An Insight into Limestone Pillar Stability in Dipping Environments Using Actual Mine Geometries

Details

• Personal Author:
  Evanek N ; Rashed G ; Slaker B
• Description:
  As stone mine operations continue to develop in more challenging conditions including inclined seams, more complex loading conditions and pillar geometries are generated. The main objective of this study is to gain more understanding about the effect of seam inclination on the strength, the loading path, deformation of sidewalls, and yield patterns of a stone pillar using numerical models. The modeled width-to-height (W/H) ratio of the pillars, the unconfined compressive strength of limestone material, in situ stress field, and roof interface were varied to consider their potential distribution across underground limestone mines in the United States. Two actual mine geometries, referred to as a-type and b-type, were modeled. In a-type mine geometry, the roof is dipping while the floor is flat, making one side of the pillar shorter than the other side. In b-type mine geometry, the roof and floor lines of pillars are dipping while the headings/crosscuts are flat. The intention is not to compare pillar stability in these mine geometries, but to show pillar response in different dipping environments because these environments are different in pillar size, shape, and extraction ratio. Numerical modeling results indicate that dip pillars have reduced strength compared to flat pillars. The shear strength between the pillar and the surrounding rock has an impact on dipping pillar response. Dipping pillars experience high shear stresses, highly non-uniform stress distributions, and asymmetric yield pattern with more yielding compared to flat pillars. All these reasons place dipping pillars, particularly those with a small width-to-height ratio (<1) at an elevated risk of instability. The yield pattern for a flat pillar is simple while it is complex for a dipping pillar and depends on numerous parameters such as the width-to-height ratio of the pillar and seam inclination. The down-dip side of dipping pillars experiences more outward normal displacement compared to the up-dip side, while it experiences less vertical displacement. The results of this study improve the understanding of pillar stability in dipping environments and advance the ultimate goal of reducing the risk of dipping pillar instability in underground stone mines. [Description provided by NIOSH]
• Subjects:
  Mining Occupational Health Safety
• Keywords:
  Author Keywords: Dip Pillar Compressive Strength Limestone Mining Pillar Mechanics Pillar Strength Roof Supports Seam Inclination Stone Mines Underground Mining Underground Stone Pillar
• Series:
  Mining Publications
• ISSN:
  2524-3462
• Document Type:
  Text
• Genre:
  Journal Article
• Place as Subject:
  Pennsylvania ; Philadelphia Region [OSHA]
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Division:
  PMRD - Pittsburgh Mining Research Division
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  45-59
• Volume:
  42
• Issue:
  1
• NIOSHTIC Number:
  nn:20070459
• Citation:
  Min Metall Explor 2025 Feb; 42(1):45-59
• Contact Point Address:
  Gamal Rashed, CDC/NIOSH/PMRD, Pittsburgh, Pennsylvania
• Email:
  mqx3@cdc.gov
• Federal Fiscal Year:
  2025
• Peer Reviewed:
  True
• Source Full Name:
  Mining, Metallurgy & Exploration
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:3c25316186055b4304ec6bd196f3bda455580d1a8e012bee91ee0b6f2a528dd9186dfc8b56c5ffdb5ef2265de8f763670ad81e4f795a093df5d7333b5ee38732
• Download URL:
  https://stacks.cdc.gov/view/cdc/215738/cdc_215738_DS1.pdf
• File Type:
  [PDF - 3.74 MB ]