IMPACT OF GEOLOGICAL AND MINING CONDITIONS ON TO COSTS OF DRILLING THE ACCESS WORKING IN HARD COAL MINE WITHIN THE UPPER SILESIAN COAL BASIN (POLAND)

Mining investments are encumbered with a high risk and level of uncertainty. In hard coal mining plants, the geological and mining conditions of the deposit play a significant role in the appraisal of economic feasibility of the investment. In the coal mines of the Upper-Silesian Coal Basin, which are mostly several years old and some have existed for a few centuries, it is often a practice to access seams located at increasing depths, often exceeding 1000 m, which results in increasingly difficult geological and mining conditions. The conditions that render the driving of headings difficult mostly include tectonic disturbances (faulting) and variability of thickness and inclination planes of the seams. Deformations of this type may hinder the driving of the heading e.g. because of the necessity to change the heading technology to one with the application of explosives and because of the decrease in the amount of the output material from the heading. As a result, depending on the intensity of the disturbances, for technical reasons a decision may even be reached to abandon the driving of the heading in line with the previous assumptions. Moreover, natural hazards, including rock bursts, methane, temperature, fire hazard, coal dust explosion hazard, water hazard and others, hinder the exploitation. The prevention and liquidation of these hazards generate high financial costs. The article presents the analysis of geological and mining conditions in driving a sample opening-out heading (5 raise), the purpose of which was to access a part of the coal seam to be exploited using the longwall system with caving. The analysis gives consideration to the variability of the geological and mining conditions resulting from the estimations made at the stage of designing and after driving the heading. The effects of these changes on the driving costs have also been specified. The analysis of the driving costs has been made by means of grouping the costs so as to allow to cluster the expenses into work centre groups, which enables the analysis of the exploitation process in its basic elements strictly related to the geological and mining conditions. In the case in consideration, it has been exhibited that at a precise level of deposit exploration, the occurring geological disturbances did not significantly deviate from the expectations. The total costs borne in relation to prevention and liquidation of all natural hazards amounted to 6% of all costs. Unexpected natural hazards have, however, occurred - namely methane and climatic hazards. The costs of prevention and control of these hazards have not exceeded 2% of the total costs. It should, however, be assumed that a small part of these costs, which is difficult to distinguish, occurs also in other cost centres.