| The difficulty of gas disaster prevention and control increases when the high gas and low permeability outburst coal seam enters the deep mining.Though the existing technology of pressure relief and permeability enhancement as well as high-efficiency drainage can achieve better application effect under certain geological conditions,the technology of pressure relief and permeability enhancement in the deep coal seam is yet to be mature.In order to improve the efficiency of drilling construction and extraction,it is necessary to study a new method and technology on how to make full use of the floor measures to achieve the initiative and uniformity of pressure relief and permeability enhancement.Based on the National Key Research and Development Project(2017YFC0804206),a new method of floor roadway pressure relief and gas drainage in deep mime coal roadway strip is proposed in this paper.Taken Qujiang mine in Fengcheng as the engineering background,the mechanism of pressure relief and permeability enhancement,deformation characteristics of overburden and related influencing factors are studied with the combination of various research methods and based on the pressure relief and permeability enhancement test.The law of deformation,stress,permeability and the determination method of safety rock pillar are obtained.Besides,the layout technology of gas drainage drilling is optimized.The outburst prevention effect is investigated,and the regional outburst prevention mode of coal roadway strip is innovated.(1)The change path of pressure relief stress of floor roadway in the deep coal seam roadway strip is analyzed.Under constant confining pressure,the change rule of coal strength and permeability in the process of axial loading and unloading is studied and the permeability of coal in unloading process is increased.In different conditions in terms of confining pressure and gas pressure,coal permeability increases logarithmically with the increase of gas pressure and confining pressure,and the axial unloading under high stress and high gas conditions in deep coal seam can significantly improve the permeability of coal.(2)The analytical equation of stress and strain for surrounding rock in deep roadway is established based on the unified strength criterion,non-associated flow rule and rheological time effect.Taking the engineering conditions of Floor roadway 213 in Qujiang mine into consideration,the trial calculation is carried out.In addition,the pressure relief degree of the floor roadway to the coal seam gradually decreases from the center to both sides of the roadway;it decreases with the increase of the distance from the floor roadway to the coal seam and increases greatly with time.The law of fracture zone and permeability for floor roadway pressure relief in deep coal roadway strip is studied;it is found that the effective pressure relief distance of Floor roadway 213 to the overlying coal roadway is less than 13.6m.The model of safety rock pillar determination method is established.Besides,the theoretical minimum safety distance of Floor roadway 213 is 7.43m.(3)Similar simulation test of high stress under four side loading is designed,in which the displacement change,fracture development and strain distribution of overburden are simulated with Floor roadway of Qujiang mine arranged at 10m to the coal seam floor.In the case of buried depth of 800m,the influence range of the roof and both sides of the floor roadway is more than 10m;the area within the range of 15.6m on both sides of the roadway centerline is under pressure relief;after the excavation of coal roadway,the rock pillars between the two roadways function well to keep the stability.To conclude,the rationality of the determination method for the safety rock pillar and the reliability of the location of the floor roadway are verified.(4)FLAC3D finite difference numerical analysis model is established to reflect the nonlinear change of coal yield failure.With the model established,static factors are studied,including the arrangement distance of the floor roadway,the dip angle of the stratum,the buried depth,the horizontal stress and the lateral pressure coefficient,and the evolution law of the dynamic change of the excavation to the stress of the coal seam.With the increase of arrangement distance,the effect of pressure relief gradually decreases.In addition,with the increase of inclination angle,the best pressure relief position moves logarithmically downward,and the degree of pressure relief decreases gradually.The degree of pressure relief increases exponentially with the increase of burial depth;with the increase of lateral pressure coefficient of horizontal stress,the degree of pressure relief gradually decreases;with the increase of the lagging distance of heading face,the influence of pressure relief area along strike direction gradually increases before approaching the stability,as the result,a certain lag effect is achieved.When the arrangement space of Floor roadway 213 in Qujiang mine is 11.2m,the minimum lagging distance of heading face with stable pressure relief is 25m.(5)Numerical analysis model of multi field coupling COMSOL is established to reflect the deformation and gas flow of coal seam.With the model established,the influence of floor roadway on gas pressure relief and seepage velocity of coal seam is studied;it is found that the effect of gas pressure relief and seepage velocity decrease in negative exponential relationship with the increase of the distance between coal seam and floor roadway,and increase in logarithmic relationship with the increase of time and distance behind heading face.When the space between the coal seam and the floor roadway is less than 11m,Floor roadways 213 in Qujiang mine exhibits obvious effect on pressure relief and permeability enhancement of coal seam.When the spacing is 11.2m,the minimum lagging distance of heading face to achieve stable pressure relief is 30m.Besides,the influence of the layout of the drainage drilling on the pressure relief of coal seam is studied.Based on the pressure relief of floor roadway,the layout of gas drainage drilling with unequal spacing in coal roadway is put forward.(6)The outburst prevention method of floor roadway pressure relief with gas drainage is put forward in deep coal seam roadway strip based on the space-time relationship of"time,space and outburst danger",which mainly includes the determination of the reasonable position of the roadway,the safety guarantee technology of excavation and the arrangement of gas drainage drilling.The reasonable distance between floor roadway and coal seam in the test area is 10-15m.Besides,safety guarantee technology of combination of long and short drilling for excavation has been developed.The application of the research results and the investigation of the effect of pressure relief,permeability enhancement and outburst prevention are carried out as well.The permeability coefficient of the coal seam roadway strip is increased by 12.10?55.74 times,and the effective radius of drainage is increased by at least 20%-40%after pressure relief.It shows that the outburst prevention effect of pressure relief and gas drainage is significant.Figure[151]Table[32]References[196]... |
PDF Full Text Request