Numerical analysis of Ballina test embankment on a soft structured clay foundation

Abstract

This paper focuses on numerical modeling of the responses of Ballina test embankment by an improved EVP-SANICLAY constitutive model with a novel rotational hardening (RH) law. The modified RH law guarantees the uniqueness of the critical state line, prevents excessive rotation of yield surface and is particularly simple that makes it very useful for practical applications. To consider strain-rate dependency of the soil behavior, Perzyna’s overstress theory is employed. Using the newly released data at Ballina test embankment site, the values of model parameters and state variables are calibrated and evaluated for Class C predictions, and their differences with the previously determined parameter values for Class A predictions are highlighted and discussed. The elasto-viscoplastic anisotropic constitutive model is implemented in PLAXIS software to carry out the simulations of the case study embankment. The numerical modeling results, in terms of time-dependent variations of deformations and pore water pressures, both during and after the embankment construction, are compared with the physical measurements at the test site. The results of Class C analyses show that the model is capable of capturing the temporal changes in surface settlement and lateral deformations with good accuracy, with the latter being particularly challenging when modeling the behavior of soft clays. Simulation of pore water pressure variations however proved more difficult. To highlight the advantages of the proposed EVP-SANICLAY model, the simulations are also compared with those using the classical Mohr-Coulomb and modified Cam-clay models, and the results are presented and discussed in detail.