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An experimental study was carried out to investigate the effects of soil partial saturation on the behaviour of laterally loaded piles. The proposed study was conducted by means of centrifuge tests at 100g, where a single vertical pile was subjected to a combination of static horizontal load and bending moment. The study was conducted on a silty soil characterized with laboratory testing under saturated and unsaturated conditions. During flight, two different positions of water table were explored. The influence of density was investigated by compacting the sample with two different void ratios. Finally, the effects of a variation of saturation degree on the pile response under loading were studied by raising the water table to the ground surface. Data interpretation allows drawing different considerations on the effects of partial saturation on the behaviour of laterally loaded piles. As expected, compared to saturated soils, partial saturation always leads to a stiffer and resistant response of the system. However, the depth of the maximum bending moment is related to the position of the water table and the bounding effects induced by partial saturation appear to be more important for loose soils. Key words: centrifuge modelling, unsaturated soils, soil-structure interaction, piles, lateral loading. Une etude experimentale a ete realisee pour etudier les effets de la saturation partielle du sol sur le comportement de pieux charges lateralement. L'etude proposee a ete realisee au moyen d'essais en centrifugeuse a 100 g, au cours desquels un seul pieu vertical a ete soumis a une combinaison de charge horizontale statique et de moment de flexion. L'etude a ete menee sur un sol limoneux caracterise par des essais en laboratoire dans des conditions saturees et non saturees. En vol, deux positions differentes de la nappe phreatique ont ete explorees. L'influence de la densite a ete etudiee en compactant l'echantillon a deux indices des vides differents. Enfin, les effets d'une variation du degre de saturation sur la reponse du pieu sous chargement ont ete etudies lors de l'elevation de la nappe phreatique jusqu'a la surface du sol. L'interpretation des donnees permet de tirer differentes considerations sur les effets de la saturation partielle sur le comportement des pieux chargees lateralement. Comme prevu, par rapport aux sols satures, une saturation partielle conduit toujours a une reponse plus rigide et resistante du systeme. Cependant, la profondeur du moment de flexion maximal est liee a la position de la nappe phreatique et les effets de liaison induits par la saturation partielle semblent etre plus importants pour les sols meubles. [Traduit par la Redaction] Mots-cles : modelisation centrifuge, sols non satures, interaction sol-structure, pieux, chargement lateral., Introduction The significant soil volume interested by the kinematics of piles foundation under lateral loading is typically limited vertically in the first metres (several diameters of pile) of depth from [...]

The uplift capacity of helical anchors normally increases with the number of helical plates. The rate of capacity gain is variable, considering that the disturbance caused by the anchor installation is generally more pronounced in the soil mass above the upper plates than above the lower plates, because the upper soil layers are penetrated more times. The present investigation examines the effect of the number of helices on the performance of helical anchors in sand, based on the results of centrifuge model tests. Uplift loading tests were performed on 12 different types of piles installed in two containers of dry sand prepared with different densities. The measured fractions of the uplift capacity related to each individual helical plate of multi-helix anchors were compared with the fractions predicted by the individual bearing method. The results of this investigation indicate that in double- and triple-helix anchors, the contributions of the second and third plate to the total anchor uplift capacity decreased with the increase of sand relative density and plate diameter. In addition, these experiments demonstrated that the variation of the anchor load-displacement behavior with the number of helices also depends on these parameters. Key words: helical anchor, uplift capacity, installation effects, sand, centrifuge models. La capacite de soulevement d'ancrages helicoidaux augmente habituellement avec le nombre de plaques helicoidales. Le taux d'augmentation de la capacite est variable, considerant que la perturbation causee par l'installation de l'ancrage est generalement plus prononcee dans la masse de sol au-dessus des plaques superieures qu' au-dessus des plaques inferieures, puisque les couches de sol superieures sont penetrees plus de fois. La presente etude examine les effets du nombre d'helices sur la performance d'ancrages helicoi'daux dans le sable, a partir de resultats d'essais en centrifuge. Des essais de charges en soulevement ont ete realises sur 12 types de pieux installes dans deux contenants de sable sec prepare avec differentes densites. Les fractions de la capacite de soulevement mesurees associees a chaque plaque helicoidale d'ancrages multi-helices ont ete comparees avec les fractions predites par la methode de capacite individuelle. Les resultats de cette etude indiquent que pour des ancrages a double et triple helice, les contributions des deuxiemes et troisiemes plaques a la capacite de soulevement totale diminuent avec l' augmentation de la densite relative du sable et du diametre de la plaque. De plus, ces travaux demontrent que la variation du comportement en charge-deplacement de l'ancrage selon le nombre d'helices depend aussi de ces parametres. Mots-cles : ancrage helicoi'dal, capacite de soulevement, effets de l'installation, sable, modeles centrifuges. [Traduit par la Redaction], Introduction Helical anchors have been used in the construction of structures subject to uplift forces. These anchors are suitable for a wide variety of applications including transmission tower foundations, pipelines, [...]

Ref.: Can. Geotech. J. 49(9): 1102-1114 (2012) dx.doi.org/10.1139/t2012-064. Replace Fig. 5 with the figure shown herein, where the unit shown in the label on the vertical axis 'N/m' has been [...]