Numerical Model Validation and Analysis of a Dipping Limestone Pillar Using FLAC3D

Ground falls represent a significant hazard in the nation's underground stone, sand, and gravel (SSG) mines. Researchers from the National Institute for Occupational Safety and Health (NIOSH) are currently conducting detailed investigations into the complex loading conditions at underground SSG mines operating in challenging conditions. This paper presents numerical modeling using FLAC3D of a detailed case study of the conditions encountered in a dipping underground limestone mine. To accomplish this, a preliminary model was updated to include sequential development of an instrumented pillar. Stress concentrations calculated by the model provide good agreement with the observed initiation and propagation of cutter roof and a location where roof displacement was observed and measured with laser scans. Finally, the inclusion of blast-by-blast development and simulation of bedding planes in the roof provides good correlation with areas of observed and measured roof displacement that occurred in the mine.