Seismic Evaluation of Existing Earth-Cored Fill Dams based on Pseudostatic and FE-Newmark Approaches |
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학술지명 한국방재학회
저자 박동순
발표일 2016-08-31
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Pseudostatic approach is still in widespread use in industry to evaluate seismic slope stability of dams. According to the revised seismic design guideline of dams in Korea, pseudostatic seismic coefficient for dams is defined as about 70% of design PGA, and allowable factor of safety (FS) is taken as 1.2. However, in terms of serviceability, permanent deformation matters rather than the FS. In this study, seismic safety of 21 existing earth-cored fill dams in Korea was re-evaluated using updated design criteria. Accordingly the suitability of pseudostatic coefficient and allowable FS was studied. A systematic procedure was applied in a row of pseudostatic limit equilibrium analyses, steady state FE (finite element) seepage analyses, equivalent-linear dynamic response analyses, and Newmark type deformation analyses. In order to reflect in-situ dynamic soil properties as input parameters, innovative in-situ shear wave velocity profiles were adopted using up-to-date geophysical surveys. A comparison between pseudostatic limit equilibrium and FE-Newmark deformation analyses yielded that for pesudostatic method with kh of 70% design PGA and allowable FS of 1.2 were found to be significantly conservative, which is believed to be considered in the revision of design guideline in the future. As a result of FE-Newmark type analyses, existing earth-cored fill dams showed a reasonably satisfactory performance under the updated design PGA. Additional sensitivity analyses showed that the amplification of ground motion within the sliding mass, the location of critical slip surface, and the internal friction angle of shell materials are the dominant factors governing permanent displacements. |