Monitoring of Multiple-level Stress Interaction at Two Underground Limestone Mines

Abstract

The National Institute for Occupational Safety and Health (NIOSH) has previously established pillar design guidelines for shallow, flat-lying mines and single-level operations. Little guidance exists for ground control design in multiple-level stone mines, and understanding the interactions between levels would allow engineers to better select interburden thicknesses and the necessary amount of pillar columnization. To investigate these loading conditions in multiple-level environments, NIOSH has partnered with two separately operated multiple-level mines to study the stress interaction between the levels as undermining occurs. The first mine is located in Tennessee with up to a 243-m overburden and 7-m interburden thickness between levels. The second mine is located in Kentucky with a 304-m overburden and 26-m interburden thickness between levels. The monitoring program at these sites includes stressmeters and LiDAR for tracking stress redistributions and rock displacement in response to undermining. Monitoring is ongoing, but numerical modeling results show the expected interaction between levels.