| Based on the research background of the thin-seam working face under the goaf in Liangshuijing Coal Mine Goaf,this paper comprehensively adopts on-site investigation,theoretical analysis,numerical calculation,on-site experiment and other methods to analyze the law of stress evolution in the lower goaf.The influence law of the roof unloading parameters on the stability of the surrounding rock along the roadway,the stress transfer and distribution law of the surrounding rock along the roadway before and after pressure relief,the internal staggered distance between the roadway and the coal pillar above it is determined,and the key parameters of the roof cutting Key parameters of the filling body.The following main conclusions are drawn:(1)Based on the production geological conditions of the 431301 working face of Liangshuijing Coal Mine,through the mechanical formula of elastic mechanics half-plane problem,the internal staggered distance between the lower goaf and the upper coal seam coal pillar is 13.3m.Numerical simulation calculation was used to analyze the relationship between the stress and plastic zone distribution of surrounding rock and the deformation law of surrounding rock and the distance from the coal pillar in the lower coal seam of the upper coal seam goaf.Finally,the internal staggered distance between the empty roadway and the remaining coal pillars in the upper coal seam is set at 20 m.(2)Established the cutting and unloading pressure model of the goaf along the goaf in the lower part of the goaf,and analyzed the influence of the cutting height,cutting angle and pre-split hole spacing on the shaped charge blasting;using the numerical calculation method,the analysis The cutting height and the distribution characteristics of vertical stress,horizontal stress,shear stress,plastic zone,vertical displacement and horizontal displacement in the model when the cutting angle changes.Determine the cutting height to be 10.5m and the pre-crack angle to 20°.(3)Comparative analysis of the experimental results of 600 mm and 900 mm blasthole spacing.It was found that both the blasting hole and the pilot hole had smoke phenomenon,indicating that the blasting fracture gap was penetrated;from the peeping results,it can be seen that the blasting hole charge section has a clearly symmetrical longitudinal crack,and the porosity of the 900 mm hole spacing is less than the porosity of the 600 mm hole spacing However,the cracking rate of the chargesection of the blast hole is still greater than 80%,which meets the demand for cutting the roof,and the spacing between the blast holes can be adjusted to 900 mm.(4)The mechanical model of cutting and pressure relief along the empty roadway was established,and the cutting resistance of the filling body along the empty roadway in the 431301 working face was determined to be 6.5MN/m.The evolution law of roadway surrounding rock is analyzed under the conditions of different roadway backfill width and different roadside backfill strength.It is found that the stable bearing area of roadside backfill increases with the increase of roadway width and backfill strength,and finally the backfill is determined.The width is 1.6m,and the water-cement ratio of the filling material is 1.5:1.(5)In order to protect the stability of the roof and prevent the roof from collapsing,on the basis of the original support scheme,additional temporary reinforcement support is added.The "single hydraulic prop + articulated top beam" reinforced support method is adopted behind the working face,and the "retaining bracket" reinforced support method is adopted in the goaf.(6)On-site mine pressure observation shows that there is no obvious stress concentration around the roadway,the deformation of the surrounding rock of the roadway is small,the strength of the filling body can ensure the stability of the remaining roadway structure,and the effect of the remaining roadway meets the design requirements.There are 78 figures,6 tables,and 84 references in this paper. |
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