Small Strains in Soil Constitutive Modeling

Abstract

This paper reviews the state of the art of soil behavior in the range of small strains and its constitutive modeling, which is an important issue when predicting displacements under serviceability conditions. The factors that control nonlinear, hysteretic and dependent on recent history soil behavior are described. Likewise, concepts of soil constitutive modeling are explored in detail and two criteria are explained and used to classify the analyzed models: (1) a first criterion based on the concept of tensorial zones; and (2) a second criterion based on the elements that defines the hysteretic soil behavior, including reversal criteria, memory rules and the effects of reversals on soil degradation and on soil stiffness recovery. The fundamentals of the formulation of the analyzed models are provided, as well as their scope of application, advantages and disadvantages.

Development of a new advanced elastoplastic constitutive model that considers soil behavior at small strains. The EPHYSS model

“…There are numerous advanced constitutive models capable of simulating the behavior of the soil in the whole strain range, 2 although the use of many of them is reduced to an academic use. However, some of these advanced models have managed to extend to the professional practice.…”

“…The EPHYSS model has multiple tensorial zones 8,9 and, therefore, it is an incrementally multilinear model, 10 although its indirect stiffness dependence on deviatoric strain increment when describing soil behavior in the range of small strains allows to consider it, in practice, as an incrementally nonlinear model. Specifically, the EPHYSS model belongs to the subtype of incrementally multilinear models called as advanced models of the elastoplastic type following the classification of Castellón and Ledesma 2 . Such model results from the combination of the Hysteretic Quasi‐Hypoelastic (HQH) model, which aims to reproduce the quasi‐static reversible behavior of the soil in the range of small strains (Zones I and II of Jardine), and the Hardening Soil Modified (HS MOD ) model, which aims to reproduce the irreversible behavior of the soil in the range of intermediate and large strains (Zones III and IV of Jardine) 4…”

“…Differences and common assumptions between EPHYSS and HS‐SS models are discussed in Castellón 4 and Castellón and Ledesma, 2 and will be summarized in this section.…”

“…The HS‐SS model presents some small differences with respect to the HS‐S model 2 . These differences appear in the expressions that both models use to calculate the dilatancy angle and in the expression of the Cap‐surface hardening law that each model uses, in which $${\dot{p}}_{p}$$ depends on the confinement in the HS‐S model and on the state variable $${p}_{p}$$ itself in the HS‐SS model.…”

“…After analyzing in depth 54 constitutive models that consider the soil behavior in the range of small strains, there have been identified some aspects that can be improved in the elastic part of the HS-SS model in relation to: (1) nonlinear behavior; (2) hysteretic behavior; (3) deviatoric strains reversals effect on the elastic bulk modulus; (4) consideration of the strain induced anisotropy; and (5) correction of some inconsistencies that have been detected. 2,[4][5][6][7] All these points have motivated the development of the Elastoplastic Hysteretic Small Strain (EPHYSS) model with the aim of being used in the geotechnical engineering professional practice. The entire code of the EPHYSS model, implemented in the User Defined Soil Model (UDSM) modulus of Plaxis may be consulted in Castellón.…”