Economics of underground conversion in an operating limestone mine

This thesis deals with the appraisal of the economics of underground conversion in surface limestone mining operations. Software that predicts the time at which an open pit operation should be converted to underground extraction has been developed. The software is based on estimates of capital expenditures required for the underground conversion and for future equipment acquisitions and replacements under both open pit and underground operating alternatives, as well as long-term operating cost estimates for both alternatives. Open pit and underground cost estimates can be entered either directly, or estimated using O'Hara and Suboleski's (1992) cost estimation equations. It is assumed that an underground source of limestone is accessible and that its extraction is technically feasible. The program determines the cost-flow profile of each alternative and compares their present worth equivalents at yearly intervals over a pre-determined period of analysis. The program reports the optimum time for the conversion, if indeed it exists.;The report starts with a review of limestone and dolomite as mineral commodities. This is followed by a brief literature review relating to underground conversion of surface mining operations. Mining methods and costs related to industrial minerals are then described and discussed. The thesis concludes with a detailed description of the software and a hypothetical case study.