A macroelement framework for shallow foundations including changes in configuration

Abstract

Macroelement plasticity models are being increasingly applied to study non-linear soil–foundation interaction (SFI) problems. Macroelement models are particularly appealing from a computational standpoint, as they can capture the essence of SFI by means of a few degrees of freedom. However, all the macroelement formulations available in the literature suffer from the same limitation, that is the incapability of accounting for changes in both geometry and loading/boundary conditions. Accordingly, macroelement models are usually calibrated to analyse a given boundary value problem, with no chance of handling situations with significant variations in embedment, lateral surcharge and/or phreatic level. The present work shows how standard soil modelling concepts can be exploited to reproduce relevant ‘configurational features’ of non-linear SFI. A macroelement framework is here proposed to simulate the drained load–settlement response of shallow footings on sand in the presence of varying surface/body forces. As a first step, the ideal case of a weightless soil layer is exclusively considered. The macroelement constitutive equations are conceived/calibrated on a minimal set of finite-element results; the satisfactory predictive capabilities of the macroelement model are finally demonstrated by retrospectively simulating selected finite-element tests.

A simplified approach to estimate settlements of earth embankments on piled foundations: the role of pile shaft roughness

“…The macroelement approach, commonly employed to analyse different soil structure interaction problems (e.g. shallow foundations (Cremer et al, 2002;Flessati et al, 2021;Gottardi et al, 1999;Grange et al, 2009;Montrasio & Nova, 1997;Nova & Montrasio, 1991;Pisan o et al, 2016), offshore foundations and wind turbines (Byrne & Houlsby, 2003;Cassidy et al, 2006;Martin & Houlsby, 2001), buried pipelines (Cocchetti et al, 2009), rock boulders impacting on granular soil strata (di Prisco & Vecchiotti, 2006), pile foundations (Li et al, 2016), anchored wire meshes (Boschi et al, 2020(Boschi et al, , 2021(Boschi et al, , 2022 tunnel cavities (di Prisco & Flessati, 2021a) and tunnel fronts (di Prisco et al, 2018(di Prisco et al, , 2020c, stems from the idea of (i) describing the mechanical response of a complex system by means of a low number of degrees of freedom and (ii) defining an upscaled constitutive law, relating the generalized static and kinematic variables associated with the chosen degrees of freedom.…”

“…The model is an incremental generalized constitutive relationship conceived in the framework of the macroelement approach, in which the progressively increasing embankment height is interpreted as a generalized loading variable, whereas both differential and average settlements at the embankment top are the output variables. The model is the result of a sort of upscaling procedure in which both geometry and local constitutive material response play, within the upscaled constitutive model, as the micro-mechanical grain interaction in the formulation/calibration of phenomenological constitutive models for geomaterials (Flessati et al, 2021;Pisan o et al, 2016). As is shown in Flessati (2021), the model proposed in di Prisco et al ( 2020a) is a very convenient tool for designing the geometry (pile diameter and spacing) and assess the costs, once system performance (displacements) is fixed.…”

A hypoplastic macroelement formulation for single batter piles in sand

“…By macroelement, the foundation bearing capacity can be interpreted using 2D or 3D interaction diagrams rather than the classical bearing capacity factors. The geometric nonlinearity effects could be incorporated in the model formulation following an approach similar to the one proposed by Pisanò et al for shallow footings.…”

Numerical and theoretical analyses of settlements of strip shallow foundations on normally consolidated clays under partially drained conditions

“…In the past, many authors proposed different generalized constitutive relationships suitable for reproducing either the drained (Nova & Montrasio 1991, Montrasio & Nova, 1997, Gottardi et al, 1999, Houlsby & Cassidy, 2002, Bienen et al, 2006, Grange et al, 2008, Grange et al, 2009, Salciarini & Tamagnini, 2009, Salciarini et al, 2011, Pisanò et al, 2016 or the undrained (Williams et al, 1998, Martin & Houslby, 2001, Cassidy et al, 2004, Grange et al, 2009, Grange et al, 2011, Vlahos et al, 2011, Zhang et al, 2014 foundation response. In practice, all these authors assumed the loading rate to be, with respect to the system consolidation rate, either very low (drained case) or very high (undrained case).…”