mi.ttu.ee RISK ASSESSMENT OF GEOLOGICAL CONDITIONS FOR SELECTIVE EXTRACTION OF OIL SHALE IN “ESTONIA” MINE S. Sabanov & J.-R. Pastarus Tallinn University of Technology, Department of Mining, Estonia O. Nikitin & A. Viil Estonian Oil Shale Mining Company, AS Eesti Põlevkivi, Department of Development, Estonia

mi.ttu.ee Objectives The aim of the study is to determine aspects of selective extraction which suit for geological conditions in “Estonia” mine The results will be use for other mines according with geological conditions and supplying technology

mi.ttu.ee Immediate roof Commercial oil-shale bed Depth of excavation H=63 m Extraction thickness h = 2.8 and 3.8 m Compressive strength: oil shale 20 –40 MPa limestone 40 –80 MPa Volume density: oil shale 1.5 – 1.8 Mg/m3 limestone 2.2 – 2.6 Mg/m3 Schematic geological section of the oil shale bed in mining block 3104 “Estonia” mine

mi.ttu.ee B + C 13% limestone A +B +C limestone 27% Selective mining Go to backfill 79 % of limestone Go to backfill 86 % of limestone A + A1 52% limestone Go to backfill 63 % of limestone I II III IV Extraction 1 Extraction 2

mi.ttu.ee Limestone from seams goes to enrichment

mi.ttu.ee For all geological condition and all type of roadheaders («Roaheader application in mining and tunneling industries» H. Copur, L. Ozdemir, J. Rostami) UCS – Uniaxial compressive strength, ICR- Instantaneous cutting rate

mi.ttu.ee Event tree for variant 1 of selective extraction

mi.ttu.ee Event tree for variant 2 of selective extraction

mi.ttu.ee Conclusions Selective extraction allows reduction of rock mass volumes during the loading, transportation and enrichment processes. Thus, about 25% of the limestone accompanying the extracting processes will be left in the mine for backfill in the excavated areas. Such a way of development will considerably reduce storing of rock waste on the ground surface and decrease harmful influence on the environment. Preliminary calculations have shown sustainability of selective extraction for the room and pillars method under the geological condition of “Estonia” mine

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