Slope stability assessment of reclaimed lignite mines for the creation of pit-lakes - The case of Lake Most, Czech Republic

The present study examines the stability of an artificial lake, which was created for the reclamation of a 100 m deep surface lignite mine. For the geotechnical evaluation, 24 CPTu tests were utilized to estimate the undrained shear strength (cu) of the surrounding, mainly fine-grained, spoil materials. Comprehensive parametric analyses were conducted, taking into account the stratigraphy and the possible presence of a weak zone (of low shear strength) at the base of the spoil materials. Based on the results, stability issues are observed only in slopes with an inclined weak zone (towards the excavation) of 3 ° and a height greater than 60 m, as well as in slopes with a horizontal weak zone and a height greater than 120 m.