Physical and computational modeling of biaxial base excitation of sand deposits

El-Shafee, Omar Osama
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Abdoun, Tarek
Zeghal, Mourad
Dobry, R. (Ricardo), 1922-
Manzari, Majid
Bennett, Victoria Gene
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Civil engineering
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This electronic version is a licensed copy owned by Rensselaer Polytechnic Institute, Troy, NY. Copyright of original work retained by author.
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The work presented herein is a centrifuge study conducted at the Center for Earthquake Engineering Simulation (CEES) of Rensselaer Polytechnic Institute (RPI) to assess the dynamic response characteristics of level deposits and SSI under multidirectional shaking. Synthetic sinusoidal waves were used as base excitations to test loose and dense models under biaxial and uniaxial shaking. Dense arrays of accelerometers were used to monitor the deposit response along with pore water pressure transducers. Three primary and calibration tests were conducted in order to assess the behavior of the RPI 2D shaker and 2D laminar box. Followed by three uniaxial tests and three bi-axial shaking tests conducted on soil models to study the impact of multidirectional shaking on the soil liquefaction. The three uniaxial shaking tests consisted of: i)Two tests with input energy similar to that of the bi-axial input shaking energy and ii) Test with 10% increase in one of the components of the biaxial shake amplitude, as commonly done in practice for uniaxial simulation of multidirectional field shaking. For biaxial tests two studied free field and one studied SSI. The observed acceleration and pore pressure are used along with non-parametric identification procedures to estimate the corresponding dynamic shear stress-strain histories. The measured results along with the obtained stress and strain histories are used to shed the light on the mechanisms of liquefaction occurring through the stratum, excess pore pressure buildup, soil contraction and the difference in soil behavior when it is subjected to biaxial shaking. This difference is evident in the strain energy generated in the biaxial test compared to that of the equivalent and traditional uniaxial tests, and the non-proportional response of the soil under biaxial shaking.
May 2016
School of Engineering
Dept. of Civil and Environmental Engineering
Rensselaer Polytechnic Institute, Troy, NY
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