Soutenance de thèse – Jawad THAJEEL – “Kriging-based Approaches for the Probabilistic Analysis of Strip Footings Resting on Spatially Varying Soils”

Jawad THAJEEL, doctorant au sein de l’équipe TRUST du GeM, soutiendra sa thèse le 8 décembre 2017 à 9h30 au Campus Gavy Oceanis à Saint-Nazaire sur le sujet suivant:

Kriging-based Approaches for the Probabilistic Analysis of Strip Footings Resting on Spatially Varying Soils

Résumé

The probabilistic analysis of geotechnical structures involving spatially varying soil properties is generally performed using Monte Carlo Simulation methodology. This method is not suitable for the computation of the small failure probabilities encountered in practice because it becomes very time-expensive in such cases due to the large number of simulations required to calculate accurate values of the failure probability. Three probabilistic approaches (named AK-MCS, AK-IS and AK-SS) based on Active learning and combining Kriging and one of the three simulation techniques (i.e. Monte Carlo Simulation MCS, Importance Sampling IS or Subset Simulation SS) were developed. Within AK-MCS, a Monte Carlo simulation without evaluating the whole population is performed. Indeed, the population is predicted using a kriging meta-model which is defined using only a few points of the population thus significantly reducing the computation time with respect to the crude MCS. In AK-IS, a more efficient sampling technique ‘IS’ is used instead of ‘MCS’. In the framework of this approach, the small failure probability is estimated with a similar accuracy as AK-MCS but using a much smaller size of the initial population, thus significantly reducing the computation time. Finally, in AK-SS, a more efficient sampling technique ‘SS’ is proposed. This technique overcomes the search of the design points and thus it can deal with arbitrary shapes of the limit state surfaces. All the three methods were applied to the case of a vertically loaded strip footing resting on a spatially varying soil. The obtained results are presented and discussed.

Jury

Rapporteurs

• M. Olivier DECK, Professeur, Université de Lorraine
• M. Michael HICKS, Professeur, Delft university of Technology

Examinateurs

• M. Ashraf AHMED, Maître de Conférences, Aswan university
• Mme Tamara AL-BITTAR, Maître de Conférences, Lebanese university
• M. Fabrice EMERIAULT, Professeur, Université de Grenoble
• M. Franck SCHOEFS, Professeur, Université de Nantes

Directeur de thèse

• M. Abdul-Hamid SOUBRA, Professeur, Université de Nantes