Induced gravity anomalies and seismic energy as a basis for prediction of mining tremors
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The results of prediction of occurrence of mining tremors and bursts in the course of the exploitation of the remaining part of the hard coal in seam 510 of the mine “Pstrowski”, Upper Silesia, have been presented in the paper. The exploitation has taken place under extremely difficult conditions hazardous for the mining crew.
To predict the occurrence of mining tremors, bursts and direction of migration of increased elastic strain in the rock mass, the microgravity method has been applied.
The microgravity observations were carried out in the measurement points located at mutual distances equal 20 m in three profiles of the lengths 700 m, 760 m and 260 m respectively. The profiles were located in mining workings in the vicinity of the exploited part of the bed. In the course of exploitation, lasting 25 months, 29 series of measurements including 3600 individual microgravity observations were carried out. Microgravity observations were made with a Worden-Master gravimeter.
The observed time changes of gravity microanomalies were essential for prediction. Local negative changes of gravity microanomalies signalled the approaching mining tremor. The tremor would cover an area of the radius 60 m to 100 m. The regional time changes of the gravity microanomalies appearing as linear trends of these anomalies signalled the development of the fields of elastic strain in the whole investigated area and the approaching violent release of elastic strain energy from the rock mass.
The values of the amplitudes AMP of the above-mentioned trend were the measure of this hazard. In the course of the investigations each shock was preceded by considerably increased values of AMP.
Key wordsMining-tremors underground gravity measurements time changes of gravity
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- Bieniawski, Z. T. (1967),Mechanism of Brittle Fracture of Rocks, Int. J. Rock Mech. and Min. Sci.4, 395–430.Google Scholar
- Casten, U. (1982),Gravimetrische Untersuchungen zur Erfassung bergbaubedingter Dichteänderungen im Gebirge, Glückauf118, 653–657.Google Scholar
- Casten, U. (1984),Subsurface Gravity Measurements to Demonstrate Mining-induced Changes in Rock Density, Geophysikai Kozlemenyek30, 227–236.Google Scholar
- Casten, U. andFajklewicz, Z. (1986),Die Überwachung gebirgsschlaggefährdeter Bereiche mit der Mikrogravimetrie, Glückauf-Forsch. H.47, 290–295.Google Scholar
- Fajklewicz, Z. (1975),Vertical Sections of the Gravity Field and Their Relations to the Rock Mass Deformations (in Polish). Scient. Papers, Cracow University of Mining and Metallurgy522, Mining Section 76.Google Scholar
- Fajklewicz, Z. (1980a),Time Changes of Gravity and Their Relation to the Rock Mass Exploitation (in Polish). Publ. Inst. Geophys. Pol. Acad. Sc.M-3 (134), 191–199.Google Scholar
- Fajklewicz, Z. (1980b),Mining Microgravimetry (in Polish). Publ. Home Slask, Kotowice.Google Scholar
- Fajlkewicz, Z. (1981),First Attempts at Prediction of Mining Tremors by the Microgravity Method (in Polish). Prze. Górn.37, 517–525.Google Scholar
- Fajklewicz, Z. (1982),Genesis of Gravity Time Changes Preceding Mining Tremors (in Polish). Ochr. Teren. Górn., Year XVII, No. 64, 3–10.Google Scholar
- Fajklewicz, Z. (1983),Rock Burst Forecasting and Genetic Research in Coal Mines by Microgravity Method. Geophys. Prosp.31, 748–765.Google Scholar
- Fajklewicz, Z. (1986),Origin of the Anomalies of Gravity and its Vertical Gradient over Cavities in Brittle Rock. Geophys Prosp.34, 1233–1255.Google Scholar
- Fajklewicz, Z., Gliński, A., andSliz, J. (1982),Some Application of the Underground Tower Gravity Vertical Gradient, Geophysics47, 1688–1692.Google Scholar
- Fajklewicz, Z. andJakiel, K. (1986),Prediction of Mining Tremors by the Microgravity Method in Hard Coal Mine Pstrowski (in Polish), Publs. Inst. Geophys. Pol. Acad. Sc.M-8 (191), 103–124.Google Scholar
- Fajklewicz, Z., Jakiel, K., andOstrowski, C. (1981),Results of the Prediction of Mining Tremors and Rock Mass Deformations by the Microgravity Method in the Mine “Szombierki” (in Polish), Prze. Górn.38, 121–125.Google Scholar
- Fajklewicz, Z., Jakiel, K., andOstrowski, C. (1986),Results of Prediction of Rock Bursts and Rock Mass Deformations by the Microgravity Method. SME's 1986 Annual Bound Volume of Transactions, 200–203.Google Scholar
- Mjachkin, V. I., Brace, W. F., Sobolew, G. A., andDietrich, J. K. (1975),Two Models for Earthquake Forerunners, Pure Appl. Geophys.113, 169–181.Google Scholar
- Zuberek, W. (1980),Models of the Rock Burst Process (in Polish), Proc. Symp. Geophysics for the Needs of Upper Silesia, Międzybrodzie Zywieckie, October 9–11, 1980, Paper 7, 1–20.Google Scholar