Anisotropic undrained shear strength parameters for non-linear deformation analyses of embankment dams

摘要

Non-linear seismic deformation analyses (NDAs) of dams often require estimating undrained shear strengths for compacted embankment soils. These soils can range broadly in their grain size distributions, fines contents, and fines plasticity characteristics. Their shear strengths are often estimated based on results of isotropically consolidated undrained triaxial tests with adjustments to account for the anisotropic consolidation conditions in the field. The most common method for estimating anisotropic undrained shear strengths for use in limit equilibrium analyses of slope stability generally involve interpolating between the drained shear strength envelope and the isotropic undrained shear strength envelope using the stress conditions on the failure plane at the time of consolidation. While this method appears to work well for limit equilibrium analyses, its use in NDAs is complicated because a failure surface is not pre-defined. An extension of this method for use in NDAs is presented, including examination of alternative measures of consolidation stresses for interpolation of undrained shear strengths. An example of using these methods in a numerical analysis of an embankment dam is presented and issues regarding their implementation in NDAs are discussed.