Study On Mechanical Effect And Application Of Supporting And Retaining Coal Pillar In Inner Dump

Strengthen inner drainage in open-pit coal mine can reduce the area of the outer row,reduce the stripping distance,and improve the equipment operation efficiency.It is also the best measure to control coal spontaneous combustion,dust and slope stability.Supporting and retaining coal pillar is one of the important means to improve the stability of inner dump with weak basement,but it will inevitably cause certain resource loss.The previous research on the supporting and retaining effect of coal pillar only considered the shear resistance between the coal pillar and the basement,and the shape of the coal pillar was optimized by the two-dimensional rigid body limit equilibrium method,but the shear resistance of the coal pillar on both sides of the end slope was not taken into account,it is easy to cause excessive morphological parameters of coal pillar and serious loss of resources.Therefore,it is urgent to analyze the three-dimensional supporting and retaining effect of coal pillar and put forward a two-dimensional calculation method of slope stability considering the supporting and retaining effect,which can be used to solve the difficult problem in the design of morphological parameters of coal pillar in inner dump.And it is of great significance to realize safe and economic mining of open-pit mine.In this paper,on the basis of the analysis of the instability mechanism and load distribution characteristics,the mathematical expression of three-dimensional supporting and retaining effect of coal pillar in inner dump with horizontal and dip basement was obtained and quantitative characterization of three-dimensional supporting and retaining effect of coal pillar was achieved.Based on limit equilibrium theory a two-dimensional equivalent method of supporting and retaining effect of coal pillar was established and the stability analysis method of inner dump considering the supporting and retaining effect was derived,and transformed space mechanics problems into plane strain problems.Taking Shengli East No.2 open-pit mine as an example,the influence law of the coal pillar morphological parameters on the supporting and retaining effect and the stability of inner dump were revealed and regular understanding was formed,and the morphological parameters of the supporting and retaining coal pillar was optimized and designed,and verified by numerical simulation methods.The results showed that three-dimensional supporting and retaining effect of coal pillar is essentially a shear reaction force,which is expressed as the combined force of the cohesive force of the side interface and the bottom interface and the internal friction resistance.The equivalent cohesion _dc and internal friction coefficient tan_d?have has an inverse proportional function relationship with d,positive linear function relationship with h,and positive power function relationship with b,?,?.It has a linear and quadratic function relationship with?,respectively,and the latter has a positive correlation linear function and power function relationship with inner dump slope angle?_p and slope line longitudinal intercept h_p.The stability coefficient of inner dump has positive linear function relationship with b and h,negative linear function relationship with?_p and?,negative exponential function relationship with d and?H,positive exponential function relationship with D/H,negative quadratic function relationship with?,and it has an absolute value function relationship?.The top width of the coal pillar in inner dump of Shengli East No.2 open-pit mine should be at the level of+824,and the optimum size of the coal pillar is b=15m and h=36.7m.The instability mechanism of the supporting and retaining coal pillar obtained by the numerical simulation method and the stability of inner dump are in good agreement with the theoretical analysis results.There are 52 figures,14 tables and 135 references in this paper.