Study On Reasonable Position And Support Technology Of Floor Gas Drainage Roadways In Gently Inclined Coal Seams After Mining

Based on +642 east floor gas drainage roadway of chuanjing coal mine,this paper comprehensive analyses and studies the reasonable position and support technology of floor gas drainage roadways in gently inclined coal seams after mining by virtue of indoor experiments,on-the-spot detection,theoretical analysis and numerical simulation.The main research outcomes are as follows:(1)According to geological contributions available and lab tests,physical and mechanical characteristics of coal measure strata in the experimental area are obtained.Six typical sections in +642 east floor gas drainage roadway are selected to do the measurement of the surrounding rock loose circle.Finding that loosening circle thicknesses in survey sections concentrate in the range of 1.2m~3.2m which mean to be large loosening circles.And parts of surrounding rocks in roadway sections exist abscission layers and through cracks before mining jobs.And the broken areas extend to the depth of about 2~8m.All the work above supports basic parameters for the next numerical simulation analysis and design of roadways support schemes.(2)The stress distribution rule is analyzed as gently inclined coal seams mining by theoretical analyses.Based on the floor rock slip-line field theory,reasons why plastic fracture zones formed are analyzed and the largest depth of plastic fracture zones is calculated to 9.49 m.According to the elasticity theory,the stress distribution of the floor near the coal wall after mining is simplified to summarize the depth of plastic fracture zones distribution rule in vary inclinations: in the near-level coal seam,plastic fracture zones near the edge of coal walls in mined area are bigger than the other positions.The depth of plastic fracture zones gradually reduces to the central,and finally tends to a certain fixed value;situations in the gently inclined and the inclined coal seam are similar to the near-level coal seam.But the depth of the plastic fracture zones below the floor in working face lower end is larger than the other positions;things in the steep coal seam are different to situations above,the depth of the plastic fracture zones below the floor in working face upper end are larger than the other positions.After that,a numerical model is built to reveal the stress distribution rule when mining in the gently inclined coal seams.(3)Based on deformation and failure rules of surrounding rocks in coal seams floor and numerical simulation to analysis the reasonable position of floor gas drainage roadway from four factors: the lithology,the stress distribution rule,the depth of plastic fracture zones and the effect of gas extraction.Then do another numerical simulation to compare the stress state of +642 east floor gas drainage roadway in original position and other two optimized positions.The results show that in three layouts,the best choice to lay the floor gas drainage roadway is optimization scheme 2.It means that lays the floor gas drainage roadway with 7# coal seam belt conveyor roadway in the same level,and keeps horizontal 45 m from airflow roadway.On the basis of the optimization scheme 2,some requirements for the grossmeasures boreholes are put forward.(4)Observe the mine pressure in +642 east floor gas drainage roadway with original support scheme,and optimize this scheme with the enhanced arch of anchor cable,a two-arch system of anchor,bolt and cable by surrounding rock loose circle theory.With six targeted countermeasures,demonstrate the feasibility of the asymmetric optimization scheme.