عنوان مقاله [English]
The aim of this research is stability analysis of coal pillars in inclined coal seams (the variable pillar width and the variable seam dip) using the finite difference method software (FLAC2D). This aim is achieved by assessing the vertical and shear stresses distribution and their influence on the coal pillar.
In some mining method such as longwall, room and pillar and stope and pillar, the design of mine is done in such a way that the pillars are left in the seam gradient. Therefore in this case the effect of seam dip must be considered on the stability of pillar. Pillars in dipping strata are under in compression and shear load and therefore require consideration of a failure criterion that accounts for compression and shear load. The stability analysis of coal pillar can be performed by empirical, analytical, statistical and numerical methods.
Since the existing empirical methods developed to pillar design have some limitations, the application of numerical methods was widely increasing to optimize pillar size in all mining methods. Applying numerical methods, it is possible to consider seam dip on the stability of coal pillar.
Methodology and Approaches
In this study, six numerical models were analyzed in FLAC2D software for 30, 45 and 60 degree steeply coal seams with 10 and 15 m pillar width. It should be noted that 90 m width are considered for stopes in all numerical models. Moreover, exploitation has been started at the first stope and then continued to the second stope. In each step of the analyses, the model is run to equilibrium before creating the second stope.
Results and Conclusions
The numerical modeling result on 30, 45 and 60 degree steeply coal seams with 10 and 15 m pillar width showed that the vertical stresses on the pillar decreased by increase of coal seam dip and coal pillar width. Moreover, the shear stresses increased by increases of coal seam dip. Finally, according to the numerical modeling result the pillar width of 15 m on a dip of 30 degree is stable.