Engineering Solutions for Elimination of the Risk of Destruction of Moraine

Abstract

In the upper reaches of the Kumtor River (Kyrgyztan, Inner Tien Shan), behind the young end moraine, a new lake formed at approximately 3,735 m at the turn of the twentieth century. With the feeding glacier degrading, due to climate reasons, the volume of accumulated water mass has increased (up to 70 mln cu.m by 2013). The lake’s natural retaining dam, composed of permafrost rocks with inclusions of buried ice blocks, is subject to thermokarst processes. Conditions for possible dam failure have formed and have been developing. Such a failure will lead to the creeping and sloughing of slopes of the developing washout channel and to a debris flow, which may be catastrophic for the infrastructure and tailings dump of the operating Kumtor gold mine. Based on analysis of the developing geotechnical situation and on multi-variate consideration of possible discharge routes and various construction designs of outlet works, a phased water level drawdown (water volume reduction) of the lake via a cascade of gabion structures during summer, in a route and mode as to achieve the best technical and economic execution and minimum engineering risk, has been accepted as a solution.