Roof and pillar stability prognosis in Estonian oil shale mines

The paper deals with analysis, prognosis and design methods of the mining blocks in Estonian oil shale mines where the room-and-pillar mining system is used. Investigations base on special calculation methods and rheological behavior of rock. It is demonstrated that the exponential model describes adequately the rock weakening process. The theoretical investigation showed that presented method is applicable for short-term calculations (up to 8-10 months). Method is suitable for mining block parameters designing when the relative uncertainty does not exceed 34%. Collapse prognosis is of no particular interest for practical pur poses. In this case the relative uncertainty in time is over 66%.