The use of highwall mining systems (Figure 1 ) has increased substantially in open-pit coal mines. It is used where overburden depth exceeds economical recovery. Highwall stability remains the major safety concern during highwall mining. The Mine Safety and Health Administration requires highwall mining operators to follow ground control plans that specify the pillar sizes necessary to prevent a pillar collapse that would threaten highwall stability. NIOSH has developed the Analysis of Retreat

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... ining Pillar Stability-Highwall Mining (ARMPS-HWM) computer program to assist mine planners with pillar design. Based on extensive research into instances of highwall mining pillar instability and pillar collapses in underground mines, ARMPS-HWM uses the Mark-Bieniawski formula to estimate the strength of long strip pillars. The suggested design procedure addresses the following issues: