SME Annual Meeting, Denver, Colorado, 1–3 March 1999, Preprint No. 99-8
Authors: J. F. T. Agapito and R. R. Goodrich (AAI), and M. L. Andrews (OCI Wyoming, L.P.)

Two flat-lying trona seams 3- to 3.5-m thick, approximately 10 m apart, and at depths of 250 m are mined by room-and-pillar at OCI’s Big Island Mine in Wyoming. Continuous miners and a yielding pillar system have contributed to improvements in resource recovery and productivity.

Long-term stability with minimal subsidence is needed for a large portion of the mine beneath the Green River channel. This was investigated by computer modeling in 1990. Although results of the study indicated good long-term stability, recommendations were made for stress determinations to verify the model. Stress determinations made in 1997 showed pillar stresses 10% to 20% higher than the model stresses, and barrier pillar stresses 10% to 15% lower. This implies that higher panel stresses will be transmitted from the upper to the lower seam. A stability evaluation of the lower seam is planned before two-seam mining to assess entry widths and support requirements.
Downloadable PDF:  Long-Term Stability for Two-Seam Mining at OCI Wyomings Big Island Mine

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