Luís J.L. Lemos

Behavior of an Atypical Embankment on Soft Soil: Field Observations and Numerical Simulation

This paper compares the behavior of an embankment with nonsymmetric geometry built on soft soil with that predicted numerically using four elastoplastic soil models. Two of these models are based on isotropic conditions (Modified Cam-Clay on its own or in association with Von Mises) and two other are derived from anisotropic conditions (Melanie on its own or conjugated with Mohr Coulomb). The performance of the models, whose parameters are derived from experimental data, is checked against triaxial tests results. For the embankment, the measured and computed displacements and excess pore pressure are compared, with the isotropic models performing best. The maximum horizontal displacements versus settlements, the change in excess pore pressure versus vertical stress, the extent of the yield domain and the contours of the effective vertical and horizontal stress increments are also examined. The numerical results are explained based on the characteristics of the numerical models, namely the size and shape of the yield surface. The embankment, despite its nonsymmetric geometry, exhibits some similarities with typical behavior.

Experimental Study of Isotropic and Anisotropic Constitutive Models

AbstractThis paper analyzes the validity of the yield surface and flow rule of several isotropic and anisotropic constitutive models. These aspects are studied based on drained triaxial tests, with a number of different stress paths in a computer-controlled stress path cell. The Cam clay, modified Cam clay, and p-q-θ models are used to study the isotropic behavior, whereas the anisotropic conditions are analyzed using the Melanie, MIT-E3, and S-CLAY1 models. Both under the isotropic and anisotropic conditions, the results indicate that the surface described by the undrained effective stress path is suitable for simulating the yield and plastic potential surfaces. In terms of isotropic behavior, the p-q-θ model is the most suitable for predicting the yield, whereas the plastic potential function is closely simulated by the yield function of the modified Cam clay model. For the anisotropic models studied, the MIT-E3 model provides a better approximation of the anisotropic behavior of the Santa Clara clay.