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Cabala, J., L. Teper & T. Rutkowski (2004). Rock-mass deformation caused by zinc and lead ores mining in the Olkusz region (southern Poland). Acta Geodynamica et Geomaterialia 1, 1 (133), 47-58.

Abstract

In the Olkusz district the underground mining operation of zinc and lead ores has been being carried out continuously since 1970s. Shallow ore deposits from 60 to 150 metres deep have been extracted. The area of about 15 square kilometers around towns such as Olkusz, Bukowno and Boleslaw is affected by mining activity. The lower Triassic ore-bearing dolomites have been exploited. Ore beds are covered by weak dolomites of the middle Triassic age, then by plastic, argilloceous and carbonate sediments of the Keuper and finally by Quaternary sands of 50-60 thick. Up to the middle 1990s stope-pillar system with falling roof liquidation was used. Nowadays the exploitation is carried out using stope-pillar and shortwall systems with hydraulic backfilling.

In the paper the results of continuous and discountinuous deformations study are presented. The deformations of the ground surface were formed in the period from 1980 to 2002. Some of them, such as conical pot holes, depressions, cracks and scars, as well as edges like scarps and combs, have been observed in the studied area. The depth of some structures reached 25 metres and their areal dimension achieved about 500 square metres in several places. Continuous deformations might be formed as basin structures with subsidence amplitudes ranging from 500 to 600 mm. The deformations were frequently filled up with Quaternary sands from the cover. The model of the deformation development has been established.

As the result of tremors caused by blasting and other workings effect, physical and mechanical features of the Triassic complex have been changed in the close vicinity of face headings. In this region drainage of waters can be of the great importance having influence on the rockmass state.

Knowledge of the deformation development plays important role for correct planning in building engineering and to recognize the occurrence of new hydraulic contacts of the Quaternary water horizons with Triassic aquifer. Reclamation of post-mining areas will be particularly important after closing the last operating zinc and lead mine in this region what is expected in a few years.

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