Anisotropic Analysis of I-Walls in New Orleans

Many numerical analyses of New Orleans levee and floodwall sections adopted mostly isotropic soil models partly due to the inherent simplicity of isotropic models. However, the isotropic models may not be sufficient to properly address the anisotropic behavior of soils. To overcome this imperfection, this study incorporated an anisotropic Modified Cam Clay model in a commercially available finite difference code, FLAC^3D, and analyzed a floodwall and levee section in the 17th St. Canal in New Orleans. The analysis showed that the anisotropic model resulted in a similar overall deformation to the Mohr-Coulomb isotropic model. However, the anisotropic model showed more widely spread yielded elements and higher shear strain gradient in the Lacustrine clay layer, reconfirming that the Lacustrine clay layer played a major role for the failure in the 17th St. Canal. This result also signified that the isotropic Mohr-Coulomb model might be good for evaluating overall behavior in moderate deformation problems, while the anisotropic Modified Cam Clay model was good even for large strain problems where more accurate evaluation of yielding is needed.