An anisotropic Model for Structured Soils

Belokas, G.; Kavvadas, Michael

doi:10.1016/j.compgeo.2010.05.001

Cited by 23 publications

(5 citation statements)

References 22 publications

(47 reference statements)

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“…It has been determined from experiments that NCLs for clays corresponding to different stress ratios are approximately parallel in the e-lnp plane. 59,60 Once the NCL for the isotropic stress state is given, the vertical downward shift in the e-lnp plane can be F I G U R E 7 Comparison between experimental data and model simulations for Lower Cromer Till under undrained triaxial compression with various k values (overconsolidation ratio [OCR] = 1) A, effective stress paths; B, stress-strain curves calculated with ease by the following two approaches: (a) on the basis of experimental data in the literature, Belokas and Kavvadas 61 used the following equation to calculate the intercept N η of the NCL on the e axis for a given stress ratio η:…”

Section: Model Calibrationmentioning

confidence: 99%

“…Note that the current point B has a different stress ratio η 0 from point A. It has been determined from experiments that NCLs for clays corresponding to different stress ratios are approximately parallel in the e ‐ln p plane . Once the NCL for the isotropic stress state is given, the vertical downward shift in the e ‐ln p plane can be calculated with ease by the following two approaches: (a) on the basis of experimental data in the literature, Belokas and Kavvadas used the following equation to calculate the intercept N η of the NCL on the e axis for a given stress ratio η :

N_{η} = normalΓ - ((), N - normalΓ) {(1 - \frac{η}{M})}^{h},

where N and Г are the intercepts of the isotropic NCL and CSL, respectively; h is a regression factor that should be calibrated separately for each soil.…”

Section: Model Calibrationmentioning

confidence: 99%

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A bounding surface model for anisotropically overconsolidated clay incorporating thermodynamics admissible rotational hardening rule

Chen

Yang

2019

Num Anal Meth Geomechanics

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Summary A bounding surface model is formulated to simulate the behavior of clays that are subject to an anisotropic consolidation stress history. Conventional rotational hardening is revisited from the perspective of thermodynamics. As the free energy cannot be accumulated infinitely upon critical state failure, the deviatoric back stress must vanish. This requires the rotated yield surface to be turned back to eventually align on the hydrostatic axis in the stress plane. Noting that most of the previous propositions violate this restriction, an innovative rotational hardening rule is formulated that is thermodynamically admissible. The bounding surface framework that employs the modified yield surface is applied to simulate elastoplastic deformations for overconsolidated clays, with which the overprediction of strength on the “dry” side can be greatly improved with reasonable results. Other important features, including contractive or dilative response and hardening or softening behavior, can also be well‐captured. It has been shown that the model can simulate three types of reconstituted clays that are sheared with initial conditions over a wide range of anisotropic consolidation stress ratios and overconsolidation ratios under both triaxial undrained and drained conditions. Limitations and potential improvement of the model regarding the fabric anisotropy at critical state have been discussed.

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Section: Model Calibrationmentioning

confidence: 99%

N_{η} = normalΓ - ((), N - normalΓ) {(1 - \frac{η}{M})}^{h},

where N and Г are the intercepts of the isotropic NCL and CSL, respectively; h is a regression factor that should be calibrated separately for each soil.…”

Section: Model Calibrationmentioning

confidence: 99%

A bounding surface model for anisotropically overconsolidated clay incorporating thermodynamics admissible rotational hardening rule

Chen

Yang

2019

Num Anal Meth Geomechanics

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“…In E�. (17) and E�. (18), λ and κ are the slopes of the compression line and the swelling line in a volumetric strain-logarithmic mean stress plane, respectively.…”

Section: Formulation Of Structured Bounding Surface Modelmentioning

confidence: 99%

“…Maranha and Vieira [15] implemented a "bubble" bounding surface model for structured soils, formulated by Kavvadas and Belokas [16] in finite element software FLAC to evaluate the influence of the initial plastic anisotropy in the excavation of a tunnel. Belokas and Kavvadas [17] also developed an incremental plasticity constitutive Model for Structured Soils to describe the effects of structured soils, such as high initial stiffness, dilatancy, peak strength and the evolution anisotropy. Overall, the various structured bounding surface models are based on the similar bounding surface framework, and mainly differ in the precise form of destructuration laws adopted.…”

Section: Introductionmentioning

confidence: 99%

Formulation of structured bounding surface model with a destructuration law for natural soft clay

Cui¹

2017

Funct.Mater.

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A destructuration law considering both isotropic destructuration and frictional destructuration was suggested to simulate the loss of structure of natural soft clay during plastic straining. The term isotropic destructuration was used to address the reduction of the bounding surface, and frictional destructuration addresses the decrease of the critical state stress ratio as a reflection of reduction of internal friction angle. A structured bounding surface model was formulated by incorporating the proposed destructuration law into the framework of bounding surface constitutive model theory. The proposed model was validated on Osaka clay through undrained triaxial compression test and one-dimensional compression test. The influences of model parameters and bounding surface on the performance of the proposed model were also investigated. It is proved by the good agreement between predictions and experiments that the proposed model can well capture the structured behaviors of natural soft clay.Для моделирования изменения структуры естественной мягкой глины при пластической деформации предложен метод деструктурирования с учетом изотропной деструктуры и фрикционной деструктуры. Структурная модель ограничивающей поверхности была сформулирована, применяя закон реструктурирования в рамках теории ограничивающих поверхностных конститутивных моделей. Предложенная модель была проверена на глине Осаки с помощью недренированного теста на трехосный компрессионный тест и одномерного теста на сжатие. Исследованы влияние параметров модели и ограничивающей поверхности на характеристики предложенной модели. Подтверждением хорошего согласования между прогнозами и экспериментами является то, что предлагаемая модель может хорошо фиксировать структурированное поведение естественной мягкой глины.Утворення моделі структурованої граничної поверхні відповідно до руйнування природної глини. Yunliang Cui, Changguang Qi, Xinquan Wang, Shiming Zhang.Для моделювання зміни структури природної м'якої глини при пластичній деформації запропоновано метод деструктурування з урахуванням ізотропної деструктури і фрикційної деструктури. Структурна модель обмеженої поверхні була сформульована, застосовуючи закон реструктурування в рамках теорії поверхневих конститутивних моделей. Запропонована модель була перевірена на глині Осаки за допомогою недренірованого тесту на тривісний компресійний тест і одновимірного тесту на стиск. Досліджено вплив параметрів моделі і обмеженої поверхні на характеристики запропонованої моделі. Підтвердженням згоди між прогнозами і експериментами є те, що пропонована модель може добре фіксувати структуровану поведінку природною м'якої глини.

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“…The behaviour of bonded soils is significantly more complex than that of soils with unbonded grains. Many constitutive models for soils take the critical state as reference state [ 13 , 14 ]. For bonded soils, the critical state is difficult to achieve in a triaxial compression test.…”

Section: Introductionmentioning

confidence: 99%

The Stress−Dilatancy Behaviour of Artificially Bonded Soils

Szypcio

Dołżyk-Szypcio

2022

Materials

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In this study, the results of triaxial compression tests of some naturally and artificially bonded soils presented in the literature were analysed. It was shown that the three characteristic stages of plastic flow during shear can be identified. In all stages, the stress–dilatancy behaviour could be approximated by the general linear stress–dilatancy equation of the Frictional State Concept. For many shear tests, the failure states and newly defined dilatant failure states are not identical. The points representing dilatant failure states lie on a straight line, for which the position and slope in the h-D plane depend on the soil type and the amount of cement admixture. This line defines the critical frictional state angle, and its slope for bonded soils is greater than for unbonded soils.

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An anisotropic Model for Structured Soils

Cited by 23 publications

References 22 publications

A bounding surface model for anisotropically overconsolidated clay incorporating thermodynamics admissible rotational hardening rule

A bounding surface model for anisotropically overconsolidated clay incorporating thermodynamics admissible rotational hardening rule

Formulation of structured bounding surface model with a destructuration law for natural soft clay

The Stress−Dilatancy Behaviour of Artificially Bonded Soils

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