Study On Gob-side Entry Retaining Of Small Coal Pillars In Steeply Inclined Thick Seam With Hard Roof And Soft Bottom

Field practice has proved that gob-side entry retaining has obvious advantages in coal mining,but in steeply inclined hard roof and soft bottom thick seam,the mine pressure shows obvious,which seriously affects the production of the mine.In order to solve the problem of stability of gob-side retaining roadway,this paper studies the characteristics of strata pressure in stope and roadway during mining by combining theoretical analysis,numerical simulation and field test,emphatically analyses the failure mechanism of high-side coal body,puts forward effective support scheme,and carries out field test in 31322 working face.The main results are as follows:(1)The distribution of rock pressure and the law of roof and floor deformation in steeply inclined pit and pseudo-inclined stope are analyzed by numerical simulation.Analysis shows that: The distribution of rock pressure in different positions along the inclined face is asymmetric.The deformation of stope roof and floor is "floor micro-uplift,roof subsidence",and roof subsidence is larger than floor heave.The area of intense activity of roof and floor corresponds to the area of sharp change of stress.(2)Deformation and failure characteristics and stress distribution of gob-side retaining roadway and high-wall rock mass are determined by numerical simulation and field measurement.The results show that: The deformation of roof,floor and two sides of roadway is obvious,showing the characteristics of imbalance,surrounding pressure and soft rock.The deformation of the middle and high sides of coal body is larger.According to the degree of deformation,it can be divided into five different stages.The roadway deformation in the range of 46.3 m in front of the work to 83 m behind is the most severe,and tends to be stable after 150 m behind,which provides the basis for determining the range of advanced and lagging support.With the advancing of the working face,the deformation of high-side coal increases,and the peak stress point moves to the deep.The deformation of coal body tends to be stable at 150 m behind the working face,and the peak stress point is 3 m inside the coal pillar.The rationality of setting 7m coal pillar beside roadway in 31322 face is verified.(3)Based on the stress analysis of high-side coal,the criterion of shear failure on the interface between high-side coal and soft floor is obtained: Stability coefficient K= tan?/tan?,? is the internal friction angle between rock and coal seam,and ? is the dip angle of coal seam.When ???,K ? 1,that is,shear failure occurs along the interface between coal seam and floor.The paper puts forward the encrypted support method for surrounding rock of gob-side retaining roadway and the small angle anchorage method for high-side coal wall,which combines the "five-eye" anchorage with the "cross" retaining face.(4)Based on the results of numerical simulation and field measurement,four gob-side retaining roadway schemes are put forward,and UDEC is used to simulate and calculate the retaining roadway support scheme of "bolt encrypted support".The rationality of the scheme is verified by field test of 31322 working face,which meets the safety production demand of mine.