| Due to the increasing demand for coal resources,more and more mines have been gradually digging deeper in recent years.Faced with serious deep mining problems,it will cause a series of complex power disasters and mine gas accidents,causing serious economic and property losses.Therefore,it is particularly important to improve the recovery rate of coal resources at this stage and the effect of pressure relief gas drainage in overburden cracks in the goaf.In this paper,through theoretical analysis,physical experiment,numerical simulation and on-site measurement analysis methods,the stress distribution characteristics of narrow coal pillars in fully mechanized caving face of inclined coal seam and the evolution law of mining overburden fissure field under different coal pillar widths are deeply researched.The following research results were initially obtained:(1)Based on the geological conditions of the narrow coal pillars in the Liuhuanggou Coal Mine(4-5)06 working face,the stability of surrounding rock structures along the roadway in the inclined coal seam was analyzed and the mechanical structure model of the narrow coal pillar was established.The physical test of strength test obtains the strength parameter and failure form of coal and rock mass in working face.(2)The mechanical model of the basic roof along the gob of the inclined coal seam was established,and parameters such as section coal pillar load and coal pillar reasonable value range,overburden "three zones" and key layer height were obtained through theoretical derivation and calculation.(3)Design a numerical simulation scheme for driving along the roadway with different coal pillar widths.By using the simulation software ABAQUS4.0 to simulate the change of coal pillar stress and stability,the analysis of the different coal pillar size pairs.The change relationship of coal pillar stress establishes the change model of coal pillar stress and width.(4)Based on the complexity of the overburden mining crack distribution in the narrow coal pillars of inclined coal seams,the three-dimensional discrete element software 3DEC5.0 was used to simulate the mining plan of multi-section working face,and the mining of overburden rock with different widths of empty coal pillars was analyzed.The influence of stress,displacement,evolution law and distribution characteristics of mining fractures,and at the same time,the relationship between the key parameters of the key stratum and the width of coal pillars is established.(5)According to the conditions of multi-segment mining of narrow coal pillars in inclined coal seams,the characteristics of overburden failure and migration of narrow coal pillars are analyzed,and a three-dimensional space model is constructed to provide certain theoretical and technical support for the design of reasonable gas drainage key parameters,Thereby ensuring the efficient mining of the working face.The research results in this paper are important for improving the gas drainage efficiency of the narrow coal pillar mining overburden gas movement law in the inclined coal seam,the layout of the gas drainage system in the goaf fissure field and the key parameters of gas drainage. |
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