Thème :
NUMERICAL MODELING OF OPEN ENDED PILES.
Présentation :
Abstract. Deep foundations are generally used when significant loads are applied, and the site conditions do not allow for the implementation of soil reinforcement processes. This research focuses on studying the behavior of piles in a frictional environment, used as foundations for offshore structures in dense sands, involving anchor depths and overloads significantly higher than those encountered in onshore applications. The bearing capacity of open-ended driven piles plays a crucial role in this study. Therefore, a series of tests were conducted in the literature on model piles in a calibration chamber, which is considered a tool for physical modeling, allowing for significant penetration of instrumented model piles under confinement conditions similar to those experienced by real piles. Emphasis is placed on predicting the ultimate load capacity of open-ended piles using numerical methods. Calculations were performed using the finite element code PLAXIS to numerically reproduce the same shear stresses as those measured on the model during various phases of the experiment. The approach aims to validate the documented experiments in the literature and compare the ultimate load capacity of an open-ended pile to that of a closed-ended pile. Our study is limited to the case of a single pile, subject to static and axial force. The results show that it is possible to achieve a good agreement between the experiment and the numerical modeling with a relatively simple model, provided that the soil parameters are chosen correctly and the interface stiffness is adequately simulated.
Thème :
ETUDE THEORIQUE DU MECANISME DE FORMATION DU BOUCHON A L’INTERIEUR DES PIEUX BATTUS A BASE OUVERTE.
Présentation :
Ce type de pieux est utilisé généralement dans les ouvrages offshores; ce sont des tubes ouverts mis en place par battage dans les sables très denses de mer du nord.
Pendant l’installation du pieu cylindrique à paroi mince, le sol progresse à l’intérieur du tube jusqu'à ce qu’il développe la résistance nécessaire pour s’opposer à toute autre pénétration du matériau, créant ainsi le "bouchon".
Cet article tente de modéliser ce phénomène de bouchon, par la détermination d’un modèle basé sur le théorème cinématique de la théorie de l’analyse limite dans le cas du critère de Mohr-Coulomb. Ce modèle est en accord dans la forme du mécanisme, ainsi qu’en valeur de l’effort maximum que peut supporter ce genre de pieux.
Thème :
Reliability of geotechnical structures: case of bearing capacity failure
of strip footing
Présentation :
Traditionally, the design of geotechnical structures is based on a deterministic approach in which all parameters take a fixed value,
which leads to an oversized and unjustified underestimation of the bearing capacity of soil, as well as the overestimation of stress.
However, the effects on structure safety of uncertainties associated with the design parameters are not quantifiable. An alternative
method with which to study the reliability of geotechnical structures is based on the theory of probability and involves the
application of partial safety factors for all design parameters (random variables). These factors are derived using probabilistic
methods and take into account the dispersion of soil parameters (stochastic model). In this paper, a benchmark for a strip footing
with axial load was used, with security expressed via a probability of failure or reliability index and evaluated by means of a
universal computer code based on probabilistic methods. Analysis is carried out by considering the various types of parameter
distributions, thereby enabling a better assessment of the effects of uncertainty and the identification of a set of parameters with
high incidence.