Research On Mining Coal Rock Failure And Gas Migration Law In Gently Inclined Coal Seam Group

It is of great theoretical and practical value to study the coal-rock failure and the law of gas migration in the slow-dip inclined coal bed group.Coal seam occurrence in Kailuan mining area is a typical slow-dip inclined coal bed group,with complex geological conditions,many mining coal seams and a large number of goaf.High drilling and low buried pipe extraction are common techniques to effectively solve the pressure relief gas in the goaf and prevent the gas concentration in the upper corner from exceeding the limit,and are also the key to ensure the safe mining.Therefore,the paper takes the slow inclined coal bed group in Kailuan mining area as the research object,studies the moving failure law of the slow inclined coal bed group,obtains the characteristics of the fracture distribution,pressure relief range and evolution law of the coal and rock strata,studies the porosity distribution characteristic of the goaf,studies the gas migration law of the goaf,determines the gas enrichment area in the fissure zone of the stope,and therefore optimizes the parameters of the high borehole bed and the low drainage buried pipe for the slow inclined coal bed group of Kailuan Group to optimize the layout of the pressure relief gas drainage system and improve the effect of pressure relief gas extraction and provide technical support.In this dissertation,the comprehensive research methods of engineering data analysis,theoretical analysis,similarity simulation experiment,numerical simulation and industrial test site are used to study the coal-rock failure and gas transport law of coal mining in slow-dip coal seam group.(1)Analysis of mining stress of surrounding rock in gently inclined coal seam mining.During the mining process,the coal roof and bottom slab along the driving direction of the coal face are affected by the mining,and the original stress balance state is broken.The mechanical model of mining roof and floor control is established,and the stress distribution characteristics of mining roof and floor in mining roof and floor control mode are analyzed.Through the continuum model of FLAC3D,a finite difference numerical calculation software,the coal seam group model of different coal seam dip is constructed to study the vertical stress,shear stress,displacement and plastic distribution characteristics of surrounding rock in mining.(2)A similar experimental study on the evolution of mining fractures in coal seam groups with gentle slope.Taking the slow inclined coal seam group of Tangshan mine in Kailuan mining area as the research object,the physical similarity model of T1452 working face and Y484 working face of 8 and 9#coal seam in 5#coal seam is selected to study the mining of thick coal seam in the lower part of goaf,the distribution of surrounding rock fissures in stope and the law of overburden rock caving settlement.(3)Three-dimensional distribution of porosity in goaf of slow-dip coal seam group.Taking the T1452 coal face and Y484 coal seam Y484 coal face of 5#coal seam as the research object in Tangshan Mine of Kailuan mining area,the dispersion model of the discrete element simulation software UDEC was constructed to construct the numerical simulation model to study the vertical stress,the caving settlement and the fissure field distribution of the surrounding rock in the goaf during the mining process of the lower coal seam working face.(4)Study on the law of gas transport in surrounding rock fissures in goaf.The dissertation summarizes and analyzes the gas origin and emission characteristics of fully-mechanized caving face with Y484 working face as the research object.According to the distribution characteristics of the fracture zone of mining overburden and the direction of gas rising and floating diffusion in the fracture zone,the influence factors(coal seam inclination and gravity factors)affecting the gas distribution in the stope are studied.It provides a theoretical basis for gas prevention and control in caving face.(5)Optimal design and engineering application of pressure relief gas extraction in goaf.According to the actual situation of the test site,the parameters of the final hole position,the final hole spacing,the control range of the borehole in the tendency,the stubble pressure distance and so on are studied.and engineering application in the field to test the drainage effect and determine the gas enrichment area.