Research On Stability Mechanism And Control Of The Surrounding Rock Of Lower Coal Roadway In Close Distance Coal Seams

In view of technical problems in the layout of lower coal roadways and the stability control of surrounding rock in close distance coal seams,research was conducted based on the mining of 3upper and 3lower coal seams in East 10 mining area of a coal mine.Field measurement,theoretical analysis,physical similarity experiments,numerical calculation and industrial tests were adopted in this paper to carried out a systematic research on the migration law of 3upper overburden strata in the mining process,the damage depth of the floor induced by the mining and time-space evolution of strata stress.Firstly,theoretical analysis and physical similarity simulation were adopted to analyzing the mechanism of intense pressure in the lower coal roadway during the mining of close distance coal seams.Based on a comprehensive analysis of overburden structure and its deformation and failure characteristics,time-space evolution of abutment pressure during the mining process and the temporal-spatial relationship between the mining of 3upper coal seam and the tunneling of 3lower roadway,this paper proposed that the mining of 3upper coal seam has a certain influence on the migration of high-position key strata.In the mining of the adjacent working face,high-position key strata rotate and break due to the expansion of the goaf.The overburden load acts on the floor stratum of the goaf,causing a rise in the pressure of the mining roadway in the 3lower coal seam.This hypothesis was verified by the measured time-space evolution law of the deformation and failure of the surrounding rock in 3lower 1001 material roadway.Secondly,theoretical analysis was also carried out on the transmission of abutment pressure and the mining damage of the floor during the mining of the upper coal seam in the close distance coal seams.The vertical stress distribution formula at any point of the floor was derived and the maximum damage depth of the floor is worked out.Then,a numerical calculation model was established considering the full-period mining of close distance coal seams to analyse the time-space evolution of the floor stress during the mining of 3upper working face.Afterwards,the layout of 3lower 1007 transportation roadway under the goaf was determined.Finally,the reasons for the failure of the roadway in the lower coal seam during the mining process and the existing problems are summarized and analysed,so as to put forward the well-focused supporting principle of the mining roadway in the lower coal seam.The supporting technical parameters of the roadway was determined though the measurement of surrounding rock loose circle and theoretical analysis.The feasibility of the supporting scheme was verified by numerical calculation.The on-site application of the 3 lower 1007 transportation roadway shows a success of the proposed roadway layout and the stability control scheme of surrounding rock which have good technical and economic effects.