Sensitivity Analysis of the Main Factors Controlling Floor Failure Depth and a Risk Evaluation of Floor Water Inrush for an Inclined Coal Seam

Abstract

The main factors controlling floor failure depth are highly consistent with those of floor water inrush. In this paper, a mechanical model was developed to calculate the maximum failure depth of the upper and lower sides of a mining working face floor along the coal seam’s inclination. The results indicated that the main factors controlling floor failure depth are mining thickness, working face slanting length, coal seam dip angle, mining depth, water pressure, cohesion, and internal friction angle. The floor failure depth of the 3303 working face in the Yangcheng coal mine was calculated using FLAC3D numerical simulation software. Based on matrix and variance analyses, the sensitivity of each of these factors with respect to floor failure depth followed the order: working face slanting length (extremely significant) > mining depth (highly significant) > cohesion (significant) > mining thickness (not significant) > coal seam dip angle (not significant) > water pressure (not significant) > internal friction angle (not significant). Also, the optimal plan for orthogonal simulation is A1 B1 C1 D1 E2 F1 G1, in which the floor failure depth is minimized. Finally, the average accuracy of logistic regression analysis of the principal component was up to 90.4% accurate, about 10% better than conventional logistic regression analysis.