3D modeling of an NATM tunnel in high K0 clay using two different constitutive models / David Mašín in Journal of geotechnical and geoenvironmental engineering, Vol. 135 N° 9 (Septembre 2009)  

Public ISBD [article]  inJournal of geotechnical and geoenvironmental engineering > Vol. 135 N° 9 (Septembre 2009) . - pp. 1326–1335 Titre : 3D modeling of an NATM tunnel in high K0 clay using two different constitutive models Type de document : texte imprimé Auteurs : David Mašín, Auteur Année de publication : 2009 Article en page(s) : pp. 1326–1335 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Nonlinear analysisTunnelingClaysConstitutive modelsThree-dimensional analysis Résumé : This paper studies the accuracy of the three-dimensional finite-element predictions of a displacement field induced by tunneling using new Austrian tunneling method (NATM) in stiff clays with high K0 conditions. The studies are applied to the Heathrow express trial tunnel. Two different constitutive models are used to represent London Clay, namely a hypoplastic model for clays and the modified Cam-clay (MCC) model. Good quality laboratory data are used for parameter calibration and accurate field measurements are used to initialize K0 and void ratio. The hypoplastic model gives better predictions than the MCC model with satisfactory estimate for the displacement magnitude and slightly overestimated width of the surface settlement trough. Parametric studies demonstrate the influence of variation of the predicted soil behavior in the very-small-strain to large-strain range and the influence of the time dependency of the shotcrete lining behavior. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000017 [article] 3D modeling of an NATM tunnel in high K0 clay using two different constitutive models [texte imprimé] / David Mašín, Auteur . - 2009 . - pp. 1326–1335. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 9 (Septembre 2009) . - pp. 1326–1335 Mots-clés : Nonlinear analysisTunnelingClaysConstitutive modelsThree-dimensional analysis Résumé : This paper studies the accuracy of the three-dimensional finite-element predictions of a displacement field induced by tunneling using new Austrian tunneling method (NATM) in stiff clays with high K0 conditions. The studies are applied to the Heathrow express trial tunnel. Two different constitutive models are used to represent London Clay, namely a hypoplastic model for clays and the modified Cam-clay (MCC) model. Good quality laboratory data are used for parameter calibration and accurate field measurements are used to initialize K0 and void ratio. The hypoplastic model gives better predictions than the MCC model with satisfactory estimate for the displacement magnitude and slightly overestimated width of the surface settlement trough. Parametric studies demonstrate the influence of variation of the predicted soil behavior in the very-small-strain to large-strain range and the influence of the time dependency of the shotcrete lining behavior. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000017

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Hypoplastic cam-clay model / David Mašín in Géotechnique, Vol. 62 N° 6 (Juin 2012)  

Public ISBD [article]  inGéotechnique > Vol. 62 N° 6 (Juin 2012) . - pp. 549 –553 Titre : Hypoplastic cam-clay model Type de document : texte imprimé Auteurs : David Mašín, Auteur Année de publication : 2012 Article en page(s) : pp. 549 –553 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Stiffness Stress path Plasticity Constitutive relations Clays Résumé : A rearrangement of the hypoplastic constitutive equation is proposed that enables the incorporation of an asymptotic state boundary surface of an arbitrary predefined shape into the model, with any corresponding asymptotic strain-rate direction. This opens the way for further development of hypoplastic models. To demonstrate the flexibility of the proposed approach, a hypoplastic equivalent of the modified Cam-clay model is developed. A comparison of the predictions of the elasto-plastic and hypoplastic models reveals the merits of the hypoplastic formulation. Although both models predict the same asymptotic states, hypoplasticity predicts a smooth transition between overconsolidated and normally consolidated states, and thus accounts for the non-linearity of the soil behaviour inside the state boundary surface in a natural manner. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.11.T.019 [article] Hypoplastic cam-clay model [texte imprimé] / David Mašín, Auteur . - 2012 . - pp. 549 –553. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 6 (Juin 2012) . - pp. 549 –553 Mots-clés : Stiffness Stress path Plasticity Constitutive relations Clays Résumé : A rearrangement of the hypoplastic constitutive equation is proposed that enables the incorporation of an asymptotic state boundary surface of an arbitrary predefined shape into the model, with any corresponding asymptotic strain-rate direction. This opens the way for further development of hypoplastic models. To demonstrate the flexibility of the proposed approach, a hypoplastic equivalent of the modified Cam-clay model is developed. A comparison of the predictions of the elasto-plastic and hypoplastic models reveals the merits of the hypoplastic formulation. Although both models predict the same asymptotic states, hypoplasticity predicts a smooth transition between overconsolidated and normally consolidated states, and thus accounts for the non-linearity of the soil behaviour inside the state boundary surface in a natural manner. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.11.T.019

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Small-strain behaviour of cemented soils / J. Trhlikova in Géotechnique, Vol. 62 N° 10 (Octobre 2012)  

Public ISBD [article]  inGéotechnique > Vol. 62 N° 10 (Octobre 2012) . - pp. 943 –947 Titre : Small-strain behaviour of cemented soils Type de document : texte imprimé Auteurs : J. Trhlikova, Auteur ; David Mašín, Auteur ; J. Bohac, Auteur Année de publication : 2012 Article en page(s) : pp. 943 –947 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Stiffness Fabric/structure of soils Laboratory tests Constitutive relations Résumé : The shear modulus of cemented soils at very small strain (G 0) was studied. For artificially cemented clay, G 0 was found to be independent of the mean effective stress until the yield stress. After yield, a significant effect of structure degradation on G 0 was observed. The experimental data were interpreted by an equation, which relates G 0 of cemented soils to mean stress, apparent overconsolidation ratio and the state of structure (sensitivity). The equation was also found to represent G 0 of cemented sands. ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.P.100 [article] Small-strain behaviour of cemented soils [texte imprimé] / J. Trhlikova, Auteur ; David Mašín, Auteur ; J. Bohac, Auteur . - 2012 . - pp. 943 –947. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 10 (Octobre 2012) . - pp. 943 –947 Mots-clés : Stiffness Fabric/structure of soils Laboratory tests Constitutive relations Résumé : The shear modulus of cemented soils at very small strain (G 0) was studied. For artificially cemented clay, G 0 was found to be independent of the mean effective stress until the yield stress. After yield, a significant effect of structure degradation on G 0 was observed. The experimental data were interpreted by an equation, which relates G 0 of cemented soils to mean stress, apparent overconsolidation ratio and the state of structure (sensitivity). The equation was also found to represent G 0 of cemented sands. ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.P.100

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