A study of highwall mining panel stability

This study describes numerical work carried out to investigate the stability of a highwall mining panel using local mine stiffness (LMS) theory. This theory estimates whether any small change in the equilibrium state of the stress field in the mining region provokes a sudden release of energy or induces a large change in the geometry of the mine system. This study focuses solely on panel instability that may arise due to pillar crushing. Panel instability that may arise due to slip along pre-existing faults has not been considered. The major conclusion of the study is that the use of the LMS concept, leading to a calculation of a panel factor of stability (PFS). used in conjunction with a factor of safety (FoS), can provide added confidence to a highwall mining panel layout design. A wide range of sensitivity analyses was conducted to gauge the most significant factors (such Lis pillar width-to-height ratio, mass coal strength, host rock stiffness, and rock/coal interface properties. panel configuration. etc.) that would affect the highwall mining panel stability. The major finding is that a FoS value of about L2 is the critical level below which the PFS starts to decrease rapidly, so that the stability of the panel is threatened, This statement is true over the wide range of factors considered in this paper, However, the results of this study may not be directly applied outside these ranges of geomechanical parameters and panel geometries or for different analysis techniques. If the input parameters lie outside the ranges of this study. both the FoS and the PFS need to be calculated for the layout and the specific trend of the PFS versus the FoS be further established. Previous back-analyses undertaken in a number of highwall mining pits have found that a design FoS of less than 1.2 did not ensure even short-term (C) 2002 Elsevier Science Ltd, All rights reserved.