| The recovery of stratified mined coal pillars in the upper strata and the maximization of the mining of the remaining coal pillars are of great significance for the sustainable development of the coal industry and the construction of a safe and stable supply security system for coal.This paper takes the 13604 lower stratified surface of the coal industry of Tuncheng as the research background,and combines the specific geomechanical environment of Tuncheng Coal Industry,establishes the overall mechanics of the relationship between the surrounding rock structure of the roadway with narrow coal pillars in the upper stratum.Model,analysis of the structural relationship between the narrow coal pillar excavation lanes and the overlying strata under the section pillars,the stability and destruction rules of the surrounding rock during the excavation and mining,the deformation and failure mechanism of the narrow pillars,and the surrounding rock during the excavation and mining Deformation and control mechanisms.On the basis of the traditional narrow-column road protection technology,through theoretical analysis,numerical simulation and site rock deformation observation research methods,the narrow coal pillar excavation roadway is adopted for stratified mining of thick coal seams under the upper stratum coal pillars.The systematic and detailed studies on the deformation and control mechanism of the surrounding rock during mining and mining,the determination of a reasonable narrow pillar size,and the surrounding rock control countermeasures during excavation were carried out.(1)By analyzing the relationship between the narrow coal pillar excavation lanes and the overlying strata under the section coal pillars,the fracture characteristics of the old top rock block in the upper section working face and the shape after stabilization are obtained.Analyze the stability of large and small structures in the overlying strata of coal pillars and the relationship between them.Based on the theory of limit equilibrium of narrow coal pillars,determine the narrow coal pillar width of the test face.(2)Studying stratified mining The stability and damage rules of surrounding rock during the mining and excavation of narrow coal pillar excavation lanes under the coal pillars in the upper stratum section are studied,and the migration of overlying strata along the roadway during the excavation and mining stages is preliminarily determined.Laws and characteristics of the destruction of surrounding rocks: The stress concentration of narrow coal pillars during the mining phase is much greater than that of the excavation roadway.The degree of deformation and damage on the coal pillar side of the roadway is greater than that of the solid coal side.The maximum deformation of the two gangs and top and bottom slabs during mining is respectively Three and four times as many times as the stage of excavation,it is concluded that the overlying key structure has undergone four “break-rotation-stability”,and the last movement has a more severe impact on the stability of the surrounding rock.(3)Taking the basic characteristics of coal pillars as the entry point,the mechanical calculation models of solid coal gangs and narrow coal pillars were established,and the influencing factors of coal pillar stability,the failure mechanism of narrow coal pillars,and the pressure and strength of different roofs were obtained.Under the conditions of the coal pillar deformation law;on the basis of the mechanics of the remaining narrow coal pillar excavation lane overlying the size of the structural relationship,the upper layer of the coal pillar under the remaining pillars to make the narrow tunneling of the surrounding rock excavation and mining the entire process of damage characteristics and Destruction mechanism.(4)Simulate the characteristics of stress and plasticity of surrounding rock under different narrow pillar widths by means of numerical simulation.Combining with theoretical analysis,a reasonable narrow pillar width of 6m is finally obtained;the stress after excavation of roadway is analyzed.Distribution and roadway deformation and failure characteristics,proposed roadway asymmetry support technology,simulation of bolting during the roadway support of different rock bolts(cable)geometric parameters and mechanical parameters when the bolt(cable)prestressed diffusion effect,The optimal static support scheme during the road excavation process is the bolted mesh(cable)coupled asymmetric support technology.Based on the law of deformation and failure of surrounding rock in the mining stage,the dynamic support technology during mining is proposed,namely,the grouting reinforcement technology in the crushing section,and the concrete grouting reinforcement scheme is given.(5)Field tests showed that the 13604(lower)lane has a better integrity of the narrow coal pillars,and the asymmetric support technology used during excavation can effectively control the deformation and destruction of the surrounding rock.During the excavation,the maximum displacements of the two gangs,top and bottom slabs are respectively 65 mm and 57 mm,and the deformation is within the controllable range;the deformation of the surrounding rock is very fast during the initial period of tunnel excavation,and then gradually smaller,the tunneling period is approximately 14 days..During mining,for the grouting reinforcement section: the maximum approaching distances on the side of the narrow coal pillars and the solid coal side are 109 mm and 246 mm,respectively.The displacement of the solid coal ribs is larger than the displacement of the narrow coal pillars,and the leading bearing pressure peak or high stress The area is located 35 to 40 m in front of the working face;for the non-grouting reinforced section: the maximum approaching side of the narrow coal pillar side and the working face side is 187 mm and 86 mm,respectively.The lateral shift of the narrow coal pillar is larger than the lateral displacement of the working face,and the peak of the leading support pressure is about 30 m in front of the working face.From the perspective of technology and economy,comparisons were made between large and narrow coal pillars.It was concluded that the larger coal pillars of narrow coal pillars,in addition to having many technical advantages,also yielded 69.21 million yuan more than large coal pillars and achieved better results.The technical and economic benefits. |
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