Design Methods in Rock Mechanics, Proceedings of the 16th U.S. Symposium on Rock Mechanics, University of Minnesota, Minneapolis, September 1975
Authors: M. P. Hardy and J. F. T. Agapito (Golder Associates, Inc.)
The Colony pilot mine provided valuable pillar strengths that should form the basis of any subsequent mine designs. As no commercial oil shale mine has yet been developed, neither a comprehensive empirical pillar strength formula can be developed, nor a proposed empirical formula tested. This paper summarizes the strength data available for oil shale pillars and suggests a strength formula similar to that in common usage for coal pillar design, but with constants compatible with the pillar strength available data in oil shale. Confidence in the use of this formula is limited to situations where the ground conditions are similar to that at the Colony pilot mine, so in application of this formula to a new oil shale area, a comprehensive geotechnical data collection program must be undertaken so that a valid comparison can be made. The paper points out the possible conservative nature of the strength formula for barrier pillar design where the pillar width to height ratio is high. Finally, additional stress measurements and back analysis in existing and planned pilot mines is encouraged to improve pillar strength design formulae and to clarify the interaction of individual pillars in the mine.