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Browsing by Author "Patrick, William Charles"

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    Investigation, Analysis, and Modeling of Longwall Face-to-Face Transfers
    Patrick, William Charles (Virginia Tech, 1993)
    This dissertation reports on research efforts to investigate, analyze, and model longwall face-to-face transfers through the use of operations research techniques. The purpose is to reduce overall transfer time and the variation of transfer times among operations within the U. S. longwall industry. The research includes: (1) investigation of existing longwall transfers to determine standard and variant procedures; (2) development of comprehensive activity sequence models of existing longwall transfers; (3) generation of a simulation model for longwall transfers in various geological and mining conditions; and, (4) investigation of the economic feasibility of time-cost tradeoffs in the transfer procedure. Face transfer field data were collected from three eastern U.S. mining operations. From these data, general operational characteristics, transfer personnel utilization, and transfer procedures are described. A comparison of methods provide a breakdown of transfer activities, identify critical activities, and establish the state-of-the-art in transfer technology. Project scheduling models are developed for each operation using precedence networking analytical techniques and are applied through a computerized commercial software package. The project scheduling models accurately represent each of the operations' transfer procedures and provide information on the criticality of transfer activities and estimated project duration. Simulation models are developed, using Monte Carlo techniques, to combine analytical project scheduling with probability-based transfer activity durations. The simulation models closely match the results of the project scheduling models and provide information on the statistical tendencies of critical activities, paths, and project durations. The economic feasibility of reducing transfer time is analytically evaluated by collapsing critical activities and attempting an alternative roof control method. When compared to the lost production potential of longwall mining systems, the two time-cost trade-off procedures are proven, by the transfer simulation model, to be economically viable. This research is expected to contribute to the longwall mining industry by offering an objective approach that can be used in the prediction, planning, preparation, and implementation of longwall face equipment transfers.