Quantifying the uncertainty of pillar safety factor by Monte Carlo simulation - A case study

The pillar failure hazards are the major problems in underground coal mines, which are generally unpredictable due to associated uncertainties arising out of the complexity of geological conditions and variability in mining parameters. The pillar safety factor, always considered in pillar design and planning of underground coal mines, may be an important predictor for pillar failures. In this paper, contributing parameters on pillar safety factor for the main panel of Tabas Central Coal Mine, located in the mid-eastern part of Iran which is going to be extracted by room and pillar method, are collected. The mean value of probabilistic pillar safety factor for the case study mine was found to be 1.47. However, the probability of the estimated pillar safety factor of less than or equal to one, was found to be 22.5%. The effects of the random variables on pillar safety factor and probability of pillar failure were determined using Monte Carlo simulation method. Based on results of simulation runs for each variable, the probability of pillar failure was determined. In addition, a multi-variable regression analysis was performed to determine the correlation between the random variables and the pillar safety factor. Uniaxial compressive strength of coal, with the coefficient of correlation of +0.61, was found to be the most important parameter to control the pillar safety factor.