Mining in a landslide - Is it possible? Geotechnical investigation and analysis

This paper presents a case study of a large open pit lignite mine excavation taking place on a moving landslide. The Mavropigi mine in Northern Greece has reached depths of more than 120m from the ground surface and produces a substantial amount of lignite for an adjacent power plant. The lignite is important for the power supply of Greece and the mine must constantly operate. The southwest slopes of the mine started moving after 2011 and large tension cracks appeared in the ground surface. The landslide has reached displacement values of more than 8m until today. This paper presents the geotechnical investigation conducted for the evaluation of the sliding mass, which consisted of boreholes, inclinometers, survey measurements, inSAR and geophysical investigation. Based on the information gathered from the investigation a detailed geological - geotechnical - kinematic model of the sliding mass was proposed and validated with the execution of limit equilibrium back analysis. The verified model was then used to provide the appropriate excavation balance between the toe and the crest for the mine to continue operation even with moving slopes but with controlled displacements.