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Yielding pillar gate road design considerations for longwall mining.

New technology for longwall ground control. Proceedings: U.S. Bureau of Mines Technology Transfer Seminar. Pittsburgh, PA: U.S. Bureau of Mines, 1994 Aug; :19-36
With the ever present pressures to both expedite longwall gate road development and optimize panel entry stability, the use of yield pillars, either alone or in combination with larger, stiff abutment pillars, has become a topic of considerable interest worldwide. To help provide mine operators with a clearer understanding of the successful application of yielding gate road systems, this paper summarizes western U.S. longwalling experiences with yield pillar design, artificial support installation, entry configurations, and the general degree of gate stability achieved for various mining settings. Additionally, the concepts of the "critical pillar" and "optimum-time-to-yeidl" are discussed, and a brief qualitative analysis of a limited database is presented that demonstrates a potentially high correlation between a number of mining parameters and the stability performance of the yielding entry system. Preliminary conclusions drawn from this cursory evaluation include the following: no successful yield pillar designs were achieved in settings where the Coal Mine Roof Rating (CMRR) (5) superscript 2 was less than 50 (on a scale of 0 to 100). No successful yield pillar designs employed width-to-height ratios (w/h) greater than 5. Mining depth and floor quality are largely insignificant where the performance of yielding designs are concerned, but greatly influence whether a critical pillar design will bump violently or damage roof and floor members due to pillar punching. While U.S. Bureau of Mines (USBM) research continues to develop a proven, comprehensive design methodology for yielding gate road systems, this report serves as a summary reference in support of the emerging acceptance of yield pillar usage in U.S. longwalling.
Longwall-mining; Mining-industry; Ground-control; Ground-stability; Geology; Computer-software; Computer-models
Publication Date
Document Type
Book or book chapter
Mark-C; Tuchman-RJ; Repsher-RC; Simon-CL
Fiscal Year
NIOSH Division
Source Name
New technology for longwall ground control. Proceedings: U.S. Bureau of Mines Technology Transfer Seminar.
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division