Design Optimization in Underground Coal Systems. Volume III. Structural Characterization of Coal. Final Technical Report as of February 28, 1981

摘要

Although it appears to be a simple concept, the uniaxial compressive strength is a rather complex parameter and much influenced by a broad range of variables, most of which are extremely difficult to isolate and quantify. During the investigation, an extensive number of specimens, representing 14 major coal seams in the nation, were tested and the following results were obtained: coal strength is dependent upon the loading rate, recommended range 50 to 150 psi/sec; results indicated a random distribution of uniaxial compressive strength regarding the moisture content; the elastic modulus appeared to be independent of the specimen size; given equivalent areas and W/H ratios, a difference existed between the strengths of cubical and cylindrical specimens; and when applied to the Holland-Gaddy pillar design equations, this strength difference can substantially alter pillar sizes and hence the extraction ratio. Based on this research effort, a procedure was developed for modifying the traditional pillar-design equation so that it may be used in conjunction with drill-core strength data. An example is presented to illustrate the application of this approach. Such a procedure may prove invaluable when developing new mining properties for which cubical coal samples are not available. (ERA citation 06:015234)