Mining Publication: Pillar and Roof Span Design in Stone Mines

Underground stone mines in the United States use the room and pillar method of mining in relatively flat laying deposits. Roof and rib falls account for 15% of all lost time incidents. This paper presents the result of a study to improve pillar and roof span design methods so that unexpected ground instabilities will be reduced. A pillar design equation and related design guidelines are presented based on the observation of pillar performance at 34 different underground operations. A roof span design procedure is also proposed that systematically addresses the main issues related to roof instability. The guidelines are based on the observation of actual pillar and roof span performance in stone mines in the Eastern and Midwestern United States and therefore only apply to stone mine design within these regions.