Displacement-based design procedure for slope-stabilizing piles

Vertical piles are widely employed around the world to prevent landslides, and they are commonly designed with the aim of reducing the soil displacement rate well before the activation of the potential failure mechanism. The design strategies usually adopted in engineering practice are often based on oversimplified approaches, not taking into account any realistic interaction mechanism between pile and soil, and they are not suitable for predicting the effectiveness of the mitigation structure in terms of reduction in the soil displacement rate. This paper attempts to address the problem by proposing a simplified displacement-based numerical procedure, providing engineers with a simple, physically based and easy-to-run tool, particularly useful in pre-dimensioning phases for the system. The importance of a correct description of the soil-pile mechanical interaction and even of possible nonlinearities in pile behaviour is quantitatively discussed by means of numerical analyses based on simplified geometries, proving that the soil-structure interaction forces cannot a priori be foreseen, but that their evaluation requires a displacement-based procedure. The proposed approach appears to be very useful even for prediction of the long-term behaviour of the system. This framework allows the capture of even the remarkable influence that the shape of the soil displacement profile has on the mechanical response of the system, thus implying that a reliable on-site monitoring system is necessary for the optimum design of the structure. Key words: displacement-based design, stabilizing piles, horizontally loaded piles, simplified numerical modeling. Des pieux verticaux sont couramment utilises a travers le monde pour prevenir les glissements de terrain, et sont souvent concus dans le but de reduire le taux de deplacement des sols bien avant l'activation des mecanismes de rupture potentiels. Les strategies de conception normalement adoptees dans la pratique sont souvent basees sur des approches tres simplifiees qui ne tiennent pas compte des mecanismes d'interaction realistes entre le pieu et le sol, et ne sont pas appropriees pour predire l'efficacite de la structure de mitigation en termes de reduction du taux de deplacement des sols. Cet article tente de repondre a la problematique en proposant une procedure numerique simplifiee basee sur les deplacements, qui offre aux ingenieurs un outil simple, base sur la physique et facile a utiliser, qui sera particulierement utile dans les phases de predimensionnement de la systeme. L'importance d'une description correcte de l'interaction mecanique sol-pieu, et aussi des non-linearites possibles dans le comportement des pieux, sont discutees quantitativement par des analyses numeriques basees sur des geometries simplifiees, ce qui prouve que les forces d'interaction sol-structure ne peuvent pas etre predites a priori, mais que leur evaluation necessite une procedure basee sur les deplacements. L'approche proposee semble etre tres utile meme pour les predictions du comportement a long terme du systeme. Cette approche permet meme de capturer l'influence remarquable que la forme du profil de deplacement du sol a sur le comportement mecanique du systeme, impliquant ainsi qu'un systeme de suivi fiable sur le site est necessaire pour une conception optimale de la structure. [Traduit par la Redaction] Mots-cles: Mots cles: conception basee sur les deplacements, pieux stabilisants, pieux sollicites horizontalement, modelisation numerique simplifiee.
Introduction As is well known, the social, economic, and environmental impact of gravitational mass movements is extraordinarily high and mitigation of the associated risk is therefore of interest to many [...]