The methane hazard concerns a growing number of longwalls in the Polish coal mining industry each year. Mitigating this hazard, both of work safety and economic reasons requires the application of preventive measures adequate to its level. Commonly threat level is estimated based on registered methane concentrations, which fluctuate and highly depends on the place of measurement. The article presents studies on the average and maximum methane concentrations at the longwall outlet, including analyses of the interdependence of methane concentration in methanometry sensors installation locations.
The article describes the recommended procedure for conducting methane forecasts and selection of the methane prevention measures that adequately reflect the level of risk of methane combustion and explosion. The appropriate selection of measures to prevent methane exposure can be effective at mitigating the exposure risk of the miners and other mine employees. Implementation of these measures can have the additional benefit of increasing mine output and efficiency. For example, prediction of methane concentrations can reduce the instances of unplanned equipment downtime to maintain mine safety and integrity. The presented procedure is the culmination of extensive research on three predictive models of short-term average methane concentrations. Identifying the advantages and disadvantages of the models became possible by verifying the models against a nearly 500-day dataset obtained from 7 longwalls with identified significant methane content. Furthermore, selected studies were presented based on one of the datasets obtained from the U-ventilated longwall.
Abstract.One of the ways to protect objects exposed to the influences of mining exploitation is establishing protective pillars for them. Properly determined pillar provides effective protection of the object for which it was established. Determining correct dimensions of a pillar requires taking into account contradictory requirements. Protection measures against the excessive influences of mining exploitation require designing the largest possible pillars, whereas economic requirements suggest a maximum reduction of the size of resources left in the pillar. This paper presents algorithms and programs developed for determining optimal dimensions of protective pillars for surface objects and shafts. The issue of designing a protective pillar was treated as a nonlinear programming task. The objective function are the resources left in a pillar while nonlinear limitations are the deformation values evoked by the mining exploitation. Resources in the pillar may be weighted e.g. by calorific value or by the inverse of output costs. The possibility of designing pillars of any polygon shape was taken into account. Because of the applied exploitation technologies the rectangular pillar shape should be considered more advantageous than the oval one, though it does not ensure the minimization of resources left in a pillar. In this article there is also presented a different approach to the design of protective pillars, which instead of fixing the pillar boundaries in subsequent seams, the length of longwall panels of the designed mining exploitation is limited in a way that ensures the effective protection of an object while maximizing the extraction ratio of the deposit.
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