Mechanics Mechanism Of Instability On Overburden-coal Pillar Group

In three underμ coal mining, often leaving in coal pillars to support the roof,control surface subsidence, in other mining methods, but also ofen leaving in coalpillars to protect the roadway, isolate water and sand, etc. Stability of coal pillar isvital for strata movement control and surface subsidence. In this paper, the integrateduse of theoretical analysis, numerical simulation and other research methods andmeans for coal pillar stability were studied, obtained the following results:(1) According to the interaction relationship between the pillar and surroundingrock, coal pillar mechanical model was established by considering the binding forceof coal piilar and roof and floor, and the displacement variational method of elasticitymechanics was used to obtain the analytical solution of stress field and displacementfield of coal pillar, given the distribution of coal pillar stress field, displacement fieldwith coal pillar width, mining depth and coal seam dip angle.(2) Based on the creep properties of the coal rock, the rheological properties ofcoal pillar group were analyzed with numerical simulation method, the timecorrelation characteristics of coal pillar group about stress, deformation and plasticzone was investigated, the results showed that: the stress, the deformation and theplastic zone of coal pillar group had a substantial increase with time, andcharacterized by rapid early growth, late gradually stabilized. At the beginning of thecreep, the stress, deformation and plastic zone of each coal pillar were close, with thegrowth of time the differences between each pillar was increasing, and the deeper thecoal pillar occurrence increase, the stress, deformation and plastic zone is larger.(3) According to the occurrence environment of coal pillar, a numericalsimulation mechanics model including the roof, the pillar and the floor wasestablished, and by the means of FLAC3Dnumerical analysis software, the variationof the stress, the deformation and the plastic zone of coal pillar group with coal pillarwidth, mining depth and coal seam dip angle was obtained. The results of numericalsimulation and theoretical analysis had a good seal.The research results can provide a theoretical reference for coal pillar design andcoal pillar long-term stability analysis of strip mining and other mining methods.