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Evaluation of the strength of slender pillars.

Authors
Esterhuizen-GS
Source
Trans Soc Min Metal Explor 2006 Jan; 320:69-76
NIOSHTIC No.
20032623
Abstract
Pillars with width-to-height ratios of less than 1.0 are frequently created in underground hard-rock mines. The strength of slender pillars can be estimated using empirically developed equations. However, the equations can provide variable results when the width-to-height ratios approach 0.5. This paper investigates some of the issues affecting pillar strength at low width-to-height ratios in hard, brittle rock. The investigation includes an evaluation of empirical pillar strength data presented in the literature and observations of pillar performance in underground limestone mines in the Eastern United States, supplemented by numerical modeling in which failure processes and sensitivity of slender pillars to variations in rock mass properties are evaluated. The results showed that the strength of slender pillars is more variable than that of wider pillars. The numerical model results demonstrated the increasing role of brittle rock failure in slender pillar strength. The absence of confinement in slender pillars can result in a fully brittle failure process, while wider pillars fail in a combined brittle and shearing mode. The onset of spalling in slender pillars occurs at or near the ultimate strength, while this is not the case for wider pillars. Slender pillars are shown to be more sensitive to the presence of discontinuities than wider pillars, which can partly explain the increased variability of slender pillar strength. Two examples are presented that illustrate failure initiation by brittle spalling and the sensitivity of slender pillars to the presence of discontinuities.
Keywords
Mining-industry; Underground-mining; Safety-research; Hazards; Hard-rock-mines; Stone-mines; Nonmetal-mining; Room-and-pillar-mining; Models; Metal-mining; Ground-control
Contact
NIOSH Pittsburgh Research Laboratory, P.O. Box 18070, Pittsburgh, PA 15236
CODEN
TMENAE
Publication Date
20060101
Document Type
Journal Article
Editors
Yernberg-WR
Fiscal Year
2006
NTIS Accession No.
NTIS Price
ISBN No.
0873352556
ISSN
1075-8623
NIOSH Division
PRL
Priority Area
Disease and Injury: Traumatic Injuries
Source Name
Transactions of the Society for Mining, Metallurgy, and Exploration
State
PA; TN
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