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Dynamic Analysis and Liquefaction Evaluation of Earth Dams, Mahabad Dam case Study

Fallah Moshfeghi, Sogol | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42099 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Jafarzadeh, Fardin
  7. Abstract:
  8. Liquefaction due to the earthquake loading is one of the most important threats in the earth structure. Analysis of liquefaction of structures such as dam/foundation systems utilizing numerical methods such as finite difference and finite element, can considerably determine the real response of the structures during strong ground motions. Mahabad rockfill dam, located in upper vicinity of Mahabad city, in North-West of Iran, completed and impounded in 1970. This embankment dam was designed as a zoned dam with a slightly inclined impervious clay core and 47.5 m in height. Studying such structures, which have been designed with simple methods in olden times, can recognize the potential risks due to the seismic loadings. This can prevent disastrous failures with performing appropriate rehabilitation actions. The Mahabad dam is located on an alluvium foundation with maximum depth of 20 m, mainly consisting of gravelly materials with fine content (silt and clay). This layer has liquefaction potential which was not considered during its former design. Research reported here represents determining seismic stability and liquefaction potential of Mahabad Dam using records appropriate to the dam's site, obtained from ground strong motions of the region. In this study, dynamic response of the dam is carried out using FLAC 5 software incorporating the non-linear soil behavior and effective stress method. Soil properties are calibrated against data obtained from laboratory and field geotechnical and geophysical investigations. Due to the present conditions of the site and previous studies, stability of the dam investigated under four earthquakes, Bam record in Maximum Considered Earthquake level (MCE), Karebass record in Maximum Design Earthquake level (MDE), Asalem record in Design Basis Earthquake (DBE) and Masjed-Soleyman record in Operating Basis Earthquake (OBE). The results showed that liquefaction occurs in upstream shell and upstream foundation during MCE scenario as in MDE scenario, but it is much more stronger in MCE scenario. Displacemnets in MCE shows a great instability in the dam due to the earhquake. According to analyses results structure is safe under DBE and OBE earthquakes.
  9. Keywords:
  10. Liquefaction ; Seismic Response ; Mahabad Embankment Dam ; Rockfill Dam ; Earth-Rockfill Dam

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