Fracture Geometries in Three Ore Bodies Mined by Undercut Caving as Determined from Oriented Drill Core and Scanline Mapping

Louis Anthony Panek · Michael T. Melvin

Jan 1987 · U.S. Department of the Interior, Bureau of Mines

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Block carving, a low-cost method of mining large low-grade deposits, has the potential for application to a larger class of mineral deposits than has been attempted heretofore, provided that quantitative methods can be developed to predict the span required to induce caving and the size distribution of the caved fragments. Prerequisite to employing a numerical method of structural analysis to evaluate the stability or failure of the rock mass in the vicinity of an excavation are the specifications of rock mass strength and fracturing (jointing). This Bureau of Mines report characterizes the fracturing geometries in three ore bodies that are mined by undercut-cave methods, utilizing data that were generated by measurements on oriented diamond drill cores and along multiple scanlines on underground exposures. Procedures employed for data acquisition and for data analysis are described in detail. Numerous polar equal-area plots of fracture orientation and histograms of fracture spacing, obtained by Bureau-developed codes FRACTAN and GDIST, are presented. Fracture-trace-length estimates are derived from the multiple-scanline mapping measurements, a new procedure.