Risk assessment of feasibility of roadheaders in estonian undergound mining

This paper deals with the risk assessment method of roadheader feasibility in underground conditions of Estonia mine. In modernization of Estonian underground mining, roadheaders that extract oil shale selectively play the most important role. Selective extraction allows reduction of rock mass volumes during the loading, transportation and enrichment processes. Thus, about 23% of limestone extracted together with oil shale will be left in the mine for backfilling the excavated areas. Backfilling increases carring capacity of pillars reducing losses of oil shale and restores, in a certain measure, filtrational, hydrodynamical, and aerodynamic properties of the geological environment. For selective extraction four variants of different excavation thicknesses, depending on geological conditions, have been proposed. Risk analysis allows comparison of the advantages and disadvantages of full and selective extraction. Risks of oil shale losses during selective extraction are estimated using the event tree. Preliminary calculations have shown sustainability of roadheaders for selective extraction under the mining and geological conditions of Estonia mine.