Statistical analysis of long-term earth dam settlements

Earth dams are widely used nowadays for water supply, irrigation and hydroelectric power generation. They are an integral part of modern society’s infrastructure and good construction is essential. Given their long lifetime, robust systems for continuous monitoring should be in place for long-term performance evaluation. Earth dams may sustain significant settlements or deformations over time, and these may be due to a number of different factors, such as earthquakes, climate change, unexpected ground conditions etc. Controlling the long-term settlements of earth dams is a critical issue for long-term monitoring and maintenance. This is important for determining the expected freeboard loss, any excessive seepage flow and dam slope deformation patterns. In addition to the magnitude of crest settlements, one needs to understand their spatial and temporal variation patterns which are usually related to different environmental factors. This paper presents long-term (> 25 years) monitoring data from the Kouris earth dam, which is the largest dam in Cyprus. An array of instruments was installed at the crest of the dam and time-domain processing and analysis is performed. A frequency-domain analysis is also performed which reveals a dominant frequency of the monitoring crest settlements which appears to be compatible with the dominant frequency of the reservoir fluctuations. It is therefore shown that the dam crest settlement variations are very strongly related to the reservoir changes. Comments are also made regarding the applicability of different frequency-domain analysis techniques.