Gorny Klyuch LLC, Moscow, Russia:

N. V. Korobovsky, Chairman of the Board of Directors

Vertex Gold Company, Bishkek, Kyrgyzstan:
E. A. Babkin, Head of Geotechnical Department, e.babkin@gam.kg
K. K. Zhakanov, Deputy Head of Geotechnical Department—Chief Geotechnical Engineer in Open Pit Mining
D. A. Plaksin, Leading Specialist in Modeling and Hydrogeology

The article presents the monitoring data of a landslide happened under an overburden dump at the Bel-Alma coal deposit in Kyrgyzstan. The landslide took place in August 2020 during formation of the western dump 30 m high and 25 m wide. The volume of the dump by the moment of landsliding was round 100 km³. The monitoring data show that not less than 30–40 % of piled overburden rocks have crept down as a landslide for 650 m long. In 2021 the landslide monitoring included continuous visual inspection of the landslide and the dump. The situation was very complex as stripping continued and the dump grew and widened, although dumping was mostly carried out westward the landslide. The data available are used in modeling various possible scenarios, and the modeling results per different cross-sections are described. The modeling shows that the slope stability number drops to 0.921 when the modeling is added with the ground water table after long-term fallout. Thin and weakly cohesive overburden reduces the slope stability number to 0.807. The least stable site lies in the area of the landslide. The recommendations are given for the further observation of the landslide and the dumping process. In particular, it is proposed to revise the project parameters of the dumps. With a view to avoiding possible subsidence, it is required to construct a buttress at the dump bottom. Furthermore, it is required to monitor water flows and accumulations of water, and to ensure water withdrawal from the body of the landslide.

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