Mathematical identification of diffuse and localized instabilities in fluid‐saturated sands

Mihalache, Constance; Buscarnera, Giuseppe

doi:10.1002/nag.2196

Cited by 23 publications

(16 citation statements)

References 48 publications

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“…A similar concept has been suggested by Mihalache and Buscarnera [60]. It is obvious that flow liquefaction instability occurs in the elastic-plastic regime of behavior and thus, H(L) = 1 was considered in Eq.…”

Section: Criterion For Flow Liquefaction Instabilitymentioning

confidence: 71%

Prediction of flow liquefaction instability of clean and silty sands

Lashkari

2015

Acta Geotech.

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Adding a small amount of non-plastic silt to clean sands may lead to dramatic loss of shear strength and a noteworthy tendency toward contraction when the mechanical behavior of the mixture is compared with that of the clean host sand. Thus, simulation of the behavior of silty sands with varying fines content is still a challenging subject in geomechanics. A unified constitutive model for clean and silty sands is presented in this paper. To eliminate the factitious decrease of void ratio associated with inactive silt particles in various silty sand mixtures, the concept of equivalent void ratio is used in the model formulation instead of the global void ratio. In addition, the instantaneous soil state is expressed in terms of intergranular state parameter taking into account the combined influence of intergranular void ratio, mean principal effective stress and fines content. Then, dilatancy and plastic hardening modulus are directly linked to the intergranular state parameter. To improve the model capacity in simulation of cyclic tests, new features are added to the plastic hardening modulus. It is shown that the proposed model can reasonably reproduce the mechanical behavior as well as the onset of flow liquefaction instability of clean and silty sands using a unique set of parameters. List of symbolsA Dilatancy parameter (Eq. 22) B Model parameter (Eq. 31) b Fines participation factor (Eq. 2) c (=M e /M c ) Model parameter c h Plastic hardening parameter (Eq. 23) D pp , D pq , D qp , D qq See Eqs. (45)-(49) d Dilatancy function (Eq. 22) e Global void ratio e* Equivalent intergranular void ratio (Eq. 2) e 0

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Section: Criterion For Flow Liquefaction Instabilitymentioning

confidence: 71%

Prediction of flow liquefaction instability of clean and silty sands

Lashkari

2015

Acta Geotech.

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“…We have adopted the constitutive parameters of loose Hostun sand given in Ciceri and Mihalache and Buscarnera for the numerical simulations. Hostun sand is a fine‐grained sand with specific gravity, G s , between 2.65 and 2.67.…”

Section: Brief Description Of the Elasto‐plastic Constitutive Modelmentioning

confidence: 99%

“…In the past, several theoretical studies on localized deformation in sand and clay have been conducted with the Lode angle‐dependent constitutive framework . However, the additional effects of those constitutive laws over the two‐invariant framework for shear localization prediction have not been explored for the cohesionless granular materials.…”

Section: Introductionmentioning

confidence: 99%

“…In the past, several theoretical studies on localized deformation in sand and clay have been conducted with the Lode angle-dependent constitutive framework. [27][28][29][30] However, the additional effects of those constitutive laws over the two-invariant framework for shear localization prediction have not been explored for the cohesionless granular materials. An exception could be the study by Andrade and Borja,30 in which a similar comparison was partially examined based on the evolution of localization tensor while simulating a true triaxial compression in dense sand.…”

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confidence: 99%

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Influence of Lode angle‐dependent failure criteria on shear localization analysis in sand

Sisodiya

Das

2018

Num Anal Meth Geomechanics

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Summary Geotechnical experiments show that Lode angle‐dependent constitutive formulations are appropriate to describe the failure of geomaterials. In the present study, we have adopted one such class of failure criteria along with a versatile constitutive relationship to theoretically analyze the effects of Lode angle on localized shear deformation or shear band formation in loose sand for both drained and undrained conditions. We determine the variation in the possible stress states for shear localization due to the introduction of Lode angle by considering the localized deformation as a bifurcation problem. Further, similar bifurcation analysis is performed for the stress states along a specific loading path, namely, plane strain compression at the constitutive level. In addition, the plane strain compression tests have been simulated as a boundary value finite element problem to see how Lode angle affects the post‐localization response. Results show that the inclusion of a Lode angle parameter within the failure criterion has considerable effects on the onset, plastic strain, and propagation of shear localization in loose sand specimens. For drained condition, we notice early inception of shear localization and multiple band formation when the Lode angle‐dependent failure criterion is used. Undrained localization characteristics, however, found to be independent of Lode angle consideration.

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“…Indeed, since the observation of failure in experiments is always subjected to interpretation, the assessment of failure conditions must be based on precise theoretical statements, that can be eventually used to specify mechanical criteria and back-analyse failures [109]. With this goal in mind, the paper summarizes some of the recent works proposed by the first author together with many other collaborators [16,17,22,23,81], and discusses how these fundamental mechanical notions relate with the state of saturation, the static/kinematic conditions, the pressures of the pore fluids and the perturbation of the hydrologic variables. The general mechanical problem is presented first, with reference to material point analyses and laboratory tests.…”

Section: Introductionmentioning

confidence: 99%

Instability of unsaturated soils: A review of theoretical methods

Buscarnera

Mihalache

2014

Journal of Geo-Engineering Sciences

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The paper reviews a series geomechanical approaches for interpreting instabilities in unsaturated geomaterials, a class of solids involved in numerous geo-engineering problems, such as hazard forecasting, infrastructure management, underground disposal of by-products and energy technologies. The review details the connection between second-order work input, loss of controllability and material failure. Hydro-mechanical problems are addressed, focusing on a specific class of environmental perturbations that can cause sharp changes in both mechanical and hydrologic variables. A procedure to define the second-order work input to an unsaturated soil volume is discussed first. It is pointed out that this energy measure motivates the incremental form of the constitutive laws for stability analyses. It is then discussed how to link the theory of hydro-mechanical controllability with constitutive approaches for unsaturated soils, which are typically based on the framework of strain-hardening plasticity with extended hardening. In doing so, the crucial role of the properties that govern the interactions between soil skeleton and fluid-retention processes is emphasized. The implications of these findings are commented with reference to a specific application: the forecasting of landslide triggering in natural slopes. It is shown that the use of suitable stability indices allows one to differentiate between frictional slips and volumetric collapses turning into flows. These results suggest that geomechanical theories calibrated for site-specific properties can support the quantitative assessment of landslide susceptibility, as well as a number of other engineering applications involving the instability of unsaturated porous media.

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Mathematical identification of diffuse and localized instabilities in fluid‐saturated sands

Cited by 23 publications

References 48 publications

Prediction of flow liquefaction instability of clean and silty sands

Prediction of flow liquefaction instability of clean and silty sands

Influence of Lode angle‐dependent failure criteria on shear localization analysis in sand

Instability of unsaturated soils: A review of theoretical methods

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