Documents disponibles écrits par cet auteur

Bayesian model calibration using geotechnical centrifuge tests / L. L. Zhang in Journal of geotechnical and geoenvironmental engineering, Vol. 135 N°2 (Février 2009) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°2 (Février 2009) . - pp. 291–299 Titre : Bayesian model calibration using geotechnical centrifuge tests Type de document : texte imprimé Auteurs : L. L. Zhang, Auteur ; W. H. Tang, Auteur ; Zhang, L. M., Auteur Année de publication : 2009 Article en page(s) : pp. 291–299 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Centrifuge  model  Geotechnical  models  Slope  stability  Rainfall  Calibration  Bayesian  analysis  Reliability Résumé : The predicted performance using a geotechnical prediction model is expected to deviate from reality. A practical approach to assess the model error is through calibration with observed performances in physical model tests. In this paper, a Bayesian framework of model calibration using centrifuge modeling tests is proposed and the procedure of model calibration is illustrated. Two centrifuge tests conducted to investigate the performance of soil slopes under rainfall conditions are used to calibrate a coupled hydromechanical analysis model. It is found that for centrifuge tests with different levels of soil variability, the test with a smaller variability of soil properties is more efficient for model calibration. According to the concept of random field, a centrifuge model with a larger model size and accelerated to a lower acceleration is better for model calibration. When the discrepancy between the performance interpreted from the centrifuge model and the field performance is small, the improvement of the reliability estimation for a new slope is significant. However, when there is little information about the discrepancy, the reliability estimation cannot be significantly improved by the information from centrifuge modeling. The proposed procedure is shown to be able to quantify the calibration effects of centrifuge tests and may be used to achieve a more reliable calibration. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A2%2829 [...] [article] Bayesian model calibration using geotechnical centrifuge tests [texte imprimé] / L. L. Zhang, Auteur ; W. H. Tang, Auteur ; Zhang, L. M., Auteur . - 2009 . - pp. 291–299. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°2 (Février 2009) . - pp. 291–299 Mots-clés : Centrifuge  model  Geotechnical  models  Slope  stability  Rainfall  Calibration  Bayesian  analysis  Reliability Résumé : The predicted performance using a geotechnical prediction model is expected to deviate from reality. A practical approach to assess the model error is through calibration with observed performances in physical model tests. In this paper, a Bayesian framework of model calibration using centrifuge modeling tests is proposed and the procedure of model calibration is illustrated. Two centrifuge tests conducted to investigate the performance of soil slopes under rainfall conditions are used to calibrate a coupled hydromechanical analysis model. It is found that for centrifuge tests with different levels of soil variability, the test with a smaller variability of soil properties is more efficient for model calibration. According to the concept of random field, a centrifuge model with a larger model size and accelerated to a lower acceleration is better for model calibration. When the discrepancy between the performance interpreted from the centrifuge model and the field performance is small, the improvement of the reliability estimation for a new slope is significant. However, when there is little information about the discrepancy, the reliability estimation cannot be significantly improved by the information from centrifuge modeling. The proposed procedure is shown to be able to quantify the calibration effects of centrifuge tests and may be used to achieve a more reliable calibration. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A2%2829 [...]

Uncertainties of field pullout resistance of soil nails / L. L. Zhang in Journal of geotechnical and geoenvironmental engineering, Vol. 135 N° 7 (Juillet 2009) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 7 (Juillet 2009) . - pp. 966–972 Titre : Uncertainties of field pullout resistance of soil nails Type de document : texte imprimé Auteurs : L. L. Zhang, Auteur ; Zhang, L. M., Auteur ; W. H. Tang, Auteur Année de publication : 2009 Article en page(s) : pp. 966–972 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Soil  nailing  Slope  stability  Pull-out  In  situ  tests  Uncertainty  principles  Soil  suction Résumé : A large number of field pullout tests on soil nails have been carried out to provide valuable information for enhancing the understanding of pullout resistance of soil-grout interface and for reliability evaluation of soil-nailed slopes. In this paper, a data set of 167 field pullout tests performed in 23 nailed completely decomposed granite cut slopes is used for a statistical evaluation of four factors influencing the pullout resistance of soil nails, namely overburden pressure, grout length, soil suction, and soil dilatancy. For the tests in which nails were pulled out, the measured pullout resistance is essentially independent of the effective overburden pressure. A bias factor r∗ is defined as the ratio of the measured pullout resistance and the calculated value using a design equation. The mean value of r∗ is 4.30 and the coefficient of variation is 47%. When the uncertainties in grout length, soil suctions around nails, and the soil shear dilatancy are considered, the mean value of r∗ can finally be reduced to 0.99. The quantification of the uncertainties provides a better physical understanding of the working mechanisms of soil nails. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000014 [article] Uncertainties of field pullout resistance of soil nails [texte imprimé] / L. L. Zhang, Auteur ; Zhang, L. M., Auteur ; W. H. Tang, Auteur . - 2009 . - pp. 966–972. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 7 (Juillet 2009) . - pp. 966–972 Mots-clés : Soil  nailing  Slope  stability  Pull-out  In  situ  tests  Uncertainty  principles  Soil  suction Résumé : A large number of field pullout tests on soil nails have been carried out to provide valuable information for enhancing the understanding of pullout resistance of soil-grout interface and for reliability evaluation of soil-nailed slopes. In this paper, a data set of 167 field pullout tests performed in 23 nailed completely decomposed granite cut slopes is used for a statistical evaluation of four factors influencing the pullout resistance of soil nails, namely overburden pressure, grout length, soil suction, and soil dilatancy. For the tests in which nails were pulled out, the measured pullout resistance is essentially independent of the effective overburden pressure. A bias factor r∗ is defined as the ratio of the measured pullout resistance and the calculated value using a design equation. The mean value of r∗ is 4.30 and the coefficient of variation is 47%. When the uncertainties in grout length, soil suctions around nails, and the soil shear dilatancy are considered, the mean value of r∗ can finally be reduced to 0.99. The quantification of the uncertainties provides a better physical understanding of the working mechanisms of soil nails. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000014