الفهرس 
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Abstract
The behavior of soils under cyclic loading plays a crucial role in determining the extent and distribution of ground displacements, which in turn are directly related to the potential for causing earthquake damage. In the literatur, the state in which the soil loses a large percentage of its shear strength when subjected to monotonic or cyclic loading (i.e. earthquake) is called liquefaction.
Great effort is carried out by the government through Water Resources and Irrigation Ministry to evaluate and rehabilitate the old water constructions such as the Barrages, Weirs and Regulators along the Nile to repair and enhance the efficiency of those structures, against all the possible problems including liquefaction.
Based on factual parameters, estimated from series of field and laboratory tests, numerical study was conducted to simulate the effect of seismic excitation on a water construction rested on liquefiable soil. The case study of the work, Zefta Barrage has been analyzed considering liquefaction prospect in one, two, and three dimensional finite element analyses. The ground motions used in the models are time-histories; real records spectrally matched the spectral acceleration curves for Zefta site using an updated earthquake catalog and updated seismotectonic model. Pseudo Spectral Acceleration curves (PSA) are calculated using probabilistic seismic hazard approach at Zefta site.
The analysis results are as follows:
1- Comparison has been conducted between constitutive models to identify the most appropriate one to simulate the site response analysis; Hardening Soil with small strain has the ability to use small strain stiffness and Rayleigh damping characteristics during dynamic loading.
2- The two dimensional finite element model gives a good preliminary result and shows the effect of extending the loose sand layer beneath the barrage section counter to the one dimensional model.
3- the structure is stable against liquefaction in case of operating bases earthquake (OBE) except in downstream zone just after the concrete blocks.
4- In case of subjecting maximum design earthquake (MDE), the downstream of the structure itself is highly affected by liquefaction state, but it is in a limited zone and can be overcome if this zone will be protected.
5- The three dimensional finite element model in case of subjecting maximum design earthquake (MDE) is safe against liquefaction.
6- If the soil is not extended in the same depth in the project site, we recommend to use three-dimension analysis instead of two-dimension analysis.
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