Pieux sous charges latérales : étude de l'effet de groupe

Abstract

RESUME: Afin d'étudier l'effet de groupe sur des pieux chargés latéralement, des essais sur modèles réduits de couples de pieux ont été réalisés avec la centrifugeuse du Laboratoire Central des Ponts et Chaussées. Une méthode a été établie pour obtenir les courbes de réaction P-y à partir des résultats expérimentaux. On compare ensuite ces courbes à des codes de calcul reconnus : Fascicule 62 (France), Port and Harbour Research Institute (Japon) et l'American Petroleum Institute (D.S.A). Les déplacements en tête et les profils de moments fléchissants obtenus permettent de déterminer l'effet de groupe. On établit finalement des coefficients de réduction sur la réaction latérale du sol.

Scaling issues in centrifuge modelling of monopiles

“…This is clearly an outlier and it is concluded that the ratio between diameter of the pile and diameter of average grain size d/d 50 5 88 is too small, which leads to a grain size effect. This ratio is 30% higher than reported by Remaud (1999). The response is more or less identical until a normalised deflection of 0?1 is reached for the four other piles, and the loaddeflection curves start to deviate at larger deflections.…”

“…This is called 'modelling of models'. This technique has been used before for laterally loaded piles (Barton, 1985;Nunez et al, 1988;Remaud, 1999;Terashi, 1989) to investigate solely the grain-size effect. Garnier et al (2007) developed a scaling catalogue for 'TC2 -physical modelling in geotechnics' and noted that no grain-size effect was detected in 'modelling of models' if the ratio between pile diameter and average grain size was larger than 45 (Nunez Table 2.…”

“…Several studies have shown that the installation method is also important for the lateral response (Craig, 1985;Dyson and Randolph, 2001). The majority of centrifuge tests on laterally loaded monopiles are still performed on piles installed at 1g (Li et al, 2010;Remaud, 1999;Ubilla et al, 2006). The process that occurs at particulate scale during pile installation is complex, with significant displacement of the sand grains combined with particle abrasion and crushing (De Nicola and Randolph, 1999;McDowell and Bolton, 2000;Randolph et al, 1994;Weber et al, 2010;White and Bolton, 2004;White and Lehane, 2004).…”

“…Garnier et al (2007) developed a scaling catalogue for 'TC2 -physical modelling in geotechnics' and noted that no grain-size effect was detected in 'modelling of models' if the ratio between pile diameter and average grain size was larger than 45 (Nunez Table 2. Dimensionless ratios Scaling issues in centrifuge modelling of monopiles Klinkvort, Hededal and Springman et al, 1988) or 60 (Remaud, 1999) for laterally loaded piles. However, both of these test-sets were performed on long slender piles and the results from these tests should be used with caution for short stiff piles such as monopiles, which are subjected to a high ratio between bending moment and shear force by the wind turbines.…”

“…Scale effects have been investigated by Bouafia and Garnier (1991), Nunez et al (1988), Remaud (1999) and Terashi (1989) for long, slender piles that have been loaded laterally, in order to develop reliable modelling techniques. No investigation seems to have been carried out into scale effects for rigid monopiles loaded with a high moment to shear ratio.…”