The contribution of constitutive modelling to sustainable geotechnical engineering: examples and open issues

This paper discusses the role of constitutive modelling in the context of modern sustainability-driven geotechnical engineering. The necessary definitions and fundamental relations among the elements characterising sustainability in civil and geotechnical engineering are first provided, based on the available scientific literature, to then introduce the key topic here discussed by some examples, characterised by increasing level of complexity in terms of constitutive modelling assumptions. This objective is first attempted by presenting the results of the analyses of two boundary value problems, one related to the staged construction of an earth dam and the other devoted to the analysis of the seismic performance of a tunnel, which clearly show that a slight improvement in the constitutive assumptions can lead to rather more realistic, instructive and sustainable representations of reality. The second part of the paper is devoted to the discussion of some specific issues related to more recent advances in plasticity-based constitutive modelling of soils, focusing on clayey natural soils affected by structure, and its degradation, and by anisotropy, and its evolution. In this context, some well-established advanced constitutive frameworks are discussed, specifically focusing on the advantages and limitations of their use in the numerical analyses of geotechnical boundary value problems. It emerges that more research efforts are needed to define effective procedures to initialise at the deposit level the, often many, internal variables typically characterising advanced constitutive laws.