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

Abstract

In the geotechnical community, the macroelement approach nowadays is largely considered to be a successful theoretical tool for solving soil–structure interaction problems. This approach is based on the definition of a generalised constitutive law putting in relation a small number of suitably defined generalised stress/strain variables. The macroelement formulations proposed in the literature take into consideration either drained or undrained cases, but disregard the hydro-mechanical coupling. In this paper, the authors intend to generalise the theory by introducing a new formulation for shallow foundations overpassing this limitation and capable of accounting for the influence of loading rate on the system response. To conceive and to calibrate the model, the authors numerically analysed the case of a shallow foundation positioned on a normally consolidated clayey soil stratum whose mechanical behaviour is reproduced by means of the modified Cam Clay model. Finally, the approach is discussed critically from the perspective of its use as a design tool according to approaches based on the ultimate limit state and displacement.

A Cyclic Macro-Element Framework for Consolidation-Dependent Three-Dimensional Capacity of Plate Anchors

“…Partial drainage is therefore simulated through the application of fully undrained shear induced by the load followed by pure consolidation during a period of time equal to the duration of the load. This follows a similar approach to that employed in other studies, where partial drainage was simulated through a series of undrained loading phases followed by consolidation phases during which the load was kept constant [19,[33][34][35]. Fundamental model parameters are shared between the consolidation and shearing mechanisms as detailed in the following.…”

“…The consideration of these processes is particularly important in offshore geotechnical applications, when considering operational conditions and the whole design life of geotechnical systems [15][16][17]. Few macro-element models have included the hydro-mechanical effects to account for partial drainage, yet all in the context of penetrometers and shallow foundations [18,19]. Houlsby and Cassidy [18] used a mechanical analogy in which springs and sliders connected in series represent the elastic and plastic undrained deformations of the foundation, respectively.…”

“…The results from the model were compared to experimental data and it was shown to capture the effect of different load rates applied to a spudcan. Similarly, Flessati et al [19] used a spring and a slider to represent the elastic and plastic deformations of a strip shallow foundation under undrained conditions. The partial drainage process was represented by a viscous damper (representing the drainage process) in parallel with a spring in series with a slider (to represent the elastic and plastic deformations during perfectly drained conditions).…”

Coupling Effect and Superposition Law in Soil Treatment Systems Incorporating Vacuum Preloading

“…In their solution, they proposed that vacuum pressure induces negative pore pressure while embankment loading induces positive pore pressure. (Flessati, Di Prisco et al 2021) stated that the macro-element approach nowadays is largely considered to be a successful theoretical tool for solving soil-structure interaction problems. This approach is based on the definition of a generalized constitutive law putting in relation a small number of suitably defined generalized stress/strain variables and can be used as designing tool according to ultimate limit state and displacement based approaches.…”

“…This approach is based on the definition of a generalized constitutive law putting in relation a small number of suitably defined generalized stress/strain variables and can be used as designing tool according to ultimate limit state and displacement based approaches. Particularly in the last decades, the application of the macro-element approach in soilstructure interaction problems has gained an increased popularity in the practical and academic implications (Vlahos, Cassidy et al 2011, Zhang, Cassidy et al 2014, Flessati, Di Prisco et al 2021.…”