Geotechnical Investigations of Mine-Induced Ground Movements in Polish Opencast Mines

Mine-induced landslide hazard in Polish opencast mines and spoil dumps are a common phenomena. It is caused by a high depth of exploitation, low strength parameters of clayey soils on the slopes and geological or groundwater triggers. In this paper chosen examples of landslides occurring in the largest Polish lignite opencast mines together with implemented investigation and remedial measures are presented. These included the latest monitoring results obtained inside EU Euracoal SLOPES project “Smarter Lignite Open Pit Engineering Solutions” conducted by six European partners. The Polish part of the investigation in this project was performed in the largest lignite opencast excavation in Europe, with a length of 13 km and a width of 3 km. Belchatow mine with a depth of 310 m is affected by numerous landslides with volumes of few thousand to 3.5 million m³. Geotechnical investigations carried out for the SLOPES project on the western slope of the mine included 100 m depth on-line shape accelerated inclinometer and pore pressure transducer at 30 m depth. The obtained data should allow for better risk management and were implemented in numerical modeling of instability associated with the pit slope.