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Pillar design and strategies for retreat mining.

Chase FE; Mark C
Improving safety at small underground mines. Peters RH ed. Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, SP 18-94, 1994 Jan; :15-23
Information gathered during this investigation lends credence to the following conclusions: 1. Properly sized production pillars that are designed considering the front and/or side abutment pressures generated by gob creation can result in better miner safety and more efficient recovery of reserves. 2. Case histories analyzed using the ARMPS method examined an extensive range of geographic locations, depths of cover, width-to-height ratios, roof rock cavability characteristics, floor conditions, and extraction methods that are representative of the population as a whole. It appears that production pillars with an ARMPS SF of 1.50 or greater have a high probability of being extracted without a problem. 3. Multiple-seam interactions can have detrimental effects on pillar line stability. The effect is dependent upon the sequence in which the seams are mined, the thickness and geology of the interburden, overburden, and the presence of production pillars or stumps left in the gob. 4. Normally stable pillar line conditions often deteriorate if the pillar line moves slowly or remains idle for an extended amount of time. This deterioration can manifest itself in the form of excessive sloughage, heave, and squeezes. 5. Airblasts or squeezes have occurred in mines that have competent and massive roof rock units that will not cave. If partial pillaring is to be conducted under competent roof that will not cave, the long-term stability of the gobbed-out area should be considered. This can be accomplished either by increasing the size of the production pillar remnants or by leaving rows of unsplit pillars as barriers between smaller areas of split pillars.
Mining-industry; Miners; Safety-measures; Underground-miners; Underground-mining
Publication Date
Document Type
Conference/Symposia Proceedings
Fiscal Year
NIOSH Division
Source Name
Improving safety at small underground mines
Page last reviewed: March 25, 2022
Content source: National Institute for Occupational Safety and Health Education and Information Division