Study On Mechanical Characteristics And Control Of Layered Roof Damage In Goaf

The stability and control of goaf roof is one of the key technical problems restricting the safety of mine.The failure of layered roof is particularly prominent,and the disharmony of deformation between rock strata results in extremely severe ground pressure in the mining process.In serious cases,roof damage and other phenomena will occur,resulting in hidden safety hazards.It is of great significance to explore the failure mode of layered roof,study its damage mechanism and put forward corresponding control measures for mine safety production.Relying on central south university graduate student independent exploration innovation project "mined-out area of layered roof breakage mechanics characteristic and control research",three ning water river in hubei mining area industrial phosphate rock mining as the research object,using theoretical analysis and model experiment,numerical simulation and empirical research,from the layered roof breakage mechanics characteristic and control technology research,The main research contents and results are as follows:(1)The preparation of the layered structure of rock material sample,carried out a stratified sample of uniaxial compression test,combined with acoustic emission,such as digital speckle monitoring means,analyzes the formation thickness,distance of rock bridge,lateral restraint factors such as the influence on strength,summarize and put forward the nine kinds of typical crack penetration type and two kinds of sample failure mode.The peak strength of samples increases with the increase of rock thickness,and increases first and then decreases with the increase of rock bridge distance.The failure of the sample is mainly the buckling instability failure dominated by horizontal load,and there is an evolution process of gradual expansion of the stripping range,and the acoustic emission law of the transition from the quiet stage to the rising stage to the active stage.The type and failure mode of the proposed roof cracks are consistent with the field observation.(2)The mechanical theoretical model of layered roof in goaf is established,and the stress distribution law and deflection deformation characteristics of strata in goaf roof are obtained by using the combined beam and thin plate theory.The maximum value of stress distribution and deflection deformation of roof is obtained in the middle part.On this basis,combined with the experimental results,the roof stability criterion is proposed.(3)A three-dimensional numerical model of goaf roof deformation and failure based on actual working conditions is constructed to reveal the influence rules of different factors on roof stability.The stress distribution,displacement and plastic zone range of surrounding rock in goaf of different schemes were compared and analyzed,and the influence rule of horizontal stress and chamber span on roof stability was obtained.(4)Investigation and analysis of roof damage in mining area is carried out.Combining with the results of test and theoretical research,the idea and technology of stability control of layered roof is put forward,and the parameters of various supporting materials are calculated.The results of experimental and theoretical research indicate that the stability control of layered roof should be dominated by "ensuring the stability of rock beam and preventing the whole caving".Accordingly,the combined support system of "prestressed long anchor cable and multi-angle anchor bolt and anchor net" is of positive significance to the stability control of layered roof.