Mathematical equations for pressure relief angle of protective seam inclination in outburst coalmine

Abstract

Protective seam mining is one kind of most effective measure to reduce coal and gas outburst risk. The pressure relief angles along inclination (δm) are key parameters for evaluating the effect of protective seam mining. However, the numerical relation between δm and coal seam dip (a) is defined by discrete data and is difficult to determine δm accurately. In this study, the variations of δm with respect to seam dips are analyzed to derive analytical equations that can be used to accurately calculate δm. The relationship between δm and seam dip (a) can be expressed as parabolic or inverted parabolic curves. Mathematical equations for δm are derived by curve fitting technique. Furthermore, polynomial equations are determined as the most appropriate for δm calculation when the polynomial order is selected as 7, 6, 4 and 5 respectively. These derived equations are computationally solved and verified using actual and field test data of δm. with satisfactory consistency and accuracy. The equations are suggested as supplement and improvement for Detailed Rules on Prevention of Coal and Gas Outburst.