| An innovative non-pillar longwall mining approach by fracturing roofs to maintain entry(FRME)is used widely in recent years,which is realized by using mine pressure and the broken expand characteristics of roof strata.One side of the roadway formed by FRME approach is solid coal wall and the other side is the gangue rib composed by crushed falling rocks.The crushed falling rocks is a typical discrete medium with poor anti-deformation and low stability,which may result in large axial compression deformation and lateral expansion deformation of gangue rib.Combined with laboratory test,numerical simulation,theoretical analysis and others research method,the compaction and creep deformation characteristics of crushend rocks were studied,both macro and micro mechanism of axial load bearing and deformation of crushed rocks in gangue rib were revealed.Mainwhile,the mechanical model for lateral pressure analysis of gangue rib were established,and the change and distribution rule of lateral pressure were analyzed.Moreover,the influences of roof strata pressure,rock lithology,etc on lateral pressure of gangue rib were studied as well,which revealed the lateral deformation mechanism of gangue rib from the perspective of stress generating device.Ultimately,the following innovative results were obtained:(1)The compaction and creep deformation properties of crushed rocks were studied.In addition,the influences of gradation composition on the compaction and creep deformation properties of crushed rocks were analyzed.Moreover,the prediction equations of the uniaxial compression deformation and creep deformation of crushed rocks were obtained.Then,the relationship between the axial compression deformation and settlement of entry roof close to gangue rib was conducted.(2)A device for compression test,which can simulate the real stress condition of crushed rocks was developed.Based on it,the axial compression mechanical characteristics of crushed rocks with larger particle size and lateral stress change rule of gangue rib under step loading condition were studied.Additionally,the influences of grain size on the compressive deformation characteristics and lateral pressure of crushed rocks were analyzed.Then,the axial compression mechanism of crushed rocks in gangue rib was revealed from a microscopic point of view combined with the numerical simulation method of PFCZD.(3)A mechanical model for lateral pressure analysis of gangue rib was established,and the formula for calculating the lateral pressure at different evolution stages of the gangue rib was derived.In addition,the dynamic change rule of lateral pressure of gangue rib was obtained.Meanwhile,the influences of roof strata pressure,gravel mechanics parameters and other factors on the lateral pressure value were analyzed as well.Trough above analysis,the stress generating device and quantitative aomputation method of lateral stress were explicated.Ultimately,the feasibility of the research results was proved by the engineering measured data. |
PDF Full Text Request