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This paper presents centrifuge model test data that relate to the problem of tunneling beneath driven or jacked end-bearing piles in sand. The centrifuge model consisted of a tunnel and two piles and allowed for the acquisition of subsurface digital images throughout the tests. Soil and pile displacements were measured using particle image velocimetry and close-range photogrammetry techniques. The piles were jacked into the ground in-flight prior to tunnel volume loss to obtain ground stress profiles representative of conditions around driven or jacked piles. Patterns of displacements and calculated soil strains are presented to illustrate mechanisms of displacement and soil behavior. The measured soil and pile displacements are compared against greenfield test measurements. The results indicate that driving the piles significantly alters greenfield conditions and that greenfield displacements should not be used as an input for analytical tunnel-soil-pile interaction analyses for driven or jacked piles. Large pile displacements were observed to occur suddenly in the tests, illustrating the brittle nature of the soil in the areas affected by pile installation. A relationship between relative pile-tunnel location and the volume loss at which large pile displacements occurred is presented, which provides useful guidance to tunnel design engineers. Key words: tunnel, pile, sand, centrifuge, displacement mechanism, strain. Cet article presente des donnees d'essais en centrifuge modelisant le creusage de tunnels sous des pieux a pointe portante fonces ou a verin dans du sable. Le modele de centrifuge consiste en un tunnel et deux pieux et permet l'acquisition d'images digitales sous la surface pendant toute la duree des essais. Les deplacements du sol et des pieux ont ete mesures a l'aide des techniques d'images velocimetriques des particules et de photogrammetrie rapprochee. Les pieux ont ete installes avec un verin dans le sol en vol avant la perte de volume du tunnel afin d'obtenir les profils de contrainte du sol representatifs des conditions autour des pieux fonces ou a verin. Les patrons des deplacements et les deformations du sol calculees sont presentees afin d'illustrer les mecanismes de deplacement et le comportement du sol. Les deplacements mesures du sol et du pieu sont compares a des mesures sur un sol naturel vierge. Les resultats indiquent que le foncage des pieux altere significativement les conditions naturelles du sol et que les deplacements du sol naturel ne devraient pas etre utilises comme donnees de base pour les analyses analytiques des interactions tunnel-sol-pieu pour des pieux fonces ou a verin. On a observe que des grands deplacements des pieux se produisent de facon soudaine durant les essais, ce qui illustre la nature fragile du sol dans les zones affectees par l'installation des pieux. Une relation entre l'emplacement relatif pieu- tunnel et la perte de volume a laquelle les grands deplacements des pieux se sont produits est presentee, et ainsi offre des informations utiles pour les ingenieurs qui concoivent des tunnels. Mots-cles : tunnel, pieu, sable, centrifuge, mecanisme de deplacement, deformation. [Traduit par la Redaction], Introduction Urban development inevitably involves the construction of tunnels, be it small-scale for water and waste, or large-scale for transportation purposes. The estimation of ground displacements under greenfield conditions (just [...]

Excavation of a tunnel induces small movements at the surface of the ground above. Those movements are often estimated by empirical methods. This paper presents a simple derivation of formulas for elastic ground, based on the reciprocal theorem. It confirms that the effect of removal of the weight of the soil in the tunnel is not negligible. Key words: tunnels, settlements, volume loss, elasticity. L'excavation de tunnels provoque des petits mouvements a la surface du sol au-dessus de l'excavation. Ces mouvements sont souvent estimes a l'aide de methodes empiriques. Cet article presente une derivation simple de formules pour les sols elastiques, basee sur le theoreme de reciprocite. Ceci confirme que l'effet de retirer le poids du sol dans le tunnel est non negligeable. Mots-cles: tunnels, tassements, perte de volume, elasticite. [Traduit par la Redaction], Introduction Excavation of a tunnel induces ground movements around the tunnel and at the surface of the ground above. Those movements can induce structural damage in buildings, railways, pipelines, buried [...]

Abstract: The problem of tunneling effects on existing jointed pipelines is studied using the boundary integral method. Normalized solutions to evaluate the maximum bending moments and rotations are presented. They [...]