Preliminary Abutment Stability Analysis for Tekeze Dam, Ethiopia

Tekeze Dam is a variable radius, thin arch structure with a height of 188 meters and is a major component of the Tekeze Hydropower Project, currently under construction on the Tekeze River in northern Ethiopia. During construction, significant differences were found between the pre-design and actual bedrock surface topography in the upper left abutment which resulted in adverse geometrical configurations between the dam and foundation bedrock. The conditions prompted concerns that the upper left abutment would lack sufficient mass to fully support the design loads. A systematic analytical approach was adopted to address each of the potential failure modes and identify the controlling failure mechanism in order to evaluate mitigation options to improve abutment stability. Block theory, kinematic and finite element analyses (FEA) were performed for a number of potential scenarios and configurations. The analyses indicated that although key block failure and progressive slope failures are feasible modes, the significant lack of rock mass confinement in the upper 55 m of the abutment is the controlling failure mechanism. These results strongly suggested that support or treatment measures of the upper left abutment ridge would be required to adequately reinforce and/or stabilize the rock mass and prevent excessive deformations that could potentially destabilize the dam foundation. 22 pp., 14 references.