SME Annual Meeting, Phoenix, Arizona, 25–28 January 1988, Preprint No. 88-73
Authors: J. F. T. Agapito (AAI) and R. V. Hunter (Stauffer Chemical Company of Wyoming)
Significant increases in extraction ratio on the order of six to eight percent, equivalent to as much as 142 t/m of panel advance, have occurred at the Big Island Mine during the last five years with the help of a practical rock mechanics program. This increase in resource recovery also has contributed to improvements in productivity. Both conventional and continuous machine mining have been used to mine two flat-laying trona beds at depths of 250 to 260 m in the Green River Formation in southwestern Wyoming.
Conventional room-and-pillar mining originally was conducted in panels with extraction ratios of 58 to 60 percent. The use of yield pillars has allowed the panel extraction to increase to 66 percent. Continuous machine mining was introduced recently, with a 64 percent extraction ratio using long, narrow pillars and wide rooms. Further improvements in resource recovery seem feasible in the light of present mining experience.
The rock mechanics program consisted of field instrumentation to determine the pillar and roof response to mining, and computer modeling to evaluate and help determine the stability of various layouts, which were then adopted for mining.