Relationship between the Seismic Coefficient and the Unfactored Geosynthetic Force in Reinforced Earth Structures
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 138, Issue 10
Abstract
This paper presents an integrated analytical method for calculating the resultant unfactored geosynthetic force in reinforced earth structures under seismic loading conditions. The method utilizes a pseudostatic limit equilibrium approach for assessing the internal stability of a reinforced earth structure, assuming a potential rotational failure along a log spiral trace. A closed-form solution is presented for determining the sum of all horizontal forces mobilized in the geosynthetic reinforcement along their intersection with the critical log spiral surface. This mobilized sum is then redistributed among the individual layers to determine the unfactored reinforcement forces that are needed to resist the applied seismic acceleration. Parametric studies were utilized, and the results are presented in a series of design charts for different conditions. Such charts can be used to determine the required tensile strength of the reinforcement for a given seismic coefficient. Alternatively, for a given reinforcement strength, the formulation can also be used to determine the yield acceleration that is required for calculating seismic displacements. An advantage of the proposed methodology is that it determines the yield acceleration caused by rotation of the reinforced mass (internal stability), which allows for a rational, yet simple, assessment of the displacement related to the internal movement of the reinforced mass. The design charts illustrate the effect of earth structure backslope and the vertical seismic coefficient. The results also show the impact of the assumed location of the resultant reinforcement force under seismic loading conditions. Variations in the location of this force over a reasonable range have little impact on the results. The inclination of the backslope has a significant effect for earth structures with smaller batters and/or larger horizontal seismic coefficients. Additionally, vertical seismic coefficients with a downward direction increase the mobilized force in the geosynthetic reinforcement.
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Acknowledgments
This material is based on work supported by the National Science Foundation under Grant No. CMMI-0844836. This National Science Foundation grant partially supported the first and third writers in conjunction with their work on this project. The writers would also like to extend their thanks to Mr. Fan Zhu for his valuable assistance with the formulation and programming that was conducted during this project.
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Information & Authors
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Published In
Journal of Geotechnical and Geoenvironmental Engineering
Volume 138 • Issue 10 • October 2012
Pages: 1209 - 1221
Copyright
© 2012 American Society of Civil Engineers.
History
Received: Jan 11, 2011
Accepted: Jan 25, 2012
Published online: Jan 28, 2012
Published in print: Oct 1, 2012
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