Study On Protective Coal Seam Mining And Testing Technology Of Protection Effect Colose Distance Coal Seam Group In Qianbei Mining Area

Provisions on prevention and control of coal and gas outburst points out that regional outburst measures should give priority to the use of mining protective coal seam.Protective coal seam mining is our main regional coal and gas outburst measures.At present,the research on the long-distance,ultra-long-distance protective coal seam is more.On the contrary,close coal seam group protective coal seam mining and gas control&effectiveness of drilling depth reliability test of protected coal seam is less.Based on this,this paper carried out this research.Based on the scientific theorys,this paper using theoretical analysis,numerical simulation,laboratory experiments,on-site test,combining the close distance protective coal seam mining of Guizhou Ruiguang coal mine,this paper is completed.Finally,the research results are applied to the mining practice of protective coal seam mining of Ruiguang minefield.The conclusions are following:(1)Based on the actual situation of the Rongguang coal mine,the deflection of the protective layer is calculated,and the maximum bottom drum volume of the protected layer C6 coal seam is 82.7mm.At the same time,the protective layer Calculation model of surrounding rock stress was constructed.(2)FLAC3D numerical simulation software is used to analyze the stress and deformation law of the protected layer in the process of mining the upper protective layer.In the mining process of protective layer,because the mined-out area provides the pressure relief space,the surrounding rock of the upper and the lower part of the gob is not moved to the goaf.Meanwhile,the surrounding rock at the cut-off and stopping positions moves horizontally in the direction of the mined-out area.Due to the inconsistency of the deflections of different rock strata during the moving process,the damage of the inside of the rock mass is not caused,and the permeability coefficient is not increased.(3)Based on the characteristics of the stress and displacement of the surrounding rock during the exploitation of the protective layer,the change of the permeability of the protective layer caused by the mining of the protective layer of the close coal seam is analyzed by the laboratory mechanical penetration test.There are great differences between loading and unloading failure of coal sample.Before the unloading point,with the increase of stress,the crack in the specimen is compacted and the permeability decreases.However,from the point of unloading,with the constant unloading of the load,equivalent to the tensile stress applied to the sample,the internal cracks of sample begins to increase.When the unloading continues,the cracks began to expand further infiltration increase.(4)By studying the law of sound wave propagation in water and air,the propagation characteristics of acoustic wave in equal diameter and variable diameter drill pipe are obtained,which lays a theoretical foundation for acoustic measurement of borehole depth.(5)Appling the drilling depth measurement technology to drillings for effect test and pressure relief gas drainage of protected coal seam ensure that the calibration parameters of the measurement accuracy and the effectiveness of pressure relief gas drainage of protected coal seam.