2004 SME Annual Meeting & Exhibit, February 23–25, Denver, Colorado
Authors: J. F. T. Agapito and L. J. Gilbride  (AAI), and K. Hollberg (OCI Wyoming, LP)

Room-and-pillar mining at the Big Island Mine uses narrow, yield (i.e., load transferring) pillars to achieve high resource recovery and productivity.  Two flat-lying 3- to 3½-meter (10- to 11½-ft) seams are mined.  The interburden between the seams is about 10 meters (33 ft) and the cover depth is 250 to 330 meters (820 to 1,080 ft).  Most of the mining has been single-seam, but two-seam mining will begin in the near future.  However, it is important that good long-term stability be maintained to prevent subsidence over a large portion of the mine beneath the Green River channel.

Three stress issues impacting stability are discussed in this paper: (1) higher-than-gravity vertical pre-mining stresses, (2) time-dependent stress transfer or arching, and (3) stresses induced by strata gas.  Although the stress environment and behavior is not fully understood, steps have been taken in mine design and operations to minimize impacts to stability.  Stress determinations have been very important to verify analytical predictions used in mine design and in long-term stability assessment.
Downloadable PDF:  Stress Issues Impacting Design and Stability at OCI Wyomings Big Island Trona Mine

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