GEOTECHNICAL PROCESSES IN CLOSED OIL SHALE MINES

• Published in: Oil shale (Tallinn, Estonia : 1984) Vol. 20; no. 3S; pp. 398 - 403
• Main Authors: Reinsalu, E, Valgma, I
• Format: Journal Article
• Language: English
• Published: Estonian Academy Publishers 01.01.2003
• ISSN: 0208-189X
• DOI: 10.3176/oil.2003.3S.14

During the years 1998-2001 geotechnical processes in closed underground oil shale mines and opencasts were investigated. In addition to kukersite oil shale deposit, the closed Sillamae uranium (Dictyonema shale) mine was prospected. The main tools and methods included mine plans, aerial photographs and Geographical Information System data. 290 [km.sup.2] of underground and 130 [km.sup.2] of strip-mined areas were studied. The mining maps of Estonian underground and surface mines were created. The stability of underground mined area, where room-and-pillar method was used, was the main objective of the study. It was studied with the help of aerial photographs, mine drawings, maps of quaternary sediments and mathematical modeling of rock failure. The main results are: 20% of subsidences remain undiscovered and 42% of subsidence occurrences have no remarkable influence to the land cover; the probability of subsidence remains and may increase in the case of mine drowning. As several mines will be closed during the next few years, the problems of drowned waste (which were not subjects of this study) are going to be more actual than before: increasing underground water level, pollution of underground water, formation of technogenic water sources, overflooding of reclaimed areas, etc.