Study On The Stability Mechanism And Control Technology Of Roadway Under The Residual Coal Pillar In Close-range Coal Seams Mining

The overburden fracture and movement of the upper coal seam in close-range have a high stress loading effect on the residual coal pillar,which is an important cause of large deformation damage and even impact ground pressure disaster of the coal column floor roadway,generally the lower coal seam roadway is arranged under the upper coal seam goaf area,but due to the development plan,mining parameters and other changes,the lower coal seam roadway has to cross or directly arrange under the upper remaining coal column.Under the superposition of the mining stress of the working face and the concentrated stress of the upper residual coal column,the lower roadway of the remaining coal column is extremely difficult to maintain.In this thesis,the stability of the coal column floor roadway of close-range coal seams mining is taken as the research object,and the methods of theoretical analysis,laboratory experiments,numerical simulation,physical similarity simulation and on-site industrial test are comprehensively used to study the stress evolution law of the coal column floor of the coal column mining near seam,reveal the deformation and failure mechanism of the dynamic pressure roadway of the coal column floor left over from the coal seam at close distance,develop the surrounding rock stability control technology of the mining roadway under the coal column left over from the coal seam at close distance,and carry out the industrial test of deformation control of the mining roadway under the coal column left over from the coal seam at close range,and the main results are as follows:(1)The stress evolution law of the coal column floor of the coal seam mining at close distance was obtained.The mechanical model of supporting stress transfer in vertical anisotropic coal rock layer left over from the coal seam was established,and the interface disturbance stress transfer mechanism of reducing the supporting stress concentration coefficient,reducing the depth of the directional transfer of the plumb hammer and increasing the horizontal transmission range of the supporting stress was proposed at the discontinuous interface,and the stress calculation formula of the support stress transfer to the coal column floor was derived,and it was found that the interface position,the shear modulus of the medium on both sides of the interface and the Poisson’s ratio were the key factors affecting the law of supporting stress transfer,and the interface position of the coal rock was obtained.The disturbance superposition law of the working face mining stress and supporting stress on the stress of the coal column floor.(2)The deformation mechanism of the dynamic pressure roadway of the coal column floor left by the coal seam at close range was revealed.The analysis model of the surrounding rock of the coal column floor mining roadway was established,and the deformation mechanism of the surrounding rock of the coal column floor roadway was revealed,and the stress,plastic zone and deformation of the surrounding rock of the coal column floor were gradually reduced and stabilized with the increase of the distance between the coal rock interface and the lead hammer of the lower roadway,the horizontal stagger of the joint mining of the upper and lower working faces,and the increase of the distance between the coal column and the lead hammer of the lower roadway.With the increase of the width of the thick hard roof overlying the upper roadway,the stress,plastic zone range and deformation of the surrounding rock of the lower roadway gradually increased and tended to be stable.(3)The active control principle of weakening the coal column supporting stress source,increasing the propagation resistance of supporting stress,avoiding multisource support stress superposition,and improving the deformation resistance of the surrounding rock of the roadway under the coal column was proposed,and the deformation control method of "pressure relief-decompression-release" of thick hard roof cutting and unloading,roadway layout decompression,and strengthening the support strength to make the pressure protection alley was developed,and the hydraulic fracturing inclined cutting top fault,mining arrangement and bolt support technology were determined to realize the fracture and pressure relief of thick hard roof structure,and the reduction of narrow coal column support stress.The effect of reducing the stress of the coal column floor and improving the maintenance effect of the roadway.(4)An industrial test of deformation control of the mining roadway under the coal column left over from the coal seam was carried out at close range.The above theoretical results were applied to determine the cutting height of the thick hard roof plate of the test roadway,the cutting top angle,the horizontal wrong distance of the joint mining of the upper and lower working faces,the width of the coal column and the supporting strength of the lower roadway section,and the field application effect showed that the determined technical scheme effectively reduced the stress of the surrounding rock of the test roadway and controlled the deformation of the surrounding rock of the roadway.The thesis has 96 figures,15 tables,and 143 references.