Research On Pressure Regulation And Surrounding Rock Control Of Fully Mechanized Face With Shallow Depth And Huge Mining Height

After years of study and practice,Shendong Coal Company has increased the mining heitht of fully mechanized mining technology from 4.5m,5.3m,6.3m to 7m and has a wealth of experience.They have been in a leading position in the world.In four panel of Shangwan Coal mine,the average thickness of 1-2 coal seam is 8.9m.In some other mine coal mines,coal seams with more than 8m thick are also very rich in reserves.The present fully mechanized mining yield of Shagnwan Coal Mine is 14000000 t per year.By comparison of various mining methods,it shows that it is a more effective way to increase the fully mechanized mining height further,also it can provide basic data of technology and equipment for Shendong high yield production in 8m above coal seams.So,basing on existing full mechanized mining technology and equipment for 7m and the following,the engineering analogy,theoretical analysis,numerical simulation and similar materials simulation research methods are comprehensively used to research the pressure regulation and surrounding rock control technology in a fully mechanized workingface with 8.8m thick coal seam and thin cover rock.The study work targets Shangwan Coal Mine 12401 workface and some mines with similar seams as the objects.Firstly,the tensile strength,elastic modulus,Poisson's ratio,internal friction angle,cohesive force and other mechanical parameters of the coal and its roof and bottom in Shangwan Coal Mine and adjacent mines are obtained by a lot of field or laboratory tests.Secondly,by using the critical layer theory calculation and simulation analysis,key layers overlying coal 1-2 are determined: the main key layer is 87.3m above seam 1-2,medium grained sandstone with 8.14 m thick,the sub critical layer is 9.3m above the seam 1-2,medium grained sandstone with 13.71 m thick.Theoretical calculation and engineering analogy show that the height of the caving zone is50m~70m and the height of the fracture zone is 130m~150m,connecting with the surface of the earth for fully mechanized workface 12401.Again,engineering analogy,theoretical calculation and simulation analysis shows that in workface 12401 the peak of support pressure is 12 MPa with 12.5~13.0m away from the front of the coal wall.The influence range of the support stress is 80 m away from the front of the coal wall.The initial breaking length of the immediate roof is45 m with pressure strength 0.93 MPa.The initial breaking length of the main roof is form 49 m to52.0m with pressure strength 1.68 MPa,and the cycle breaking length is from 20 m to 22.0m.During normal mining,the pressure strength in working face is about 1.55 MPa.Finally,basing on the pressure regulation of working face 12401,through engineering analogy,theoretical calculation and simulation analysis,it shows that the rib spalling usrually takes place 3.7m under the roof with a depth from 2.90 m to 3.37 m.Comprehensively considering relationship between working face pressure strength,the roof subsidence and the rill spalling depth,the hydraulic support strength of full mechanized mining face 12401 is determined forml 1.8 to 2.0MPa.In addition,the roadway support scheme,the advanced support scheme and the rill spalling control measures are also given.This paper is focused on the pressure regulation and surrounding rock control of 8.8m shallow buried and large mining height fully mechanized working face,the study results have important significance for safely and efficiently mining the extra thick coal seam and promoting the level of large mining height fully mechanized technology and equipment.