Impact of Various Factors on Roof Stability in Underground Coal Mines

Extraction of coal in underground during depillaring operations poses several ground control problems. Understanding the behavior of overlaying roofs in underground coal mines is important for the efficient extraction of coal. Hence knowledge of the above overlaying roofs becomes critical. In roof stability of the pillars, Factor of Safety (FOS) will provide useful information to take care of the design of the pillar taking consideration about the strength and load on the pillar. FOS is an important parameter used to give a more rational assessment of risk for roof stability. Statistical analysis has been carried out for an underground coal mine to identify the role of various roof stability factors with the Factor of Safety (FOS) (1.1-1.39) and FOS (2-2.6) during caving operations. ANOVA univariate analysis, Multivariable linear regression analysis, and Curve fit analysis are carried out for the case study mine using MATLAB software. ANOVA univariate analysis reveals that the factors namely extracted area, gallery width, gallery height, depth, deformation and hanging goaf indicates a significant correlation to FOS (1.1-1.39) and similarly, there is a significant correlation established between depth and deformation for FOS (2-2.6). Multivariable linear regression analysis is carried out to predict the FOS. A number of statistical parameters are associated with multivariable linear regression were determined. Predictors that were used in multiple linear model of FOS are extracted area, hanging goaf, thickness, gallery width, deformation, depth and gallery height. The developed regression model showed that significant independent variables affecting the FOS gives R² and adjusted R² for FOS (1.1-1.39) are 0.93 and 0.87 respectively and also R² and adjusted R² for FOS (2-2.6) gives 0.96 and 0.94 respectively. Change in the FOS changes the roof stability parameters.