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Title: Finite element analyses of stresses and movements in embankments during construction
Authors: University of California, Berkeley. College of Engineering. Office of Research Services
United States. Army. Office of the Chief of Engineers
Kulhaway, F. H.
Duncan, J. M. (James Michael)
Seed, H. Bolton (Harry Bolton)
Keywords: Earth movements
Earth stresses
Finite element method
Publisher: Soils and Pavement Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Description: Contract report
Abstract: The objective of this investigation was to develop procedures for conducting finite element analyses of stresses and movements in embankments during construction. The procedures developed involve incremental analyses, simulating successive stages during construction of the embankment, and employ nonlinear stress-strain parameters determined from the results of laboratory tests. Previous studies of the nonlinear, stress-dependent stress-strain behavior of soils were extended during this investigation to include variations of Poisson’s ratio values as well as modulus values for use in incremental analyses. In order to examine the suitability of these procedures for representing the stress-strain characteristics of a wide variety of soils under both drained and undrained test conditions, the procedures were applied to 46 different soils, ranging from cobble sizes to highly plastic clays, for which stress-strain information had been published or was available from other sources. In each case it was found that the simple procedures developed for representing nonlinear, stress-dependent soil stress-strain behavior were convenient and provided reasonably accurate representations of the actual soil behavior. A finite element computer program was developed for incremental analyses of embankment stresses and deformations, incorporating these nonlinear stress-strain characteristics, and this computer program was used to conduct a series of analyses of the deformations in Otter Brook Dam during construction. These analyses showed that the vertical displacements (settlements) within an embankment during construction are affected very strongly by the value of soil modulus, and the horizontal displacements are affected very strongly by the value of Poisson's ratio. The vertical and horizontal displacements calculated using nonlinear stress-strain characteristics were in close agreement with those measured during construction of the dam. Studies of embankment stability showed that the values of stress calculated by the finite element method may be used to define a factor of safety with respect to either local overstress or overall stability. Provided that the factor of safety with regard to overall stability is defined in a manner consistent with that employed in limit equilibrium analysis procedures, the value of the factor of safety calculated using finite element stresses is nearly identical to that calculated using the best limit equilibrium procedures of slope stability analysis. Studies were also conducted to determine the effectiveness of these finite element analysis procedures for calculating stresses and displacements in zoned dams. Analyses were performed for two hypothetical zoned dams which had the same cross-section, but which differed with regard to the stiffness of the core material. These analyses showed that the settlements of embankments are influenced considerably by the stiffness of the core material, and that the stress conditions are strongly affected by the relative stiffnesses of the core and shell.
Rights: Approved for public release; distribution is unlimited.
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