| In recent years,with the increase of coal mining depth and intensity in China,the Coal Seams Mined at one time by fully mechanized top coal caving mining are becoming thicker and thicker.The research on the influence of the evolution of overburden structure formed by the breaking of roof rock beam on the stability of section coal pillar in fully mechanized top coal caving mining in extra thick coal seam is insufficient.The selection of roadway layout along the goaf and the determination of reasonable reserved width of section coal pillar in fully mechanized top coal caving mining in extra thick coal seam still need to be further studied.Based on the 1307 and1305 fully mechanized top coal caving faces in 3 coal seams(average coal thickness of15m)in Zhaoxian coal mine,this paper studies the influence of overburden structure evolution on section coal pillar stability in fully mechanized top coal caving mining in extra thick coal seams.By means of theoretical analysis,physical similarity simulation test and FLAC3 D numerical simulation,this paper studies the overburden structural characteristics of fully mechanized top coal caving mining in extra thick coal seam and the plastic failure range and stress distribution characteristics of roadway surrounding rock under the condition of different width coal pillars,and reveals the overburden load transfer mechanism of fully mechanized top coal caving mining in extra thick coal seam,which provides a basis for the layout of roadway along the goaf side and the determination of the reasonable reserved width of section coal pillars in fully mechanized top coal caving mining in extra thick coal seam.The main conclusions are as follows:(1)Based on the Mechanical Model of Overburden Rock Structure in extra-thick coal seam,the lateral abutment pressure is deduced and calculated.This paper reveals the load transfer mechanism of overburden rock in fully mechanized top coal caving mining of extra-thick coal seam,and combined with the field geological conditions and working conditions,it is known that in order to weaken the mine pressure manifestation strength,protective coal pillar should be retained in the roadway,and the reasonable width of the pillar in the section of the wind roadway of 1305 working face is solved by using the calculation model of the coal pillar width.(2)According to the physical simulation experimental study,in the mining process of the working face,the top direct roof and the main roof cantilever beam,the masonry beam and the falling arch appear alternately,one of the causes of stress concentration in lateral coal is the effect of“Cantilever Block” in roof rock.The propagation distance of additional stress is positively related to the active range of overlying rock above the coal pillar,and the lateral abutment pressure also increases When the width of the coal pillar is between 15 m and 10 m,the load on the coal pillar is the largest,the abutment pressure Coefficient is 1,and the coal pillar is destroyed when the width of the coal pillar is 10 m.(3)The side 2.0 m-6.0 m of Goaf in 1307 working face is stress concentration area,the stress influence area is 6.0 m-12.0 m,the maximum stress is 57 MPA Eight schemes of coal pillar with width of 35 M,30m,28 m,25m,20 m,15m,10 m and 5m were designed,and the stability of protecting coal pillar in 1305 drift was studied.The analysis shows that the stability of the gateway can be ensured when the width of coal pillar is 28 m.(4)Based on the analysis of site working condition,the optimum width of coal pillar is 28 m,which is verified by industrial test.The monitoring results show that the surrounding rock of Return Air Roadway in 1305 working face is stable and reliable,and the effect is good,can ensure the safety of the subsequent mining face.This paper reveals the evolution law of overburden structure and stress distribution characteristics of fully mechanized top coal caving mining in extra thick coal seam,and compares the failure range and stress distribution law of surrounding rock plastic zone under the condition of roadway pillar with different width,which provides a reference basis for the selection of roadway layout along the goaf and the determination of the reasonable reserved width of section pillar in fully mechanized top coal caving mining in extra thick coal seam;At the same time,the engineering practice of section coal pillar reservation is carried out in the fully mechanized top coal caving face of 1305 extra thick coal seam,and the effect is good,which provides a reference for the production design of coal mine with similar working conditions.Figure [76] Table [8] Reference [84]... |
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