BLAST VIBRATIONS IN OIL SHALE UNDERGROUND MINING
A. TOOMIK
Institute of Ecology
North-East Estonian Department
15 Pargi St., Jõhvi
EE0045 Estonia
T. TOMBERG
Tallinn Technical University
Mining Institute
Tallinn, Estonia
| The blasting is the predominating method of braking mineable rocks in oil shale mines. Regardless of fewer weights of charges than in opencast mining due to shallow location of mineable seam, the distance to possible endangered objects is short. The vibrations were studied in the soil of Quaternary sediments and in Ordovician limestone in the level of underground blasting. The measurements were performed by seismographs DS-277 Blast-Mate Series II of Instantel Inc. and UVS-1500 of ABEM Instruments AB. The results pointed more intensive vibration decay in vertical direction, transversely to overburden strata than in horizontal direction. The formulas for prediction of vibration velocity and for maximum permitted charge weights were elaborated for basic rocks (limestone) and for soil, for minimum and maximum blasting depths. |