Formulation of a Basic Constitutive Model for Fine - Grained Soils Using the Hypoplastic Framework

Filip Gago,Alessandro Valletta,Juraj Mužík

doi:10.2478/cee-2021-0047

Filip Gago, Alessandro Valletta + Show 1 more

Open Access

https://doi.org/10.2478/cee-2021-0047

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Abstract

Abstract A hypoplastic approach to constitutive modelling was developed by Kolymbas 1996 considering a non-linear tensor function in the form of strain and stress rate. However, the implicit formulation of the hypoplastic model with indirect material parameters severely limits its applicability to real-world geotechnical problems. In many cases, the numerical analysis of geotechnical problems relies on simple elastoplastic constitutive models that cannot model a wide range of soil response aspects. One promising paradigm of constitutive modelling in geotechnics is hypoplasticity, but many of the hypoplastic models belong to advanced models. In the article, we present the simple hypoplastic model as an alternative to the widely used Mohr-Coulomb elastoplastic model.

Highlights

We can characterize the strength of soils and other granular materials in terms of the friction angle φ and cohesion c
The hypoplastic model requires only one stiffness parameter, and in other aspects, the material behaviour is primarily captured by the tensor member generator itself
The results showed the qualitative drawbacks of simple elastoplastic models, such as MohrCoulomb, in the "elastic" domain, wherein in the case of simple models, an engineer needs to assume stress conditions to define the model stiffness parameters

Summary

Introduction

We can characterize the strength of soils and other granular materials in terms of the friction angle φ and cohesion c These parameters define a failure criterion and provide a sufficient description of the material properties relevant to stability problems (e.g. bearing capacity of foundations) that are mostly handled using the standard Mohr-Coulomb model. The hypoplastic model requires only one stiffness parameter, and in other aspects, the material behaviour is primarily captured by the tensor member generator itself. This is why most constitutive laws so far proposed for soils belong to the family of elastoplastic laws Such laws consist of a set of linear relations connecting the increments of stress and strain. A constitutive equation is proposed that departs entirely from the theory of elastoplasticity

Constitutive equation formulation using the hypoplastic framework

Numerical simulation of shallow foundation settlement

Conclusions