Análise paramétrica de grupos de estacas helicoidais à tração

Abstract

Helical piles have advantages over other foundations systems, like high productivity and the possibility of receiving loads immediately after installation. These piles can be integrated into reaction systems for static load tests, in which, depending on the spacing between them, group effects may appear and reduce their efficiency. The literature about groups of helical piles is relatively scarce. Given the difficulty of testing different configurations of pile groups, this article proposes using Finite Element Method analysis on numerical models of pile groups to assess their performance in sand. A reference numerical model was created using soil properties obtained from SPT surveys and realistic modeling hypothesis, and then calibrated against field load tests performed by Costa (2017b). Further models were developed to simulate groups with 2 and 4 piles, with on-center spacing ratios (S/D) ranging from 1.14 to 6. The failure criterion by Livneh & El Naggar (2008) and a modified version of the Davisson Offset Limit method (2007) were used in the analyses of uplift load capacity and group efficiency. The results from the numerical simulations were compared with the theoretical method presented by Perko (2009). The failure surfaces show that interference between piles decreases when on-center spacing increases. Piles behave independently with S/D greater than 5. Groups with the pile heads connected by a cap exhibit smaller displacement than groups with free-standing piles. The increased stiffness provided by the cap results in higher efficiency.