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SEISMIC ACTIVITY INFLUENCE ON CONVERGENCE OF MINE WORKINGS-CASE STUDY FROM A POLISH COPPER ORE MINE

Anna Gogolewska

Abstract

The copper ore deposit in Poland is extracted by three underground mines which belong to KGHM Polish Copper JSC. Since the very beginning, copper ore mining has been accompanied by seismic activity and rock-burst hazard controlled by means of several prevention activities aiming at assessing and combating the danger. Seismology is the prime method to measure seismic activity i.e. the number and energy of rock mass shocks. The hazard monitoring also encompasses measurements of the convergence of mine workings, i.e. their squeezing. The convergence means changes in dimensions of mined-out empty space as a consequence of its squeezing. An increase in the convergence indicates an increase in the crushing of excavations. The convergence can be linear, surface or volume. The linear shows changes in vertical or horizontal dimensions of excavations. The vertical is used to recognize the rock-burst hazard in KGHM?s mines. It can reflect the relaxation of the rock mass, deformation of the surroundings, deformation of the excavation walls and show the effects that may be caused by diversified mining conditions around the mining panel. Upon observing changes in the convergence over time, one can determine the progress of the excavation deformation and predict its shape. Moreover it has been claimed that the increase in the seismic risk may be indicated by the convergence increase, vanishing or irregular course. The paper depicts an attempt to determine the relationship between changes in the vertical linear convergence of excavations and seismic activity of rock mass as well as rock-burst prevention effectiveness. The analysis makes it possible to check whether the convergence is closely related with the seismic activity. The investigation was carried out in one mining division of mid seismic activity in the Polkowice-Sieroszowice copper ore mine. The convergence was analyzed over the periods of high and low seismic activity. The changes in the 30-day (over the last 30 days) and in the 24-hour vertical convergence were described. The substantial changes and sudden disappearance of the convergence were considered in detail. The connection between the vertical convergence and the seismic energy was determined. The convergence variability was correlated with the effectiveness of the active and technological rock-burst prevention.

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