling type pressure frame accident,and the roof of working face is difficult to be controllable.Under the influence of gob,the overlying strata structure stope of that fully mechanized top coal caving mining face with extra large coal seam will form a similar but identical to shallow deep and thick impact layer structure,which has its own particularity.Through the analysis of the overlying rock strata in the process of the extra-thick coal seam in the mined-out area,the similarity test is carried out by means of similar simulation,numerical simulation and theoretical analysis.Combined with the method of field measurement,the effects of different thickness and lithology,under the conditions of the interbedded strata,stope overlying structure and caving characteristics,this paper draws the main conclusions are as follows:(1)From the perspective of whether the structure collapse of the interlayer rock strata has a direct impact on the lower coal mining,whether the lower coal caving level is connected with the upper coal goaf as the limit of close coal seam.For the extra 15 m thick coal seam in shuangxi mined-out area,the stratum thickness of hard layer is less than 60 m,it belongs to thin rock stratum,and the stratum thickness of soft rock stratum is less than 15 m,it belongs to thinner layer.Take inclined coal mine as an example,when the story stratum is less than 56 m,it belongs to the stratum between thin layer.(2)When the interlayer rock is thin,the interlayer rock falls in the form of block structure caving,overlying strata is "arch structure" in the form of caving;when the interlayer is thick,the interlayer rockes in the form of "arch structure".(3)Compared with the weak roof condition,the cantilever length of the cantilever structure is larger than that in the weak roof condition,and the face advancing distance is longer when the top coal first cave.The accumulation angle of the goaf dirt and the top coal caving angle of the face is smaller,the periodic weighting interval is larger.(4)This paper analyzes the calculation formula of the working resistance of the bracket under the different layers of Goaf.