Study On Determination And Extender Technology Of Protection Range In Upper Protective Layer Mining With Closed Distance

Coal and gas outburst is one of the most serious coal mine disasters,the protective layer mining is the most effective measure to prevent it,which determination of protection range is a key point.Take upper protective layer mining with closed distance of Qinglong coal mine for example,by means of numerical simulation and field measurement methods,studied the pressure relief antireflection effect of protected seam after 21604 protective seam mining in Qinglong coal mine,measured the actual protective range of protected seam,analysis the influence factors leading to extender protection range.Analysis the stress and strain of protected seam as 21604 protective seam mining 20 m,40m,60 m,80m and 100 m with the COMSOL Multiphysics software.Combined with protection standard of seam deformation,results showed that 14 m interior protected seam is protection range along coal seam with pressure relief angle 60°,13 m interior protected seam is protection range vertical coal seam with pressure relief angle 62°.Field measurement parameters such as expansion deformation of protected seam,gas flow of borehole and permeability coefficient,the maximum expansion deformation of protected seam is 13 mm,the maximum relative expansion deformation 4.1‰.The maximum gas flow of borehole is 194 L/min,an increase of about 27 times.Permeability coefficient of protected seam pressure relief up to 101.2 m2/(MPa2·d),an increase of 13 times.Residual gas content in coal seam used to measurement the protection range of protected seam,the along protection range of field measurement,the pressure relief reached 83°,the pressure relief angle reached 90° of vertical protection range.The protection range of protected seam is nearly equal to the range of protective layer mining,realizing extender the protection range of protected seam.The most important reason leading to extender the protection range is the effect of removing outburst measures of protective layer coal roadway mining to the protected seam.It is calculated to obtain that,protected seam transport trough to the interior area achieve a range of 16.5m removing outburst,so is track trough to the interior area achieve a range of 13.8m,and starting cut inside 5m to the interior area achieve a range of 23.4m,it is the most important reason why the protection range of field measurement extender.When calculating the effective drainage radius of borehole of proteceted seam,proposed a way to determine the multi-seam gas extraction borehole gas extraction ratio of each layer,and field verification was carried out.The research getting protection range of protected seam after 21604 protective seam mining in Qinglong coal mine,provides a theoretical basis to mine the protected seam.