A numerical exercise for the definition under undrained conditions of the deep tunnel front characteristic curve

Prisco, Claudio di; Flessati, Luca; Frigerio, Gabriele; Lunardi, Pietro

doi:10.1007/s11440-017-0564-y

Cited by 14 publications

(6 citation statements)

References 33 publications

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“…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.…”

Section: Generalized Constitutive Relationshipmentioning

confidence: 99%

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

Flessati

Prisco

Corigliano

et al. 2022

European Journal of Environmental and Civil Engineering

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The use of piles as settlement reducers in the design of artificial embankments on soft soil strata is nowadays very common. The design methods employed in the current engineering practice are based on simplified approaches not allowing the assessment of average and differential settlements at the top of the embankment. In this paper, a model to estimate both differential and average displacements at the top of the embankment is introduced. This, based on the choice of substructuring the spatial domain and employing a suitably conceived upscaling procedure, is an extension to the case of rough pile shafts of a model originally conceived by the authors for smooth piles. To conceive and calibrate the model, the authors performed a series of numerical simulations mainly aimed at highlighting the mechanical processes taking place at the pile shaft. From a practical point of view, this model can fruitfully be employed in displacement based design approaches and to optimize pile diameter and spacing.

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Section: Generalized Constitutive Relationshipmentioning

confidence: 99%

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

Flessati

Prisco

Corigliano

et al. 2022

European Journal of Environmental and Civil Engineering

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“…The nonlinear and irreversible response of caisson foundations to vertical load is strongly influenced by the embedment ratio: as H/D increases, the ''structural hardening'' related to the progressive increase in the plastic zone developing in the soil surrounding the caisson's base and shaft becomes more and more evident. Similarly to what observed in [11] for the unloading occurring at the face of a deep tunnel, the progressive loading of the foundation causes an expansion of the plastic domain: yielding starts from the edges of the foundation's base to deepen and widen as loading increases, with plastic strains spreading over the soil surrounding the caisson. As soon as the mechanism reaches the upper boundary, the horizontal asymptote of the load-displacement curve is attained and failure occurs.…”

Section: Centred Vertical Loadingmentioning

confidence: 65%

“…Under the assumption of a sufficiently large ratio of the cover to tunnel diameter, the mechanism (Fig. 3a) involves the soil surrounding the tunnel face and lining without reaching the ground surface, this resulting in the absence of a plateau in the load-displacements curve [11].…”

Section: Centred Vertical Loadingmentioning

confidence: 99%

Use of interaction domains for a displacement-based design of caisson foundations

et al. 2022

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Caisson foundations, typically adopted for both onshore and offshore structures, are usually subject to combined loading acting during working conditions and exceptional events such as earthquakes. Assessment of their performance under general loadings is therefore fundamental, for both serviceability and ultimate limit states. In this study, a simplified displacement-based approach, aimed at preliminary designing caisson foundations subjected to combined loading, is presented. Such an approach requires the definition of both interaction domains (IDs) and generalised pushover curves, together with the assumption of an associative flow rule. The IDs and pushover curves are obtained by interpreting the results of a set of 3D finite element nonlinear static analyses, where the response of massive cylindrical onshore caisson foundations, embedded in a layered soil profile and subjected to both centred vertical (N) and combined loads (N–Q–M), is investigated. Following previous works, the influence of initial loading factor and caisson embedment ratio on both IDs shape and size is investigated. Additionally, the effect of soil drainage conditions on the IDs is discussed. Role of load reference point (LRP) is also assessed, since a suitable choice of LRP may strongly simplify the geometrical representation of the ID. Analytical expressions for dimensionless IDs and pushover curves are presented and used at a preliminary design stage to evaluate the maximum generalised load acting on the caisson for a given threshold generalised displacement, so as not to exceed either serviceability or ultimate limit states.

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“…As was expected, the initial elastic response and the ultimate load factor are not affected by 𝑘 ̅ . 𝑘 ̅ only influences the value of Q for which the transition from the linear and to the non-linear response occurs (di Prisco et al, 2018).…”

Section: Undrained Total Stress Numerical Analyses Resultsmentioning

confidence: 99%

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

2021

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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.

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A numerical exercise for the definition under undrained conditions of the deep tunnel front characteristic curve

Cited by 14 publications

References 33 publications

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

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

Use of interaction domains for a displacement-based design of caisson foundations

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

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