Surrounding Rock Failure Mechanism And Control Of Road Driving Along Next Goaf On Very Soft And Thick Coal Seam

Taking Weijiadi Coal Mine East 1100 fully mechanized caving face as the research object,the theoretical analysis,numerical simulation,industrial test and other research methods are used comprehensively to analyze the Failure and Control of the surrounding rock on the extremely soft and thick seam.It focused on the analysis of the mining thickness and hardness.Because they have an important impact on basic roof lateral fracture position and goaf lateral support pressure.Also it determined the reasonable width of coal pillars under the different mining thicknesses and carried out industrial test analysis.The main research results are as follows.(1)Based on elastic foundation beam theory,the mechanical model of the "direct bottom-coal seam-direct roof" foundation beam was established.Basic top bending moment expression and basic top lateral break position expression were derived.And it analyzed the influence law of the basic top lateral break position caused by the mining thickness and hardness.It is revealed that the increase of coal seam mining thickness or the decrease of coal seam hardness leads to the decrease of foundation stiffness and the increase of the maximum bending moment.The position of the maximum bending moment of the basic roof shifts to the deep coal seam as the foundation stiffness decreases.Based on the geological conditions of the working face of the East 1101,it is determined that when the coal seam mining thickness is 8?24m,the basic top lateral fracture position is 7.735?13.125m.(2)It reveals the influence law of the lateral supporting pressure of the transportation lane of Dong 1100 fully mechanized caving face caused by the mining thickness and hardness of coal seam.Under medium-hard and hard coal seam conditions,as the mining thickness of the coal seam increases,the peak position of the lateral support pressure gradually moves away from the boundary of the goaf,and the peak value is negatively correlated with the coal seam mining thickness.Under soft coal seam conditions,with the increase of coal seam mining thickness,the peak position is gradually away from the boundary of the goaf;when the coal seam mining thickness is less than 12m,the peak lateral support pressure is negatively correlated with the coal seam mining thickness.When the coal seam mining thickness is greater than 12m,the peak value of lateral support pressure is basically unchanged.Coal seam hardness has a greater influence on the peak position of lateral support pressure.when the coal seam mining thickness is less than 17m,the peak lateral bearing pressure is positively correlated with coal seam hardness.When the mining thickness is greater than 17m,the lateral bearing pressure peak is negatively correlated with coal seam hardness.(3)The average thickness of coal seam in east 1100 fully mechanized caving face is 18m.Based on the calculation of the "direct bottom-coal seam-direct roof" foundation beam mechanical model,the basic top lateral break position is 11.458m.Through the calculation formula of limit equilibrium zone,the width of stress limit equilibrium zone is 11.417m.The results of the two are basically the same,indicating that the established "direct bottom-coal seam-direct roof" foundation beam mechanical model is scientific and accurate.(4)The average mining thickness of coal seam in Dong1100 fully mechanized caving face is 18m,and the width of coal pillars is 3-12m.The roof near the coal pillar is mainly damaged by tension and shear,the roof near the solid coal gang and the solid coal are mainly damaged by shear,and the coal pillar is mainly damaged by tension and shear.As the width of the coal pillar increases,the vertical stress concentration factor in the coal pillar increases from 1.2 to 3.1,which is greatly affected by the width of the coal pillar.The vertical stress concentration factor of the solid coal gang increased from 2.3 to 2.8,which is less affected by the width of the coal pillar.The effect of roadway shear stress is enhanced,and the effect of roof tensile stress is enhanced.When the width of the coal pillar is 8m,a stable pressure zone appears in the coal pillar,and its width is greater than 1.5m,which meets the need for support.So the reasonable width of the coal pillar is 8m.(5)The joint support method of "high-strength screw steel resin bolt+anchor cable reinforcement+anchor mesh" is proposed.The high-strength bolt suppresses the destruction trend of the roadway to reduce the area of the tensile shear damage area.And anchor cable connects the broken Rock block in the shallow part of the roadway with the stable rock block deep in the rock layer,enhancing the stability of small structure.Surrounding rock control effect of transportation lanes in East 1100 fully mechanized caving face is good.