Study On Layout And Support Technologyof Mining Roadway In Coal Seam Under Short Distance

The rapid development of coal industry reflects the key position of coal in the resource structure,and the coal resources with better burial conditions are close to exhaustion,so the close coal seam mining with relatively poor coal seam occurrence conditions has gradually attracted people's attention.Close-range coal seams are widely distributed in many minefields in China.Close-range coal seams have some differences in traditional single seam mining.The differences include reasonable mining sequence,stress distribution characteristics of left pillars in upper and lower seams,rational layout of mining roadways and roadway maintenance.Especially in the downward mining of close coal seam,the stress redistribution of the remaining pillars and surrounding rock in goaf after the upper coal seam mining will have a negative impact on the stability of the lower coal seam mining roadway,and when the lower coal seam mining,the roof has been damaged by the upper coal seam mining,thus increasing the difficulty of surrounding rock control of the lower coal seam mining roadway.The key of surrounding rock control of lower coal seam mining roadway is the reasonable layout of mining roadway and the construction of support system of close coal seam.Therefore,the reasonable layout of lower coal seam mining roadway and roadway support system are the important and difficult research contents of safe and efficient mining of close coal seam.In this paper,based on the research background of the southern flank of Shenzhou Coal Mining Area No.1(8,10)mining,through the combination of theoretical analysis,calculation and numerical simulation,a detailed and in-depth analysis and research is carried out on the rational layout of the mining roadway and the construction of support system for the close coal seam(8,10)in Shenzhou Coal Industry.And the following research conclusions:(1)The lithology,joint and fissure development of coal seam roof and floor are preliminarily analyzed in combination with mine geological conditions,coal(rock)physical and mechanical parameters testing and surrounding rock peeping.(2)Collect the classification index of surrounding rock stability of coal roadway with similar geological conditions,use the method of fuzzy mathematics to carry out the fuzzy clustering analysis,use the MATLAB to calculate iteratively,and then get the surrounding rock stability level of the lower group coal mining roadway in Shenzhou Coal Industry,which provides theoretical support for the rational layout of roadway and the construction of support system.(3)Analyzing the stress distribution law under the coal pillar,through theoretical analysis of slip line field theory,the theoretical calculation formula of the maximum damage depth of the coal pillar left over from the goaf of the upper coal seam to the floor is simplified by mathematical method.Combining with the geological data and the test data of mechanical parameters of surrounding rock,the theoretical calculation value of the maximum damage depth of the floor caused by the mining of the upper coal seam is 1.45 m.The formula for calculating the width of the plastic zone in the goaf on one side of the coal pillar is obtained by using the limit equilibrium theory.(4)The distribution characteristics of abutment pressure and stress of coal pillars in one side and two sides of goaf are studied respectively,so as to obtain the stability analysis of the remaining pillars in the upper coal seam under different conditions.Combining with the geological data of the mine and the physical and mechanical parameters of coal rock,the width of the plastic zone of the remaining pillars in the upper coal seam(8)is calculated to be 1.90 m,and the pillars are the most stable.The range of small width is 5.13m~6.46 m.According to the operation rules of 8103 working face,the width of the remaining pillars in the goaf of 8103 working face of upper coal seam is 20 m,which is much larger than the theoretical width of the pillars in stable state.The theoretical calculation shows that the width of plastic zone of the lower coal(10)pillars is 3.78 m,and the minimum width of the pillars in stable state is 9.86m~12.16 m.(5)Analyzing the influence range of the simplified distribution of abutment pressure of coal pillars and the stress propagation of coal pillars,the theoretical calculation formula of the reasonable offset between the lower coal seam mining roadway and the upper coal seam remaining coal pillars is obtained.Combining with mine geological data and coal rock physical and mechanical properties parameters,the calculation results show that L is more than 4.4m.According to the theoretical reasonable staggered distance value and combined with the actual situation of the mine,three schemes of roadway layout in lower coal seam are put forward,and the primary scheme of roadway layout is obtained by comparing the control of surrounding rock,recovery rate and cost.(6)According to the different layout of mining roadways under different staggered intervals,FLAC3 D numerical simulation software is used to simulate and calculate the influence of staggered intervals on the stability of surrounding rock of roadways.Finally,the reasonable internal staggered interval of mining roadways in lower coal seams is obtained to be 10 m.(7)By analyzing the mechanism of bolt support in the roadway with broken surrounding rock in the close coal seam,the theory and principle of bolt support in the close coal seam,and checking the strength of the existing support in the roadway of 8103 working face in the upper coal seam,the supporting scheme of the roadway in the lower coal seam is further proposed as follows: bolt + metal net + I-shaped steel shed combined support,and the corresponding supporting parameters are given.The deformation of surrounding rock of Roadway after support in coal seam mining is monitored on site,and the supporting effect is further tested.