Stability Mechanism Study Of Coal Pillar And Slope Body Under Strip Mining Of End-slope Coal

Strip mining is an important method and approach to effectively recover the endslope coal and increase the recovery rate of resources in open-pit,and has been quickly and widely used in leftover coal mining of open-pits.Strip mining of end-slope coal will cause strong disturbance to the stress field and deformation field of the slope body,and even endanger the stability of the slope body.At the same time,the stability of coal pillars is also an important guarantee to realize the safety and high efficiency of the strip mining of end-slope coal.At present,there have been rich achievements in the equipment and technology development of the strip mining of end-slope coal.However,the study on the instability mechanism of the coal pillar and slope body of strip mining of end-slope coal is lagged behind,which limits the development of the strip mining of end-slope coal technology at some extent.A systematically study mean combined with experimental research,theoretical analysis and numerical simulation is applied to study the stability mechanism and control method of the coal pillar and slop body of strip mining of end-slope coal.The main research work and achievements in this paper are as follows:(1)The direct shear and shear creep tests are carried out for the rock medium of an end slope in an open-pit.The direct shear strength characteristics and shear creep laws of the rock medium are obtained.At the base of experiments,the corresponding creep constitutive model is established and the concrete model parameters are given,which provide the basis for the stability analysis of the slope under the strip mining of end-slope coal.(2)The mechanical model of coal pillar of strip mining of end-slope coal is established,and the formula for calculating the width of plastic zone on both sides of coal pillar is derived.The formula takes into account the influence of the interface of coal seam and the plastic zone on both sides of coal pillar on the stability of coal pillar,improves the existing formula for calculating the width of plastic zone of coal pillar.The influence of the height of coal pillar,cohesive force and angle of internal friction of coal,and limit stress of coal pillar on the width of plastic zone on both sides of coal pillar are analyzed.(3)Based on the plate stability theory,the mechanical model of the stability of coal pillar is established,and the theoretical estimation formula of the critical load of the stability of coal pollar is given.The influence of the mining depth,the mining height and the width of coal pillar of strip mining of end-slope coal is obtained.(4)A numerical calculation model of the stability of the coal pillar in the strip mining of end-slope coal of open pit is established.The distribution characteristics of the stresses,deformations and plastic zone in the surrounding rock of the cavern in strip mining of end-slope coal are given and analyzed.The influence of width and height of coal pillar on the deformation and stability of coal pillar is obtained.(5)The numerical calculation model of the stability of slope body in the strip mining of end-slope coal of open pit is established.The influence of the mining depth,mining height,setting parameters of coal pillar,slope angle and rock mass occurrence conditions(strata inclination and weak interlayer properties etc.)on the deformation and stability of the end-slope are obtained.Based on the shear creep constitutive model established in this paper,the variation laws of creep deformation characteristics and the stability of the slope body of the strip mining of end-slope coal with time are analyzed and obtained.The research results in this paper can provide important reference for the stability control of coal pillar and slope body under similar conditions.