Safety of small and medium dams in permafrost regions

摘要

Safe operation and performance of dams is one of the key issues in permafrost regions. At present, the existing dams are 40–45 years old and they are reaching their design life limit. Intensive geocryological processes(thermokarst, thermal erosion, frost heaving, suffosion, concentrated seepage along the voids left by melt ice and others) begin to develop at the early stages of construction. These processes are even more intensive under severe climatic conditions of the permafrost zone due to the large thermal and moisture gradients and the resulting complex thermal stress-strain state in the structures. Determining safety criteria is a critical and difficult task in dam safety management. The existing procedures need to be continuously refined and improved depending on dam importance class. Some researchers recommend introducing process development criteria(stability, destabilization, and extremality) for more objective assessment of dam safety, in addition to the existing two condition criteria. In other words, they call for a multi-factor dam – environment interaction system. A case study of safety declaration for an existing dam is presented.