Comparison of Pseudo-Static and Dynamic Response Analysis of Sibilu Dam

No Thumbnail Available



Journal Title

Journal ISSN

Volume Title


Addis Ababa University


Dynamic loads induced by earthquakes are often major factors in the design of earth dams. Earthquake induced stresses are major factors in determining the angles of the dam slopes and significantly influence the selection of materials, the zoning of the dam, and the construction method. Awareness about more rigorous seismic stability analysis is also growing during recent years. In Ethiopia dams are being constructed for various purposes. The analysis and design of dams has been carried out by taking many factors in to account. Among these factors earthquake effect is considered mainly for major dams. One of these dams is the Sibilu Dam, which is under design for the Addis Ababa water supply. Until the present, in Ethiopia, seismic effect is commonly considered by the pseudo-static analysis method. But representation of the complex, transient and dynamic effects of earthquake shaking by constant pseudo-static forces is obviously not accurate. In this thesis an attempt was made to compare the pseudo-static and dynamic response analysis by taking the Sibilu Dam as a case study. The main purpose of the study is to show the shortcomings of the pseudo-static analysis method as compared to the dynamic response analysis when applied to the analysis of earth/ rock fill dams. The thesis is organized as follows: initially a background is given on seismicity and seismic hazards in general and Ethiopia in particular. The second chapter covers summary of previous works related to this study. In the third chapter some description is given about the Sibilu Dam, the dam under the case study. In chapter four, the definition of the expected seismic excitation for the dam site is presented. The historical records of earthquake events are collected and geotechnical data of the dam site are reviewed 2 paying special attention to the location of active faults. The obtained data set is analyzed to give the required earthquake parameter for two different return periods. In fifth chapter, the pseudo-static slope stability analysis is done with the conventional limit equilibrium method by using the design ground motion as an input. The analysis is performed for the upstream and down stream slopes of the dam by varying the possible critical cases. In chapter six, analysis and design is done based on permissible deformation. The dynamic response analysis is done by varying the material behavior. Non-linearity is considered by the Equivalent Linear Method. Finally, comparison of the different analysis methods is made and conclusions and recommendations are drawn.



Response Analysis of Sibilu Dam