Monitoring of Multiple-level Stress Interaction at Two Underground Limestone Mines
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Monitoring of Multiple-level Stress Interaction at Two Underground Limestone Mines Brent Slaker 1 Kristin Floyd 2
&
Michael Murphy 1 & Gamal Rashed 1 & Vasu Gangrade 1 & Mark Van Dyke 1 & Todd Minoski 1 &
Received: 26 May 2020 / Accepted: 21 October 2020 # This is a U.S. government work and its text is not subject to copyright protection in the United States; however, its text may be subject to foreign copyright protection 2020
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. Keywords Ground control . Limestone . Multi-level . Pillar stability
1 Introduction The National Institute for Occupational Safety and Health (NIOSH) is investigating the stability of pillars in challenging underground stone mines. At the time of this publication, there are approximately 110 underground stone mines in the USA, many of which are operating in multiple-level environments. Many existing surface quarries are also transitioning underground due to reach their economic stripping ratio, approaching reserve boundaries, and the dust, noise, and blasting concerns to surrounding urban and suburban areas [1]. The decision to take an existing underground mine into multiple levels may be due to property boundary issues but can also be grade-dependent. The efforts outlined in this paper intend to build on the work of Esterhuizen et al. and the investigations that led to the development of the pillar strength equations found in the S-Pillar software [2, 3]. The applicability of this research is intended for
* Brent Slaker [email protected] 1
National Institute for Occupational Safety and Health, Pittsburgh, PA, USA
2
Rogers Group, Nashville, TN, USA
shallow, flat-lying, single-level underground stone mines, because the empirical database represents conditions from a majority of underground limestone mines that were operating at the time. This does not necessarily preclude its use in other situations, but numerical modeling is frequently employed alongside it to better understand t
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