| Different geological and rock formation conditions and mining methods make the mine pressure appear different.The presence of a composite hard roof often leads to an increase in the impact range of the working face mining,and the main road in the front mining area is severely affected by dynamic pressure and difficult to maintain.Under this circumstance,it will be of great engineering significance if the passive increase of coal pillar size can be avoided,the continuous support investment can be reduced,and the stability of the roadway can be improved.Therefore,this paper takes the 20207 working face of Huajin Mingzhu Mine as the research background,and comprehensively uses the methods of on-site investigation,theoretical analysis,numerical simulation,industrial practice,etc.,and focuses on the evolution law of the advanced bearing stress of the working face under the condition of composite hard roof blasting.,using deep hole blasting to cut the top and relieve pressure to change the stress distribution in front of the working face,optimize the position of the stop line,and obtain the following main research results:(1)Through drilling peep and coal and rock mass physical and mechanical tests,combined with mine geological data,the lithology and horizon characteristics of the top and bottom rock layers of the working face were understood,and the specific physical and mechanical parameters of the coal rock layer were obtained.The key strata and composite hard roof are identified for the roof stratum,and the distribution of the basic roof sub-key strata and the characteristics of the composite hard roof stratum are clarified.(2)The fracture and migration law of the composite hard roof rock stratum is studied and analyzed,the stress and deformation analysis model of the roadway is established,and the important factors and influence laws that affect the stability of the roadway are obtained.Combined with numerical simulation,it is analyzed that the stress of the surrounding rock of the roadway is supported by the working face in advance.The pressure is superimposed,and it is concluded that the influence of advanced support mining is the main factor for the continuous deformation of the main road in the mining area.Theoretically analyzed the stress distribution and state partition when the coal pillars in front of the working face stopped mining were wide coal pillars and narrow coal pillars.If the size of the coal pillar is insufficient,the mining stress of the working face reaches the stress area of the surrounding rock of the roadway,which will disturb the stress area of the roadway and affect the instability and deformation of the roadway.And based on the fault theory,the evolution mechanism of the advanced support stress blocking pressure relief after blasting top cutting is revealed.(3)Using FLAC3D numerical simulation software to study the influence of different blasting top cutting positions,top cutting tendency and top cutting height factors on the evolution of mining stress in front of the working face,the analysis shows that a reasonable blasting top cutting scheme can effectively cut off the transmission.The combined rock beam with load reduces the influence range of working face mining.By simulating and comparing the deformation of the roadway with or without roof cutting,the plastic zone of the surrounding rock in the roadway is reduced by 15.7%after roof cutting and pressure relief,and the reduction in displacement and deformation of the surrounding rock exceeds 60%.Therefore,actively constructing the pre-split surface and cutting off the main bearing rock strata mainly composed of composite hard strata can effectively maintain the stability of the roadway.(4)Combined with engineering geology and field conditions,based on theoretical analysis and numerical simulation research results,a deep hole blasting roof cutting implementation plan was formulated,and the position of the mining stop line was optimized and adjusted to be 90m away from the return air lane.The surface displacement monitoring of the roadway is used to detect the effect of on-site roof cutting and pressure relief.The deformation of the surrounding rock is significantly reduced,the deformation of the roof and floor is about 81mm,and the distance between the two sides is about 70mm.Finally,it is concluded that rock blasting can effectively block the transfer of mining stress,shorten the mining influence range of the working face,reduce the size of the coal pillar for roadway protection,and effectively control the deformation of the surrounding rock of the roadway. |
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