Landslide Monitoring and Counteraction Technologies in Polish Lignite Opencast Mines

Abstract

The paper presents slope instabilities together with monitoring and counteraction techniques in lignite opencast mines. It includes examples of landslides in two of the largest open-pit mines and external spoil dumps in Poland. The Belchatow mine, one of the largest excavations in Europe, is located in the central part of Poland and has lignite resources of 2 bln tons and an annual production of 42 mln tons. Landslides are registered there every year. The largest with a volume of a few thousand to 3.5 mln m3 with displacements of 2 mm-2 m per day. In the past, similar threats have occurred at the Turow mine, the second largest in Poland. It is located in the Lower Silesia District, close to the German and Czech borders. Its estimated lignite reserves are equal to 760 mln tons, with an annual production of 27.7 mln tons. In previous years, the author of this paper had the opportunity to participate in parts of landslide investigations at these mines. The research included CPTU in situ tests, laboratory tests, displacement monitoring and numerical modelling. It was difficult to come up with an interpretation of soil strength parameters. Dump soils varied in strength due to their anthropogenetic nature. The interpretation of the clayey soils parameters in the pit was complicated because of high preconsolidation and partial saturation. The new Euracoal Slopes Project conducted by an international consortium of six European countries aims for the practical implementation of new geotechnical monitoring methods. Complementary methods should allow for better prediction of landslide activity. PSI interferometry, UAV and ground-based laser scanning, in situ monitoring, shallow geophysics and laboratory triaxial and centrifuge testing should deliver new data for slope stability analysis. Although the mines have advanced monitoring systems and remediation procedures, the full elimination of hazards in mines of this size and depth is not possible.