Critical Assessment of Nonlocal Strain-Softening Methods in Biaxial Compression

Summersgill, Freya; Kontoe, Stavroula; Potts, David M.

doi:10.1061/(asce)gm.1943-5622.0000852

Cited by 31 publications

(23 citation statements)

References 11 publications

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“…To avoid the mesh dependency seen in FE analyses involving strain localisation (e.g. Summersgill et al, 2017aSummersgill et al, , 2017b, a non-local strainsoftening model was employed. The analyses results show that the interaction of a vertical stabilisation pile and slope is complex, particularly in strain-softening materials where the developed failure mechanism evolves significantly with time.…”

Section: Discussionmentioning

confidence: 99%

“…The adopted permeability values are from subsequent work of Hight et al (2007). It is well established that the conventional FE solution of strain-softening problems, in which strain localisation occurs within a zone of limited thickness, can lead to numerical instability and significant mesh dependency of the solution (Galavi & Schweiger, 2010;Summersgill et al, 2017aSummersgill et al, , 2017b. The non-local method (Eringen, 1981;Bazant & Jirasek, 2002) alleviates these issues, adopting a distribution function that spreads the strain of the material at a point over a pre-defined surrounding volume.…”

Section: Description Of the Numerical Model Analysis Arrangement And mentioning

confidence: 99%

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Stabilisation of excavated slopes in strain-softening materials with piles

2017

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The use of a row of discrete vertical piles is an established method, successfully used to remediate failure of existing slopes and to stabilise potentially unstable slopes created by widening transport corridors. This paper challenges the assumptions made in current design procedures for these piles, which treat the pile only as an additional force or moment and simplify soil-pile interaction. Two-dimensional planestrain finite-element analyses were performed to simulate the excavation of a slope in a stiff clay and the interaction of vertical piles within the slope. A non-local strain-softening model was employed for the stiff clay to reduce the mesh dependency of the solution. An extensive parametric study was performed to systematically examine the impact of pile position, dimensions (length and diameter) and time of pile construction on the stability of a cutting in London Clay, which was chosen as a representative strainsoftening material. A variety of different failure mechanisms were identified, depending on pile location, dimensions and time of construction. The variability of the pile and slope interaction that was modelled suggests that an oversimplification during design could miss the critical failure mechanism or provide a conservative stabilisation solution. Given the prevalence of stiff clay slopes in the UK, increased capacity requirements of transport infrastructure and the age of slopes in this material, an informed and more realistic design of stabilisation piles will become increasingly necessary.

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Section: Discussionmentioning

confidence: 99%

Section: Description Of the Numerical Model Analysis Arrangement And mentioning

confidence: 99%

Stabilisation of excavated slopes in strain-softening materials with piles

2017

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“…Afterwards stress-like hardening variables (p s , p t and p m ) are directly computed by evaluating Equations 11and 12. The weighting function proposed by Galavi and Schweiger (2010) is employed here as it has been found to outperform other weighting functions in removing the mesh bias (Summersgill et al, 2017a;Mánica et al, 2018). This weighing function may be expressed:…”

Section: Nonlocal Reformulationmentioning

confidence: 99%

“…Oñate, 2016). Indeed, since the failure pattern is generally not known a priori, nonlocal approaches that rely on a fixed mesh are penalized by the need to lay out a very fine discretization (Mánica et al, 2018;Summersgill et al, 2017a). In this work, the refinement criterion used in the h-adaptive routines is the product of the accumulated plastic shear strain, α, and the area of the element.…”

Section: G-pfemmentioning

confidence: 99%

“…Within regularization techniques, the nonlocal integral type solution has the advantage of not changing the field equations which facilitates numerical implementation (Bažant and Jirásek, 2002;Lu et al, 2009;Galavi and Schweiger, 2010;Jin and Arson, 2018a,b;de Pouplana and Oñate, 2016;Summersgill et al, 2017a;Goodarzi and Rouainia, 2017;Mánica et al, 2018). In this approach chosen nonlocal variables are valuated from spatially averages of field variables in a neighborhood, and the constitutive models is updated by replacing a local variable with its nonlocal counterpart.…”

Section: Introductionmentioning

confidence: 99%

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A stable mesh-independent approach for numerical modelling of structured soils at large strains

Monforte

Ciantia

Carbonell

et al. 2019

Computers and Geotechnics

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We describe the large strain implementation of an elasto-plastic model for structured soils into G-PFEM, a code developed for geotechnical simulations using the Particle Finite Element Method. The constitutive model is appropriate for naturally structured clays, cement-improved soils and soft rocks. Structure may result in brittle behavior even in contractive paths; as a result, localized failure modes are expected in most applications. To avoid the pathological mesh-dependence that may accompany strain localization, a nonlocal reformulation of the model is employed. The resulting constitutive model is incorporated into a numerical code by means of a local explicit stress integration technique. To ensure computability this is hosted within a more general Implicit-Explicit integration scheme (IMPLEX). The good performance of these techniques is illustrated by means of element tests and boundary value problems.

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The deformation and failure of strip footings on anisotropic cohesionless sloping grounds

Gao

Zhao

2021

Num Anal Meth Geomechanics

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Footing foundations are sometimes built on sloping grounds of natural sand which is highly anisotropic. The anisotropic mechanical behaviour of sand can significantly influence the bearing capacity of a foundation and the failure mechanism of its supporting slope. Neglecting sand anisotropy may lead to overestimated bearing capacity and under‐design of foundations. A numerical investigation on the response of a supporting slope under a strip footing is presented, placing a special focus on the effect of sand anisotropy. A critical state sand model accounting for fabric evolution is used. The nonlocal method has been used to regularize the mesh‐dependency of the numerical solutions. Predictions of the anisotropic model on the bearing capacity of strip footings on slopes are validated by centrifuge test data on Toyoura sand. Compared to the centrifuge test data, an isotropic model may overpredict the bearing capacity of the footing by up to 100% when the model parameters are determined based on test data on a horizontal bedding plane case. When the isotropic model parameters are determined based on test data where the bedding plane is vertical, the predictions of bearing capacity can be improved for some cases but the settlement at failure may be significantly overestimated. The soil body tends to move along the bedding plane upon the footing loading due to the non‐coaxial strain increment caused by fabric anisotropy. The slip surface appears to be deeper with lower bearing capacity when the preferred soil movement direction caused by bedding plane is towards the slope.

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Critical Assessment of Nonlocal Strain-Softening Methods in Biaxial Compression

Cited by 31 publications

References 11 publications

Stabilisation of excavated slopes in strain-softening materials with piles

Stabilisation of excavated slopes in strain-softening materials with piles

A stable mesh-independent approach for numerical modelling of structured soils at large strains

The deformation and failure of strip footings on anisotropic cohesionless sloping grounds

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