Study On The Supporting Technology Of Close-multiple Coal Seams Mining Roadway Passing Through Overburden Goafs And Coal Pillars

With the continuous exploitation of coal resources,coal seams with better mining conditions are gradually being mined,and the mining of difficult-to-find coal resources is increasingly valued by major coal mines,of which close-multiple coal seam mining accounts for a large proportion.Due to the close spacing of coal seams,the mining of different coal seams will cause disturbances between each other,and the strata will be broken severely,which will cause great difficulties for the exploitation of the lower coal seams,especially when the lower coal seams meet the coal seam stress concentration coal pillars.The mine pressure is obvious.The mining of close-multiple coal seam can improve the utilization of coal resources and achieve high production efficiency.In this thesis,the Supporting Technology of close-multiple Coal Seams Mining Roadway Passing through Overburden Goafs and Coal Pillars is studied.By reviewing the relevant literature data,the research status at home and abroad was analyzed,and the mechanical model of the top and bottom structure of the stope was established based on the engineering geological data.The theoretical analysis and calculation were conducted to obtain the depth of floor damage of the old working face of the upper coal seam.The lower working face was overlaid with coal pillars.The breaking rules of key blocks and their influenceon the support of the mining roadway in the lower face,especially in the stage of coming out coal pillars,the roof can be easily cut down,The surrounding rock of the roadway is seriously damaged ahead of working face.The whole process is simulated by the FLAC3 D numerical calculation software.The working face is more intense in the stage in and out of the coal pillars.In view of the regular alternation of the lower face through overlying goafs and coal pillars,the characteristics of the surrounding rock failure in the roadway and the law of stress variation in the roadway surrounding rock are studied.Under the coal pillars,the surrounding rock stress is high and the surrounding rocks are easily destroyed.Roadways within the influence of pillars need to be reinforced.On the face of the working conditions of the actual mining conditions on the two-slotted support of the lower face of the proposed alternative program,through the numerical simulation of stress and strain analysis,the final optimization program.The scheme was applied to the engineering practice of Shanxi Coal Mining Group's Jinda Coal Mining Group working face mining project under extremely close coal seams,and using the field data monitored by different methods to analyze the supporting effect of the roadway.The specific conclusions are as follows:(1)According to the empirical formula and the slip line field theory to calculate the maximum depth of the floor damage,the establishment of the key structure of the small pillar above the pillar mechanical model and analysis of the lower coal seam mining lane in the face of the coal pillars when the confining pressure changes And the law of destruction of surrounding rocks.Mining lanes are affected by the coal pillars overlying the working face,especially during the entry and exit of the pillars,which are affected by the dynamic load of the working face.(2)Affected by the pressure relief effect of the goafs in the roadway below the goafs,the pressure of the surrounding rock is small and the deformation of the roadway is small.It can give full play to its own stability,but due to the influence of mining on the top face,the roof is relatively broken.Support is difficult.After the underground roadway of coal pillars is excavated,the vertical stress increases sharply due to the stress concentration phenomenon of coal pillars in the covered rock area.Shear fractures occur in the two shoulder rock masses,the shear damage scope increases,and the amount of roof subsidence is large,leading to serious roadway deformation and damage.(3)After 9# coal mining,the stress of the 10+11 coal seam beneath it is redistributed,and there is a clear increase and decrease in the area.The vertical stress of the rock mass below the centerline of the coal pillar is the largest,from the centerline to the two.Lateral extension,the vertical stress of surrounding rock decreases gradually.When the 10+11# coal seam face is located within the range of 10 m directly below the coal pillar and outside of the boundary,the destruction of the surrounding rock is affected by the concentrated coal pillars on both sides of the mining lane,and the roof of the 15 m roadway in the leading face is seriously damaged.Therefore,when the roadway passes through the pillar-affected zone,the roadway must be reinforced and supported by measures such as increasing the length of the bolt,reducing the spacing between the bolts,and supplementing the anchor cable.(4)Based on theoretical analysis,engineering analogy and numerical simulation,the anchoring method and anchoring parameters of the anchor rod and anchor cable in the south wing of the 10+11# coal mining area were finally determined.The support plan meets the engineering requirements.