References(29) Engineering problems concerned either directly or indirectly with unsaturated soils are more and more common, ranging from aspects related to seepage to those related to shear strength and volume change. A few constitutive models have been conceived to describe and quantify these problems all of them with some advantages and drawbacks. Regarding mechanical behavior, the so-called Barcelona Basic Model (BBM) has achieved wide acceptance in geotechnical engineering, basically due to its simple mathematical formulation and good description of phenomena associated with unsaturated soils, especially collapse. Another concept that has emerged as a powerful framework to tackle three-dimensional states in granular materials is that of a modified stress tensor, such as tij. In this paper both BBM isotropic structure and tij concepts are combined to propose a new elastoplastic model for unsaturated soils, called tij-unsat. Modifications and generalizations for unsaturated states are introduced to accommodate those frameworks and overcome some inherited drawbacks. At the end of this work, experimental data gathered from specialized geotechnical literature is used to support the theoretical framework. The satisfactory agreement between simulations and tests results emphasizes the applicability of the proposed formulation to real boundary value geotechnical problems.
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