Abstract
The seismic response of a stiff levee structure placed on soft peat foundation soil is studied using centrifuge testing. The model levee was 5.1 m tall in prototype dimensions and rested atop 6.1 m of peat. The model was shaken with a suite of earthquake ground motions scaled to various intensities. Vertical and horizontal displacement records obtained from accelerometer arrays embedded in the peat were interpreted using bilinear quadrilateral interpolation to obtain in-plane components of the Cauchy strain tensor at each time increment. A direct-simple-shear-equivalent shear strain invariant, , was computed from the tensors. Values of as high as 7% were observed for input accelerations of . Residual excess pore pressures were mobilized at shear strain amplitudes higher than 1%, reaching maximum residual pore pressure ratios near 0.2. The observed relationship between the residual excess pore pressure ratio and mobilized shear strain agrees reasonably well with results from a laboratory simple shear testing program. Vertical strains in the levee toe region were 2.5 times larger than beneath the crest attributable to levee rocking under seismic loading. These vertical strains contribute to and therefore constitute an important demand on the underlying peat.
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Acknowledgments
This research was funded by the National Science Foundation under Grant No. CMMI 1208170. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. The writers would like to acknowledge the assistance of the UC Davis centrifuge team during the experimental testing program. Dr. Ali Shafiee is gratefully recognized for his willingness to share his DSS test data. Professors Jonathan P. Stewart and Samuel Yniesta are thanked for numerous fruitful discussions during the data evaluation process.
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©2017 American Society of Civil Engineers.
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Received: Feb 8, 2016
Accepted: Feb 3, 2017
Published online: Jul 5, 2017
Published in print: Sep 1, 2017
Discussion open until: Dec 5, 2017
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