ASSESSMENT OF LONG-TERM DEFORMATIONS OF ATATURK DAM

The 170 m high Ataturk rockfill dam was completed in 1990 and dam safety has been monitored continuously since then. The monitoring system comprises visual inspections, comprehensive geodetic surveys, and various types of sensors and instruments. For the safety monitoring, a detailed finite element (FE) model of a representative section of the dam was created, in which slip movements were allowed at the core-filter and filter-rockfill interfaces. The elasto-plastic model was assumed for the main dam materials. The material properties were determined based on laboratory tests, published data, and engineering judgment. Two basic load cases were considered, i.e. (i) dead load and (ii) water load. The geodetically measured dam displacements could be fitted satisfactorily with a linear combination, with time-dependent coefficients, of the computed displacements due to the gravity and water loads obtained from the FE analysis. It was further shown that the history of the time-dependent coefficients, which represented the creep-type post-construction deformations of the dam, could be fitted with asymptotic exponential trends. This model was calibrated based on displacements measured until the year 2000. The calibrated model was used to predict the dam displacements for a period of ten years. The dam displacements measured since 2001 show good agreement with the predicted values. This comparison of measured and predicted displacements is most beneficial for the safety monitoring of the Ataturk dam. The calibrated dam model allows an insight into the processes in the dam body that lead to the observed deformations of the dam surface. However, the physical phenomena responsible for the creep deformations have to be studied by separate laboratory tests. The possible effect of the increase of the reservoir water level on the dam deformations could also be estimated using the calibrated dam model.